It is well known that aboveground productivity usually increases with precipitation.However,how belowground carbon(C)processes respond to changes in precipitation remains elusive,although belowground net primary produ...It is well known that aboveground productivity usually increases with precipitation.However,how belowground carbon(C)processes respond to changes in precipitation remains elusive,although belowground net primary productivity(BNPP)represents more than one-half of NPP and soil stores the largest terrestrial C in the biosphere.This paper reviews the patterns of belowground C processes(BNPP and soil C)in response to changes in precipitation from transect studies,manipulative experiments,modeling and data integration and synthesis.The results suggest the possible existence of nonlinear patterns of BNPP and soil C in response to changes in precipitation,which is largely different from linear response for aboveground productivity.C allocation,root turnover time and species composition may be three key processes underlying mechanisms of the nonlinear responses to changes in precipitation for belowground C processes.In addition,microbial community structure and long-term ecosystem processes(e.g.mineral assemblage,soil texture,aggregate stability)may also affect patterns of belowground C processes in response to changes in precipitation.At last,we discuss implications and future perspectives for potential nonlinear responses of belowground C processes to changes in precipitation.展开更多
Soil microbial biomass is critical for biogeochemical cycling and serves as precursor for carbon(C)sequestration.The anthropogenic nitrogen(N)input has profoundly changed the pool of soil microbial biomass.However,tra...Soil microbial biomass is critical for biogeochemical cycling and serves as precursor for carbon(C)sequestration.The anthropogenic nitrogen(N)input has profoundly changed the pool of soil microbial biomass.However,traditional N deposition simulation experiments have been exclusively conducted through infrequent N addition,which may have caused biased effects on soil microbial biomass compared with those under the natural and continuous N deposition.Convincing data are still scarce about how the different N addition frequencies affect soil microbial biomass.By independently manipulating the frequencies(2 times vs.12 times N addition yr^(–1))and the rates(0–50 g N m^(−2) yr^(−1))of N addition,our study aimed to examine the response of soil microbial biomass C(MBC)to different N addition frequencies with increasing N addition rates.Soil MBC gradually decreased with increasing N addition rates under both N addition frequencies,while the soil MBC decreased more at low frequency of N addition,suggesting that traditional studies have possibly overestimated the effects of N deposition on soil microbial biomass.The greater soil microbial biomass loss with low N frequency resulted from the intensifed soil acidifcation,higher soil inorganic N,stronger soil C and N imbalance,less net primary production allocated to belowground and lower fungi to bacteria ratio.To reliably predict the effects of atmospheric N deposition on soil microbial functioning and C cycling of grassland ecosystems in future studies,it is necessary to employ both the dosage and the frequency of N addition.展开更多
基金supported by the National Key Research and Development Program of China(2023YFF0806900)the National Natural Science Foundation of China(31930072,32241032,42203076)the Natural Science Foundation of Heilongjiang Province of China(ZD2021C002).
文摘It is well known that aboveground productivity usually increases with precipitation.However,how belowground carbon(C)processes respond to changes in precipitation remains elusive,although belowground net primary productivity(BNPP)represents more than one-half of NPP and soil stores the largest terrestrial C in the biosphere.This paper reviews the patterns of belowground C processes(BNPP and soil C)in response to changes in precipitation from transect studies,manipulative experiments,modeling and data integration and synthesis.The results suggest the possible existence of nonlinear patterns of BNPP and soil C in response to changes in precipitation,which is largely different from linear response for aboveground productivity.C allocation,root turnover time and species composition may be three key processes underlying mechanisms of the nonlinear responses to changes in precipitation for belowground C processes.In addition,microbial community structure and long-term ecosystem processes(e.g.mineral assemblage,soil texture,aggregate stability)may also affect patterns of belowground C processes in response to changes in precipitation.At last,we discuss implications and future perspectives for potential nonlinear responses of belowground C processes to changes in precipitation.
基金supported by the National Natural Science Foundation of China(42130515 and31770506)the Open Foundation of the State Key Laboratory of Urban and Regional Ecology of Chinathe Open Foundation of the State Key Laboratory of Grassland Agro-ecosystems of China。
文摘Soil microbial biomass is critical for biogeochemical cycling and serves as precursor for carbon(C)sequestration.The anthropogenic nitrogen(N)input has profoundly changed the pool of soil microbial biomass.However,traditional N deposition simulation experiments have been exclusively conducted through infrequent N addition,which may have caused biased effects on soil microbial biomass compared with those under the natural and continuous N deposition.Convincing data are still scarce about how the different N addition frequencies affect soil microbial biomass.By independently manipulating the frequencies(2 times vs.12 times N addition yr^(–1))and the rates(0–50 g N m^(−2) yr^(−1))of N addition,our study aimed to examine the response of soil microbial biomass C(MBC)to different N addition frequencies with increasing N addition rates.Soil MBC gradually decreased with increasing N addition rates under both N addition frequencies,while the soil MBC decreased more at low frequency of N addition,suggesting that traditional studies have possibly overestimated the effects of N deposition on soil microbial biomass.The greater soil microbial biomass loss with low N frequency resulted from the intensifed soil acidifcation,higher soil inorganic N,stronger soil C and N imbalance,less net primary production allocated to belowground and lower fungi to bacteria ratio.To reliably predict the effects of atmospheric N deposition on soil microbial functioning and C cycling of grassland ecosystems in future studies,it is necessary to employ both the dosage and the frequency of N addition.
