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Can nitrogen amendment increase soil carbon storage? SETH ADAMS*, SUE J. GRAYSTON Belowground Ecosystem Group, Department of Forest Sciences, Faculty of Forestry, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4 [email protected] Keywords: nitrogen cycling, carbon sequestration, fertilization, enzymes Canada’s forest companies have expressed considerable interest in forest fertilization as a method for increasing tree growth and shortening rotation times. Additionally, nitrogen (N)-amendment may also increase soil carbon (C) sequestration due to suppression of the enzymes that decompose recalcitrant (e.g. high lignin) forest litter (Berg and Matzner, 1997). As part of a larger study assessing N fertilization effects on forest productivity (eddy covariance), C stocks and N2O emissions I am determining soil enzyme activities following N fertilization. I am also studying N mineralization and nitrification following fertilization to understand the processes which may lead to N2O emissions. Denitrification rates are determined using in-situ soil bag incubations which are analyzed for beforeand-after NH4+ and NO3- concentrations, enzyme activities are measured using colorimetric and fluorimetric assays and denitrification potential is measured with a sealed-jar experiment using a gas chromatograph. Studies are on-going, I hypothesize that urea will quickly mineralize to NH4+, N-amendment will increase nitrification and denitrification and N-amendment will decrease ligninolytic enzyme activity. Microbial biomass N will be much higher in the N-amended samples than control, supporting the assumption that the easily-consumed labile N is replacing the need for enzymatic “N-mining” (Craine et al., 2007). Reduced enzyme activity can result in lower decomposition of recalcitrant litter, leading to an increase in soil C storage. Denitrification potential will increase, possibly resulting in the release of additional N2O. Reference List Craine, J.M., C.M. Morrow, N. Fierer. 2007. Microbial nitrogen limitation increases decomposition. Ecology. 88(8): 2105-2113. Berg, B. and E. Matzner. 1997. Effect of N deposition on decomposition of plant litter and soil organic matter in forest systems. Environ. Rev. 5: 1-25

Comparative effectiveness of auxin and l-tryptophan blended compost for improving growth and yield of maize RIZWAN AHMAD1, M. ARSHAD2, AZEEM KHALID2, M. ASLAM1, S.N. KHOKHAR1AND M. NAVEED2 1

Land Resources Research Program, National Agriculture Research Centre , Islamabad-54400, Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad-30408. [email protected]

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Soil microorganisms are capable of producing auxins from its physiological precursor, L-tryptophan (L-TRP). Significant improvement in growth and yield of plants has been reported by applying L-TRP directly to soil, but its effectiveness through compost has yet not been reported. In the present study compost was prepared from fruit and vegetable waste material and enriched with 25% (44 kg ha-1) of full dose (175 kg ha-1) of N fertilizer for maize. Pure auxin, indole 3-acetic acid (IAA) and L-TRP (precursor), were blended with respective batches @ 10 mg kg-1 compost for the value addition of Nenriched compost. Comparative effectiveness of IAA or L-TRP-blended N-enriched compost was studied, in the presence or absence of 50% (88 kg N ha-1) of full dose of N fertilizer, through pot and field trials. Compost treatments were applied @ 300 kg ha-1, and compared with full dose of N fertilizer. Results indicated that N-enriched compost with or without IAA supplemented with half dose of N fertilizer was as effective as full dose of N fertilizer in improving growth and yield of maize, saving 25% N fertilizer. However, precursor (L-TRP)-blended compost was found better than pure auxin (IAA)-blended, when both were compared with full dose of N fertilizer. It significantly improved growth, yield and nutrient uptakes (up to 8.5, 10.2 and 21% respectively) of maize over full dose of N fertilizer. The technology bears its promise not only to improve crop yield on sustainable basis but also reduce huge piles of organic wastes causing environmental pollution.

Serpentine soils and vegetation of northwestern North America EARL B. ALEXANDER Soils and Geoecology 1714 Kasba Street Concord CA 94518 U.S.A. [email protected] Keywords: ultramafic, geoecology, British Columbia, Yukon, Alaska Ultramafic rocks with serpentine soils are widely distributed in accreted terranes southwest of the Rocky Mountain trench-Tintina fault zone and in Alaska-type bodies of British Columbia and Southeast Alaska. Although the areas of serpentine soils are small, many of them have vegetation that is distinctly different than that on adjacent soils. Soil classes in the World Reference Base and Canadian (in parentheses) systems are predominantly Cambisols (mostly Eutric Brunisols, but with Dystric and Humo-Ferric Brunisols where tephra or glacial drift have been deposited over the serpentine materials). Regosols (Orthic Regosols), Phaeozems (Mellanic Brunisols), and Luvisols (Gray Brown Luvisols) are also represented by serpentine soils. The most distinctive feature of the serpentine soils, other than the serpentine minerals inherited from the parent materials, is low exchangeable Ca/Mg ratios. This is the soil property that has the greatest effect on serpentine plant distributions. The common serpentine plant communities are alpine tundra, savanna, and forest. Most of the forests are coniferous (for example; white spruce, subalpine fir, and Douglas-fir), but paper birch (Betula papyrifera) is common toward the north and aspen (Populus tremuloides) is a successional species, along with lodgepole pine (P. contorta). Shrub species and herbs differ from north to south, although some shrubs such as low juniper (J. communis) are widespread on serpentine. Some of the more common genera of grass and sedges, from coldest to warmest, are Arctagrostis, Carex (C. bigelovii), Festuca (F. altaica), Calamagrostis, Pseudroegnaria (P. spicata), and Poa (P. secunda). Bryophytes and lichens are common ground cover toward the north and near the Pacific Coast.

Preferential flow of gas in soil SUZANNE E. ALLAIRE1 1

Horticultural Research Center, Université Laval, Québec, Qc, Canada, G1K 7P4 [email protected]

Keywords: gas movement, soil physics, macropore flow, heterogeneity Preferential flow (PF) is known to favour faster movement of solutes in soil toward surface and ground waters. PF seems as important for gas flux in soils especially for plant and biological respiration, oxidation, volatilisation of molecules, and for other processes. The goal of the project was to measure the relative importance of PF of gas under different soil conditions. Small, large, intact, and repacked soil columns were used to evaluate in laboratory the impact of soil heterogeneity on the PF of gas by diffusion. Macropores may increase gas diffusion by an order of magnitude. The impact of PF will further be discussed relative to gas diffusion in soil with macroporosity.

A history of soil classification in Canada DARWIN ANDERSON Department of Soil Science, University of Saskatchewan, Saskatoon, SK, S7N5A8 [email protected] Keywords: soil taxonomy, pedology, soil survey The origins of soil classification in Canada go back to the first soil surveys nearly a century ago. The first soil mapping in Ontario in 1914 followed a system developed in the USA and adapted to Ontario. It was based on soil colour and texture, with only nine series recognized for much of southern Ontario. Surveys using provincial classifications began in the Prairie Provinces in the 1920s. Many elements of the classifications used are evident in J.H. Ellis’ 1932 paper entitled “A Field Classification of Soils for Use in the Soil Survey”. The classification recognizes the soil zone as the highest category, consistent with early work by Ellis, A.H. Joel in Saskatchewan and F.A. Wyatt in Alberta. Subdivisions within the soil zone were the combination, association and associate, the latter similar to a soil series. Following a quiet period for pedology during the Great Depression and war years, the first meeting of the National Soil Survey Committee (NSSC) was held in Quebec in 1945. The NSSC, later the Canada SSC, brought together Canadian (provincial and federal) soil surveyors, pedology professors from the universities, and researchers in soil management. Generally there were representatives from the American soil survey community. Meetings every two to three years dealt with refinements to an emerging classification system. The 1955 meeting in Saskatoon was a milestone, in that a taxonomic system was introduced, in which higher hierarchical levels are conceptual, based on definition of a central concept. The Sub-Committee on Classification decided to continue with a Canadian system, not join the American effort that eventually led to Soil Taxonomy, although joint work is evident as both taxonomies developed. The Organic Order was added as the seventh order at the 1965 meeting at the Universite Laval, Quebec. The 1968 meeting in Edmonton resulted in a move to a more definitive system, and diagnostic horizons with defined criteria. There were major revisions to the Podzolic and Brunisolic orders, and the Luvisolic Order was added as the eighth order. “The System of Soil Classification for Canada” was published officially in 1974 as Publication 1455 of Agriculture Canada. It was a durable binder suitable for field use and able to accept later revisions. Eight orders, guidelines for describing profiles, and an interpretive classification, soil capability for agriculture, are included. A hard-cover edition entitled “The Canadian System of Soil Classification” was published by Agriculture Canada as Publ. 1646 in 1978. The Cryosolic order was included and, for the first time, a key for classifying soils. A second edition with revisions to the Gleysolic and Organic orders was published in 1987. The third edition (1998) includes a more complete key and a tenth order, the Vertisolic Order. Despite a present attitude of a job completed, it is evident that soil taxonomy in Canada is an enterprise that will continue to evolve as knowledge of our soils grows.

Properties of organic matter in a Chernozemic to Luvisolic sequence in soils at the grassland- forest transition DARWIN ANDERSON Department of Soil Science, University of Saskatchewan, Saskatoon, SK, S7N5A8 [email protected] Keywords: Gray Luvisol, Chernozem, humic acids, fulvic acids, carbon stores Soils at the grassland forest ecotone range from Black Chernozem soils under grassland to Gray Luvisol soils under aspen forest. Organic matter stores are somewhat higher in Chernozems and the OM is closely associated with mineral colloids in Ah and B horizons. The Gray Luvisols have nearly equivalent stores of OM, mainly as LFH or organic horizons at the soil surface, and at low concentrations distributed to considerable depth. More structurally complex, higher molecular weight humic acids are dominant in Chernozems, with about two-thirds of the OM present as clay-humus complexes. More soluble, organic materials of lower molecular weight ( fulvic acids) are the main OM component in Gray Luvisols, particularly in illuvial Bt horizons. Both visible fragments and the nature of humic materials suggest that charcoal accounts for much of the OM in surface horizons of Gray Luvisols, whereas clay-humus complexing is more important in Ah horizons of Chernozems.

Decrease in C availability following the cultivation of a forage stand DENIS A. ANGERS1, JAMES D. MACDONALD1, PHILIPPE ROCHETTE1, MARTIN H. CHANTIGNY1, ISABELLE ROYER1, MARC-OLIVIER GASSER2 1

Agriculture and Agri-Food Canada, Soils and Crops Research and Development Centre, 2560 Hochelaga Blvd, Québec, QC, Canada, G1V 2J3 2 Institut de recherche et développement en agroenvironnement, Québec, Canada, G1P 3W8 [email protected] Keywords: carbon, inversion tillage, water-extractable carbon, soil respiration, grassland Mixed cropping systems such as those practiced in dairy production usually involve periodic cultivation of perennial forage stands. By incorporating crop residues (above and below ground) inversion tillage increases the contact between fresh organic matter and the soil matrix. The incorporation of crop residue may increase or decrease C availability. The purpose of this work was to monitor the early changes in C availability following ploughing by inversion tillage of a perennial forage stand. In the fall of 2007, two long-term research plots were divided into 16 subplots (2 treatments x 4 replicates x 2 long-term plots) that were either cultivated by inversion tillage or chemically treated with herbicide (non-tilled). One of the two long-term plots had received large doses of liquid swine manure annually since 1978 (100 m3 ha-1) and the other was an unfertilized grassland (0 m3 ha-1). The plots were seeded to timothy and were turned and renewed each 7 years. Carbon availability was characterized by the water extractable fraction and field measurements of soil respiration. In both the unfertilized and fertilized plots, the cumulative emissions of CO2 were 30 and 18% lower, respectively, in the soil that had undergone inversion tillage compared to the non-tilled soil. Likewise, in the unfertilized plot, on average, the quantities of water-extractable organic carbon (WEOC) were 35% lower in the ploughed than in the non-tilled treatment. The non-tilled soils had high concentrations of WEOC in the surface profile in the period immediately after treatment, but these concentrations decreased over time. By the end of the monitoring period, quantities of WEOC in the non-tilled soils were similar to those submitted to tillage. Differences in respiration rates following inversion tillage may be in part explained by the incorporation of the plant residues in a zone of lower temperature and oxygen levels. However, the immediate reduction in WEOC after tillage also suggests that decomposing organic material is being adsorbed to mineral surfaces. This process may be, in part, responsible for reductions in respiration and may be acting as a protection mechanism for organic carbon. These results provide additional evidence that inversion tillage may result in carbon accumulation at depth in the soil profile.

The effects of soil resources on tree neighborhood dynamics in sub-boreal spruce forests of British Columbia RASMUS ASTRUP1, K. DAVID COATES2, ERICA B. CLOSE1 1

Bulkley Valley Centre for Natural Resources Research and Management, Box 4274, Smithers, BC, V0J2N0; 2 British Columbia Ministry of Forests and Range, Research Section, Bag 6000, Smithers, BC V0J2N0 [email protected] Keywords: forest dynamics, soil nutrient regime, sub-boreal spruce zone, SORTIE-ND Traditional even-aged forest management has relied on the concept of site index to characterize productivity for single-species stands. Site index is a critical component of many growth and yield models used to project stand growth, however, it provides little insight into how the competitive interactions among tree species in complex stands may be affected by resource gradients. Previous research in forest community dynamics has divided competitive interactions among trees into shading and crowding interactions, where neighbor trees shade each other and compete for underground resources (Canham et al. 2004). We used a multiple working hypotheses framework and maximum likelihood methods to determine if a soil resource gradient affected tree neighborhood shading or crowding interactions, or simply affected the maximum growth rate of individual trees. We sampled 1,952 lodgepole pine (Pinus contorta), interior spruce (Picea glauca×engelmanii), and subalpine fir (Abies lasiocarpa) trees ranging from highly suppressed to dominant in canopy position. Sampling targeted a range of stand types, competitive relationships, and soil resource conditions. Neighborhood trees within an 8 m radius were measured and used to model the amount of light reaching each sampled tree (with SORTIE-ND), and the amount of crowding experienced by each sample tree (with a neighborhood competition index). We classified soil nutrient regime according to B.C.’s Biogeoclimactic Classification System and measured tree growth as the average annual radial increment over the past five years. Models were compared that predicted tree growth from tree size (diameter), light, and crowding and allowed those relationships to change with soil nutrient regime. In our best models, the maximum growth rate of trees increased with increasing soil nutrients and the effect of crowding decreased with increasing soil nutrients, suggesting that underground competition has a more adverse effect on tree growth on poor sites then on rich sites. The effect of shading did not change with soil nutrients, suggesting that trees respond similarly to light across site types. Canham, C. D., LePage, P. T. and Coates, K. D. 2004. A neighborhood analysis of canopy tree competition: effects of shading versus crowding. Can. J. For. Res. 34: 778-787.

Limited impact of warming and defoliation on nitrogen dynamics in a rough fescue grassland BEHNAZ ATTAEIAN*1, SCOTT X. CHANG 1, JAMES F. CAHILL 2 1

Dept. of Renewable Resources, University of Alberta, Edmonton, Alberta, T6G 2E3 Biological Sciences Centre, University of Alberta, Edmonton, Alberta, T6G 2E9 [email protected]

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Keywords: global warming, defoliation, nitrogen cycling In Canada, temperature has risen about 1.2°C over the last 50 years in Prairie Provinces (Natural Resources Canada 2007). Higher temperature may influence productivity and sustainability of rangeland ecosystems, which are an essential part of the cattle industry in Canada. We need to know how to maintain the productivity and carbon sequestration function of rangelands faced with global warming and overgrazing. The “Law of the Minimum” states that productivity in an ecosystem is proportional to the availability of the most limited nutrient. Rangeland ecosystems are often Nlimited. Therefore, nitrogen availability can regulate productivity and carbon fixation processes in rangeland ecosystems. Climate change models overestimate carbon fixation/sequestration by not considering the nitrogen deficiency in natural ecosystems (Hungate et al. 2003). In rangeland ecosystems, the effect of global warming may be influenced by grazing. The purpose of this study was to investigate the temperature sensitivity of nitrogen dynamics in response to grazing in a rangeland ecosystem. Soil temperature was increased using open top chambers (OTCs), a standard passive tool to increase air and soil temperature in high-latitude areas (Marion et al. 1997). As the OTC’s design prevented cattle grazing, grazing was simulated by defoliation through manual clipping to a height of 5 cm. The study site was located in a remnant grassland of aspen parkland in the grassland-forest transition zone. The response of available nitrogen, nitrogen mineralization and nitrous oxide emission to warming and defoliation were studied over a two-year period (2006-2007). Soil and gas samples were collected monthly during the growing season. Data loggers were used to record soil temperature and moisture in 15 min intervals during the growing season. Nitrification appeared to be the dominant process affecting nitrogen dynamics; however, nitrogen dynamics seems little affected by warming and defoliation treatments. Reference List Biello, D. 2007. Conservative climate, Scientific American 296 (4):16 Hungate, B. A., Dukes, J.S., Shaw, M.R., Luo, Y. and Field, C.B. 2003. Nitrogen and climate change. Science, 302: 1512-1513. Marion, G.M., Henry, G.H.R, Freckman, D.W., Johnstone, J., Jones, G., Jones, M.H., Levesque, E., Molau, U., Molgaard, P., Parsons, A.N., Svoboda, J. and Virginia, R.A., 1997. Open-top designs for manipulating field temperature in high-latitude ecosystems. Global Change Biology, 3 (Suppl. 1) 33-34. Natural Resources Canada, September 2007. www.adaptation.nrcan.gc.ca

Quantifying soil carbon pools: the influence of trees in temperate agroforestry systems AMANDA D. BAMBRICK*1, JOANN K. WHALEN1, NARESH V. THEVATHASAN2 AND ANDY M. GORDON2 1

Macdonald Campus, McGill University, Ste-Anne-de-Bellevue, QC; University of Guelph, Guelph, ON; [email protected]

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Keywords: agroforestry, soil organic carbon, intercropping Tree-based intercropping (TBI) is an agroforestry system where a crop, generally an annual, is planted between established tree rows. TBI systems have a greater potential for carbon storage than conventional cropping systems because (1) carbon is stored in the biomass of growing trees and (2) trees provide additional carbon inputs (leaves, roots) that contribute to soil organic carbon (SOC) storage. Since trees are grown in rows, spaced 8 to 15 m or wider across the field, this could lead to considerable spatial heterogeneity in the SOC content. The objectives of this research were to quantify the horizontal and vertical spatial variation of SOC in TBI systems, and to compare SOC pools in autumn 2007 with historical pools in TBI systems, thus quantifying temporal changes in SOC storage. Soils were taken for SOC analysis from a TBI research site in Guelph, Ontario. At Guelph, 23-yearold hybrid poplar and Norway spruce were intercropped with corn. Results from the site indicate that the SOC content was affected by the presence of trees in the top 0-5 cm layer, but not in deeper layers. There was a significant (P 1.6 g mL-1) fractions. The results showed that C concentrations (g kg-1 of fraction) in the SOM density fractions decreased in the order of LFo > LF > HF, while the C/N ratio was in the order of LF > LFo > HF. The amount of C stored in the LF, LFo and HF fractions and bulk soil in the top 10 cm of soil was 149-504, 70-336, 1380-2876 and 1617-3776 g C m-2, respectively. From 2004 to 2006, C storage decreased in the LF and LFo fractions but increased in the HF fraction in the youngest stand. However, stand-age effects were likely muted by high inherent soil variability among the stands. Carbon storage in the light fraction was responsive in the short term to hybrid poplar plantation establishment. In the second experiment, we investigated the effects of landuse (including agricultural, hybrid poplar plantation, rangeland, and native forest) and temperature (7, 14 and 21 °C) on the mineralization of organic C associated with different soil particle size fractions (bulk soil, 250-2000 (medium to very coarse sand), 53-250 (very fine and fine sand), 2-53 (silt), and subhygric> mesic (107, 95, and 84 t ha-1), respectively. Stand age had no significant effect on either mineral soil or forest floor litter C stocks indicating their resilience to partial-cut and clearcut forest harvesting systems historically implemented throughout the study area. Woody debris, herbs, shrubs, small trees and large trees were all significantly influenced by stand age. Large trees were the only ecosystem component that showed a strong positive linear relationship with stand age while the remaining components displayed nonlinear changes. Soil C, as a proportion of ecosystem C, was proportionately higher in hygric versus drier sites and in younger versus older stands. In the final analysis, subhygric stands had the highest total ecosystem C stocks in the ALRF, having approximately 18% more C than mesic and hygric stands, principally due to higher mineral soil C stocks (than mesic stands) and higher large tree carbon stocks (over hygric stands).

Beyond ‘k’: Vegetation and disturbance drivers of boreal forest soil carbon JAMES W. FYLES Department of Natural Resource Sciences, McGill University, 21111 Lakeshore, Ste Anne de Bellevue, QC H9X 3V9 [email protected] Keywords: forested peatlands, Sphagnum, aspen, fire, forest management Getting ‘k’, the decomposition rate constant(s) right is a crucial aspect of modelling soil carbon. Estimating the values for carbon inputs is another. But these modelling parameters are, themselves, under the influence of less proximate ‘drivers’, which may be linked to each other or to different drivers. This presentation explores soil carbon in the context of a system that involves several drivers, as well as feedback loops that can lead to stability or push the system in one direction or another. The research deals with a complex of soils that occur in the boreal black spruce forest south of James Bay in northwestern Quebec. The undulating terrain, developed following deglaciation and the draining of glacial Lake Ojibway, is dominated by clay-rich tills with occasional coarser glacial-fluvial deposits. The current land surface is a complex of peatlands and forested uplands. Upland soils range from brunisolic to gleysolic and organic but the dominant functional feature of all soils is the thick organic layer on the surface, which is derived mainly from moss and stores as much as 200 Mg C/ha. Carbon dynamics and storage in these soils is intimately linked to the genesis of the surface organic horizons which is controlled by interactions among vegetation composition, plant residue quality, decomposition rate, and the chemical quality, water retention capacity and ignitibility during fire of the remaining organic matter. Sphagnum organic residues are inherently slow to decompose. As in peatlands, the presence of Sphagnum is associated with organic accumulation. Ericaceous shrubs may also retard decomposition. Aspen litter decomposes more rapidly and may exclude Sphagnum due to its physical presence, in contrast to black spruce needles which pass through the photosynthetic moss layers. As decomposition progresses, water holding capacity of organic layers increases and hydraulic conductivity drops, resulting in conditions that promote Sphagnum and reduce the potential for loss of organic horizons during a fire. Ignitability during fire depends on ash and moisture contents meaning that deeper, more decomposed layers are less likely to burn. ‘H’ horizons in these soils may represent long-term residual layers accumulated over many fire rotations. Fire, and to some extent logging, remove surface organic layers result in compact fibric organic horizons with a black surface that can reach very high temperatures on sunny days and limits revegetation. Exposed, highly decomposed ‘H’ layers appear to promote the establishment of Polytrichum moss, which itself provides conditions facilitating entrance of other plant species including feathermoss and aspen.

Ultimately, it may be possible to model the dynamics of carbon in these ‘peaty’ forest soils by finding a ‘k’ value that integrates the complexity of processes involved. However, linking such a model to changing disturbance or climate may require more explicit representation of these processes and their interactions.

Estimation du stock de carbone dans les sols de la Tunisie TAHAR GALLALI1, NADHEM BRAHIM1 1

Unité de Recherche Pédologie 04/UR/10-02. Faculté des Sciences de Tunis, Département de Géologie Campus Universitaire, Tunis 2092, Tunisie. [email protected]

Mots clés:, Carbone organique, stock, séquestration, sol, Tunisie En Tunisie, les différents types de sols peuvent être groupés en sept grandes unités de sols. A partir de l’estimation du stock de carbone organique dans chacune des sept grandes unités pédologiques, nous avons estimé le stock total du pays. Les calculs pour tous les sols sont pour les deux tranches 0-30cm et 0-100cm. Les résultats montrent que d’une manière générale le stock de carbone diminue en allant du Nord vers le Sud de la Tunisie, cette différence de stockage est liée au climat et au couvert végétal qui semblent les deux facteurs majeurs agissant sur la séquestration du carbone. L’unité des sols la plus riche est celle des sols bruns au nord du pays sous forêts et sous climat subhumides : 217t/ha, alors que la plus pauvre est celle de l’unité des lithosols au sud du pays sous végétation maigre et sous climat désertique : 25t/ha. La répartition verticale du stock de carbone organique dans les différents sols montre une décroissance avec la profondeur. De ce fait, les couches superficielles sont les plus riches en les comparant avec les autres les plus profondes et jusqu’à un mètre de profondeur. Le stock de la tranche 0-30cm par rapport à celle de un mètre de sol varie de 24% à plus que 40%, respectivement pour les sols les plus pauvres aux sols les plus riches. Par sommation des stocks des différentes unités de sols, on a obtenu le stock total dans les sols de la Tunisie. Sur la profondeur des trente premiers centimètres, le stock est évalué à 0.961Gtc, alors qu’il est de 1.353Gtc pour un mètre de profondeur.

Importance des matières organiques dans la stabilisation des sols sableux de la Tunisie et leur résistance à l’érosion TAHAR GALLALI & ABDELHAKIM BOUAJILA Unité de Recherche Pédologie. Faculté des Sciences de Tunis. El Manar 2092 Tunis. Tunisie [email protected] Mots clés : matière organique, substances humiques, stabilité structurale, érosion, Tunisie Une très grande partie de la surface de la Tunisie, caractérisée par des sols à texture grossière, supporte une activité agricole intense. Dans ces Terres l’importance de régénérer la réserve organique est fondamentale pour améliorer les propriétés physiques des sols et augmenter leur résistance à l’érosion éolienne et hydrique. Cette étude vise à (i) étudier le rôle des différentes fractions organiques dans la formation et la stabilité des agrégats de ces sols (ii) discuter les conséquences de cette relation sur la résistance à l’érosion hydrique et éolienne. Sept différents horizons de surface A ou Ap, échantillonnés dans les régions du Nord et du Centre de la Tunisie, constituent le support de ce travail. L’analyse de la matière organique a concerné le carbone organique total (COT), le carbone organique particulaire (COP), les polysaccharides (PEEC) et les composés humiques (AH+AF). Deux techniques de la mesure de la stabilité des agrégats sont utilisées, la stabilité structurale à sec et la stabilité structurale à l’eau. Les résultats sont présentés sous forme de DMP (stabilité à sec) ou MWD (stabilité à l’eau). L’analyse des différentes fractions organiques prouve que les sols agricoles ne disposent que d’une faible quantité des matières organiques totale, labile (POC + PEEC) et humifiée (AF+AH). Les résultas montrent aussi que la stabilité structurale à sec est importante pour tous les horizons (2.71 mm 0.17) were determined. Response probability within soil fertility classes was computed with a power test. Preliminary results will be presented during the poster presentation. Reference List CRAAQ. 2003. Reference guide for crop fertilization. 1st Ed., Centre de Référence en Agriculture et Agroalimentaire du Québec, Québec, Canada, 297 pp. Guérin, J., L.E. Parent, and R. Abdelhafid. 2007. Agri-environmental thresholds using mehlich III soil phosphorus saturation index for vegetables in histosols. Journal of Environmental Quality. 36:975982. Lucas, R. 1982. Organic soils (Histosols). Formation, distribution, physical and chemical properties and management for crop production. Res. Rep. 435, Agric. Exp. Sta. and Coop. Ext. Serv., Michigan State Univ., East Lansing, and Agric. Exp. Sta., Inst. Food Agric. Sci., Univ. Florida, Gainesville, FL, 79 pp. Sanchez, C.A. 1990. Soil-testing and fertilization recommendations for crop production on organic soils in Florida. Techn. Bull. 876, Agric. Exp. Sta., Inst. Food Agric. Sci., Univ. Florida, Gainesville, FL, 44 pp.

Basal and potential denitrification of soils under monoculture and rotational cropping of corn, soybean and winter wheat with/without red clover XIAOBIN GUO*1,2, CRAIG F. DRURY 1, XUEMING YANG 1, RENDUO ZHANG 2 1

Greenhouse and Processing Crops Research Centre, Agriculture & Agri-Food Canada, Harrow, Ontario, Canada N0R 1G0 2 School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, P.R. China [email protected] Keywords: basal denitrification, potential denitrification, monoculture soil, rotational soil Denitrification is controlled by a number of environmental variables and soil factors including the cropping history. The objective of this study was to compare the basal and potential denitrification rate of soils collected from both monoculture cropping of corn, soybean, winter wheat with/without underseeded red clover and from 2 and 3-yr crop rotations (corn-soybean, and corn-soybean-winter wheat with/without underseeded red clover). Each phase of the rotation was present each year and hence 12 treatments were examined. Using the acetylene inhibition technique, the basal denitrification rate with/without added nitrate (75 mg N kg-1 dry soil) and potential denitrification rate with a soluble C source (glucose at 300 mg C kg-1 dry soil) and NO-3-N (50 mg N kg-1 dry soil respectively) were measured at 20°C over a 5 hr period. Basal denitrification rates (no N added) ranged from 0.53 to 3.84 mg N2O-N kg-1 d-1, the lowest rate in monoculture winter wheat with red clover and the highest rate in soybean phase of the 3yr rotation (C-S-WW). Denitrification with added N ranged from 0.50 to 3.84 mg N2O-N kg-1 d-1, the lowest rate in monoculture soybean and the highest rate in winter wheat with red clover phase of the 3-yr rotation (C-S-WW+RC). Potential denitrification rates ranged from 6.24 to 11.04 mg N2O-N kg-1 d-1, the lowest rate in monoculture corn and the highest rate in the corn phase of the 2-yr rotation (C-S). No significant relationship was found between basal denitrification rate and soil nitrate concentration. However, there was a significant correlation between basal denitrification rate and soil anaerobic respiration rate (CO2) (R2=0.74, P 14 d. Moreover, four-fold coordinated Al persists relative to six-fold coordinated Al under increasingly acidic conditions, and a new phase consistent with Al2SO4 was observed. The Si XANES results also demonstrated the dissolution of Si-tetrahedral layers and subsequent precipitation of a higher ordered tectosilicate Si coordination at pH < 0.0 and t > 90 d. An overall description of how mineral dissolution and reprecipitation occurs in clay liners subjected to hyperacidic conditions was then developed.

Selenium oxyanion adsorption at the metal oxide/water interface: A Se Kedge XAS spectroscopic study DEREK PEAK1 1

Department of Soil Science, University of Saskatchewan [email protected]

Keywords: mineral dissolution, XAS, mineralogy, environmental chemistry Sorption processes at the mineral/water interface typically control the mobility and bioaccessibility of many inorganic contaminants, including selenium oxyanions. Selenium is an important micronutrient for human and animal health, but at elevated concentrations selenium toxicity is a concern. The objective of this study was to determine the bonding mechanisms of selenate (SeO42-) and selenite (SeO32-) on a variety of iron and aluminum oxide surfaces over a wide range of reaction pH using Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy.

This presentation will compare and contrast selenate and selenite bonding mechanisms on aluminum and iron oxides with Me2O3, MeOOH, and Me(OH)3 structures. From these studies, we will support the overall conclusion that the surface structure of metal oxide minerals has a rather dramatic effect on bonding mechanisms of oxyanions for these systems.

Hydrological triggers for CH4 and N2O emission events from Prairie wetlands DAN PENNOCK1, TOM YATES1, KIM PHIPPS1, RICHARD FARRELL1, BING SI, and ANGELA BEDARD-HAUGHN1 1

Department of Soil Science, University of Saskatchewan, 51 Campus Drive, Saskatoon, SK S7N 5A8 [email protected] Keywords: greenhouse gases, wetlands The defining feature of the Prairie Pothole Region is the countless wetlands embedded in agricultural landscapes and no accounting of greenhouse gas emissions from these landscapes can be complete without assessing their contribution. Emissions from wetlands and surrounding agricultural catchments were made over four years at the St. Denis National Wildlife Area 40 km east of Saskatoon SK. Emissions of both gases from a large semi-permanent pond at the site were relatively low in all four years of the study. Interannual differences in emissions of CH4 and N2O were greatest from the basin centers of the ephemeral ponds in the agricultural landscape. The major triggering event for emissions of both gases from the basin centers of these ponds was drainage of water from the pond surface and a rapid decrease in water-filled pore space from 80-90% to less than 60%. High emissions of CH4 were also associated with a 100 mm precipitation event that occurred on June 17 and 18th 2005. Modeling of greenhouse gas emissions from wetlands in these landscapes will require integration of hydrological processes that control pond flooding and drainage with biogeochemical models of the greenhouse gas emission processes.

The water is moving the wrong way: Prairie hydrology and discharge soils DAN PENNOCK1 1

Department of Soil Science, University of Saskatchewan, 51 Campus Drive, Saskatoon, SK S7N 5A8 [email protected] Keywords: wetlands, salinity, hydrology The dominant model to explain water movement in hummocky terrain in the Prairie Pothole region has undergone a substantial revision in the past decade. Studies on the direction and magnitude of water flow in these landscapes have demonstrated that the contribution of depression-focused deep drainage to groundwater is limited and that instead the dominant direction of water flow is lateral from the wetland to the surrounding wetland fringe. Rather than groundwater discharge, the source of the pond water in many wetlands is now understood to be from spillover of other wetlands during episodic fill-and-spill events, and the solute content of these ponds is largely controlled by their position in the spillover sequence and the long-term retention of salts in the underlying pond sediments. As the laterally moving water is evapo-transpired from the wetland fringe, the solutes are precipitated out in the surrounding soils. For these discharge soils the dominant direction of water flow is vertically towards the surface, rather than from the surface to depth in the soil; the balance between the two directions will change over time in response to climatically driven changes in site hydrology during the Holocene. The resulting soils typically have A and B horizons enriched in secondary carbonates or more soluble salts (depending on the chemistry of the pond water) and often formation of the typical indicators of reducing conditions (e.g. reduced matrix or iron mottling) is suppressed by the high pH conditions. Soils with an Ahca/Bmca/Cca sequence are common, yet this is a horizon sequence that fits very uncomfortably in the Canadian System of Soil Classification and indeed even the use of the ca suffix with A and B horizons is problematic. These are a widespread class of wetland soils that require a more coherent place and nomenclature within the Canadian System of Soil Classification.

Automated ecological mapping - what is it and how does it work? TANIA E. PERZOFF1, ROBERT A. MACMILLAN2 1

EBA Engineering Consultants Ltd., Oceanic Plaza, 9th Floor, 1066 West Hastings Street, Vancouver, BC, V6E 3X2 [email protected] 2 LandMapper Environmental Solutions Inc. 7415 118 A Street NW, Edmonton, Alberta, T6G 1V4 Keywords: predictive, mapping, ecological, automated Automated ecological mapping (or predictive mapping) uses computer, Geographic Information Systems (GIS), and knowledge-based methods to stratify landscapes into ecologically meaningful map units. Map units are based on the overlaying of existing mapped data and the processing of resulting attributes by automated inferencing software that use formalized knowledge bases that identify ecological-landscape relationships (Resources Inventory Committee 1999). Predictive mapping relies on a few, simple protocols, which include: (1) deciding what to map; (2) obtaining (appropriate) input data; (3) developing predictive equations or rules; (4) applying the equations or rules; (5) evaluating the predictive accuracy; and (6) producing final maps. These protocols can work for soils mapping (and by extension soil carbon) as much as they have been shown to work for ecosystem prediction. Virtually all digital mapping share common traits. The approach for predicting entities (i.e., ecosystems or soils) assumes that a predictive relationship exists between input environmental attributes and the output classes or properties to be predicted. Emphasis is placed upon the importance of landform, and assumes that a process-form or cause-effect relationship exists between landforms and soils or ecosystems. Many predictor variables are derived from Digital Elevation Models (DEMs). Modelling soil carbon using a digital mapping approach would be similar to that used to map other entities such as ecosystems; the approach rests with the identification of appropriate relationships and linkages. What to map or predict (in this case, soil carbon), what predictor variables will be used (e.g., soil types, vegetation types, landforms), and what methods will be used to develop and apply rules or equations (e.g., fuzzy logic, rule sets) could all be formulated in a similar manner. Information such as that provided by the Canadian Soil Organic Carbon Database (Tarnocai and Lacelle 1996) and the Soil Landscapes of Canada (Shields et al. 1991) can also be incorporated into map development, as appropriate. Reference List Resources Inventory Committee (RIC). 1999. Standard for Predictive Ecosystem Mapping. Inventory Standard. Version 1.0. Province of British Columbia. Tarnocai, C. and B. Lacelle. 1996. Soil Organic Carbon Digital Database of Canada (Revised 1999). Eastern Cereal and Oilseed Research Centre, Research Branch, Agriculture and Agri-Food Canada, Ottawa, Canada. Shields, J.A., C. Tarnocai, K.W.G. Valentine, and K.B. MacDonald. 1991. Soil Landscapes of Canada. Procedures Manual and User’s Handbook.

Effects of broadleaved tree species on nutrient cycling and carbon sequestration in forest floors: myths, surprises, and a solution CINDY E. PRESCOTT Faculty of Forestry University of British Columbia 2005-2424 Main Mall Vancouver, BC, Canada V6T 1Z4 [email protected] Keywords: nitrogen, litter, decomposition, mineralization, soil fauna Broadleaved tree species, in comparison to conifers, are believed to have higher-quality litter which, both directly and by stimulating activities of soil fauna, cause to it decay faster. This, in turn, leads to higher availability of nitrogen (including nitrate) and smaller accumulations of organic matter (hence carbon sequestration) under broadleaf species. Results from a number of field and laboratory experiments have not been consistent with some of these assumptions. Although many broadleaves have higher litter quality (higher N and Ca; less recalcitrant components) than most conifers, differences in decay rates are small and temporary, and organic matter accumulation and C sequestration are usually not lower under broadleaves. Ammonium and nitrate availability are often higher under broadleaves, but this can be attributed to higher N and Ca contents of litter rather than faster decomposition and mineralization of N. A new hypothesis is proposed to explain differences in the characteristics of broadleaf and conifer forest floors.

Assessing suitability of woody wastes and co-composts for rehabilitation of forest roads and landings in British Columbia CAROLINE M. PRESTON1, CINDY E. PRESCOTT2, KIRSTY H. VENNER2 1Pacific Forestry Centre, Natural Resources Canada, 506 West Burnside Road, Victoria BC V8Z 1M5 2Faculty of Forestry, University of British Columbia, Vancouver BC V6T 1Z4 [email protected] Keywords: 13C CPMAS NMR, phenolics, condensed tannins, wood waste, leaching Rehabilitation and reforestation of disused forest roads and landings can be facilitated by incorporation of organic matter. The British Columbia forest industry creates residual woody materials, but they are nutrient-poor and there is concern that they may leach phenolic compounds after application. We assessed the potential for wood wastes (chipped cedar wood waste, sort-yard waste, hogfuel) and co-composts with shellfish waste or municipal biosolids to provide inorganic N and release phenolics and condensed tannins, compared with natural forest floor and mineral soil. This laboratory study was undertaken to complement field studies established to monitor soil and vegetation responses to woody waste amendment of forest roads and landings. The wastes and corresponding natural soils were collected for establishment of the field trials at coastal (near Tofino, Vancouver Island) and interior (near Okanagan Falls) sites. Initial concentrations of tannins and phenolics were low, and 13C nuclear magnetic resonance (NMR) spectroscopy with cross-polarization and magic-angle spinning (CPMAS) showed that composts were still dominated by wood. During a 426-day laboratory leaching experiment, release of phenolics from woody amendments (other than cedar wood) was lower than from native forest floor. The pH of woody amendments and their leachates were also within the range of native forest floor and soil (except cedar wood which was the most acidic material). Co-composts had higher total N and available P, greatly reduced tannins and phenolics, and negligible leaching of polyphenols. Uncomposted materials released very little N during the incubation. Hogfuel-biosolids compost released a large amount of nitrate, but only during the first 100 days. Shrimp-wood compost released moderate amounts of both ammonium and nitrate throughout the incubation, had high available P and low tannin content and released less polyphenols than did native forest floors. Our results support use of these amendments to facilitate soil rehabilitation and forest re-establishment on disturbed sites, with low environmental risk under appropriate conditions (Venner et al. 2008). Venner, K.H., Prescott, C.E. and Preston, CM. 2008. Leaching of nitrogen and phenolics from wood waste and co-composts used for road rehabilitation. J. Environ. Qual., in press April/08.

How important is black (pyrogenic) C to the C cycle in Canadian forest soils? C.M. PRESTON Pacific Forestry Centre, Natural Resources Canada, 506 W. Burnside Rd., Victoria BC V8Z 1M5 [email protected] Keywords: carbon cycle, boreal forest, black carbon, fire Despite the high current interest in black carbon (BC) as a stable component of soil C, it has so far hardly been integrated into C cycle modeling, especially for forests. We refer to the whole range of fire-transformed biomass and soil organic matter as pyrogenic C (PyC), reserving BC and charcoal for specific stages along the “BC continuum” from lightly charred biomass to soot and graphite. Fire is the major disturbance in boreal forests, with production estimated at 7-17 Tg BC/y as solid residues (around 1-3% of original mass) and 2-2.5 Tg BC/y as aerosols (Preston and Schmidt 2006). However, there is scant and scattered information on production, stocks, or loss rates, exacerbated by differences used to measure various forms of PyC. Incorporation of efficiently-produced “biochar” into agricultural soil is being considered to enhance both fertility and C sequestration. However, the stocks and sequestration potential of PyC in forest ecosystems may be limited, due to several factors. Compared to production charcoal, wildfire-produced PyC is generally less highly transformed, but higher in N, other nutrients, and oxygen-bearing functional groups. This and its high porosity make it less resistant to physical, chemical and microbial degradation. It is produced, and largely remains above, on, or just below the surface. Charred snags may remain standing or suspended for many years. While this prevents soil contact, the PyC is still vulnerable to physical and chemical processes, including possible effects of photochemical oxidation followed by leaching of water-soluble fragments. PyC on or in surface horizons is also vulnerable to oxidation by subsequent fires, which may be the main constraint on its sink potential. We are exploring research requirements and approaches for establishing the role of PyC in boreal forest soils, and also for its integration into the Carbon Budget Model of the Canadian Forest Sector 3 (CBM-CFS-3). Preston, C.M., Schmidt, M.W.I. 2006. Black (pyrogenic) carbon: a synthesis of current knowledge and uncertainties with special consideration of boreal regions. Biogeosciences 3: 397-420. (open access at: http://www.copernicus.org/EGU/bg/bg/recent_papers.html)

Lignin, black boxes and SOM mythbusting CAROLINE M. PRESTON1, J.A. (TONY) TROFYMOW1 1

Pacific Forestry Centre, Natural Resources Canada, 506 W. Burnside Rd., Victoria BC V8Z 1M5 [email protected]

Keywords: decomposition, CIDET, proximate analysis, lignin, ecological myth Advances in soil ecology continue to be further decoupled from advances in soil organic matter (SOM) chemistry. Decomposing litter or SOM is often described as a “black box” of unimaginable complexity, or else limited to its composition from sequential proximate analysis (non-polar and polar extractives, acid-hydrolyzables, acid-unhydrolyzable residue (AUR). However, it has been possible for decades to account for high proportions of litter and poorly-decomposed SOM as single compounds (e.g., sugars, amino acids, cutin and lignin monomers). While the yields of recognizable structures generally decrease with decomposition and mineral interaction, they are non-negligible, and it is time to retire the “black box” cliché, which is largely an excuse for avoiding the issue. Second, for most low-tannin woods, the yield of AUR (originally called “Klason lignin”) closely corresponds with their content of lignin, a complex 3-dimensional phenylpropane-based polymer produced only by higher plants. However, it has been now known for approximately 1/4 century that lignin is a minor component of most foliar litters which can also have substantial proportions of tannins and cutins. Both of these (or suberin in roots and bark) contribute to the AUR. Third, AUR or AUR/N is a robust indicator of relative resistance to decomposition, and because of its “lignin” misnomer, widespread in ecological and modelling literature, the leap has been made that “lignin” is resistant and the primary controller of decomposition. However, this well-entrenched myth is becoming a stranglehold on innovative approaches to decomposition research. For example, the commonly-observed negative influence of N on decomposition is largely considered only with respect to inhibition of lignindecomposing enzymes of white-rot fungi, although resistance is more likely due to a combination of other factors. These include: high proportions of other structures at least as recalcitrant as lignin – suberin, cutin, plant waxes, tannins, crystalline cellulose; physical interactions such as tannin-protein complexes and hydrophobic interactions; covalent bonds causing cross-linking; increasing concentrations of heavier elements that increase chemical stability, and are in themselves toxic. This gulf between geochemical and ecological approaches is usually dismissed as “it doesn’t matter” and “I can’t afford NMR… or whatever in my lab”, but in addition to the stranglehold on scientific progress, also has serious ethical considerations. Is it right to deny students well-established knowledge about litter and SOM structure – much of which was already known before most of them were born? Is it right to feed them myths upon which to base erroneous hypotheses and maybe their whole careers? Do not scientists, funding agencies, and journals have some collective responsibility to truth and good science, even if this means engaging in extra-tribal collaborations? Would we stick with a working hypothesis that the world is flat, because we personally are not going to sail around the world to check it out? Would it be appropriate to call all ungulates, cows or all white-rot-fungi, Mycena sp., “for convenience”? The main limitations to dealing with the substrate side of soil ecology are presently tribal and cultural not technical, or even monetary, although this is often used as the excuse, and blame is certainly not all on the ecologists’ side. Much more collaboration and less reliance on rote hypotheses can allow plants, litter and SOM to tell their own wonderous and complex stories, which in turn can only facilitate further advances in soil ecology.

Changes in dissolved organic carbon from a peatland under experimentally altered hydrological regimes MICHAEL PRESTON*1, SHAUN A. WATMOUGH2, M. CATHERINE EIMERS3 1

Watershed Ecosystem Graduate Program, Trent University, 1600 West Bank Drive, Peterborough, ON, K9J 7B8 2 Environmental and Resources Studies Department, Trent University, Peterborough 3 Department of Geography, Trent University, Peterborough [email protected] Keywords: DOC, Decomposition, Peatlands, Climate change Peatlands are large repositories for atmospheric carbon, and are also important sources of dissolved organic carbon (DOC) export to downstream surface waters. Climate model projections for changes in precipitation quantity and quality could have serious implications for wetland hydrology and DOC export, by altering water table height and thus DOC production. In order to investigate the potential impact of changes in water table height in peatlands, a peat microcosm study was established using peat collected from a coniferous swamp at a lake catchment in south-central Ontario. Two scenarios have been tested: drought and waterlogged conditions. In both experiments, a variety of chemical and biological parameters were measured to gain insight into the processes controlling DOC production, including the concentration of major ions, pH, microbial biomass and the activity of the extracellular enzyme β-glucosidase which is indicative of carbon mineralisation. Chemical structure of DOC was also measured in the two treatments, to further elucidate mechanisms controlling DOC production, and because changes in DOC structure may impact freshwater ecosystems by altering light transmission and the bioavailability of trace metals and organic contaminants.

Influence of annual papermill biosolid applications on field earthworm populations GORDON W. PRICE1, R. PAUL VORONEY2 1

Dept. of Engineering, Nova Scotia Agricultural College, Truro, NS, Canada B2N 5E3 Dept. of Land Resource Science, University of Guelph, Guelph, ON, Canada, N1G 2W1 [email protected]

2

Keywords: papermill biosolids, earthworm populations, organic amendments Papermill biosolids (PB) have been used as soil conditioners on agricultural soils, to reclaim mining soils, and to rehabilitate old landfill sites. Earthworm population responses to a de-inked PB were measured on three agricultural soils in southern Ontario, Canada. Four rates of PB, 0, 50, 100, and 150 Mg ha-1, were applied annually for three years. In addition, plots receiving the PB treatments were planted to corn (Zea mays L.) and soybean (Glycine max L.). Earthworm populations prior to PB applications ranged from 9 to 22 individuals m-2 on the sandy loam and loam soils. Linear increases in earthworm populations were observed ranging from approximately 153 to 280 individuals m-2 after 3 years of PB amendments. On the clay loam soil, initial fall earthworm populations were about 124 individuals m-2 which increased to 482 individuals m-2 after two years of PB applications. Earthworm population increases to PB amendments were evident after two to three years at the sites measured.

The transfer of prion-mediated animal diseases through soils and environmental pathways: a review GORDON W. PRICE1 1

Dept. of Engineering, Nova Scotia Agricultural College, Truro, NS, Canada B2N 5E3 [email protected]

Keywords: prions, transmissible spongiform encephalopathy, BSE, environmental pathways Controlling animal disease outbreaks requires an understanding of the pathogen transfer mechanisms in order to develop appropriate bio-security protocols. Diseases such as Scrapies, Chronic Wasting Disease, and Bovine Spongiform Encephalopathy (BSE) which are believed to be mediated by prions (derived from proteinaceous and infectious) have placed, in some cases, severe economic burdens on the livestock industry. Recent research is beginning to highlight the potential for soils to act as a reservoir for these infective proteins. Prions added to certain soils have been shown to remain highly infective for as much as 3 to 5 years. However, the mechanisms of transfer and the role of soils in degrading or protecting these proteins is still unclear.

Optimal soil physical quality: application of “S-Theory” W. DANIEL REYNOLDS1, CRAIG F. DRURY1, XUEMING YANG1, CHIN S. TAN1, CATHERINE A. FOX1 1

Agriculture & Agri-Food Canada, Harrow, Ontario, Canada N0R 1G0 [email protected] Keywords: soil physical quality, S-theory, desorption curve, pore volume distribution, indicators According to “S-Theory”, good soil physical quality (SPQ) is attained when the slope of the soil water desorption curve at the inflection point, S, exceeds a magnitude of 0.035 (Dexter 2004). Although the S criterion has been successfully correlated with soil strength, stability and workability indicators, there are few comparisons with the soil air-water storage indicators, such as relative field capacity (RFC), plant-available water capacity (PAWC) and air capacity (AC). In addition, there have been no attempts to develop “optimum” soil hydraulic properties using optimal SPQ indicator values. Hence, the objectives of this study were to: i) assess the S indicator relative to RFC, PAWC and AC for several agricultural soils and other porous materials with widely varying SPQ; and ii) use the calculated values and optimum ranges of S, RFC, PAWC and AC to propose for agricultural soils an “optimum” pore volume distribution function, and an “optimum” soil water desorption curve. Fifteen porous materials were examined including glass beads, “builders sand”, and 13 agricultural soils which ranged in texture from sand to clay. Land management on the soils included “virgin soil” (VS), and corn-soybean-winter wheat rotational cropping under no-tillage (NT) or moldboard plow tillage (MP). The S, RFC, PAWC and AC indicators were calculated using soil water desorption curves measured on intact or repacked soil cores; and the pore volume distribution functions were determined by plotting the slopes of the desorption curves against equivalent pore diameter (EPD). The RFC, PAWC and AC values were consistent for all 15 porous materials with respect to their indication of “optimal”, “aeration limited” or “water limited” SPQ conditions. For the clayey and loamy soils, the S parameter values were consistent with the RFC, PAWC and AC values, which indicated “optimal” or “aeration limited” SPQ. For the sandy soils, glass beads and builders sand, on the other hand, the S parameter suggested “very good” SPQ (i.e. S ≥ 0.05), whereas the other parameters indicated poor SPQ due to substantial water limitation. Poor SPQ due to water limitation was the expected result for these materials owing to their coarse, single-grain textures and low organic carbon contents. Four of the agricultural soils were judged to have optimal SPQ because of favorable values obtained from all four of the SPQ indicators. The normalized pore volume distribution functions from these soils were closely clustered and were therefore averaged to produce a proposed “optimal” pore volume distribution function and an “optimal” desorption curve (saturation basis) for agricultural soils. The inflection point of the optimal desorption curve occurred at about 76 % of saturation; and the optimal pore volume distribution was strongly left skewed (skewness = -0.42), mildly peaked (kurtosis = 1.13), and it produced modal, median and mean EPDs of about 100, 4 and 1 micron, respectively. It was concluded that S ≥ 0.035 can be a useful indicator of good SPQ from an air-water storage perspective for clayey and loamy soils, but not for sandy soils or other coarse, single-grain materials. The apparent existence of an optimum pore volume distribution function (normalized) and an optimum desorption curve (saturation basis) should assist in further characterization of desirable hydraulic properties for agricultural soils. References Cited Dexter, A.R. 2004. Soil physical quality. Part I: Theory, effects of soil texture, density and organic matter, and effects on root growth. Geoderma 120: 201-214.

Soil carbon sequestration in the boreal transition Saskatchewan: historical and current perspectives

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NAVID ROBERTSON*, BRADLEY D. PINNO, NICOLAS BÉLANGER Department of Soil Science, University of Saskatchewan, 51 Campus drive, Saskatoon, Saskatchewan, S7N 5A8 [email protected] Keywords: Chernozemic Ah horizons, charcoal, Holocene, tree farming, C dynamics The development of C-rich Chernozemic Ah horizons in the northern Great Plains is believed to come from the addition of organic matter through the roots of herbaceous vegetation and the limited degradation of this organic matter due to dry soils, thus forming stable humus compounds. However, these C-rich and Ca-saturated diagnostic soil horizons are often found under trembling aspen forests of the Boreal Transition ecoregion, suggesting that a transient vegetation cover between grasslands and forests has influenced the development of these soils during the Holocene. Recent research, including ours, shows that episodic burning of the forest has led to very significant charcoal incorporation into the Ah horizons, a significant long-term sink of C. In our study, charcoal pools were greater on richer sites (lacustrine deposits and glacial tills) where forests are thought to have been the dominant vegetation during the Holocene. The drier conditions of the fluvial sites have favoured the dominance of frequently burning grasslands. These conditions promoted the development of relatively thick Ah horizons but these sites had generally less charcoal than the others as herbaceous vegetation produces more ashes than charcoal when it burns. The Boreal Transition ecoregion where most of the Black and Dark Gray Chernozems occur are now being suggested as ideal for tree farming projects. Tree farming is being advanced as a means to provide an increased timber supply for mills, create another cropping option for agricultural producers and be part of the solution to meeting Canada’s carbon sequestration commitments. Despite the inherently high C pools in these Chernozemic soils, some suggest that tree farming will favour belowground C sequestration. We have data supporting that 50 years of growth of white spruce and Siberian larch planted on well-drained dark Chernozems (pasture) has favoured ecosystem C gains because of the standing wood biomass. However, C pools in the Ah horizons were decreased under trees and were redistributed to the B horizons. Multiple linear models indicate a significant shift from soil C being controlled by root litter quality in the Ah horizons to being controlled by root litter quantity in the B horizons. Our model of C redistribution therefore appears to be closely tied to root production and quality. Despite the clear role of trees and fire on long term C sequestration in these soils (i.e. charcoal production/incorporation), our data and previous research suggest that tree invasion on grassland/pasture/agricultural crop land leads to the devolution of well-drained dark Chernozems through acidification and C loss in the Ah horizon

Root-associated microbial communities differ with Pinus contorta and Vaccinium vitis-idaea co-inhabiting sub-boreal forest soils SUSAN J. ROBERTSON*1, P. MICHAEL RUTHERFORD2 AND HUGUES B. MASSICOTTE3 1

Natural Resources and Environmental Studies Program, 2Environmental Science and Engineering Program , and 3Ecosystem Science and Management Program, University of Northern British Columbia, 3333 University Way, Prince George, British Columbia, Canada V2N 4Z9 [email protected] Keywords: mycorrhizas, shared rhizosphere, functional guild, petroleum hydrocarbons, LH-PCR Rhizosphere communities, including mycorrhizas and closely associated heterotrophic microorganisms, represent critical functional groups for decomposition and carbon/ nutrient cycling processes in northern forest ecosystems. The spatial heterogeneity of the soil environment contributes to the great biodiversity of soil microorganisms; however, the complexity of the system and the multifunctional nature of many microorganisms have made it difficult to comprehend linkages between communities and ecosystem processes and also to predict how ecosystems may respond to environmental disturbances such as soil contamination. In this study, we used a bioassay approach to assess the relative contributions of plant and soil properties to spatial distribution patterns of ecto(ECM) and ericoid (ERM) mycorrhizal fungi as well as root-associated bacterial communities inhabiting the shared rhizosphere of pine (ECM host) and lingonberry (ERM host); soil systems were either untreated or treated with petroleum hydrocarbons (PHCs), simulating contamination events. Surface-sterilized pine (Pinus contorta var latifolia) seeds and lingonberry (Vaccinium vitis-idaea) seedlings were planted into ConetainerTM pots containing an organic layer (mor humus [FH] or coarse woody debris [CWD]) overlying sandy mineral horizons (Ae and Bf) of field-collected forest soils obtained from central BC, Canada. After 4 months, BC light crude oil (219 mg cm-2) was applied to the soil surface around the seedling stem; systems were destructively sampled at 1 and 16 weeks following treatment. Soils from each layer were analyzed for PHC concentration (not presented here), pH and total C and N content. The composition, relative abundance and vertical distribution (ie. variation with soil layer) of eight frequently occurring ECMs on pine roots were assessed using light microscopy. Community profiles (i.e. based on the relative abundance of all genotypes) were generated for all root systems using length heterogeneity PCR and primers targeting the ITS (fungi) and 16S (bacteria) regions of ribosomal DNA. We found that the main components of ECM communities were consistent with those described from field-based studies. Genotype analysis by non-metric multidimensional scaling (NMS) and multi-response permutation procedures (MRPP) revealed that both plant and soil properties influenced the structure of root-associated fungal and bacterial communities; however, patterns of community structure varied among the different functional groups. Fungal communities were distinctly different on pine (ECM) and lingonberry (ERM) roots; only ECM fungal communities were structured vertically in the three layers of soil, representing direct interactions between fungi and soil in the ectomycorrhizal association. In contrast, ERM communities appeared to vary more between soil systems (i.e. FH-Ae-Bf and CWD-Ae-Bf) than between soil layers. Bacterial community structure varied between mycorrhizal root systems and between soil layers, indicating that differences between the ECM and ERM root environment and soil properties are both important with respect to bacterial niche differentiation. PHC contamination appeared to have little effect on the composition of root-associated microbial communities.

Riparian exclusion fencing for cattle impacts on suspended sediment in the Salmon River, southern interior B.C. BRUCE H. RODDAN, KLAAS BROERSMA Agriculture and Agri-Food Canada, 3015 Ord Rd. Kamloops B.C. V2B8A9 [email protected] Keywords: suspended sediment; exclusion fencing; cattle impacts; riparian Exclusion fencing is classed as a beneficial management practice (BMP) for controlling cattle grazing impacts on riparian soils, vegetation and water quality. Agriculture and Agri-Food Canada has studied the effectiveness of BMP fencing at the watershed scale at several locations across Canada since 2004 (WEBs study). From November 2004 to May 2006, an evaluation of riparian fencing was conducted within the property boundaries of three cow-calf pastures spread along a 10 km length of the Salmon River watershed in the Southern Interior of British Columbia, Canada. All three pastures had degraded riparian zones and eroded river banks. Cattle were fenced out of the river from the upstream half of each pasture and allowed access to the lower half. Fluvial suspended sediment (FSS) samples were collected from a point within the river cross-section using a time-integrated passive sediment sampler (TIPS) on a continuous basis. The TIPS samplers were deployed in the river for 2 week intervals at each of the pastures, at 3 sampling locations: the upstream and downstream boundary of the fenced treatment and the downstream boundary of un-fenced treatment. Throughout each year, measurements of FSS organic, mineral and bacterial components were taken to determine compositional differences between the fencing treatments. The results suggest that riparian exclusion fencing may have positively influenced water quality during times that cows were present within the three pastures between November 2004 and May 2006. Escherichia coliform was measured in greater numbers in the sediment collected from the un-fenced treatment compared to the fenced treatment. The TIPS samplers detected significant mean differences in collected sediment Escherichia coliform (0.53 colonies/ml of diluted re-suspended sediment, n=53, SD=1.77, p=0.033) between treatments. Reference List McDowell, R.W. and Wilcock, R.J. 2004. Particulate phosphorus transport within stream flow of an agricultural catchment. Journal of Environmental Quality 33: 2111-2121. Agriculture and Agri-Food Canada. 2008. Watershed evaluation of beneficial management practices (WEBs) Salmon River British Columbia. www.agr.gc.ca/webs 8pp. AAFC# 1031E.

Recreating a functioning forest soil in reclaimed oil sands in northern Alberta SARA M. ROWLAND*1, CINDY E. PRESCOTT1, SUSAN J. GRAYSTON1, SYLVIE QUIDEAU2, GARY BRADFIELD3 1

Department of Forest Sciences, University of British Columbia; 2424 Main Mall, Vancouver, BC, V6T 1Z4 2 Department of Renewable Resources, University of Alberta; 751 General Services Building, Edmonton, AB, T6G 2H1 3 Department of Botany, University of British Columbia; 3529-6270 University Blvd, Vancouver, B.C. V6T 1Z4, [email protected] Keywords: reclamation, nutrient, decomposition, PRS probes, ecotypes During oil-sands mining all vegetation cover, soil, overburden and oil-sand is removed, leaving pits several kilometres wide and hundreds of metres deep. These pits are reclaimed for commercial forestry by a variety of treatments using sub-soil or a mixed peat:mineral soil as the capping layer that may or may not be fertilised. Using non-metric multidimensional scaling and cluster analysis, reclamation treatments covering different age classes were compared with a range of natural forest ecotypes to discover which treatments were moving towards natural forest ecotype status and at what age this occurs. Ecosystem function was estimated from bio-available nutrients, plant community composition, litter decomposition rate and development of a surface organic layer. On reclaimed sites, bio-available nutrients including nitrate generally were outside the natural range of variability, while phosphorus, potassium and manganese were generally very low. Plant diversity was similar to natural sites but declined after 30 years with canopy closure. Peat:mineral mixtures generally retained more moisture than sub-soil caps, and created better conditions for decomposition but decomposition processes on reclamation treatments were depressed overall. Development of an organic layer appeared to be facilitated by the presence of shrubs. With repeated applications of fertilisers, peat:mineral amendments became similar to a target ecotype at about 20 years. An intermediate sub-soil layer reduced fertiliser dependency, and so long as this is not over tailings sand it achieved a target ecotype about 15 years after a single application. Treatments over tailings sand receiving only one application of fertiliser appeared to be on a different trajectory to a novel ecosystem.

Response of boreal forest carbon dynamics and storage to experimental drought (1989-2005) in interior Alaska SARAH A. RUNCK*1, DAVID W. VALENTINE1, JOHN A. YARIE1 1

Department of Forest Sciences, University of Alaska, PO Box 757200, Fairbanks, AK 99775-7200 [email protected] Keywords: drought, soil moisture, boreal forest, decomposition, carbon storage In interior Alaska, projected increases in potential evapotranspiration exceed those for precipitation, implying increased moisture stress in forests. Since 1989, we have erected “rain-out” shelters every May and removed them every September in order to induce summer drought in 10 x 15 m midsuccessional forested plots in upland (rock- and permafrost-free loessal Alfic Cryochrepts) and floodplain (rock- and permafrost-free Typic Cryofluvents) landscape positions (n=3). Treatment vs. control differences in near-surface soil moisture generally increased throughout each growing season as imposed summer drought (ISD) restricted soil moisture recharge from late-season rains. From 1989-2005, ISD slowed total aboveground biomass growth in upland sites but not in floodplain sites, where groundwater availability may have mitigated ISD. Although we observed slight or no difference in annual litterfall between treatments, ISD severely slowed decomposition of standard substrates (wooden tongue depressors) in the surface O horizon. Between 1989 and 2005, ISD caused O horizon C stocks to increase 15% faster in floodplain sites and 40% faster in upland sites relative to untreated controls. ISD had no effect on mineral soil C contents in floodplain sites, where buried O horizons comprise much of the subsurface C; in upland sites, ISD slowed mineral soil C accumulation. Taken together, these results suggest that future summer droughts are likely to reduce productivity, decomposition, and mineral soil C accumulation in upland forests but are unlikely to alter floodplain forest dynamics or soils in the absence of changes in groundwater availability.

Grassland soils in northwestern Canada: Chernozems (almost) north of 60? PAUL T. SANBORN1 1

Ecosystem Science and Management Program, University of Northern British Columbia, 3333 University Way, Prince George, BC, Canada V2N 4Z9 [email protected] Keywords: grassland, Chernozem, soil classification, micromorphology, soil temperature In the rain shadow of the Coast and St. Elias Mountains, grasslands occupy many south-facing slopes at low elevations in major valleys of northwestern British Columbia and southwestern Yukon. Although not extensive, these ecosystems provide locally important range resources. Botanically, these plant communities are noteworthy for their Beringian floristic affinities, and have been suggested as possible analogues for the full-glacial steppe-tundra inferred from the fossil record. Soils of these grasslands have been documented in southwestern Yukon at a limited range of sites influenced by Holocene deposition of loess and tephra. In northwestern British Columbia, only reconnaissance soil surveys have been conducted, and the characteristics and genesis of these grassland soils have not been investigated. A brief 2007 exploratory study of natural rangelands in the valleys of the Tuya and Stikine Rivers enabled an initial examination of soils in these grassland settings. Two pedons in the lower Tuya River valley, formed on complex colluvial and glaciolacustrine materials, show considerable affinities with Chernozemic soils documented in grasslands elsewhere in central and southern British Columbia. Ah horizons exhibit the spongy and granular microstructures typical of Chernozemic A horizons. Morphological and chemical criteria for the Chernozemic order appear to be met, but the scarcity of local climatic records makes it difficult to determine if these sites have the required soil temperature and soil moisture regimes. However, recent soil temperature research in central Yukon suggests that south-facing slopes at this latitude would easily satisfy the requirement for mean annual soil temperatures of 0ºC or higher.

Pedology and ephemeral environments: forest soils on Klutlan Glacier, Yukon Territory PAUL T. SANBORN1 1

Ecosystem Science and Management Program, University of Northern British Columbia, 3333 University Way, Prince George, BC, Canada V2N 4Z9 [email protected] Keywords: tephra, glaciers, refugia, soil genesis, Cryosols The ca. 1200 BP deposition of the White River tephra created a unique pedogenic environment in southwestern Yukon: supraglacial forest soils on the terminus of the Klutlan Glacier. Several meters of pumice gravel and finer tephra cover the stagnant toe of the glacier, and provide a parent material for Cryosols and Regosols that support a patchy forest dominated by white spruce (Picea glauca). Wasting of the underlying glacier ice has created a complex hummocky landscape with numerous thaw ponds that expand laterally, triggering slumping and repeated disturbance of the juvenile soils. Despite the instability of this substrate, forest floors have locally accumulated to > 15 cm in thickness, and an absence of charcoal suggests that fire is unusual in this setting. Morphologically, these soils have limited B horizon development, and their coarse texture has restricted the activity of cryoturbation. Cryptogamic crusts appear to be important in initial stabilization of exposed tephra surfaces created by slumping and erosion. Pedogenic modification of tephra may be accelerated by these crusts, as well as by root penetration into porous tephra particles. Although this pedogenic environment may be viewed as an ephemeral novelty, eastern Beringia has likely seen repeated interactions between glacial and volcanic activity during the Quaternary. Evidence of soil formation in these transient environments may not be preserved in the geological record, but since supraglacial vegetation occurs on other modern glaciers, such settings may have provided refugia on the margins of continental ice sheets. As such, these soils deserve further study as part of understanding ecosystem functioning through glacial-interglacial cycles.

Evaluating the N leaching potential for two different hydrological soil groups using a conservative tracer J.K. SASO1*, G.W. PARKIN1, J.D. LAUZON1, C.F. DRURY2 1

Department of Land Resource Science, University of Guelph, Guelph, Ontario Greenhouse and Processing Crops Research Centre, Agriculture and Agri-Food Canada, Harrow, Ontario [email protected] 2

Keywords: leaching, Ontario, N, conservative tracer Evaluating the Nitrogen (N) leaching potential of soils is important to agronomists, as they work to improve the efficiency of surface applied N fertilizers and reduce the amount of N moving beyond the root zone and into groundwater via tile drainage (Schoen et al., 1999). A field study is being conducted at the Elora Research Station, Elora, Ontario to evaluate the leaching potential of two soils with different hydraulic and textural properties. A conservative chloride tracer (applied as KCl) will be used as a surrogate to infer about the fate of NO3-N in the soil profile. In addition to the tracer, corn (Zea mays L.) will be used to evaluate plant N uptake from the residual N remaining in the soil compared to spring applied fertilizer N. Four instrumentation methods will be used to evaluate N movement and the use of Cl. Time Domain Reflectometry, a non-obtrusive, in-situ method to measure flux concentrations of Cl from the 0-43 cm depth; funnel lysimeters (at 30 cm depth) will evaluate solute movement via infiltrated water and solution samplers (similar design to Lord and Shepherd, 1993) will measure soil water concentrations of N and Cl at 60 cm depth. Soil coring, conducted when feasible, will evaluate resident concentrations of N and Cl at six different depths (up to 1 m). In addition to soil coring, plant samples will be taken throughout the growing season (May to August) to measure plant N uptake compared to residual N in the soil. Pending results will demonstrate if Cl is a good predictor of the leaching potential of a particular soil and can lead to more accurate quantification of N movement through the soil profile. Reference List Schoen, R., J.P. Gaudet, T. Bariac. 1999. Preferential flow and solute transport in a large lysimeter, under controlled boundary conditions. Journal of Hydrology 215:70-81 Lord E.I., Shepherd M.A .1993. Developments in the use of porous ceramic cups for measuring nitrate leaching. Journal of Soil Science 44:435-449

The occurrence and nature of a dominant coprogenous limnic layer in organic soils: challenges to the Canadian System of Soil Classification DANIEL SAURETTE1, LUC LAMONTAGNE2, ANDRÉ MARTIN2 1

Jacques Whitford AXYS Ltd., 103-611 Corydon Avenue, Winnipeg, MB, R3L 0P3 Agriculture and Agri-Food Canada, Pedology and Precision Agriculture Laboratories, 140-979 de Bourgogne Avenue, Quebec, QC, G1W 2L4 [email protected] 2

Keywords: organic soils, limnic materials, coprogeneous earth, soil classification, physical properties Organic soils cover approximately 10% (927,100 km2) of the Canadian land base, of which 60 % are found south of the permafrost line (Lévesque et al. 1981). In the Quebec Saint-Lawrence plain, deep organic soils (>1.6 m) occupy 145,000 ha and are of great local importance for supporting the peat production and agricultural sectors. In the South-Eastern area of the Montreal plain, 25,000 ha (Duguet 2005) of these organic soils play an important role in the local production of large harvests of root and leafy vegetables because of their climate regime and high fertility. It is called “The Quebec Garden”. Fibrisol, Mesisol and Humisol great groups are common in the region; however Mesisols and Humisols are dominant. A layer of limnic materials occurs frequently in these organic soil profiles and typically remains well below the surface. As a consequence of agricultural land drainage, an annual subsidence rate of 2.06 ± 0.35 cm/yr has been observed (Parent et al. 1982) and linked to increased wind and water erosion. The potential of exposing the limnic material layer at the surface is ever increasing. The typical limnic materials identified in these organic soils originate from sedimentary peat (coprogenous earth (Oco layer), also known as ‘gyttja’) which are a nutrient-rich peat composed of plankton, plant and animal residues (fecal matter) and mud. Morphologically, it is fine-textured, plastic and often gelatinous when wet. The gyttja soils pose challenges in two fields of soil science: soil classification and agronomy. Organic soils are classified based primarily on the dominant material present in the middle tier (40-120 cm) of the control section (0-160 cm). We have identified numerous organic soil profiles in which the middle tier is dominated, if not entirely composed of a limnic deposit. These soils are poorly captured by the current taxonomic criteria used in the Canadian System of Soil Classification (SCWG 1998) and present a strong case for modifications at the great group (i.e limnosols) or subgroup levels of the Organic Soil Order. From an agronomic perspective, little is known about the effects of coprogenous materials of this type on agriculture. Although it is high in nutrients, gyttja has been found to have physical properties which could make soils unsuitable for agriculture, either as a component ploughed into the organic soil at the surface or directly exposed. For example, when air-dried, it shrinks greatly, becomes hard and lumpy and is relatively inert. The overall philosophy of the Canadian system is pragmatic and the aim is to organize the knowledge of soils in a usable way based on properties of the soil. The CSSC should continue to evolve to better recognize these soils. Reference List Duguet, F. 2005. Minéralisation de l’azote et du phosphore dans les sols organiques cultivés du sudouest du Québec. M. Sc. Thesis, Laval University. 95pp. Soil Classidfication Working Group. 1998. The Canadian System of Soil Classification. Agriculture and Agri_Food Canada. Publication 1646 (Revised0. 187 p. Lévesque, M., Morita, H., Schnitzer, M., Mathur, S. P. 1981. Les propriétés physiques, chimiques et morphologiques de quelques tourbes du Québec et de l’Ontario, Agri. Can. 74 p. Parent, L. E., Millette, J. A. and Mehuys, G. R. 1982. Subsidence and erosion of a Histosol. Soil Sci. Soc. Am. J. 46: 404-408.

Predicting runoff dissolved P losses: which soil test is best for neutral to alkaline soils? CLAY SAWKA1, DON FLATEN1, XUDONG WANG1, WOLE AKINREMI1 AND RANJAN SRI RANJAN2 1

Soil Science Department, University of Manitoba, Winnipeg MB R3T 2N2 Biosystems Engineering, University of Manitoba, Winnipeg MB R3T 5V6 *[email protected]

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Key words: P runoff, degree of P saturation, soil test P Eutrophication in water bodies such as Lake Winnipeg has been linked to increased concentrations of phosphorus (P). In Manitoba (Canada) the Lake Winnipeg Stewardship Board has reported that agricultural practices contribute approximately 15% of Manitoba's portion of the P loading into Lake Winnipeg. The objective of our study was to evaluate four different soil test methods and eight methods of determining degree of P saturation to predict P loss in laboratory simulated runoff from neutral to alkaline soils. Most of the phosphorus losses from Manitoba’s agricultural land is in the form of dissolved P (Glozier et al., 2006 and Sheppard et al., 2006). In our study, Olsen, Modified Kelowna, Mehlich-3 and water extractable soil test P concentrations were strongly related to the concentrations of total dissolved P (TDP) measured in runoff from the coarse and medium textured soils. The R square values for these tests and soils ranged from 0.72 to 0.92, with water extractable P showing the strongest relationship with TDP concentrations in the initial 30 minutes of runoff. However, in the fine textured soils the relationships with runoff TDP declined substantially, with Olsen P showing the strongest relationship, accounting for 77% of the variation in runoff TDP. Olsen P was also the soil testing method most strongly related to runoff TDP when considered across all soils, showing a very similar relationship for both textural groups. Within each textural group, several DPS methods were reasonably well related with TDP concentrations in runoff. However, due to different relationships between soil DPS and runoff TDP for each textural group, the DPS methods were not strongly related to runoff TDP across all soils. Therefore, although the Olsen soil test is not the most accurate method for predicting runoff TDP losses from Manitoba's coarse textured soils, this test was the strongest predictor of TDP losses across a broad range of soils, especially fine-textured soils where the risk of runoff and P loss is greatest. Several DPS methods show promise for predicting P losses within textural groups, but need further refinement for use with neutral to alkaline soils across a range of soil textures. Reference List Glozier, N.E., J.A. Elliot, B. Holliday, J. Yarotski, and B. Harker. 2006. Water quality characteristics and trends in a small agricultural watershed: South Tobacco Creek, Manitoba, 19922001. Sheppard, S.C., M.I. Sheppard, J. Long, B. Sanipelli, and J. Tait. 2006. Runoff phosphorus retention in vegetated field margins on flat landscapes. Can. J of Soil Sci. 86:871-884.

Forms and cycling of phosphorus in Saskatchewan soils as affected by tillage system JEFF J. SCHOENAU1, P.QIAN1, M.GREVERS1 AND G. LAFOND2 1

Department of Soil Science, 51 Campus Drive, University of Saskatchewan, Saskatoon, SK S7N-5A8 Agriculture and Agrifood Canada, Indian Head, SK S0G-2K0 [email protected]

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Keywords: phosphorus, no-till, strategic tillage, nutrient cycling, soil fertility Introduction: There is a need to address unresolved issues in the relationship between tillage and phosphorus availability in Saskatchewan soils. The objective of this paper is to provide insight into how low disturbance direct seeding (no-till) system in Saskatchewan impacts phosphorus availability. This is accomplished by reviewing research that addresses the initial stages (1 yr), short-term (5yr) versus long term (25 yr), and what happens to P availability when a long-term no-till soil receives a cycle of tillage. Initial Stages: The effect of pre-seeding tillage with a heavy duty cultivator: fall + spring (CT); spring only (MT) and no-till (NT) on pea stubble was examined at sites in the Brown and Black soil zone. The sites were under conventional tillage previously. In this study, supply rates of nitrate, phosphate and sulfate were measured using PRS anion exchange membrane probes placed in PVC cylinders in the field. In general for the two sites over the two years, the supply of available phosphorus as affected by tillage was: NT > MT> CT. Since this was the first year of the tillage treatments, the higher supplies of soil phosphorus were attributed to higher soil moisture content under no-till that enhanced the ability of P to move by diffusion in the soil. Short-term versus Long-Term: To reveal the effects of adopting low disturbance direct seeding on P availability over a longer time frame, five year (short-term) and twenty-five year (long-term) no-till plots were sampled in the Black soil zone at Indian Head, SK. This comparison revealed significantly higher supplies of available nitrogen as nitrate and also higher supplies of available phosphorus after 25 years of no-till compared to 5 years. In a sequential P fractionation, readily bioavailable P forms including resin and bicarbonate extractable P were increased in the long-term no-till soils. The results of the soil P supply measurements were consistent with observations at this site that crops grown on the long-term no-till soil were not as responsive to added P fertilizer. Imposing a Cycle of Tillage on a Long term No-till Soil: A cycle of tillage was imposed on long-term (10 yrs +) no-till soils at sites in the Brown, Black and Gray soil zones. Following tillage treatment, cores of soil (0-15 cm) were taken from each plot and segmented into 0-5 cm, 5-10 cm and 10-15 cm depth increments and extractable (modified Kelowna) P concentrations determined. Grain yield and P uptake in the crop were also assessed. The mixing by the tillage operation reduced the stratification. However, there was no large effect on P availability as revealed in similar crop P uptake among treatments. Conclusion: The no-till systems that were evaluated appear to be associated with increased soil P availability in the short and long-term, with effects that accrue over time. Stratification of P as a factor affecting P availability to crops does not appear to be an issue, and tillage to address this does not seem warranted based on the results. Chemical fractionation and synchrotron spectroscopy techniques are being applied to provide additional insight into the relationship between cropping system and soil P fertility.

Determination of carbon sequestration and nitrate leaching under different irrigation and dairy manure levels in wheat (Tritcum aestivum L) on Typic Calciagrids KHURAM SHAHZAD* University of Agriculture, Faisalabad. Institute of Soil & Environmental Sciences [email protected] Nitrogen (N) losses from agriculture are negatively impacting groundwater, air, and surface water quality. New tools are needed to quickly asses these losses and provide nutrient managers and conservationists with effective tools to assess the effects of current and alternative management practices on N loss pathways. A field experiment was conducted to study the effect of different levels of irrigation and Farmyard manure on nitrate leaching in wheat (Tritium aestivum). Before sowing of wheat, all the FYM @ 0,150and 300 kg ha-1 as per the requirement of the treatments was applied on the surface and incorporated thoroughly into the soil. A basal doze of 1/3rd of required N as per treatment along with 60kg P2O5 ha-1 and 30kg K2O ha-1 was applied prior to sowing and the remaining dose of N was applied at second and third irrigation of each treatment. A control of nitrogen and FYM was included for comparison. First treatment regarding Irrigation was applied after 30, 60,100 and 125 days. Second and third treatments of irrigation was applied after 30, 60, 80,100,125 and 18, 36, 60, 80,100,125 days simultaneously. Samples for nitrate analysis was collected with auger before sowing and at harvest from six different layers (0-5, 5-10, 10-30, 30-60, 60-90 cm). Samples was collected in each replication. Core sampler was use to determine the characteristics of soil e.g. soil texture, pH, bulk density, field capacity and permanent wilting point, organic carbon, available N, available P and available K. The yield parameters related to root weight, root length, root breath, plant leaf biomass and protein contents was calculated for each treatment after harvesting of wheat. Rate of carbon sequestration was analyzed by determining the organic matter contents.The data obtained was analyzed statistically by using Fisher s analysis of variance technique and difference among treatment means was compared by using least significant difference test (LSD) at 5% probability level.

Estimating forest soil carbon and nitrogen stocks with double sampling for stratification CINDY SHAW1, JIM BOYLE2, AND A.Y. OMULE3 1 Canadian Forest Service, Northern Forestry Centre, 5320 122 Street, Edmonton,AB, T6H 3S5 2 Forest Resources, Oregon State University, 280 Peavy Hall, Corvallis, OR 97331-5703 3 Agro Forestry Limited, 1564 Granada Crescent, Victoria, BC, Canada V8N 2B8

[email protected] Keywords: forest soil, sampling, humus forms, carbon, nitrogen Precise and accurate estimation of C and N in forest soils is important for monitoring long-term site productivity and carbon stock changes. However, obtaining such estimates remains a major challenge, especially because of high natural variability in the forest floor. Although most researchers have used simple random sampling (SRS) for within-plot soil sampling, double sampling for stratification (DSS) can be used to decrease costs, increase precision, and increase power. Estimates of C and N stocks based on DSS were compared with those estimated by SRS, in the humus forms of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) stands in the Cascade Mountains of Oregon, USA. Generally, DSS was 1.34 to 5.11 times more efficient than SRS for total C, and 1.07 to 2.00 for total N. Coefficients of variation estimated from DSS were about one-half of those estimated by SRS and reported elsewhere in the literature. The cost for sampling using DDS was one-third to one-half of that for SRS, depending on the number of strata used. Costs were reduced because fewer samples were required using DDS to provide the same precision as SRS. The DSS design was more powerful than SRS and could detect smaller changes than SRS with the same number of samples. Results suggested that the most efficient design for total C would use two strata where samples were allocated proportional to variance rather than proportional to area. Overall, large gains in efficiency can be realized with a more complex within-plot sampling design, i.e. DSS, compared with SRS.

The impact of fertilization on soil enzyme activities in two coniferous forest soils JOYCE SHEN*, SUE GRAYSTON Belowground Ecosystem Group, Department of Forest Sciences, Faculty of Forestry, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4

[email protected] Keywords: forest fertilization, coniferous forests, enzyme activity, litter decomposition The response of litter decomposition to N fertilization has been inconsistent. Such inconsistent observations seem to be related to litter lignin contents and soil microbial enzymes involved in the decomposition process. To better understand the effects of fertilization on enzyme activity and C sequestration, a study was conducted in the fertilized DEMO plots at the SCHIRP (Salal Cedar Hemlock Integrated Research Program) installation located between Port McNeill and Port Hardy (50° 36’, 127° 20’). The study contains stands of cedar and hemlock with 3 levels of N ( 0, 200 and 300 Kg N/ha ) and 3 levels of P fertilization ( 0, 100, 100 + micronutrients). Samples of forest floor and mineral soil were taken from each plot (composite of 5 soil cores) from Aug 12 to Aug 16, 2007. The activities of enzymes involved in breakdown of cellulose (cellobiosidase), chitin (1, 4- β -Nacetylglucosaminidase) and organic P (phosphatase) were assayed using fluorescent method. Activity of the lignin-degrading enzymes, phenol oxidase and peroxidase was determined using colorimetric assays. Based on the analysis to date, soil enzyme activities in the organic layer were significantly different from mineral layer. Meanwhile, forest type had a significant impact on enzyme activities. When it came to treatment effect, phosphatase activity was higher in plots that did not receive P fertilization, while cellobiosidase activity was generally higher in plots that did not have N fertilization.

Net CO2 exchange at the forest floor: effects of hybrid poplar stand age and land uses ZHENG SHI*1, BARB THOMAS1,2, SCOTT CHANG1 1

Dept. of Renewable Resources, 4-42 Earth Science Building, University of Alberta, Edmonton, Alberta, T6G 2E3; 2 Alberta-Pacific Forest Industries Inc., Box 8000, Boyle, Alberta, T0A 0M0 [email protected] Keywords: net CO2 exchange, forest floor, land uses, hybrid poplar Abstract: Net CO2 exchange was measured at the forest floor in three different aged hybrid poplar stands (Populus deltoids × Populus × petrowskyana var. walker; 3, 6, and 14 years old in 2007) and two different land uses — Barley and Walker poplar (Populus deltoids × Populus × petrowskyana var. walker), in northern Alberta, Canada. Continuous measurements were made every 2 hours using an automated chamber system for four months between early June and early October, 2007. The measurement chambers were transparent and thus rates of soil respiration were measured at night, and net CO2 exchange was measured in the daytime as CO2 efflux was reduced by photosynthetic uptake by forest floor vegetation during the day. Over the 4 month period in different aged hybrid poplar plantations, July had the largest while October had the smallest CO2 fluxes, except for the small flux in the 3-year-old hybrid poplar plantation which happened in early September. Under different land uses, July had the largest CO2 fluxes for both barley and Walker poplar, while late August or early September the smallest fluxes. The mean rate of CO2 fluxes during the growing season increased across stand ages, with rates being 0.35, 1.57 and 1.93 µmol CO2 m-2 s-1 in the 3, 6 and 14-year-old hybrid poplar plantations, respectively, and mean rate of CO2 fluxes during the growing season were greater in the barley plots (1.30 µmol CO2 m-2 s-1) than in the Walker poplar plots (0.56 µmol CO2 m-2 s-1) two years after the agricultural land was converted to a poplar plantation.

Soil ecology science: challenges for promoting a sustainable planet SUZANNE W. SIMARD University of British Columbia, 2424 Main Mall, Vancouver, BC, Canada, V6T 1Z4 Keywords: climate change, soil feedbacks, species migration, exotic invasions Soil ecology science has contributed greatly to our understanding of natural soil patterns and processes, the impact humans have had on them, and management approaches useful in soil conservation and restoration. With exponential human population growth over the past 100,000 years, soil science has also played an important role in revolutionizing ecosystems, from sustainable hunter-gatherer systems, to self-sufficient farming systems, and, more recently, to globally trading industrial, agricultural and forest harvesting systems. This revolution has had multiple feedbacks, however, with ecosystem effects that occur at increasingly larger scales, to where humans have influenced the global climate. Global climate change has the potential for disastrous effects on ecosystems, biodiversity and genetic diversity that could lead to rapid mass extinctions (Thomas et al. 2004). We need only look at climate model predictions for species migrations over the next century to understand the enormity of ecological problems that lay ahead (Hamann and Wang 2006). In addition to the Arctic and Antarctic, it is predicted that terrestrial ecosystems most threatened by climate change will include coniferous forests, grasslands, deserts, wetlands, and alpine and coastal areas -- the very ecosystems in which we live (Walther et al. 2002). The basic understanding of soil ecology that humans have developed provides an invaluable baseline for predicting and managing these changes. However, ecological sciences, including soil ecology, need to refocus toward interdisciplinary, large-scale, international research that helps ensure a future where humans live sustainably within ecosystems. Although I am reluctant to come to terms with this myself, this research needs to acknowledge that, with exponential human population growth, managed ecosystems and intensive resource exploitation will define our future. To rise to this urgency, soils research must be closely linked to solutions through environmental policy. In my talk, I review what I think are some important soil ecology research issues for enhancing resilience of terrestrial ecosystems to climate change. Of basic importance to soil ecologists is understanding the changing roles played by below- and aboveground biota in feedbacks among climate change, disturbance regimes, carbon and nutrient dynamics (e.g., Kurz et al. 2008), and biodiversity itself. Soil organisms, for example, will play crucial roles in facilitating or limiting native and exotic plant species migrations in response to climate change, which is one of the complex mechanisms (along with evolutionary adaptation and phenotypic plasticity) by which species and ecosystems will respond (Geber 2008). Here, identifying, protecting, managing, and understanding changing processes in belowground functional groups and keystone species will be as important for preventing native diebacks (McDowell et al. 2008) or exotic invasions as they are for facilitating species migrations (Reinhart and Callaway 2006) and reorganizing ecosystems. Similar research is needed to address the crucial role soil organisms play in stabilizing soils (Rillig and Mummy 2006), mitigating nutrient losses and sequestering carbon as disturbance regimes change. I illustrate these points with examples of research conducted within my group. Reference List Geber, M.A. 2008. To the edge: studies of species’ range limits. New Phyt. 178: 228–230. Kurz, W.A., et al. 2008. Mountain pine beetle and forest carbon feedback to climate change. Nature 452: 987-990. McDowell, N., et al. 2008. Mechanisms of plant survival and mortality during drought: why do some plants survive while others succumb to drought? New Phyt. 178: 719–739 Reinhart, K.O., Callaway, R.M. 2006. Soil biota and invasive plants. New Phyt. 170: 445-457. Rillig, M.C., Mummy, D.L. 2006. Mycorrhizas and soil structure. New Phyt. 171: 41– 53. Thomas, C.D., et al. 2004. Extinction risk from climate change. Nature 427: 145-148. Walther, E.R., et al. 2002. Ecological responses to recent climate change. Nature 416: 389-395.

The status of soil survey in Manitoba: an exciting future DIANE M. SMITH¹, LYNN MANAIGRE², PETER HALUSCHAK², RONGGUI WU¹, YI ZHANG¹ ¹Manitoba Agriculture, Food and Rural Initiatives, 36 Armitage St., Minnedosa, MB R0J 1E0 ² Manitoba Agriculture, Food and Rural Initiatives, 13 Freedman Cres. Winnipeg, MB R3T 2N2 [email protected] Keywords: soil survey, MAFRI In response to the growing need for detailed soil survey, Manitoba Agriculture Food and Rural Initiatives has recently rejuvenated the Soil Survey program. The objective of the program is to expedite the continued mapping of soils to ensure the best possible decisions are made about land use and land management in Manitoba. In addition to its implementation, the Soil Survey Program has adopted new technologies to enhance the program. The Soils Information Management System (SIMS), an electronic data entry tool, has been developed to facilitate data collection in the field and the laboratory, and digital stereoscopic viewing imagery using PurVIEW has been incorporated into the program. The Soil Survey program also participates in the development of provincial programs and policies including land use, land management, the validation of national environmental risk predictive models to determine their ability to predict risk at a watershed and on-farm scale, validation of beneficial management practices (BMPs) in cooperation with the provincial Watershed Evaluation of Beneficial Management Practices (WEBs) program, and developing strategies to address Ecological Goods and Services (EG&S) policy and programs.

Effect of soil forming processes on the distribution of soil organic carbon in a dissected, unglaciated landscape in west-central Yukon C.A.S. SMITH1, P.T. SANBORN2 AND J.D. BOND3 1

Agriculture and Agri-Food Canada, P.O. Box 5000, Summerland, BC V0H 1Z0 University of Northern British Columbia, 3333 University Way, Prince George, B.C. V2N 4Z9 3 Yukon Geological Survey, Energy Mines and Resources, P.O. Box 2700, Whitehorse, YT Y1A 2C6 [email protected] 2

Keywords: Cryosols, colluviation, unglaciated, soil organic carbon Soils were observed from recently excavated mineral exploration trenches on a range of slope aspects and positions within the discontinuous permafrost zone of the unglaciated Klondike Plateau in central Yukon. Soil parent materials are composed of variable thicknesses of loess and colluvium. In general, westerly and southerly facing slopes and ridge crests are free of near-surface permafrost and support the development of Dystric Brunisols with thin (