●Soil erosion decreased soil microbial CUE and increased microbial uptake of carbon.●Soil erosion decreased microbial CUE by decreasing substrate C,N and MBC and increasing soil pH.●Soil microbes had to increase th...●Soil erosion decreased soil microbial CUE and increased microbial uptake of carbon.●Soil erosion decreased microbial CUE by decreasing substrate C,N and MBC and increasing soil pH.●Soil microbes had to increase their uptake rate to cope with the loss of substrates with increasing erosion rate.●Soil microbial respiration increased with increasing degree of erosion.●Soil microbial growth rate remained relative stable under different degrees of soil erosion.●Microbial CUE in soil surface was less responsive to erosion than that in deeper soil.Soil microbial carbon use efficiency(CUE)is an important synthetic parameter of microbial community metabolism and is commonly used to quantify the partitioning of carbon(C)between microbial growth and respiration.However,it remains unclear how microbial CUE responds to different degrees of soil erosion in mollisol cropland.Therefore,we investigated the responses of soil erosion on microbial CUE,growth and respiration to different soil erosion rates in a mollisol cropland in northeast China based on a substrate independent method(18O-H2O labeling).Soils were sampled at four positions along a down-slope transect:summit,shoulder,back and foot.We found microbial CUE decreased significantly with increasing soil erosion rate in 5−20 cm soil,but did not change in 0−5 cm.The decrease of microbial CUE in subsoil was because microbes increased C uptake and allocated higher uptake C to microbial basal respiration with increasing soil erosion rate.Microbial respiration increased significantly with soil erosion rate,probably due to the more disturbance and unbalanced stoichiometry.Furthermore,soil microbes in surface soil were able to maintain their growth rates with increasing degree of erosion.Altogether,our results indicated that soil erosion could decrease microbial CUE by affecting soil physical and chemical properties,resulting in more decomposition of soil organic matter and more soil respiration,which had negative feedbacks to soil C sequestration and climate changes in cropland soil.展开更多
Aims We aimed to quantify the variation of leafδ^(13)C along an arid and semi-arid grassland transect in northern China.We also evaluated the effects of environmental factors(i.e.precipitation,temperature and altitud...Aims We aimed to quantify the variation of leafδ^(13)C along an arid and semi-arid grassland transect in northern China.We also evaluated the effects of environmental factors(i.e.precipitation,temperature and altitude)on the spatial variation of leafδ^(13)C in northern grasslands and Tibetan Plateau,China.Method We sampled leaves of plant species belonging to three herb genera(Stipa spp.,Leymus spp.and Cleistogenes spp.)and three shrub genera(Caragana spp.,Reaumuria spp.and Nitraria spp.)for carbon isotope analysis from 50 locations along a 3200-km arid and semiarid grassland transect in northern China.Leafδ^(13)C data in Tibetan Plateau and northern grasslands in China were also compiled from studies in literature.Important Findings Along the transect,leafδ^(13)C for C_(3)plants ranged from−28.0‰to−23.3‰,and from−16.3‰to−13.8‰for C_(4)plant Cleistogenes spp..The change in leafδ^(13)C ranged from−0.26‰to−3.51‰with every 100 mm increase of annual precipitation,and leafδ^(13)C of shrubs(Nitraria spp.,Reaumuria spp.and Caragana spp.)responded more markedly to climatic factors(precipitation and temperature)than that of herbs(Stipa spp.,Leymus spp.and Cleistogenes spp.),indicating higher sensitivity of shrubδ^(13)C to climatic changes.The most important factor regulating spatial variations of leafδ^(13)C in Tibetan Plateau was altitude,while it was precipitation in northern grasslands.Our results suggested that shrubs are more adapted to increasing drought in arid and semi-arid grassland.Controls of environmental factors on leafδ^(13)C depended on the most limiting factors in arid grassland(precipitation)and Tibetan grasslands(atmospheric CO_(2)concentration).展开更多
Background:Freeze–thaw events are common in boreal and temperate forest ecosystems and are increasingly infuenced by climate warming.Soil microorganisms play an important role in maintaining ecosystem stability,but t...Background:Freeze–thaw events are common in boreal and temperate forest ecosystems and are increasingly infuenced by climate warming.Soil microorganisms play an important role in maintaining ecosystem stability,but their responses to freeze–thaw cycles(FTCs)are poorly understood.We conducted a feld freeze–thaw experiment in a natural Korean pine and broadleaf mixed forest in the Changbai Mountain Nature Reserve,China,to determine the dynamic responses of soil microbial communities to FTCs.Results:Bacteria were more sensitive than fungi to FTCs.Fungal biomass,diversity and community composition were not signifcantly afected by freeze–thaw regardless of the stage.Moderate initial freeze–thaw resulted in increased bacterial biomass,diversity,and copiotrophic taxa abundance.Subsequent FTCs reduced the bacterial biomass and diversity.Compared with the initial FTC,subsequent FTCs exerted an opposite efect on the direction of change in the composition and function of the bacterial community.Soil water content,dissolved organic carbon,ammonium nitrogen,and total dissolved phosphorus were important factors determining bacterial community diversity and composition during FTCs.Moreover,the functional potentials of the microbial community involved in C and N cycling were also afected by FTCs.Conclusions:Diferent stages of FTCs have diferent ecological efects on the soil environment and microbial activities.Soil FTCs changed the soil nutrients and water availability and then mainly infuenced bacterial community composition,diversity,and functional potentials,which may disturb C and N states in this temperate forest soil.This study also improves our understanding of microbial communities regulating their ecological functions in response to climate change.展开更多
Soil-emitted N_(2)O contributes to two-thirds of global N_(2)O emissions,and is sensitive to global change.We used DayCent model to simulate major plant-soil N cycling processes under different global change scenarios...Soil-emitted N_(2)O contributes to two-thirds of global N_(2)O emissions,and is sensitive to global change.We used DayCent model to simulate major plant-soil N cycling processes under different global change scenarios in a typical temperate mixed forest in north-eastern China.Simulated scenarios included warming(T),elevated atmospheric CO_(2) concentration([CO_(2)])(C),increased N deposition(N)and precipitation(P),and their full factorial combinations.The responses of plant-soil nitrogen cycling processes including net N mineralization,plant N uptake,gross nitrification,denitrification and soil N_(2)O emission were examined.Concurrent increase of elevated[CO_(2)]and N deposition displayed most strong interactive effects on most fluxes.Using the results from experimental studies for evaluation,simulation uncertainty was highest under elevated[CO_(2)]and increased precipitation among the four global change factors.N deposition had a fundamental impact on soil N cycle and N_(2)O emission in our studied forest.Despite forest soil acting as a N sink for added N,scenarios which included increased N deposition showed higher cumulative soil N_(2)O emissions(summed up from 2001 to 2100).In particular,the scenario which included T,P,and N had the largest cumulative soil N_(2)O emission,which was a 24.4% increase over that under ambient conditions.Our study points to the importance of the interactive effects of global change factors on plant-soil N cycling and the necessity of multi-factor manipulation experiments.展开更多
Background:Rare earth elements(REE)are a group of trace elements that behave geochemically coherently.REE fractionation patterns normalized to reference materials provide a powerful tool for documenting pedogenesis.In...Background:Rare earth elements(REE)are a group of trace elements that behave geochemically coherently.REE fractionation patterns normalized to reference materials provide a powerful tool for documenting pedogenesis.Insoil processes are particularly difficult to illustrate with respect to contemporary and past climate conditions.In this study,we characterize the rare earth element(REE)contents in bulk soils and respective geochemical fractions(e.g.,exchangeable,carbonate‑bound,reducible,and oxidizable fractions)and to decipher the relationships between REE geochemistry components and climatic factors across a large‑scale northern China transect(NCT).Results:Across the NCT,bulk REE concentrations ranged from 55.2 to 241.1μg g^(−1)with a main portion in the residual fraction(49–79%),followed by oxidizable fraction(2–40%),reducible fraction(3–22%),carbonate‑bound fraction(0.1–16%),and negligible exchangeable fraction.The REE contents of geochemical components(carbonate‑bound,reducible,and oxidizable)in topsoils correlated to climate factors(mean annual precipitation,mean annual temperature,potential evaporation,and aridity index(AI)).The normalized abundances to the upper continental crust(UCC)composition show that the middle REE was generally enriched than the light REE and heavy REE in topsoils along the transect.The overall UCC‑normalized bulk REE patterns in topsoils and subsoils were similar,characterized by weak negative Ce anomalies and positive Eu anomalies.Conclusions:Our data in topsoils and depth profiles collectively suggest that cycling of REE was primarily regulated by abiotic processes in area with AI<0.2,while the biological effect on REE circulation in soil played a more effective role in area with AI>0.3.The similar UCC normalized patterns in topsoils suggest that the REE was originated from a common source with limited influences from other sources(e.g.,atmospheric dusts and anthropogenic contribu‑tions).Our results to some extent provide evidence for climatic influence REE distribution patterns both in topsoils and subsoils across the continental‑scale transect.Our investigation gives insights into future studies on vertical REE mobility and its associated biogeochemical pathways.展开更多
基金funded by the National Key Research and Development Program of China(No.2022YFF1300501)the National Natural Science Foundation of China(No.41971058).
文摘●Soil erosion decreased soil microbial CUE and increased microbial uptake of carbon.●Soil erosion decreased microbial CUE by decreasing substrate C,N and MBC and increasing soil pH.●Soil microbes had to increase their uptake rate to cope with the loss of substrates with increasing erosion rate.●Soil microbial respiration increased with increasing degree of erosion.●Soil microbial growth rate remained relative stable under different degrees of soil erosion.●Microbial CUE in soil surface was less responsive to erosion than that in deeper soil.Soil microbial carbon use efficiency(CUE)is an important synthetic parameter of microbial community metabolism and is commonly used to quantify the partitioning of carbon(C)between microbial growth and respiration.However,it remains unclear how microbial CUE responds to different degrees of soil erosion in mollisol cropland.Therefore,we investigated the responses of soil erosion on microbial CUE,growth and respiration to different soil erosion rates in a mollisol cropland in northeast China based on a substrate independent method(18O-H2O labeling).Soils were sampled at four positions along a down-slope transect:summit,shoulder,back and foot.We found microbial CUE decreased significantly with increasing soil erosion rate in 5−20 cm soil,but did not change in 0−5 cm.The decrease of microbial CUE in subsoil was because microbes increased C uptake and allocated higher uptake C to microbial basal respiration with increasing soil erosion rate.Microbial respiration increased significantly with soil erosion rate,probably due to the more disturbance and unbalanced stoichiometry.Furthermore,soil microbes in surface soil were able to maintain their growth rates with increasing degree of erosion.Altogether,our results indicated that soil erosion could decrease microbial CUE by affecting soil physical and chemical properties,resulting in more decomposition of soil organic matter and more soil respiration,which had negative feedbacks to soil C sequestration and climate changes in cropland soil.
基金National Basic Research Program of China(973 program,2014CB954400)the National Natural Science Foundation of China(31522010)State Key Laboratory of Forest and Soil Ecology(LFSE2013-13 and LFSE2015-18).
文摘Aims We aimed to quantify the variation of leafδ^(13)C along an arid and semi-arid grassland transect in northern China.We also evaluated the effects of environmental factors(i.e.precipitation,temperature and altitude)on the spatial variation of leafδ^(13)C in northern grasslands and Tibetan Plateau,China.Method We sampled leaves of plant species belonging to three herb genera(Stipa spp.,Leymus spp.and Cleistogenes spp.)and three shrub genera(Caragana spp.,Reaumuria spp.and Nitraria spp.)for carbon isotope analysis from 50 locations along a 3200-km arid and semiarid grassland transect in northern China.Leafδ^(13)C data in Tibetan Plateau and northern grasslands in China were also compiled from studies in literature.Important Findings Along the transect,leafδ^(13)C for C_(3)plants ranged from−28.0‰to−23.3‰,and from−16.3‰to−13.8‰for C_(4)plant Cleistogenes spp..The change in leafδ^(13)C ranged from−0.26‰to−3.51‰with every 100 mm increase of annual precipitation,and leafδ^(13)C of shrubs(Nitraria spp.,Reaumuria spp.and Caragana spp.)responded more markedly to climatic factors(precipitation and temperature)than that of herbs(Stipa spp.,Leymus spp.and Cleistogenes spp.),indicating higher sensitivity of shrubδ^(13)C to climatic changes.The most important factor regulating spatial variations of leafδ^(13)C in Tibetan Plateau was altitude,while it was precipitation in northern grasslands.Our results suggested that shrubs are more adapted to increasing drought in arid and semi-arid grassland.Controls of environmental factors on leafδ^(13)C depended on the most limiting factors in arid grassland(precipitation)and Tibetan grasslands(atmospheric CO_(2)concentration).
基金The National Natural Science Foundation of China(31770531,32001174)the Key Research Program of Frontier Sciences,CAS(QYZDB-SSW-DQC006)+1 种基金the Key Laboratory of Geographical Processes and Ecological Security of Changbai Mountains,Ministry of Education(GPES201902)the Youth Innovation Promotion Association CAS to Chao Wang(2018231).
文摘Background:Freeze–thaw events are common in boreal and temperate forest ecosystems and are increasingly infuenced by climate warming.Soil microorganisms play an important role in maintaining ecosystem stability,but their responses to freeze–thaw cycles(FTCs)are poorly understood.We conducted a feld freeze–thaw experiment in a natural Korean pine and broadleaf mixed forest in the Changbai Mountain Nature Reserve,China,to determine the dynamic responses of soil microbial communities to FTCs.Results:Bacteria were more sensitive than fungi to FTCs.Fungal biomass,diversity and community composition were not signifcantly afected by freeze–thaw regardless of the stage.Moderate initial freeze–thaw resulted in increased bacterial biomass,diversity,and copiotrophic taxa abundance.Subsequent FTCs reduced the bacterial biomass and diversity.Compared with the initial FTC,subsequent FTCs exerted an opposite efect on the direction of change in the composition and function of the bacterial community.Soil water content,dissolved organic carbon,ammonium nitrogen,and total dissolved phosphorus were important factors determining bacterial community diversity and composition during FTCs.Moreover,the functional potentials of the microbial community involved in C and N cycling were also afected by FTCs.Conclusions:Diferent stages of FTCs have diferent ecological efects on the soil environment and microbial activities.Soil FTCs changed the soil nutrients and water availability and then mainly infuenced bacterial community composition,diversity,and functional potentials,which may disturb C and N states in this temperate forest soil.This study also improves our understanding of microbial communities regulating their ecological functions in response to climate change.
基金supported by the National Basic Research Program of China(973 program,2014CB954400)the National Natural Science Foundation of China(41401289).
文摘Soil-emitted N_(2)O contributes to two-thirds of global N_(2)O emissions,and is sensitive to global change.We used DayCent model to simulate major plant-soil N cycling processes under different global change scenarios in a typical temperate mixed forest in north-eastern China.Simulated scenarios included warming(T),elevated atmospheric CO_(2) concentration([CO_(2)])(C),increased N deposition(N)and precipitation(P),and their full factorial combinations.The responses of plant-soil nitrogen cycling processes including net N mineralization,plant N uptake,gross nitrification,denitrification and soil N_(2)O emission were examined.Concurrent increase of elevated[CO_(2)]and N deposition displayed most strong interactive effects on most fluxes.Using the results from experimental studies for evaluation,simulation uncertainty was highest under elevated[CO_(2)]and increased precipitation among the four global change factors.N deposition had a fundamental impact on soil N cycle and N_(2)O emission in our studied forest.Despite forest soil acting as a N sink for added N,scenarios which included increased N deposition showed higher cumulative soil N_(2)O emissions(summed up from 2001 to 2100).In particular,the scenario which included T,P,and N had the largest cumulative soil N_(2)O emission,which was a 24.4% increase over that under ambient conditions.Our study points to the importance of the interactive effects of global change factors on plant-soil N cycling and the necessity of multi-factor manipulation experiments.
基金supported by Chinese Academy of Sciences(No.E01X0301)National Natural Science Foundation of China(Grant No.41673005)support from China Scholarship Council.Youth Innovation Promotion Association CAS to Chao Wang(2018231).
文摘Background:Rare earth elements(REE)are a group of trace elements that behave geochemically coherently.REE fractionation patterns normalized to reference materials provide a powerful tool for documenting pedogenesis.Insoil processes are particularly difficult to illustrate with respect to contemporary and past climate conditions.In this study,we characterize the rare earth element(REE)contents in bulk soils and respective geochemical fractions(e.g.,exchangeable,carbonate‑bound,reducible,and oxidizable fractions)and to decipher the relationships between REE geochemistry components and climatic factors across a large‑scale northern China transect(NCT).Results:Across the NCT,bulk REE concentrations ranged from 55.2 to 241.1μg g^(−1)with a main portion in the residual fraction(49–79%),followed by oxidizable fraction(2–40%),reducible fraction(3–22%),carbonate‑bound fraction(0.1–16%),and negligible exchangeable fraction.The REE contents of geochemical components(carbonate‑bound,reducible,and oxidizable)in topsoils correlated to climate factors(mean annual precipitation,mean annual temperature,potential evaporation,and aridity index(AI)).The normalized abundances to the upper continental crust(UCC)composition show that the middle REE was generally enriched than the light REE and heavy REE in topsoils along the transect.The overall UCC‑normalized bulk REE patterns in topsoils and subsoils were similar,characterized by weak negative Ce anomalies and positive Eu anomalies.Conclusions:Our data in topsoils and depth profiles collectively suggest that cycling of REE was primarily regulated by abiotic processes in area with AI<0.2,while the biological effect on REE circulation in soil played a more effective role in area with AI>0.3.The similar UCC normalized patterns in topsoils suggest that the REE was originated from a common source with limited influences from other sources(e.g.,atmospheric dusts and anthropogenic contribu‑tions).Our results to some extent provide evidence for climatic influence REE distribution patterns both in topsoils and subsoils across the continental‑scale transect.Our investigation gives insights into future studies on vertical REE mobility and its associated biogeochemical pathways.