To evaluate the diurnal and seasonal variations in soil respiration(Rs) and understand the controlling factors, we measured carbon dioxide(CO2) fluxes and their environmental variables using a LI-6400 soil CO2 flux sy...To evaluate the diurnal and seasonal variations in soil respiration(Rs) and understand the controlling factors, we measured carbon dioxide(CO2) fluxes and their environmental variables using a LI-6400 soil CO2 flux system at a temperate Leymus chinensis meadow steppe in the western Songnen Plain of China in the growing season(May–October) in 2011 and 2012. The diurnal patterns of soil respiration could be expressed as single peak curves, reaching to the maximum at 11:00–15:00 and falling to the minimum at 21:00–23:00(or before dawn). The time-window between 7:00 and 9:00 could be used as the optimal measuring time to represent the daily mean soil CO2 efflux. In the growing season, the daily value of soil CO2 efflux was moderate in late spring(1.06–2.51 μmol/(m2·s) in May), increased sharply and presented a peak in summer(2.95–3.94 μmol/(m2·s) in July), and then decreased in autumn(0.74–0.97 μmol/(m2·s) in October). Soil temperature(Ts) exerted dominant control on the diurnal and seasonal variations of soil respiration. The temperature sensitivity of soil respiration(Q10) exhibited a large seasonal variation, ranging from 1.35 to 3.32, and decreased with an increasing soil temperature. Rs gradually increased with increasing soil water content(Ws) and tended to decrease when Ws exceeded the optimum water content(27%) of Rs. The Ts and Ws had a confounding effect on Rs, and the two-variable equations could account for 72% of the variation in soil respiration(p < 0.01).展开更多
Soil respiration from decomposing aboveground litter is a major component of the terrestrial carbon cycle.However,variations in the contribution of aboveground litter to the total soil respiration for stands of varyin...Soil respiration from decomposing aboveground litter is a major component of the terrestrial carbon cycle.However,variations in the contribution of aboveground litter to the total soil respiration for stands of varying ages are poorly understood.To assess soil respiration induced by aboveground litter,treatments of litter and no litter were applied to 5-,10-,and 20-year-old stands of Populus davidiana Dode in the sandstorm source area of Beijing -Tianjin,China.Optimal nonlinear equations were applied to model the combined effects of soil temperature and soil water content on soil respiration.Results showed that the monthly average contribution of aboveground litter to total soil respiration were 18.46% ± 4.63%,16.64% ± 9.31%,and 22.37% ± 8.17% for 5-,10-,and 20-year-old stands,respectively.The relatively high contribution in 5-and 20-year-old stands could be attributed to easily decomposition products and high accumulated litter,respectively.Also,it fluctuated monthly for all stand ages due to substrate availability caused by phenology and environmental factors.Litter removal significantly decreased soil respiration and soil water content for all stand ages(p < 0.05) but not soil temperature(p > 0.05).Variations of soil respiration could be explained by soil temperature at 5-cm depth using an exponential equation and by soil water content at 10-cm depth using a quadratic equation,whereas soil respiration was better modeled using the combined parameters of soil temperature and soil water content than with either soil temperature or soil water content alone.Temperature sensitivity(Q_(10))increased with stand age in both the litter and the no litter treatments.Considering the effects of aboveground litter,this study provides insights for predicting future soil carbon fluxes and for accurately assessing soil carbon budgets.展开更多
Soil respiration(SR) is the second-largest flux in ecosystem carbon cycling. Due to the large spatio-temporal variability of environmental factors, SR varied among different vegetation types, thereby impeding accurate...Soil respiration(SR) is the second-largest flux in ecosystem carbon cycling. Due to the large spatio-temporal variability of environmental factors, SR varied among different vegetation types, thereby impeding accurate estimation of CO_2 emissions via SR. However, studies on spatio-temporal variation of SR are still scarce for semi-arid regions of North China. In this study, we conducted 12-month SR measurements in six land-use types, including two secondary forests(Populus tomentosa(PT) and Robinia pseudoacacia(RP)), three artificial plantations(Armeniaca sibirica(AS), Punica granatum(PG) and Ziziphus jujuba(ZJ)) and one natural grassland(GR), to quantify spatio-temporal variation of SR and distinguish its controlling factors. Results indicated that SR exhibited distinct seasonal patterns for the six sites. Soil respiration peaked in August 2012 and bottomed in April 2013. The temporal coefficient of variation(CV) of SR for the six sites ranged from 76.98% to 94.08%, while the spatial CV of SR ranged from 20.28% to 72.97% across the 12-month measurement. Soil temperature and soil moisture were the major controlling factors of temporal variation of SR in the six sites, while spatial variation in SR was mainly caused by the differences in soil total nitrogen(STN), soil organic carbon(SOC), net photosynthesis rate, and fine root biomass. Our results show that the annual average SR and Q_(10)(temperature sensitivity of soil respiration) values tended to decrease from secondary forests and grassland to plantations, indicating that the conversion of natural ecosystems to man-made ecosystems may reduce CO_2 emissions and SR temperature sensitivity. Due to the high spatio-temporal variation of SR in our study area, care should be taken when converting secondary forests and grassland to plantations from the point view of accurately quantifying CO_2 emissions via SR at regional scales.展开更多
No consistent variation was found in soil respiration Q10 under various O2 conditions.Substrate C quality had a strong effect on Q10 in oxic soils.N limitation had a large impact on Q10 in soils under O2 limitation.Cu...No consistent variation was found in soil respiration Q10 under various O2 conditions.Substrate C quality had a strong effect on Q10 in oxic soils.N limitation had a large impact on Q10 in soils under O2 limitation.Current studies on the temperature sensitivity(Q10)of soil organic matter(SOM)decomposition mainly focus on aerobic conditions.However,varia-tions and determinants of Q10 in oxygen(O2)-deprived soils remain unclear.Here we incubated three grassland soils under oxic,suboxic,and anoxic conditions subjected to varying temperatures to compare variations in Q10 in relation to changing substrates.No consistent variation was found in Q10 under various O2 conditions.Further analysis of edaphic properties demon-strated that substrate carbon quality showed a strong influence on Q10 in oxic soils,whereas nitrogen limitation played a more important role in suboxic and anoxic soils.These results suggest that substrate carbon quality and nitrogen limitation may play roles of varying importance in determining the temperature sensitivity of SOM decomposition under various O2 conditions.展开更多
Recent studies on alkaline soils of arid areas suggest a possible contribution of abiotic exchange to soil CO2 flux(Fc).However,both the overall contribution of abiotic CO2 exchange and its drivers remain unknown.He...Recent studies on alkaline soils of arid areas suggest a possible contribution of abiotic exchange to soil CO2 flux(Fc).However,both the overall contribution of abiotic CO2 exchange and its drivers remain unknown.Here we analyzed the environmental variables suggested as possible drivers by previous studies and constructed a function of these variables to model the contribution of abiotic exchange to Fc in alkaline soils of arid areas.An automated flux system was employed to measure Fc in the Manas River Basin of Xinjiang Uygur autonomous region,China.Soil pH,soil temperature at 0–5 cm(Ts),soil volumetric water content at 0–5 cm(θs)and air temperature at10 cm above the soil surface(Tas)were simultaneously analyzed.Results highlight reduced sensitivity of Fc to Ts and good prediction of Fc by the model Fc=R10Q10(Tas–10)/10+r7q7(pH–7)+λTas+μθs+e which represents Fc as a sum of biotic and abiotic components.This presents an approximate method to quantify the contribution of soil abiotic CO2 exchange to Fc in alkaline soils of arid areas.展开更多
Microbial metabolic quotient(MMQ) is the rate of soil microbial respiration per unit of microbial biomass, and represents the capacity of soil microbes to utilize soil organic matter.Understanding the regional variati...Microbial metabolic quotient(MMQ) is the rate of soil microbial respiration per unit of microbial biomass, and represents the capacity of soil microbes to utilize soil organic matter.Understanding the regional variation and determinants of MMQ can help predict the responses of soil respiration rate to global climate change.Accordingly, we measured and analyzed MMQ-related data(e.g., soil basic respiration rate at 20℃ and soil microbial biomass) from 17 grassland sites, which located in meadow steppe, typical steppe, and desert steppe along a 1000-km transect across the Inner Mongolian grasslands, China.Results showed that MMQ varied significantly among the different grassland types(P < 0.05;desert > typical > meadow) and decreased from southwest to northeast(r =–0.81) with increasing latitude(r = – 0.50), and with increasing mean annual precipitation(r = –0.69).Precipitation accounted for 56% of the total variation in MMQ, whereas temperature accounted for 26%.MMQ was negatively correlated with precipitation across the Inner Mongolian grasslands.Therefore, climate change, especially in regard to precipitation, may influence soil microbial respiration and soil carbon dynamics through altering MMQ.These results highlighted the importance of spatial patterns in MMQ for accurately evaluating the responses of soil respiration to climate change at regional and global scales.展开更多
Soil respiration(Rs)plays an important role in regulating carbon cycle of terrestrial ecosystems and presents temporal and spatial heterogeneity.Abies nephrolepis is a tree species that prefers the cold and wet enviro...Soil respiration(Rs)plays an important role in regulating carbon cycle of terrestrial ecosystems and presents temporal and spatial heterogeneity.Abies nephrolepis is a tree species that prefers the cold and wet environment and is mainly distributed in Northeast Asia and East Asia.The Rs variations of Abies nephrolepis forests communities are generally environmental-sensitive and can effectively reflect the adaptive responses of forest ecosystems to climate change.In this study,the growing-seasonal variations of Rs,soil temperature,soil water content and soil properties of Abies nephrolepis forests were analyzed along an altitude gradient(2000,2100,2200 and 2300 m)over two years on Wutai Mountain in North China.As the main results showed,soil respiration keeps the same change trend as soil temperature and reached peaks in July at 2000 m in 2019 and 2020.During 26th July to 25th October in 2019 and 27th May to 23rd October in 2020,on the whole,the soil temperature independently explained 76.2%of Rs variations while the soil water content independently explained 26.8%.Soil temperature and soil water content jointly explained 81.8%of Rs variations.Soil properties explained 61.8%and 69.6%of Rs variation in 2019 and 2020,respectively.Soil organic carbon content and soil enzyme activity had the signifi-cant(P<0.01)negative and positive relationships,respectively,with Rs variation.With altitudes evaluated from 2000 to 2300 m,soil respiration temperature sensitivity(Q10)and the soil organic carbon content increased by 12.4%and 10.4%,respectively,while invertase activity,cellulase activity and urease activity dropped by 41.2%,29.45%and 38.19%,respectively.The results demonstrate that(1)soil temperature is the major factor affecting Rs variations in Abies nephrolepis forests;(2)weakened microbial carbon metabolism in high-altitude areas results in the accumulation of soil organic carbon;(3)with a higher Q10,forest ecosystems in high-altitude areas might be more easily affected by climate change;(4)climate warming might accelerate the consumption of soil organic carbon sink in forest ecosystems,especially in high-altitude areas.展开更多
Temperature sensitivity of soil respiration (Q10) is an important parameter in modeling the effects of global warming on ecosystem carbon release. Experimental studies of soil respiration have ubiquitously indicated t...Temperature sensitivity of soil respiration (Q10) is an important parameter in modeling the effects of global warming on ecosystem carbon release. Experimental studies of soil respiration have ubiquitously indicated that Q10 has high spatial heterogeneity. However, most biogeochemical models still use a constant Q10 in projecting future climate change and no spatial pattern of Q10 values at large scales has been derived. In this study, we conducted an inverse modeling analysis to retrieve the spatial pattern of Q10 in China at 8 km spatial resolution by assimilating data of soil organic carbon into a proc-ess-based terrestrial carbon model (CASA model). The results indicate that the optimized Q10 values are spatially heterogeneous and consistent to the values derived from soil respiration observations. The mean Q10 values of different soil types range from 1.09 to 2.38, with the highest value in volcanic soil, and the lowest value in cold brown calcic soil. The spatial pattern of Q10 is related to environmental factors, especially precipitation and top soil organic carbon content. This study demonstrates that inverse modeling is a useful tool in deriving the spatial pattern of Q10 at large scales, with which being incorporated into biogeochemical models, uncertainty in the projection of future carbon dynamics could be potentially reduced.展开更多
Salinity stress is one of the critical environmental drivers of soil organic matter(SOM)decomposition in coastal ecosystems.Although the temperature sensitivity(Q_(10))of SOM decomposition has been widely applied in E...Salinity stress is one of the critical environmental drivers of soil organic matter(SOM)decomposition in coastal ecosystems.Although the temperature sensitivity(Q_(10))of SOM decomposition has been widely applied in Earth system models to forecast carbon processes,the impact of salinity on SOM decomposition by restructuring microbial communities remains uncovered.Here,we conducted a microcosm experiment with soils collected from the coastal salt marsh in the Yellow River Estuary,which is subjected to strong dynamics of salinity due to both tidal flooding and drainage.By setting a gradient of salt solutions,soil salinity was adjusted to simulate salinity stress and soil carbon emission(CO_(2))rate was measured over the period.Results showed that as salinity increased,the estimated decomposition constants based on first-order kinetics gradually decreased at different temperatures.Below the 20‰salinity treatments,which doubled the soil salinity,Q_(10)increased with increasing salinity;but higher salinity constrained the temperature-related response of SOM decomposition by inhibiting microbial growth and carbon metabolisms.Soil bacteria were more sensitive to salinity stress than fungi,which can be inferred from the response of microbial beta-diversity to changing salinity.Among them,the phylotypes assigned to Gammaproteobacteria and Bacilli showed higher salt tolerance,whereas taxa affiliated with Alphaproteobacteria and Bacteroidota were more easily inhibited by the salinity stress.Several fungal taxa belonging to Ascomycota had higher adaptability to the stress.As the substrate was consumed with the incubation,bacterial competition intensified,but the fungal co-occurrence pattern changed weakly during decomposition.Collectively,these findings revealed the threshold effect of salinity on SOM decomposition in coastal salt marshes and emphasized that salt stress plays a key role in carbon sequestration by regulating microbial keystone taxa,metabolisms,and interactions.展开更多
Soil respiration (SR) is commonly modeled by a Q10 (an indicator of temperature sensitivity) function in ecosystem models. Q10 is usually treated as a constant of 2 in these models, although Q10 value of SR often ...Soil respiration (SR) is commonly modeled by a Q10 (an indicator of temperature sensitivity) function in ecosystem models. Q10 is usually treated as a constant of 2 in these models, although Q10 value of SR often decreases with increasing temperatures. It remains unclear whether a general temperature- dependent Q10 model of SR exists at biome and global scale. In this paper, we have compiled the long-term Q10 data of 38 SR studies ranging from the Boreal, Temperate, to Tropical/Sublropical biome on four continents. Our analysis indicated that the general temperature-dependent biome Q10 models of SR existed, especially in the Boreal and Temperate biomes. A single-exponential model was better than a simple linear model in fitting the average Q10 values at the biome scale. Average soil temperature is a better predictor of Q10 value than average air temperature in these models, especially in the Boreal biome. Soil temperature alone could explain about 50% of the Q10 variations in both the Boreal and Temperate biome single-exponential Q10 model. Q10 value of SR decreased with increasing soil temperature but at quite different rates among the three biome Q10 models. The k values (Q10 decay rate constants) were 0.09, 0.07, and 0.02/℃ in the Boreal, Temperate, and Tropical/Subtropical biome, respectively, suggesting that Q10 value is the most sensitive to soil temperature change in the Boreal biome, the second in the Temperate biome, and the least sensitive in the Tropical/ Subtropical biome. This also indirectly confirms that acclimation of SR in many soil warming experiments probably occurs. The k value in the "global" single-exponential Q10 model which combined both the Boreal and Temperate biome data set was 0.08/℃. However, the global general temperature-dependent Q10 model developed using the data sets of the three biomes is not adequate for predicting Q10 values of SR globally. The existence of the general temperature-dependent Q10 models of SR in the Boreal and Temperate biome has important implications for modeling SR, especially in the Boreal biome. More detail model runs are needed to exactly evaluate the impact of using a fixed Q10 vs a temperature-dependent Q10 on SR estimate in ecosystem models (e.g., TEM, Biome-BGC, and PnET).展开更多
The spatial and temporal variations in soil respiration and its relationship with biophysical factors In forests near the Tropic of Cancer remain highly uncertain. To contribute towards an Improvement of actual estima...The spatial and temporal variations in soil respiration and its relationship with biophysical factors In forests near the Tropic of Cancer remain highly uncertain. To contribute towards an Improvement of actual estimates, soil respiration rates, soil temperature, and soil moisture were measured In three successional subtropical forests at the Dlnghuahan Nature Reserve (DNR) In southern China from March 2003 to February 2005. The overall objective of the present study was to analyze the temporal variations of soil respiration and Its biophysical dependence in these forests. The relationships between biophysical factors and soil respiration rates were compared In successional forests to test the hypothesis that these forests responded similarly to biophysical factors. The seasonality of soil respiration coincided with the seasonal climate pattern, with high respiration rates in the hot humid season (April-September) and with low rates In the cool dry season (October-March). Soil respiration measured at these forests showed a clear Increasing trend with the progressive succession. Annual mean (± SD) soil respiration rate In the DNR forests was (9.0 ± 4.6) Mg CO2-C/hm^2 per year, ranging from (6.1 ± 3.2) Mg CO2-C/hm^2 per year in early successional forests to (10.7 ± 4.9) Mg CO2-C/hm^2 per year in advanced successional forests. Soil respiration was correlated with both soil temperature and moisture. The T/M model, where the two biophysical variables are driving factors, accounted for 74%-82% of soil respiration variation In DNR forests. Temperature sensitivity decreased along progressive succession stages, suggesting that advanced-successional forests have a good ability to adjust to temperature. In contrast, moisture Increased with progressive succession processes. This increase is caused, in part, by abundant respirators In advanced-successional forest, where more soil moisture is needed to maintain their activities.展开更多
基金Under the auspices of Special Fund for Agro-scientific Research in Public Interest,China(No.201303095-8)National Natural Science Foundation of China(No.31100403,41101207)+1 种基金National Basic Research Program of China(No.2013CB430401)Key Laboratory of Mollisols Agroecology,Northeast Institute of Geography and Agroecology,Chinese Academy of Sciences
文摘To evaluate the diurnal and seasonal variations in soil respiration(Rs) and understand the controlling factors, we measured carbon dioxide(CO2) fluxes and their environmental variables using a LI-6400 soil CO2 flux system at a temperate Leymus chinensis meadow steppe in the western Songnen Plain of China in the growing season(May–October) in 2011 and 2012. The diurnal patterns of soil respiration could be expressed as single peak curves, reaching to the maximum at 11:00–15:00 and falling to the minimum at 21:00–23:00(or before dawn). The time-window between 7:00 and 9:00 could be used as the optimal measuring time to represent the daily mean soil CO2 efflux. In the growing season, the daily value of soil CO2 efflux was moderate in late spring(1.06–2.51 μmol/(m2·s) in May), increased sharply and presented a peak in summer(2.95–3.94 μmol/(m2·s) in July), and then decreased in autumn(0.74–0.97 μmol/(m2·s) in October). Soil temperature(Ts) exerted dominant control on the diurnal and seasonal variations of soil respiration. The temperature sensitivity of soil respiration(Q10) exhibited a large seasonal variation, ranging from 1.35 to 3.32, and decreased with an increasing soil temperature. Rs gradually increased with increasing soil water content(Ws) and tended to decrease when Ws exceeded the optimum water content(27%) of Rs. The Ts and Ws had a confounding effect on Rs, and the two-variable equations could account for 72% of the variation in soil respiration(p < 0.01).
基金funded by the National Natural Science Foundation of China (Grant No.31170414)the 100 Talents Program of Chinese Academy of Sciences,and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No.XDA05060600)
文摘Soil respiration from decomposing aboveground litter is a major component of the terrestrial carbon cycle.However,variations in the contribution of aboveground litter to the total soil respiration for stands of varying ages are poorly understood.To assess soil respiration induced by aboveground litter,treatments of litter and no litter were applied to 5-,10-,and 20-year-old stands of Populus davidiana Dode in the sandstorm source area of Beijing -Tianjin,China.Optimal nonlinear equations were applied to model the combined effects of soil temperature and soil water content on soil respiration.Results showed that the monthly average contribution of aboveground litter to total soil respiration were 18.46% ± 4.63%,16.64% ± 9.31%,and 22.37% ± 8.17% for 5-,10-,and 20-year-old stands,respectively.The relatively high contribution in 5-and 20-year-old stands could be attributed to easily decomposition products and high accumulated litter,respectively.Also,it fluctuated monthly for all stand ages due to substrate availability caused by phenology and environmental factors.Litter removal significantly decreased soil respiration and soil water content for all stand ages(p < 0.05) but not soil temperature(p > 0.05).Variations of soil respiration could be explained by soil temperature at 5-cm depth using an exponential equation and by soil water content at 10-cm depth using a quadratic equation,whereas soil respiration was better modeled using the combined parameters of soil temperature and soil water content than with either soil temperature or soil water content alone.Temperature sensitivity(Q_(10))increased with stand age in both the litter and the no litter treatments.Considering the effects of aboveground litter,this study provides insights for predicting future soil carbon fluxes and for accurately assessing soil carbon budgets.
基金Under the auspices of Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA05060600)National Natural Science Foundation of China(No.51378306)
文摘Soil respiration(SR) is the second-largest flux in ecosystem carbon cycling. Due to the large spatio-temporal variability of environmental factors, SR varied among different vegetation types, thereby impeding accurate estimation of CO_2 emissions via SR. However, studies on spatio-temporal variation of SR are still scarce for semi-arid regions of North China. In this study, we conducted 12-month SR measurements in six land-use types, including two secondary forests(Populus tomentosa(PT) and Robinia pseudoacacia(RP)), three artificial plantations(Armeniaca sibirica(AS), Punica granatum(PG) and Ziziphus jujuba(ZJ)) and one natural grassland(GR), to quantify spatio-temporal variation of SR and distinguish its controlling factors. Results indicated that SR exhibited distinct seasonal patterns for the six sites. Soil respiration peaked in August 2012 and bottomed in April 2013. The temporal coefficient of variation(CV) of SR for the six sites ranged from 76.98% to 94.08%, while the spatial CV of SR ranged from 20.28% to 72.97% across the 12-month measurement. Soil temperature and soil moisture were the major controlling factors of temporal variation of SR in the six sites, while spatial variation in SR was mainly caused by the differences in soil total nitrogen(STN), soil organic carbon(SOC), net photosynthesis rate, and fine root biomass. Our results show that the annual average SR and Q_(10)(temperature sensitivity of soil respiration) values tended to decrease from secondary forests and grassland to plantations, indicating that the conversion of natural ecosystems to man-made ecosystems may reduce CO_2 emissions and SR temperature sensitivity. Due to the high spatio-temporal variation of SR in our study area, care should be taken when converting secondary forests and grassland to plantations from the point view of accurately quantifying CO_2 emissions via SR at regional scales.
基金supported by the National Key Research and Development Program of China(No.2019YFA0607303)the National Natural Science Foundation of China(No.42107315).
文摘No consistent variation was found in soil respiration Q10 under various O2 conditions.Substrate C quality had a strong effect on Q10 in oxic soils.N limitation had a large impact on Q10 in soils under O2 limitation.Current studies on the temperature sensitivity(Q10)of soil organic matter(SOM)decomposition mainly focus on aerobic conditions.However,varia-tions and determinants of Q10 in oxygen(O2)-deprived soils remain unclear.Here we incubated three grassland soils under oxic,suboxic,and anoxic conditions subjected to varying temperatures to compare variations in Q10 in relation to changing substrates.No consistent variation was found in Q10 under various O2 conditions.Further analysis of edaphic properties demon-strated that substrate carbon quality showed a strong influence on Q10 in oxic soils,whereas nitrogen limitation played a more important role in suboxic and anoxic soils.These results suggest that substrate carbon quality and nitrogen limitation may play roles of varying importance in determining the temperature sensitivity of SOM decomposition under various O2 conditions.
基金supported by the National Basic Research Program of China(2009CB825105)
文摘Recent studies on alkaline soils of arid areas suggest a possible contribution of abiotic exchange to soil CO2 flux(Fc).However,both the overall contribution of abiotic CO2 exchange and its drivers remain unknown.Here we analyzed the environmental variables suggested as possible drivers by previous studies and constructed a function of these variables to model the contribution of abiotic exchange to Fc in alkaline soils of arid areas.An automated flux system was employed to measure Fc in the Manas River Basin of Xinjiang Uygur autonomous region,China.Soil pH,soil temperature at 0–5 cm(Ts),soil volumetric water content at 0–5 cm(θs)and air temperature at10 cm above the soil surface(Tas)were simultaneously analyzed.Results highlight reduced sensitivity of Fc to Ts and good prediction of Fc by the model Fc=R10Q10(Tas–10)/10+r7q7(pH–7)+λTas+μθs+e which represents Fc as a sum of biotic and abiotic components.This presents an approximate method to quantify the contribution of soil abiotic CO2 exchange to Fc in alkaline soils of arid areas.
基金Under the auspices of National Key R&D Program of China(No.2016YFA0600104,2016YFC0500102,2017YFD0200604)National Natural Science Foundation of China(No.31770655,41671045,31772235)
文摘Microbial metabolic quotient(MMQ) is the rate of soil microbial respiration per unit of microbial biomass, and represents the capacity of soil microbes to utilize soil organic matter.Understanding the regional variation and determinants of MMQ can help predict the responses of soil respiration rate to global climate change.Accordingly, we measured and analyzed MMQ-related data(e.g., soil basic respiration rate at 20℃ and soil microbial biomass) from 17 grassland sites, which located in meadow steppe, typical steppe, and desert steppe along a 1000-km transect across the Inner Mongolian grasslands, China.Results showed that MMQ varied significantly among the different grassland types(P < 0.05;desert > typical > meadow) and decreased from southwest to northeast(r =–0.81) with increasing latitude(r = – 0.50), and with increasing mean annual precipitation(r = –0.69).Precipitation accounted for 56% of the total variation in MMQ, whereas temperature accounted for 26%.MMQ was negatively correlated with precipitation across the Inner Mongolian grasslands.Therefore, climate change, especially in regard to precipitation, may influence soil microbial respiration and soil carbon dynamics through altering MMQ.These results highlighted the importance of spatial patterns in MMQ for accurately evaluating the responses of soil respiration to climate change at regional and global scales.
基金the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi,China(2019L0826).
文摘Soil respiration(Rs)plays an important role in regulating carbon cycle of terrestrial ecosystems and presents temporal and spatial heterogeneity.Abies nephrolepis is a tree species that prefers the cold and wet environment and is mainly distributed in Northeast Asia and East Asia.The Rs variations of Abies nephrolepis forests communities are generally environmental-sensitive and can effectively reflect the adaptive responses of forest ecosystems to climate change.In this study,the growing-seasonal variations of Rs,soil temperature,soil water content and soil properties of Abies nephrolepis forests were analyzed along an altitude gradient(2000,2100,2200 and 2300 m)over two years on Wutai Mountain in North China.As the main results showed,soil respiration keeps the same change trend as soil temperature and reached peaks in July at 2000 m in 2019 and 2020.During 26th July to 25th October in 2019 and 27th May to 23rd October in 2020,on the whole,the soil temperature independently explained 76.2%of Rs variations while the soil water content independently explained 26.8%.Soil temperature and soil water content jointly explained 81.8%of Rs variations.Soil properties explained 61.8%and 69.6%of Rs variation in 2019 and 2020,respectively.Soil organic carbon content and soil enzyme activity had the signifi-cant(P<0.01)negative and positive relationships,respectively,with Rs variation.With altitudes evaluated from 2000 to 2300 m,soil respiration temperature sensitivity(Q10)and the soil organic carbon content increased by 12.4%and 10.4%,respectively,while invertase activity,cellulase activity and urease activity dropped by 41.2%,29.45%and 38.19%,respectively.The results demonstrate that(1)soil temperature is the major factor affecting Rs variations in Abies nephrolepis forests;(2)weakened microbial carbon metabolism in high-altitude areas results in the accumulation of soil organic carbon;(3)with a higher Q10,forest ecosystems in high-altitude areas might be more easily affected by climate change;(4)climate warming might accelerate the consumption of soil organic carbon sink in forest ecosystems,especially in high-altitude areas.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 40671173, 40425008, 30590384 and 40401028)the Free Research Foundation of State Key Laboratory of Earth Surface Processes and Resource Ecology (Grant No. 070105)
文摘Temperature sensitivity of soil respiration (Q10) is an important parameter in modeling the effects of global warming on ecosystem carbon release. Experimental studies of soil respiration have ubiquitously indicated that Q10 has high spatial heterogeneity. However, most biogeochemical models still use a constant Q10 in projecting future climate change and no spatial pattern of Q10 values at large scales has been derived. In this study, we conducted an inverse modeling analysis to retrieve the spatial pattern of Q10 in China at 8 km spatial resolution by assimilating data of soil organic carbon into a proc-ess-based terrestrial carbon model (CASA model). The results indicate that the optimized Q10 values are spatially heterogeneous and consistent to the values derived from soil respiration observations. The mean Q10 values of different soil types range from 1.09 to 2.38, with the highest value in volcanic soil, and the lowest value in cold brown calcic soil. The spatial pattern of Q10 is related to environmental factors, especially precipitation and top soil organic carbon content. This study demonstrates that inverse modeling is a useful tool in deriving the spatial pattern of Q10 at large scales, with which being incorporated into biogeochemical models, uncertainty in the projection of future carbon dynamics could be potentially reduced.
基金the Joint Funds of the National Natural Science Foundation of China(U2006215)the China Postdoctoral Science Foundation(2022M720462)。
文摘Salinity stress is one of the critical environmental drivers of soil organic matter(SOM)decomposition in coastal ecosystems.Although the temperature sensitivity(Q_(10))of SOM decomposition has been widely applied in Earth system models to forecast carbon processes,the impact of salinity on SOM decomposition by restructuring microbial communities remains uncovered.Here,we conducted a microcosm experiment with soils collected from the coastal salt marsh in the Yellow River Estuary,which is subjected to strong dynamics of salinity due to both tidal flooding and drainage.By setting a gradient of salt solutions,soil salinity was adjusted to simulate salinity stress and soil carbon emission(CO_(2))rate was measured over the period.Results showed that as salinity increased,the estimated decomposition constants based on first-order kinetics gradually decreased at different temperatures.Below the 20‰salinity treatments,which doubled the soil salinity,Q_(10)increased with increasing salinity;but higher salinity constrained the temperature-related response of SOM decomposition by inhibiting microbial growth and carbon metabolisms.Soil bacteria were more sensitive to salinity stress than fungi,which can be inferred from the response of microbial beta-diversity to changing salinity.Among them,the phylotypes assigned to Gammaproteobacteria and Bacilli showed higher salt tolerance,whereas taxa affiliated with Alphaproteobacteria and Bacteroidota were more easily inhibited by the salinity stress.Several fungal taxa belonging to Ascomycota had higher adaptability to the stress.As the substrate was consumed with the incubation,bacterial competition intensified,but the fungal co-occurrence pattern changed weakly during decomposition.Collectively,these findings revealed the threshold effect of salinity on SOM decomposition in coastal salt marshes and emphasized that salt stress plays a key role in carbon sequestration by regulating microbial keystone taxa,metabolisms,and interactions.
文摘Soil respiration (SR) is commonly modeled by a Q10 (an indicator of temperature sensitivity) function in ecosystem models. Q10 is usually treated as a constant of 2 in these models, although Q10 value of SR often decreases with increasing temperatures. It remains unclear whether a general temperature- dependent Q10 model of SR exists at biome and global scale. In this paper, we have compiled the long-term Q10 data of 38 SR studies ranging from the Boreal, Temperate, to Tropical/Sublropical biome on four continents. Our analysis indicated that the general temperature-dependent biome Q10 models of SR existed, especially in the Boreal and Temperate biomes. A single-exponential model was better than a simple linear model in fitting the average Q10 values at the biome scale. Average soil temperature is a better predictor of Q10 value than average air temperature in these models, especially in the Boreal biome. Soil temperature alone could explain about 50% of the Q10 variations in both the Boreal and Temperate biome single-exponential Q10 model. Q10 value of SR decreased with increasing soil temperature but at quite different rates among the three biome Q10 models. The k values (Q10 decay rate constants) were 0.09, 0.07, and 0.02/℃ in the Boreal, Temperate, and Tropical/Subtropical biome, respectively, suggesting that Q10 value is the most sensitive to soil temperature change in the Boreal biome, the second in the Temperate biome, and the least sensitive in the Tropical/ Subtropical biome. This also indirectly confirms that acclimation of SR in many soil warming experiments probably occurs. The k value in the "global" single-exponential Q10 model which combined both the Boreal and Temperate biome data set was 0.08/℃. However, the global general temperature-dependent Q10 model developed using the data sets of the three biomes is not adequate for predicting Q10 values of SR globally. The existence of the general temperature-dependent Q10 models of SR in the Boreal and Temperate biome has important implications for modeling SR, especially in the Boreal biome. More detail model runs are needed to exactly evaluate the impact of using a fixed Q10 vs a temperature-dependent Q10 on SR estimate in ecosystem models (e.g., TEM, Biome-BGC, and PnET).
基金Supported by the National Natural Science Foundation of China(30470306, 30570350)Knowledge Innovation Program of the Chinese Academy of Sciences(KSCX2-SW-120)
文摘The spatial and temporal variations in soil respiration and its relationship with biophysical factors In forests near the Tropic of Cancer remain highly uncertain. To contribute towards an Improvement of actual estimates, soil respiration rates, soil temperature, and soil moisture were measured In three successional subtropical forests at the Dlnghuahan Nature Reserve (DNR) In southern China from March 2003 to February 2005. The overall objective of the present study was to analyze the temporal variations of soil respiration and Its biophysical dependence in these forests. The relationships between biophysical factors and soil respiration rates were compared In successional forests to test the hypothesis that these forests responded similarly to biophysical factors. The seasonality of soil respiration coincided with the seasonal climate pattern, with high respiration rates in the hot humid season (April-September) and with low rates In the cool dry season (October-March). Soil respiration measured at these forests showed a clear Increasing trend with the progressive succession. Annual mean (± SD) soil respiration rate In the DNR forests was (9.0 ± 4.6) Mg CO2-C/hm^2 per year, ranging from (6.1 ± 3.2) Mg CO2-C/hm^2 per year in early successional forests to (10.7 ± 4.9) Mg CO2-C/hm^2 per year in advanced successional forests. Soil respiration was correlated with both soil temperature and moisture. The T/M model, where the two biophysical variables are driving factors, accounted for 74%-82% of soil respiration variation In DNR forests. Temperature sensitivity decreased along progressive succession stages, suggesting that advanced-successional forests have a good ability to adjust to temperature. In contrast, moisture Increased with progressive succession processes. This increase is caused, in part, by abundant respirators In advanced-successional forest, where more soil moisture is needed to maintain their activities.