ISSN 10674136, Russian Journal of Ecology, 2012, Vol. 43, No. 1, pp. 24–28. © Pleiades Publishing, Ltd., 2012. Original Russian Text © O.V. Masyagina, T. Koike, 2012, published in Ekologiya, 2012, No. 1, pp. 27–31.
Soil Respiration in Model Plantations under Conditions of Elevated CO2 in the Atmosphere (Hokkaido Island, Japan) O. V. Masyaginaa,b and T. Koikeb a
Sukachev Institute of Forest, Siberian Branch, Russian Academy of Sciences, Akademgorodok, Krasnoyarsk, 660036 Russia email:
[email protected] bHokkaido University, Sapporo, 0608589 Japan Received July 29, 2010
Abstract—The influence of longterm exposure of model plantations at elevated atmospheric CO2 (550 ppm) on soil respiration under natural conditions has been studied using an automated FreeAir CO2 Enrichment (FACE) system at the Hokkaido University, Japan. In the course of the experiment, an attempt has been made to simulate the effect of forthcoming climate change on the process of CO2 emission from different soil types. Keywords: elevated atmospheric CO2, Free Air CO2 Enrichment (FACE), soil respiration, CO2 emission, soil temperature, soil moisture. DOI: 10.1134/S1067413611060099
Since the start of industrial revolution, atmo spheric CO2 concentration ([CO2]) has been exponen tially rising to its current level of 370 ppm due mainly to human activities (Zimov et al., 1999). According to predictions (IPCC, 1995), this parameter will increase twofold during the 21st century, with consequent changes in the structure and functioning of ecosystems (Kondrashova, Kobak, and Turchinovich, 1993). The role of forest ecosystems in the carbon cycle, including its potential for carbon sequestration, is a focus of many ecophysiological studies. Experiments with growth chambers, greenhouses, and FreeAir СО2 Enrichment (FACE) systems show that elevated [CO2] has an effect on biological processes at different orga nization levels, including primary molecular, physio logical, and ecosystem responses.
elevated [CO2], the more so that components of soil respiration may differently respond to this factor, which is a hindrance to the modeling of soil respira tion response in an ecosystem. This problem needs further analysis. This study deals with the assessment of soil respira tion in a model forest ecosystem under natural condi tions at elevated [СО2], which were simulated using an automated FACE system at the University of Hok kaido, Japan. The data obtained in such experiments are necessary for elaborating models predicting the response of vegetation to climate change. The pur poses of the study were as follows: (1) to determine how soil type influences СО2 emission under condi tions of elevated [CO2] = 550 ppm, and (2) to estimate the effect of elevated [СО2] = 550 ppm on micromete orological conditions and soil СО2 emission during the growing season.
The basic direct effect of elevated [CO2] on forest ecosystems consists in activation of growth and pro duction processes. Production increases because ele vated [CO2] stimulates photosynthesis and consequent carbon assimilation by plants, which may eventually result in increased carbon deposition in terrestrial eco systems. The effect of [CO2] on the expenditure part of the ecosystem carbon budget is not direct but medi ated through ecosystem productivity, and it has not been studied sufficiently. For example, elevated [CO2] has been shown to enhance soil respiration in forest ecosystems by stimulating fine root production (Matamala and Schlesinger, 2000) and biological activity of soil microbiota (Blagodatsky et al., 2006). Butnor et al. (2003) revealed a reduction of soil СО2 fluxes under conditions of elevated [CO2] because of impairment in the quality of forest litter. It is unclear how soil СО2 fluxes will change under conditions of
MATERIAL AND METHODS The study region is characterized by plain topogra phy and dominance of brown forest soil with poor sea sonal drainage. Its density in the upper layer (0– 20 cm) is 1.07 g/cm3, pH 4.7–5.0. Soil properties are fairly uniform throughout the region, with absorbing roots concentrating in the upper 20cm soil layer. The annual average air temperature and precipitation reach 9.4°C and 680 mm (Koike et al., 2001). The automated FACE system (Fig. 1), designed after the system at the Stillberg site, Switzerland (Hat tenschwiler et al., 2002), is located in the experimental nursery of the University of Hokkaido (43°N, 141°E, 17 m a.s.l.). The system is not isolated from the exter 24
SOIL RESPIRATION IN MODEL PLANTATIONS
nal environment, which allows plants to grow under real microclimatic conditions but at the [СО2] pre dicted for the near future. The experiment of atmo spheric air enrichment with СО2 was started in 2003 and continued 4 years. Three circular FACE plots were established (diameter 7 m, the height of СО2 delivery system 5 m), where [СО2] = 550 ppm (predicted for the year 2040) was maintained during the day. Three similar plots with normal [СО2] = 370 ppm were used in the control. Air enrichment with CO2 was usually stopped in late November, after leaf fall, and resumed in the next May, before the emergence of leaves. Nei ther irrigation nor fertilizer treatment was practiced during the experiment. Two soils were tested in the experiment, each cov ering half of a FACE or control plot. One was volcan ogenic oligotrophic soil deficient in phosphorus (Regosol in the FAO classification system) delivered from a Japanese larch stand in the Tomakomai National Forest (42°N, 141°E) in the autumn of 2002. The other was local, fertile brown forest soil (Cambisol in the FAO classification). The N, P, and K contents were higher in the brown forest soil, with the N con tent averaging 0.30 mg/g vs. 0.14 mg/g in the volcano genic soil (Eguchi et al., 2005). In May 2003, all plots were planted with the same set of 2year plants of 11 woody species typical for temperate regions of Japan. They differed in succes sional parameters, forming groups characterized by fast growth (Betula platyphylla var. japonica Hara, Alnus hirsuta Turcz., B. maximowicziana Regel, Larix kaempferi Carr.), moderate growth (Fraxinus mand shurica var. japonica Maxim., Quercus mongolica var. grosseserrata Rehd., Kalopanax pictus Nakai, Ulmus daviaiana var. japonica Nakai), and slow growth (Tilia japonica Simonkai, Acer mono Maxim., Fagus crenata Blume). To avoid the edge effect, the same species were also planted outside the plots (Eguchi et al., 2005). Soil respiration was measured using a Li6400 IR gas analyzer equipped with a Li600009 soil respira tion chamber (LI600009 LiCor Bioscience, United States). Measurements were made in July, August, and October (after the active growth period) of 2005. In each plot, six soil rings (10 cm in diameter and 6 cm high) were set in the mineral soil of each type to a depth of 2.5 in a random pattern (a total of 216 rings). Experimental variants were as follows: (1) [СО2] = 370 ppm + volcanogenic soil; (2) [СО2] = 550 ppm + volcanogenic soil; (3) [СО2] = 370 ppm + brown for est soil; and (4) [СО2] = 550 ppm + brown forest soil. Since the soil respiration chamber had a temperature sensor, soil temperature at a depth of 5 cm was mea sured simultaneously with soil respiration. After these measurements, the upper 5cm layer was removed from the ring to analyze soil moisture. The effect of elevated [СО2] on root biomass and respiration remained beyond the scope of this study, because the FACE experiment was planned as a longterm project. RUSSIAN JOURNAL OF ECOLOGY
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Wind direction
25
FACE3
FACE1
Control
FACE2 N 25 m
Fig. 1. Scheme of experiment: control and FACE plots (kindly provided by Prof. T. Koike).
Thus, we studied the effects of three factors: soil type, [СО2], and the stage of the growing period. Data were processed statistically with the Statistica 7.0 pro gram package (StatSoft Inc., United States), using Tukey’s HSD test to estimate the significance of dif ferences between experimental variants. RESULTS AND DISCUSSION Effect of [СО2] on soil respiration. Elevated [СО2] = 550 ppm proved to have a significant effect on soil respiration (Fig. 2a), especially in summer months. Thus, soil respiration in July and August was increased by a factor of 1.5–2 under such conditions (p < 0.05, Tukey’s HSD test = 0.00003–0.007), but in October it did not differ significantly from the control level. Elevated [СО2] stimulated soil respiration within the range of values (15–70%) recorded by other researchers (Zak et al., 2000). Since experimental design excluded sampling of root systems for biomass analysis, it was difficult to determine which exactly soil processes (root respira tion or microbial respiration) accounted for the response of soil respiration to the increase in [СО2]. However, the authors of many publications note that elevated [СО2] promotes the growth of root biomass (Johnson et al., 1994; Matamala and Schlesinger, 2000). A strong positive correlation between root res piration and root biomass has been revealed (Johnson et al., 1994). As our model plantations were at the stage of development (5 years of age in 2005), the observed intensification of soil respiration at [СО2] = 550 ppm could be accounted for by an increase in root biomass. 2012
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MASYAGINA, KOIKE Soil respiration, µmol CO2 m2 per sec. 10 (a) 3 8
Soil moisture, % 28
4
(б)
21
2
6
14 1
4
7
2
0
0
Soil temperature,°C 25
July
August
October
(c)
20
15
0 July
August
October
Fig. 2. (a) Soil respiration, (b) mineral soil moisture, and (c) soil temperature depending on soil type (VS, volcanogenic soil; BFS, brown forest soil) and atmospheric CO2 concentration (370 or 550 ppm) during the growing season: (1) VS, 370 ppm; (2) BFS, 370 ppm; (3) VS, 550 ppm; (4) BFS, 550 ppm.
Soil respiration dynamics during the growing sea son. At [СО2] = 550 ppm, respiration of the volcano genic soil varied from 2.4 to 13.9 µmol СО2 /m2 per sec (averaging 7.3 ± 0.4 µmol CO2/m2 per sec over the sea son); at normal [СО2], from 1.2 to 10.0 (4.4 ± 0.3) µmol СО2/m2 per sec (Fig. 2a). For the brown for est soil, the respective values were 1.2 to 13.1 (5.8 ± 0.4) µmol СО2/m2 per sec and 0.8 to 10.8 (4.4 ± 0.3) µmol СО2 /m2 per sec. These data well agree with the values of soil respiration obtained by Masyagina, Prokushkin, and Koike (2010) for larch forests: 5.6– 12.1 µmol CO2/m2 per sec. Changes in soil respiration under conditions of normal and elevated [CO2] gener ally conformed to the seasonal course of air tempera ture: an increase in July to August followed by a decrease in August to October (Figs. 2a, 2c).
Mineral soil temperature and moisture. Monthly average soil temperature varied from 14 to 22°C during the growing season (Fig. 2c). Soil type and [CO2] had no significant effect on its dynamics, in agreement with data reported by other authors (Butnor et al., 2003). This parameter proved to increase 1.1fold in July to August (p < 0.05, Tukey’s HSD test = 0.00002– 0.0003) and then decreased 1.5fold in August to October (p < 0.05, Tukey’s’ HSD test = 0.00002). Mineral soil moisture varied from 7 to 24% during the growing season (Fig. 2b) and strongly depended on soil type (p < 0.05, Tukey’s HSD test = 0.00002), always being 1.5–2.8 times lower in the volcanogenic than in the brown forest soil. Differences between the soil types were more distinct at elevated [СО2] = 550 ppm, where the volcanogenic soil proved to contained 1.5 times
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Results of correlation analysis of the relationship between soil respiration at different atmospheric CO2 concentrations and soil hydrothermal parameters Soil respiration vs. soil moisture [CO2], ppm
Soil respiration vs. soil temperature
Soil type* r
p
N
r
p
N
July 370 550
VS
0.31
0.21
18
0.15
0.15
18
BFS
0.10
0.70
18
–0.08
0.76
18
VS
–0.57**
0.02
18
–0.67**
0.002
18
BFS
–0.27
0.27
18
–0.26
0.31
18
August 370 550
VS
0.22
0.38
18
0.07
0.78
18
BFS
0.14
0.58
18
–0.02
0.95
18
VS
0.35
0.16
18
–0.15
0.55
18
–0.53**
0.02
18
–0.07
0.78
18
BFS
October 370 550
VS
0.44
0.07
18
0.44
0.07
18
BFS
–0.59**
0.01
18
–0.24
0.34
18
VS
–0.22
0.39
18
0.27
0.28
18
BFS
–0.09
0.72
18
–0.34
0.16
18
Notes: * VS, volcanogenic soil; BFS, brown forest soil. ** Correlations (r) are significant at p < 0.05.
less moisture than under normal conditions (p < 0.05, Tukey’s HSD test = 0.003–0.006). Respiration depending on soil type and hydrother mal conditions. Respiration at different [СО2] showed no dependence on soil type. Although soil tempera ture changed significantly during the growing season, a correlation between soil respiration and temperature was revealed only for the volcanogenic soil in July (table). On the other hand, a soil respiration showed a significant correlation with soil moisture; i.e., soil moisture proved to be a key factor controlling soil res piration. Thus, the monthly average values of soil СО2 flux at [СО2] = 550 ppm varied from 6.0 to 8.9 µmol/m2 per sec in the volcanogenic soil and from 3.6 to 7.4 µmol/m2 per sec in the brown forest soil, being 1.5–2 times higher than at normal [СО2] = 370 ppm. Elevated [СО2] had an especially strong effect on moisture content in the volcanogenic soil, which was decreased 1.5fold compared to the normal level. Soil temperature was independent of [СО2], and soil respi ration showed no dependence on soil type during the study period. Consistent and strong stimulation of soil respiration was observed at [СО2] = 550 ppm. This fact suggests that in the future, when the climate changes, forest at the stage of development will quickly contrib RUSSIAN JOURNAL OF ECOLOGY
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ute additional amounts of СО2 to the carbon cycle due to intensification of photosynthesis and shortterm carbon deposition in the soil, with this process being likely to be stabilized upon tree stand maturation. ACKNOWLEDGMENTS The authors are grateful to L. Qu (Hokkaido Uni versity) for help in preparing the experiment. This study was supported by the Ministry of the Environment of Japan, project no. B01. REFERENCES Blagodatsky, S.A., Blagodatskaya, E.V., Andereson, T.H., and Weigel, H.J., Kinetics of the Respiratory Response of the Soil and Rhizosphere Microbial Communities in a Field Experiment with an Elevated Concentration of Atmo spheric CO2, Eurasian Soil Sci., 2006, no. 3, pp. 290–297. Butnor, J.R., Johnsen, K.H., Oren, R., and Katul, G.G., Reduction of Forest Floor Respiration by Fertilization on Both Carbon DioxideEnriched and Reference 17Year Old Loblolly Pine Stands, Global Change Biol., 2003, vol. 9, pp. 849–861. Eguchi, N., Funada, R., Ueda, T., et al., Soil Moisture Condition and Growth of Deciduous Tree Seedlings Native to Northern Japan Grown under Elevated CO2 with a FACE System, Phyton, 2005, vol. 45, pp. 133–138. 2012
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Hättenschwiler, S., Handa, T., Egli, L., et al., Atmospheric CO2 Enrichment of Alpine Treeline Conifers, New Phytol., 2002, vol. 156, pp. 363–375. IPCC, Radiative Forcing of Climate Change and an Evaluation of the IPCC 1992IS92 Emission Scenarios, Houghton, J.T., Ed., Cambridge: Cambridge Univ. Press, 1995. Johnson, D.W., Geisinger, D.R., Walker, R.F., et al., Soil pCO2, Soil Respiration, and Root Activity in CO2Fumi gated and Nitrogen Fertilized Ponderosa Pine, Plant Soil, 1994, vol. 165, pp. 129–138. Koike, T., Hojyo, H., Naniwa, A., et al., Basic Data for CO2 Flux Monitoring of a Young Larch Plantation: Current Sta tus of a Mature, Mixed ConiferBroadleaf Forest Stand, Eur. J. For. Res., 2001, vol. 2, pp. 65–79. Kondrashova, N.Yu., Kobak, K.I., and Turchinovich, I.E., Probable Responses of Terrestrial Vegetation to the Increas
ing Concentration of Atmospheric CO2 and Global Warm ing, Lesovedenie, 1993, no. 4, pp. 71–76. Masyagina, O.V., Prokushkin, S.G., and Koike, T., The Influence of Thinning on the Ecological Conditions and Soil Respiration in a Larch Forest on Hokkaido Island, Eurasian Soil Sci., 2010, vol. 43, pp. 693–700. Matamala, R. and Schlesinger, W.H., Effects of Elevated Atmospheric CO2 on Fine Root Production and Activity in an Intact Temperate Forest Ecosystem, Global Change Biol., 2000, vol. 6, pp. 967–979. Zak, D.R., Pregitzer, K.S., King, J.S., and Holmes, W.E., Elevated Atmospheric CO2, Fine Roots, and the Response of Soil Microorganisms: A Review and Hypothesis, New Phytol., 2000, vol. 147, pp. 201–222. Zimov, S.A., Davidov, S.P., Zimova, G.M., et al., Contribu tion of Disturbance to Increasing Seasonal Amplitude of Atmospheric CO2, Science, 1999, vol. 284, pp. 1973–1976.
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