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Article ID Dispatch: 18.02.12 1 5 1 No. of Pages: 10
CE: Melisa Torres ME:
land degradation & development Land Degrad. Develop. (2012) Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/ldr.2151
SOIL ORGANIC CARBON STOCK AND FRACTIONS IN RELATION TO LAND USE AND SOIL DEPTH IN DEGRADED SHIWALIKS OF LOWER HIMALAYAS D. SAHA, S. S. KUKAL* AND S.S. BAWA Department of Soil Science, Punjab Agricultural University, Ludhiana 141004, India Received: 12 February 2011; Revised: 30 January 2012; Accepted: 7 February 2012
ABSTRACT The proportional differences in soil organic carbon (SOC) and its fractions under different land uses are of significance to understand the process of aggregation and soil carbon sequestration mechanisms. A study was conducted in a mixed watershed with forest, grass, cultivated and eroded lands in degraded Shiwaliks of lower Himalayas to assess the land-use effects on profile SOC distribution and storage and to quantify the SOC fractions in water-stable aggregates (WSA) and bulk soils. The soil samples were collected from eroded, cultivated, forest and grassland soils for the analysis of SOC fractions and aggregate stability. The SOC in eroded surface soils was lower than in grassland, cultivated and forest soils. The surface and subsurface soils of grassland and forest lands differentially contributed to the total profile carbon stock. The SOC stock in the 1.05-m soil profile was highest (83.5 Mg ha1) in forest and lowest (55.6 Mg ha1) in eroded lands. The SOC stock in the surface (0–15 cm) soil constituted 6.95, 27.6, 27 and 42.4 per cent of the total stock in the 1.05-m profile of eroded, cultivated, forest and grassland soils, respectively. The forest soils could sequester 22.4 Mg ha1 higher SOC than the cultivated soils in the 1.05-m soil profile. The differences in aggregate SOC content among the land uses were more conspicuous in bigger water-stable macro-aggregates (WSA > 2 mm) than in water-stable micro-aggregates (WSA < 0.25 mm). The SOC in micro-aggregates (WSA < 0.25 mm) was found to be less vulnerable to changes in land use. The hot water soluble and labile carbon fractions were higher in the bulk soils of grasslands than in the individual aggregates, whereas particulate organic carbon was higher in the aggregates than in bulk soils. Copyright © 2012 John Wiley & Sons, Ltd. keywords:
carbon sequestration; forest land use; hot water soluble carbon; labile carbon; soil aggregation; water-stable aggregates
INTRODUCTION Quantification of profile soil carbon (C) stock under different terrestrial ecosystems is valuable input towards C budgeting and ecosystem management. Soils are the largest terrestrial active sink for atmospheric C and have the potentials to mitigate the notorious effect of global warming (Singh and Lal, 2004). Soil organic carbon (SOC) pool contains approximately twice as much C as that in the atmosphere and 2.5 times as much C as that in the biosphere. The SOC maintains soil physical (Rasool et al., 2008) and biochemical quality (Benbi and Chand, 2007). The recent concern of many scientific communities over the increasing atmospheric CO2 has resulted in an increased interest for studying SOC dynamics and C sequestration potential in various ecosystems. The land use, land-use changes and soil erosion are the paramount factors affecting SOC pools at watershed scale (Shrestha et al., 2004) apart from soil depth (Kaiser et al., 2002). For example, the mechanism of C sequestration is different between grassland and forest soils because of the obvious differences in their root architecture and density (Six et al., 2000). Appropriate *Correspondence to: S. S. Kukal, Department of Soil Science, Punjab Agricultural University, Ludhiana 141004, India. E-mail:
[email protected]
Copyright © 2012 John Wiley & Sons, Ltd.
land use and soil management can lead to an increase in SOC, improve physical and biochemical soil quality and partially mitigate the rise of atmospheric CO2 (Lal and Bruce, 1999). Cultivation leads to significant decrease in SOC and soil structural stability (Eynard et al., 2004). The studies related to comparison of SOC stock in soil profile under different land uses thus need to be carried out in different ecosystems particularly the degraded ones. The confinement of SOC in deeper layers of forest subsoil is of critical importance for long-term C sequestration as it is less vulnerable to changes induced because of human manipulations and higher turnover period. Most of the studies concerning the C input and output between soil and atmosphere have generally considered the surface soils for this purpose. However, important amounts of stable SOC pools could also be stored at greater depths (Meersmans et al., 2009). Thus, mere consideration of surface soil C would have little accuracy in producing an effective ecosystem C budget. The inputs of root C to the deeper soil SOC pool may be small compared with above-ground biomass but actively exchanging with the atmospheric C and could be an important contributor to total soil CO2 efflux. Thus, the studies on profile C storage would generate some important ecological information. The extensive deep root system of forest trees facilitates
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the transfer of SOC into the deeper soil profile, whereas the intricate network of finer but denser root mass under grasses favours smaller but stable aggregates in which C could have stabilized in the shallow layer of the surface soils. Moreover, the eroded lands could produce a different picture in the deeper soil layers as compared with the surface soils where most of the SOC have been removed by runoff water, whereas the deep soil buried SOC might have escaped from the loss. A loss of SOC due to soil erosion and incompatible land use change degrades the soil ecosystem and environmental quality (Lal, 2002). Thus, for better understanding of the profile C balance, the SOC dynamics in deeper soil layers under different land uses needs to be studied. The SOC is a complex and heterogeneous entity consisting of the fractions varying in mean residence time (Campbell et al., 1967). Thus, the SOC dynamics under varied land uses and management practices can better be understood by differential way of C allocation in different pools with different decomposition rates (Stevenson, 1994). Soil labile carbon (LC) is a dynamic pool of SOC, accounting for much of the fluctuation over time (Huggins et al., 1998) and with landuse change. Soil aggregation and SOC protection are proportionally related. The water-stable aggregates (WSA) provide a physical resistance to the microbes to decompose the C encapsulated within it and also protect it from loss due to water erosion. Some of the SOC fractions like particulate organic carbon (POC) are more responsible for water stability of aggregates (Saha et al., 2011). Being a labile intermediate fraction, the POC can be used as an early indicator of changes in C dynamics and total SOC under different land uses and management systems (Pikul et al., 2007). It accumulates rapidly under soils with minimized disturbance (Cambardella and Elliott, 1992). Furthermore, the differences in SOC fractions under different land uses can yield significant information related to the mechanism of C sequestration (BlancoCanqui and Lal, 2004). The human-induced degradation of land in the most fragile Shiwaliks region of lower Himalayas is very rapid because of soil erosion by water. This leads to a large-scale erosion of soil along with SOC, leading to downstream sedimentation. The different land uses in the region have been reported to affect the SOC (Gupta et al., 2009; Saha et al., 2011). The conversion of natural forest and grassland into arable lands accompanied by severe soil erosion hazards is very predominant in the region, resulting in degradation of soil quality. Basic background information on the differential profile distribution pattern of SOC under different terrestrial ecosystems, which is lacking in this part of India, is a critical need to frame the land management packages and a sound ecosystem C budget. The present study was thus conducted with an aim to quantify the profile variability in SOC stock and understand the dynamics of SOC fractions under different land uses in the region. Copyright © 2012 John Wiley & Sons, Ltd.
MATERIALS AND METHODS Study site descriptions A mixed watershed (district Hoshiarpur of north-west India) located in the foothills of lower Shiwaliks in lower Himalayas was selected for the investigation. It is situated at an altitude of 355 m above the mean sea level and is one of the most fragile regions of the lower Himalayas. This region has semi-arid to sub-humid type of climate and lies between 31 12′N latitude and 76 14′E longitude. The mean maximum temperatures vary from 18.6 C in the month of January to 39.1 C in May, whereas the mean minimum temperatures vary from 5.2 C in the month of December to 24.7 C in June. The region receives an annual rainfall of 850–1100 mm with a high coefficient of variation. About 80 per cent of the annual rainfall is received during a short period of 3 months (July to September), whereas the remaining 20 per cent is received during the months of October to March. The probability of occurrence of at least one dry spell greater than 6 days during individual months is between 55 and 99 per cent (Sur et al., 1998). The rainfall during the months of July to September is ill distributed, and the droughts occur frequently. The erosion of sediments by the runoff water from the hill slopes and their subsequent deposition at the foot slopes is a continuous process in the region. The soils are non-saline sandy clay loam with low to moderate water retention capacity (Table 1). Land-use characteristics The eroded, cultivated, forest and grass lands were selected in a mixed watershed. The eroded lands constituted 18 per cent of total land area (mainly under the gullies), whereas the cultivated arable, forest and grass lands constituted 54, 18 and 10 per cent of the total land of the watershed. The eroded lands in fact were previously under forest trees, which got denuded in the course of time because of human-induced destruction of natural ecosystem by severe deforestation. This has led to severe soil erosion in the form of rill and gully erosion. The eroded lands are basically exposed to the direct action of the rain drops because of lack of vegetation cover or very rarely distributed small herbs and grasses in some depressions. Thus, there is less return of litter input to these soils to maintain the SOC status particularly in the surface layers. At the same time, continuous runoff during severe rainstorms washes away the finer soil particles along with SOC and thus aggravates the degradation process. The cultivated lands were either levelled or gently sloping (0.5–2 per cent slope steepness), located towards the toe position of the watershed. These cultivated arable lands are commonly used for growing corn (Zea mays L) summer season (June–October) and wheat (Triticum aestivum L) during the winter season (November–April). The slope steepness varied from 5 to 8 per cent in forest land, 3 to 5 per cent on grassland and 8 to 10 per cent in eroded lands. The forest land comprised native trees and shrubs LAND DEGRADATION & DEVELOPMENT (2012)
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Table I. Basic physico-chemical parameters of soils under different land uses Land use Properties Sand (%) Silt (%) Clay (%) Texture Land slope (%) Bulk density (Mg m3) pH EC (d m1) Moisture content PWP (%) Field capacity (%)
Eroded
Agricultural
Forest
Grassland
67.9 3.5 8.08 0.60 22.9 1.2 Sandy clay loam 8–10 1.63 7.07 0.03 0.07 0.002
69.8 2.9 7.81 0.81 21.3 2.1 Sandy clay loam 0.5–2 1.53 7.5 0.02 0.09 0.004
68.4 3.1 8.28 0.74 22.6 1.9 Sandy clay loam 5–8 1.52 7.1 0.04 0.07 0.01
70.5 3.3 7.79 0.52 21.6 2.1 Sandy clay loam 3–5 1.50 7.4 0.03 0.08 0.04
3.9 0.6 16.9 1.3
8.5 0.8 22.3 1.9
9.5 0.9 28.4 2.2
10.1 1.2 31.0 3.2
EC, electrical conductivity; PWP, permanent wilting point.
(Carissa spiranum, Jatropha sp., etc.), which were dense at some places and scattered at others. Virtually, there is no continuous dense forest land in the lower Shiwaliks because of the human-induced deforestation that once happened. The grasslands, adjacent to the forest patches, are generally used for grazing by domestic and wild animals. The grasses comprised natural grasses viz., Cyprus rotundus, Cynodon dactylon, Saccharum munja etc. Soil and aggregate sampling Soil and aggregate sampling was carried out in different land uses in the watershed. In each land use, three locations were selected on the basis of the criterion of similar soil texture and topography. In each location, three sites were selected for actual sampling of bulk soil and aggregates. Thus, for each land use, nine samples were collected, well representing the particular land use. For soil sampling, the deep pits (1 m 1 m 1 m) were dug out, and soil samples were collected at depth intervals of 0–15, 15–30, 30–45, 45–60, 60–75, 75–90 and 90–105 cm from three sampling points in each pit. The three sub-samples were then mixed to get one composite sample for a particular depth in each pit. The composite soil samples were air dried and sieved through 2 mm sieve and analysed for SOC by Walkley and Black’s rapid titration method. The bulk density of the soil profile till 1.05 m was determined in situ at depth intervals of 15 cm by core sampling method as described by Blake and Hartge (1986). For this purpose, the cylindrical steel core of 5 cm internal diameter and 5 cm height was inserted horizontally at the centre of each depth class. The steel core was hammered into the soil till the desired depth using a concentric 2-cm high steel ring of similar diameter placed above the 5-cm core. It was then taken out and the soil outside the steel core removed with a sharp blade. The soil inside the steel core was collected, Copyright © 2012 John Wiley & Sons, Ltd.
weighed and oven dried at 105 C for 24 h. The roots were separated from the soil by sieving, and the ratio of oven-dry weight of the soil core and its total volume was expressed as soil bulk density. The soil carbon stock was calculated as given below: SOC stock ¼ d BD SOC content 10; 000 Where the SOC stock (Mg ha1), d is depth of soil layer (m), BD is soil bulk density (Mg m3) and SOC content (g g1). The value of 10,000 indicates the stock for one ha of land. The sum of the SOC stock in each soil layer throughout the whole profile depicted the total SOC stock for each dominant land use. The size distribution of WSA was measured by wet sieving technique (Yoder, 1936) with a nest of sieves of sizes 2.0, 0.25 and 0.1 mm. A 50-g sample of 4–8 mm size aggregates, obtained by dry sieving, was used for determining the water stability. The amount of material retained on each sieve was dried and determined for SOC by Walkley and Black’s titration method. The SOC fractions were determined for surface (0–15 cm) and subsurface (15–30 cm) soil layers. The POC was determined as described by Cambardella and Elliott (1992) and Hassink (1995). The hot water soluble carbon (HWC) was determined as per Schulz et al. (2003). The LC was determined by KMnO4 oxidation method (Blair et al., 1995). The detailed methodology is described in Saha et al. (2011). Statistical analysis The differences in SOC concentration and stock as affected by land use and soil depth were tested by analysis of variance using least significance difference (LSD) of mean at p < 0.05. The regression analysis was used to assess the relationship between WSA and SOC stock at p < 0.05. Standard error of mean was also calculated. LAND DEGRADATION & DEVELOPMENT (2012)
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RESULTS AND DISCUSSION Soil organic carbon concentration In the surface soil layers (0–15 cm), the concentration of SOC was significantly (p < 0.05) different among different T2 land uses (Table 2). The grassland soils recorded the highest amount of SOC (13.2 g kg1), whereas the eroded soil had the lowest concentration of SOC (1.95 g kg1). The eroded surface soils (0–15 cm) had 79 and 73 per cent lower SOC than that in forest and cultivated soils, respectively, the difference being significant at 5 per cent level of significance (Table 2). This could be due to the loss of SOC with the sediments and runoff water from the surface soil of the eroded lands. In general, there was a decreasing trend of SOC with soil depth in all the land uses except in the eroded soils where there was a successive increase in SOC concentration down the profile (Table 2). The higher amount of SOC in deeper layers of eroded soil was due to the fact that these soils were earlier under forest trees, and because of deforestation and subsequent soil erosion by water, the SOC from the surface layers got removed along with the sediments (Kukal et al., 1991). The highest decrease in SOC in the subsurface soil layers (15–30 cm) was recorded in grassland soils (62.4 per cent) followed by 34 per cent in cultivated and lowest (27 per cent) in forest soils. Except the surface soils (0–15 cm), the forest soils recorded the highest SOC among all the land uses. No significant (p < 0.05) difference in SOC was observed between cultivated and grassland soils below 45 cm soil depth. The highest amount of SOC in the surface grassland soils could be attributed to the higher root mass density of the shallow intricate grass roots (Kukal et al., 2008). The higher root mass density increases the WSA and SOC by secreting root exudates rich in binding agents, increasing physical stability and microbial activity (Holeplass et al., 2004). Nakagami et al. (2009) observed that a substantial amount of C can be accumulated
in the top soil layers of pasture lands. However, the higher SOC content in forest soils in deeper layers compared with those in other land uses indicates the role of biomass input through roots of forest trees (Gibbon et al., 2010) and leaching of dissolved organic C (Shrestha et al., 2004) in increasing the deep soil C allocation. Soil organic carbon stock and sequestration The total SOC stock in the 1.05-m soil profile was highest in forest land (83.5 Mg ha1), followed by grassland (73.0 Mg ha1) and cultivated (61.1 Mg ha1) and lowest in eroded (55.6 Mg ha1) soils (Table 3). The forest soils could store 14.4, 36.7 and 50.2 per cent higher total SOC stock than grassland, cultivated and eroded soils, respectively. The variation of SOC stock under different land uses is significantly prominent in the surface (0–15 cm) soils, and the difference became narrow with increasing soil depth. The 0–15 cm layer of grassland soils contributed 42.5 6.5 per cent of the total SOC stock in the entire 1.05-m profile, whereas it was 27 6.9, 27.6 6.1 and 6.9 5.8 per cent in forest, cultivated and eroded soils, respectively (Figure 1). In 15–30 cm soil layer, the forest soils had the highest pool of SOC (16.0 Mg ha1), followed by grassland (11.9 Mg ha1), cultivated (11.2 Mg ha1) and eroded soils (6.20 Mg ha1) (Table 3). In subsequent soil layers, the SOC stock decreased sharply in all the land uses except eroded lands, where it increased till 45–60 cm soil layers. It was almost similar till 90 cm soil depth, after which it decreased sharply by 50 per cent in eroded lands. In cultivated soils, the SOC stock decreased consistently till 90 cm depth after which it sharply declined by 50 per cent (2.8 Mg ha1) (Table 3). As in other land uses, the grassland soils also showed a sharp decline in SOC stock after 90 cm depth. This indicates that most of the active C cycling in all the land uses occurs within 0–90 cm of the soil profile. In forest Table III. Soil organic carbon stock (Mg ha1) in different soil layers under different land uses
Table II. Profile distribution of soil organic carbon concentration (g kg1) under different land uses Soil depth (cm)
0–15 15–30 30–45 45–60 60–75 75–90 90–105
Soil depth (cm)
Land use Eroded
Cultivated
Forest
Grassland
LSD (0.05)
1.95al 2.50a 3.24a 3.68a 3.98a 3.67a 3.73a
7.23b 4.72b 4.36b 3.38a 2.55b 2.21b 1.70b
10.2c 7.01c 4.73b 4.85b 4.95c 4.93c 4.67c
13.2d 4.96b 3.27a 3.48a 2.80b 2.25b 1.70b
1.57 0.38 0.40 0.77 0.80 0.80 0.95
Lower case letters indicate differences (at the 0.05 probability level) in SOC concentration at each depth classes among different land uses. Copyright © 2012 John Wiley & Sons, Ltd.
0–15 15–30 30–45 45–60 60–75 75–90 90–105 Total (0–105)
Land use Eroded
Cultivated
Forest
Grassland
4.76a 6.20a 8.97ab 10.4a 10.0a 10.1a 5.38a 55.6
16.6b 11.2b 9.93a 8.35b 6.42b 5.54b 2.80b 61.1
23.2c 16.0c 10.0a 9.70a 10.4a 9.23a 6.71c 85.2
30.0d 11.9b 7.61b 8.10b 6.44b 5.30b 2.73b 72.0
LSD (0.05) 2.41 2.13 1.52 0.74 0.41 1.01 0.36
Lower case letters indicate differences (at the 0.05 probability level) in SOC stock at each depth classes among different land uses. LAND DEGRADATION & DEVELOPMENT (2012)
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Figure 1. Proportion of SOC in surface (0–15 cm) and subsurface (15–105) soil layers to total 1.05-m profile under different land uses (vertical columns are means, and the bars on each column are standard errors of mean). This figure is available in colour online at wileyonlinelibrary.com/journal/ldr
soils, the SOC stock in the subsoils (15–105 cm) was highest among all the land uses with a small exception of eroded soils, where it was non-significantly higher from that in forest soils (Table 3). In all the land uses, the SOC stock in 15–105 cm profile is of significance as the deeper soil layers (15–105 cm) contain sufficiently higher proportion of total profile SOC stocks than the surface layers (Figure 1), which is due to the higher volume of soils lying below the surface layer. In grassland soils, the SOC stock was 42 Mg ha1 in the 15–105 cm soil layer compared with 30 Mg ha1 in the 0–15 cm soil layer. This difference widened in forest lands, where 60 Mg ha1 of SOC stock was recorded in the lower layers (15–105 cm) (Table 3). The SOC stock in 15–105 cm was 93.1 5.2, 71.7 6.8, 73 7.0 and 58.5 6.3 per cent of the total SOC stock in the 1.05-m profile of eroded, cultivated, forest and grassland soils, respectively (Figure 1). The land use is an important factor controlling SOC storage in soils because it affects the amount and quality of litter input, the litter decomposition rate and processes of organic matter stabilization in soils (Schwendenmann and Pendall, 2006). Whereas conversion of tropical forest and pasture to arable land typically decreases the total SOC stocks (Guo and Gifford, 2002), conversion of forest to pasture or vice versa can be associated either with increase, decrease or without any change of total SOC (de Koning et al., 2003). However, in the present study, it is clear that the conversion of forest lands into grasslands may result in decrease in total profile SOC stocks. The difference in the SOC stock between forest and grassland soils in surface and deeper soil layers could be attributed to the difference in the root architecture of forest trees and grasses. Nepstad et al. (1994) identified the prominent influence of living root biomass on active C cycling of tropical Amazon forest soils. The intricate network of fibrous grass roots are in Copyright © 2012 John Wiley & Sons, Ltd.
higher interaction with the few centimetres of surface soils (Kukal et al., 2008), whereas the deep tap root system of the forest trees (Gupta et al., 2009) are in maximum interaction with the deeper soils. This might have caused higher contribution of surface layer (0–15 cm) to the total profile C stock as in the case of grassland soils. Shifting from natural ecosystem (grassland and forest) to cultivated land also results in depletion of SOC stock, which was 45.5 and 25.2 per cent lower in cultivated surface layer than in grassland and forest soils, respectively (Table 3). Tillage leads to the mechanical breakdown of the soil aggregates resulting in loss of C that was once encapsulated within the aggregates, whereas minimization of the soil disturbance leads to C accumulation (Bajracharya, 2001). The increase in SOC concentration and content with increasing soil depth in eroded lands which was unusual in the other land uses could be because of the previous history of the eroded lands being under forest trees before these were cut by the local and/or migrated population. The root biomass might have contributed towards the higher SOC stock in the deeper soil layers, which escaped from erosion losses because of the recalcitrant nature of deep soil C (Rumpel and Kögel-Knabner, 2011). On the other hand, deforestation caused the tremendous decrease in the SOC stock in the surface layers, which were denuded and exposed to the impact of rainfall and other climatic factors (Starr et al., 2000). The forest soils could sequester 22.4 Mg ha1 higher SOC than the cultivated soils in the 1.05-m soil profile, whereas the grassland could sequester 11.9 Mg ha1 higher SOC in the 1.05-m profile (Table 4). In the 0–15 cm soil layer, the reverse was true; i.e. the grassland soils could sequester 13.4 Mg C ha1 more SOC than the cultivated soils, whereas the forest soils could store 6.60 Mg ha1 higher SOC than the cultivated soils. Cultivation decreases the amount of SOC by accelerated mineralization, leaching and translocation and accelerated soil erosion (Li et al., 2007). Moreover, the continuous removal of crop residues from the surface soils for domestic purpose might have caused lower SOC accumulation in the surface soils of cultivated land in the Shiwaliks region. Under forest soils, the presence of litter recycles continuously and adds to SOC storage in the top soil horizons (Garcia-Pausas et al., 2004). Potter et al. (1999) reported that SOC mass in the surface 120 cm of Table IV. Soil organic carbon sequestration (Mg ha1) in different layers of soil profile in relation to land use Soil depth (cm) Land use
0–15
15–30
0–105
Cultivated Forest Grassland
– 6.60 13.4
– 4.80 0.70
– 22.4 11.9
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the agricultural soils was significantly lower than that of native prairie grassland soils. Schwendenmann and Pendall (2006) observed that surface (0–5 cm) soil carbon stock was non-significantly higher under forest than under grasslands. In fact, the roots of the grasses in Shiwaliks apart from being dense and shallow add significant amount of biomass in the surface soil layers. Kukal et al. (2008) reported 3.89 mg cm3 higher root mass density in surface (0–15 cm) pasture soils than the forest soils of Shiwaliks region, whereas in forest soils the deeper root systems of the trees lead to accumulation of higher biomass in the deeper layers, which generally remains protected from the accelerated decomposition because of lower rate of oxygen diffusion from the atmosphere and substrate limitation (Fontaine et al., 2007) to support the microbial growth and activity in the deeper layers. Gibbon et al. (2010) estimated root C contribution of Puna grassland of about 0.05 Mg ha1, whereas it was 13.9 Mg ha1 in forest lands of Peru. Moreover, the root channels created by the dead roots could facilitate easy movement of decomposed dissolved organic matter into the lower layers through preferential flow of water, which may not be the case in the grassland soils. Soil organic carbon concentration in water-stable aggregates
F2
The SOC concentration in different sized WSA is of critical importance for understanding the mechanics of SOC sequestration. The SOC content decreased with decrease in the size of WSA (Figure 2). The SOC varied significantly in bigger macro-aggregates (WSA > 2 mm) in different land uses. It was in the order of grassland > forest > cultivated > eroded soils. The WSA > 2 mm from the eroded soils had 54.1, 49 and 26.6 per cent lower SOC, respectively. However, with
Figure 2. The variation of SOC in larger macro-aggregates (WSA>2 mm), smaller macro-aggregates (WSA 2–0.25 mm) and micro-aggregates (WSA 0.25 mm) as affected by land use [lower case letters indicate differences (at the 0.05 probability level) in SOC among land-use systems compared within each aggregate size class]. This figure is available in colour online at wileyonlinelibrary.com/journal/ldr Copyright © 2012 John Wiley & Sons, Ltd.
the subsequent decrease in the size of water-stable macroaggregates, the magnitude of SOC decrease narrowed down to 43, 44 and 30 per cent, respectively. With further decrease in stable aggregate size to micro-aggregates (WSA < 0.25 mm), the difference in SOC became negligible (Figure 2). Hence, these micro-aggregates appear to have an important role to play in C sequestration (Bajracharya et al., 1998). The mechanism of C sequestration can be better understood by the architectural organization of aggregates. The macroaggregates are the primary storage sites for SOC (Jastrow et al., 1998), which is transient in nature (Sainju et al., 2003), whereas the micro-aggregates contain relatively passive SOC pool that are more protected because of strong biochemical interaction with silt and clay particles and are less vulnerable to disruption. Hence, long-term protection of C can be enabled within the micro-aggregates (Conant et al., 2004). The change in SOC due to change in land use and erosion process is more pronounced in the macro-aggregates. The SOC stock was found to be significantly (R2 = 0.58, n = 24; p ≤ 0.05) correlated with water stability of soil aggregates (WSA) (Figure 3). Holeplass et al. (2004) reported slightly lower (53 per cent) correlation between SOC concentration and WSA. The results thus suggest that water stability of aggregates is of significance for rendering long-term C sequestration with the additional interaction with some other factors like climate and vegetation. Increase in the proportion of WSA maximizes the protection of SOC within the aggregates and protects it from erosional losses especially in the degraded regions like Shiwaliks of lower Himalayas with low soil organic matter content in the soils. Proportion of soil organic carbon fractions The proportion of HWC to the total SOC was highest in the surface (0–15 cm) soils of eroded land (8.2 per cent) and
Figure 3. The relationship between water-stable aggregates (WSA > 0.25 mm) and SOC stock in 0–30 cm of soil layer. LAND DEGRADATION & DEVELOPMENT (2012)
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lowest in grassland soils (5.82 per cent), whereas it was almost similar in cultivated (6.4 per cent) and forest (6.45 per cent) soils (Figure 4). However, among the three SOC fractions studied, the magnitude of POC to the total SOC pool was highest among all the land uses. The POC accounted for highest proportion (75 per cent) in forest soils followed by eroded (65.1 per cent), grassland (64.7 per cent) and cultivated (55.3 per cent) surface soils (Figure 4). The proportion of LC to the SOC pool was highest (15.7 per cent) in grassland soils, closely followed by forest (15.4 per cent), cultivated (10.7 per cent) and eroded (8.2 per cent) soils (Figure 4). The POC is derived from the root residues (Gale et al., 2000). The higher proportion of the POC to the SOC pool in forest soils could have been due to the presence of higher amount of extensive root biomass of the trees. New microaggregates are formed by encrusting the root-derived particulate organic matter in association with the microbial products (Six et al., 2000) and hence render the stabilization of aggregates as well as the POC encrusted within it because of reduction in microbial activity. This is also true in case of
(a)
(b) Figure 4. Proportion of different SOC fractions to total SOC in the (a) 0–15 and (b) 15–30 cm soil layers of different land uses (vertical columns are means, and the bars on each column are standard errors of mean; means followed by the same letters are not different at p < 0.05). This figure is available in colour online at wileyonlinelibrary.com/journal/ldr Copyright © 2012 John Wiley & Sons, Ltd.
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eroded soil, which was previously under forest trees that were denuded with the course of time by human-induced deforestation. Cultivation leads to the breakdown of aggregates and enhances microbial access to the POC within the aggregates and subsequent decompositions. This could be the reason for the lower proportion of POC to the SOC pool in cultivated soils. Being a very light and labile SOC fraction, LC is more prone to microbial mineralization loss due to cultivation and soil erosion. A greater proportion of LC is generally associated with the less resistant macroaggregates (Angers and Giroux, 1996). Thus the release of LC due to water erosion will occur to a greater extent from the larger soil aggregates (Jacinthe et al., 2004). The protection of SOC fractions by soil aggregates is of significance with respect of long-term C sequestration. The HWC content in the bulk soils was in the order of grassland (0.71 g kg1) > forest (0.62 g kg1) > cultivated (0.46 g kg1) > eroded (0.22 g kg1) soils (Figure 5). A similar trend was observed for HWC content in aggregates but in sufficiently lower magnitude. The aggregates of grassland soils recorded remarkably 61 per cent lower HWC content than that in the bulk soils followed by 58 per cent in forest, 52 per cent in cultivated and 14 per cent in the eroded soils. The LC content of aggregates from grassland and cultivated soils was 17 and 24 per cent lower than the bulk soils, respectively (Figure 5). However, the HWC content in aggregates and bulk soils was more or less similar in forest and eroded soils. Surprisingly, in contrast to the HWC and LC, the POC content was highest in aggregates than that in the bulk soils. The aggregate associated POC was highest in grassland (9.26 g kg1), sharply followed by forest (8.98 g kg1), followed by cultivated (6.71 g kg1) and lower in eroded (2.95 g kg1) soils (Figure 5). The bulk soil POC followed a similar trend but with a sufficiently lower magnitude. The higher reduction of POC in bulk soils than that in aggregates was observed in eroded soils (57 per cent) (Figure 5). Destruction of soil aggregates due to cultivation leads to 40 per cent loss of POC once associated with soil aggregates (Figure 5). In our present study, the HWC and LC, being labile and easily decomposable fractions of SOC, are found to be less protected by the soil aggregates. Their content was more in the bulk soils rather than in the aggregates. The LC is characterized by very rapid mineralization rate because of the nature of its constituents and lack of protection by the soil colloids (Turchenek and Oades, 1979). Our results indicate a dominant role of POC in the process of soil aggregation. In fact, POC initiates the aggregate formation by forming the nucleon of aggregates surrounded by soil colloids (Six et al., 2000). According to Gale et al. (2000), macroaggregates are formed around root-derived POC. Disruption of aggregates by cultivation and slaking due to water erosion leads to release of root-derived POC to free POC, LAND DEGRADATION & DEVELOPMENT (2012)
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(a)
(b)
(c) Figure 5. The distribution of (a) hot water soluble carbon (HWC), (b) labile carbon (LC) and (c) particulate organic carbon (POC) in aggregates (1–8 mm) and bulk soil samples of surface soils (0–15 cm) under different land uses (horizontal columns are means, and the bars on each column are standard errors of mean). This figure is available in colour online at wileyonlinelibrary.com/journal/ldr
which is easily decomposable by the microbes. That is supposed to be the reason for having lower POC content in the aggregates from cultivated and eroded soils. CONCLUSIONS The SOC stock varied significantly with land use and soil depth. The total SOC stock in the 1.05-m soil profile was in the order of forest > grassland > cultivated > eroded lands. The surface soils (0–15 cm) of grassland contributed the most (42.4 per cent) to the profile SOC stock, whereas, 15–105 cm of the soil profile contributed 58.5, 73, 71.7 and 93 per cent of the total SOC stock in grassland, forest, cultivated and eroded soils, respectively. The increase of SOC in deeper layers of eroded soils of the region is of scientific interest and indicates the resistance of subsoil C to rapid change with the change in land use. Further studies on radiocarbon age and chemical nature of the subsoil C would probably give the reason for their recalcitrance. Significant differences in SOC content in the deeper soil layers of different land uses imply the importance of considering the profile C balance rather than the mere surface soils during ecosystem C budgeting. The dynamics of root biomass among forest and grasslands are absent in this Copyright © 2012 John Wiley & Sons, Ltd.
region and needs further investigation on this aspect. Cultivation by cleaning the forest and grassland leads to decrease in SOC content. The forest soils could sequester 22.4 Mg ha1 higher SOC than the cultivated soils in the 1.05-m soil profile, whereas the grassland could sequester 11.9 Mg ha1 higher SOC in the 1.05-m profile. The SOC stored in micro-aggregates (WSA < 0.25 mm) was found to be more protected and less vulnerable to change due to change in land use. A significant variability in the SOC stock could be explained by the water stability of aggregates. The POC fraction of soil C pool has a tendency to accumulate under ecosystems with sufficient C inputs and encrusted within soil aggregates and hence renders the protection against loss of C.
REFERENCES Angers DA, Giroux M. 1996. Recently deposited organic matter in soil water-stable aggregates. Soil Science Society of America Journal 60: 1547–1551. Bajracharya RM. 2001. Land preparation: an integral part of farming system in the mid-hills of Nepal. Nepal Journal of Science and Technology 3: 15–24. Bajracharya RM, Lal R, Kimble JM. 1998. Soil organic carbon distribution in aggregates and primary particle fractions as influenced by erosion LAND DEGRADATION & DEVELOPMENT (2012)
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SOC STOCK AND FRACTIONS IN RELATION TO LAND USE phases and landscape position. In Soil Processes' and the Carbon Cycle, Lal R, Kimble JM, Follett RF, Stewart BA (eds). CRC Press: Boca Raton, FL, USA; 353–367. Benbi DK, Chand M. 2007. Quantifying the effect of soil organic matter on indigenous soil N supply and wheat productivity in semiarid sub-tropical India. Nutrient Cycling in Agroecosystems 79: 103–112. Blair GJ, Lefroy RDB, Lisle L. 1995. Soil C fractions, based on their degree of oxidation and the development of a C management index for agricultural system. Australian Journal of Agronomy Research 46: 1459–1466. Blake GR, Hartge KH. 1986. Bulk density. In Methods of Soil Analysis, Part I, Klute A (ed.). ASA Monograph No 9: Madison, WI; 363–376. Blanco-Canqui H, Lal R. 2004. Mechanisms of carbon sequestration in soil aggregates. Critical Review in Plant Science 23: 481–504. Cambardella CA, Elliott ET. 1992. Particulate soil organic matter changes across a grassland cultivation sequence. Soil Science Society of America Journal 56: 777–783. Campbell CA, Paul EA, Rennie DA, McCallum KJ. 1967. Applicability of the carbon-dating method of analysis to soil humus studies. Soil Science 104: 217–224. Conant TR, Six J, Paustian K. 2004. Land use effects on soil carbon fractions in the southeastern United States. II. Changes in soil carbon fractions along a forest to pasture chronosequence. Biology and Fertility of Soils 40: 194–200. Eynard A, Shumacher TE, Lindstrom MJ, Malo DD. 2004. Aggregate sizes and stability in cultivated South Dakota Prairie Ustolls and Usterts. Soil Science Society of America Journal 68: 1360–1365. Fontaine S, Barot S, Bdioui N, Mary B, Rumpel C. 2007. Stability of organic carbon in deep soil layers controlled by fresh carbon supply. Nature 450: 277–280. Gale WJ, Cambardella CA, Bailey TB. 2000. Root-derived carbon and the formation and stabilization of aggregates. Soil Science Society of America Journal 64: 201–207. Garcia-Pausas J, Casals P, Romanya J. 2004. Litter decomposition and faunal activity in Mediterranean forest soils: effects of N content and the moss layer. Soil Biology and Biochemistry 36: 989–999. Gibbon A, Silman MR, Malhi Y, Fisher JB, Meir P, Zimmermann M, Dargie GC, William RF, Karina CG. 2010. Ecosystem carbon storage across the grassland–forest transition in the High Andes of Manu National Park, Peru. Ecosystems 13: 1097–1111. Guo LB, Gifford RM. 2002. Soil carbon stocks and land use change: a meta-analysis. Global Change Biology 8: 345–360. Gupta N, Kukal SS, Bawa SS, Dhaliwal GS. 2009. Soil organic carbon and aggregation under poplar based agroforestry system in relation to tree age and soil type. Agroforestry Systems 76: 27–35. Hassink J. 1995. Density fraction of soil macro organic matter and microbial biomass as prediction of C and N mineralization. Soil Biology and Biochemistry 27: 1099–1108. Holeplass H, Singh BR, Lal R. 2004. Carbon sequestration in soil aggregates under different crop rotation and nitrogen fertilization in an Inceptisol in southeastern Norway. Nutrient Cycling in Agroecosystems 70: 167–177. Huggins DR, Clapp CE, Allmaras RR, Lamb JA, Layese MF. 1998. Carbon dynamics in corn–soybean sequences as estimated from natural 13C abundance. Soil Science Society of America Journal 62: 195–203. Jacinthe PA, Lal R, Owens LB, Hothem DL. 2004. Transport of labile carbon in runoff as affected by land use and rainfall characteristics. Soil and Tillage Research 77: 111–123. Jastrow JD. 1996. Soil aggregate formation and accrual of particulate and mineral-associated organic matter. Soil Biology and Biochemistry 28: 665–676. Jastrow JD, Miller RM, Lussenhop J. 1998. Contributions of interacting biological mechanisms to soil aggregate stabilization in restored prairie. Soil Biology and Biochemistry 30: 905–916. Kaiser K, Eusterhues K, Rumpel C, Guggenberger G, Kogel K. 2002. Stabilization of organic matter by soil minerals—investigations of
Copyright © 2012 John Wiley & Sons, Ltd.
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density and particle—size fractions from two acid forest soils. Journal of Plant Nutrition and Soil Science 165: 451–459. de Koning GHJ, Veldkamp E, Lopez-Ulloa M. 2003. Quantification of carbon sequestration in soils following pasture to forest conversion in north-western Ecuador. Global Biogeochemical Cycles 17: 1098. Kukal SS, Sur HS, Gill SS. 1991. Factors responsible for soil erosion hazard in submontane Punjab, India. Soil Use and Management 7: 38–44. Kukal SS, Kaur M, Bawa SS. 2008. Erodibility of sandy loam aggregates in relation to their size and initial moisture content under different land uses in semi-arid tropics of India. Arid Land Research Management 22: 216–227. Lal R. 2002. Soil carbon dynamics in cropland and rangeland. Environmental Pollution 116: 353–362. Lal R, Bruce JP. 1999. The potential of world cropland soils to sequester C and mitigate the greenhouse effect. Environmental Science Policy 2: 177–185. Li XG, Li FM, Zed R, Zhan ZY, Singh B. 2007. Soil physical properties and their relation to organic carbon pools as affected by land use in an alpine pasture land. Geoderna 139: 98–105. Martin A, Mariotti A, Balesdent J, Lavelle P, Vuattoux R. 1990. Estimates of the organic matter turnover rate in a savanna by the 13C natural abundance. Soil Biology and Biochemistry 22: 517–523. Meersmans J, VanWesemael B, De Ridder F, Fallas Dotti M, De Baets S, Van Molle M. 2009. Changes in organic carbon distribution with depth in agricultural soils in Northern Belgium, 1960–2006. Global Change Biology 15: 2739–2750. Nakagami K, Hojito M, Itano S, Kohyama K, Miyaji T, Nishiwaki A, Matsuura S, Tsutsumi M, Kano S. 2009. Soil carbon stock in typical grasslands in Japan. Grassland Science 55: 96–103. Nepstad DC, de Carvalho CR, Davidson EA, Jipp PH, Lefebvre PA, Negreiros GH, da Silva ED, Stone T, Trumbore S, Vieira S. 1994. The role of deep roots in the hydrological and carbon cycles of Amazonian forests and pastures. Nature 372: 666–669. Pikul J, Shannon O, Michael E, Walter R. 2007. Particulate organic matter and water-stable aggregation of soil under contrasting management. Soil Science Society of America Journal 71: 766–776. Potter KN, Torbert HA, Johnson HB, Tischler CR. 1999. Carbon storage after longterm grass establishment on degraded soils. Soil Science 164: 718–725. Rasool R, Kukal SS, Hira GS. 2008. Soil organic carbon and physical properties as affected by long term application of FYM and inorganic fertilizers in maize–wheat system. Soil and Tillage Research 101: 31–36. Rumpel C, Kögel-Knabner I. 2011. Deep soil organic matter—a key but poorly understood component of terrestrial C cycle. Plant and Soil 338: 143–158. Saha D, Kukal SS, Sharma S. 2011. Landuse impacts on SOC fractions and aggregate stability in typic ustochrepts of Northwest India. Plant and Soil 339: 457–470. Sainju UM, Terrill TH, Gelaye S, Singh BP. 2003. Soil aggregation and carbon and nitrogen pools under rhizoma peanut and perennial weeds. Soil Science Society of America Journal 67: 146–155. Schulz E, Deller B, Hoffmann G. 2003. C and N in Heibwasser extract. In VDLUFA Methodenbuch. 1, Method A 4.3.2. VDLUFA- Verlog: Bonn. Schwendenmann L, Pendall E. 2006. Effects of forest conversion into grassland on soil aggregate structure and carbon storage in Panama: evidence from soil carbon fractionation and stable isotopes. Plant and Soil 288: 217–232. Shrestha BM, Sitaula BK, Singh BR, Bajracharya RM. 2004. Soil organic carbon stocks in soil aggregates under different land use systems in Nepal. Nutrient Cycling in Agroecosystems 70: 201–213. Shukla MK, Lal R. 2005. Soil organic carbon stock for reclaimed minesoils in northeastern Ohio. Land Degradation and Development 16: 377–386. Singh BR, Lal R. 2004. The potential of soil carbon sequestration through improved management practices in Norway. Environment, Development and Sustainability (in press).
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Six J, Elliott ET, Paustian K. 2000. Soil macroaggregate turnover and microaggregate formation: a mechanism for C sequestration under no-tillage agriculture. Soil Biology and Biochemistry 32: 2099–2103. Starr GC, Lal R, Malone R, Hothem D, Owens L, Kimble J. 2000. Modelling soil carbon transported by water erosion processes. Land Degradation and Development 11: 83–91. Stevenson FJ. 1994. Humus Chemistry: Genesis, Composition, Reaction, 2nd edn. Wiley: New York; 496.
Copyright © 2012 John Wiley & Sons, Ltd.
Sur HS, Kukal SS, Maskina MS. 1998. Indigenous Technical Knowledge for Soil and Water Conservation and Crop Management in Kandi area of NW India. Research Bulletin, Zonal Research Station for Kandi Area, Punjab Agricultural University: Ludhiana, India. Turchenek LW, Oades JM. 1979. Fractionation of organomineral complexes by sedimentation and density techniques. Geoderma 21: 311–343. 'Yoder RE. 1936. A direct method of aggregate size analysis of soils and a study of the physical nature of erosion losses. Journal of American Society of Agronomy 28: 337–351.
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