Background:Old-growth forests are irreplaceable with respect to climate change mitigation and have considerable carbon(C)sink potential in soils.However,the relationship between the soil organic carbon(SOC)turnover ra...Background:Old-growth forests are irreplaceable with respect to climate change mitigation and have considerable carbon(C)sink potential in soils.However,the relationship between the soil organic carbon(SOC)turnover rate and forest development is poorly understood,which hinders our ability to assess the C sequestration capacity of soil in old-growth forests.Methods:In this study,we evaluated the SOC turnover rate by calculating the isotopic enrichment factor β(defined as the slope of the regression between ^(13)C natural abundance and log-transformed C concentrations)along 0-30 cm soil profiles in three successional forests in subtropical China.A lower β(steeper slope)is associated with a higher turnover rate.The three forests were a 60-year-old P.massoniana forest(PF),a 100-year-old coniferous and broadleaved mixed forest(MF),and a 400-year-old monsoon evergreen broadleaved forest(BF).We also analyzed the soil physicochemical properties in these forests to examine the dynamics of SOC turnover during forest succession and the main regulators.Results:The β value for the upper 30-cm soils in the BF was significantly(p<0.05)higher than that in the PF,in addition to the SOC stock,although there were nonsignificant differences between the BF and MF.The β value was significantly(p<0.05)positively correlated with the soil recalcitrance index,total nitrogen,and available nitrogen contents but was significantly(p<0.01)negatively correlated with soil pH.Conclusions:Our results demonstrate that SOC has lower turnover rates in old-growth forests,accompanied by higher soil chemical recalcitrance,nitrogen status,and lower soil pH.This finding helps to elucidate the mechanism underlying C sequestration in old-growth forest soils,and emphasizes the important value of old-growth forests among global C sinks.展开更多
Aims The aim of this study was to investigate the effects of precipitation changes on soil organic carbon(SOC)fractions in subtropical forests where the precipitation pattern has been altered for decades.Methods We co...Aims The aim of this study was to investigate the effects of precipitation changes on soil organic carbon(SOC)fractions in subtropical forests where the precipitation pattern has been altered for decades.Methods We conducted field manipulations of precipitation,including ambient precipitation as a control(CK),double precipitation(DP)and no precipitation(NP),for 3 years in three forests with different stand ages(broadleaf forest[BF],mixed forest[MF]and pine forest[PF])in subtropical China.At the end of the experiment,soil samples were collected to assay SOC content,readily oxidizable organic carbon(ROC)and non-readily oxidizable organic carbon(NROC),as well as soil microbial biomass carbon(MBC),pH and total nitrogen content.Samples from the forest floors were also collected to analyze carbon(C)functional groups(i.e.alkyl C,aromatic C,O-alkyl C and carbonyl C).Furthermore,fine root biomass was measured periodically throughout the experiment.Important Findings Among the forests,ROC content did not exhibit any notable differences,while NROC content increased significantly with the stand age.This finding implied that the SOC accumulation observed in these forests resulted from the accumulation of NROC in the soil,a mechanism for SOC accumulation in the mature forests of southern China.Moreover,NP treatment led to significant reductions in both ROC and NROC content and therefore reduced the total SOC content in all of the studied forests.Such decreases may be due to the lower plant-derived C inputs(C quantity)and to the changes in SOC components(C quality)indicated by C functional groups analyses under NP treatment.DP treatment in all the forests also tended to decrease the SOC content,although the decreases were not statistically significant with the exception of SOC and ROC content in PF.This finding indicated that soils in MF and in BF may be more resistant to precipitation increases,possibly due to less water limitations under natural conditions in the two forests.Our results therefore highlight the different responses of SOC and its fractions to precipitation changes among the forests and suggest that further studies are needed to improve our understanding of SOC dynamics in such an important C sink region.展开更多
The mutual interdependence of plants and arbuscular mycorrhizal fungi(AMF)is important in carbon and mineral nutrient exchange.However,an understanding of how AMF community assemblies vary in different forests and the...The mutual interdependence of plants and arbuscular mycorrhizal fungi(AMF)is important in carbon and mineral nutrient exchange.However,an understanding of how AMF community assemblies vary in different forests and the underlying factors regulating AMF diversity in native tropical forests is largely unknown.We explored the AMF community assembly and the underlying factors regulating AMF diversity in a young(YF)and an old-growth forest(OF)in a tropical area.The results showed that a total of 53 AMF phylogroups(virtual taxa,VTs)were detected,38±1 in the OF and 34±1 in the YF through high-throughput sequencing of 18S rDNA,and AMF community composition was significantly different between the two forests.A structural equation model showed that the forest traits indirectly influenced AMF diversity via the plant community,soil properties and microbes,which explained 44.2%of the total observed variation in AMF diversity.Plant diversity and biomass were the strongest predictors of AMF diversity,indicating that AMF diversity was dominantly regulated by biotic factors at our study sites.Our study indicated that forest community traits have a predictable effect on the AMF community;plant community traits and soil properties are particularly important for determining AMF diversity in tropical forests.展开更多
基金jointly supported by the China Postdoctoral Science Foundation(No.2020 M682951)the National Natural Science Foundation of China(No.NSFC41773088)the Key Research Program of the Chinese Academy of Sciences(No.QYZDJ-SSW-DQC003).
文摘Background:Old-growth forests are irreplaceable with respect to climate change mitigation and have considerable carbon(C)sink potential in soils.However,the relationship between the soil organic carbon(SOC)turnover rate and forest development is poorly understood,which hinders our ability to assess the C sequestration capacity of soil in old-growth forests.Methods:In this study,we evaluated the SOC turnover rate by calculating the isotopic enrichment factor β(defined as the slope of the regression between ^(13)C natural abundance and log-transformed C concentrations)along 0-30 cm soil profiles in three successional forests in subtropical China.A lower β(steeper slope)is associated with a higher turnover rate.The three forests were a 60-year-old P.massoniana forest(PF),a 100-year-old coniferous and broadleaved mixed forest(MF),and a 400-year-old monsoon evergreen broadleaved forest(BF).We also analyzed the soil physicochemical properties in these forests to examine the dynamics of SOC turnover during forest succession and the main regulators.Results:The β value for the upper 30-cm soils in the BF was significantly(p<0.05)higher than that in the PF,in addition to the SOC stock,although there were nonsignificant differences between the BF and MF.The β value was significantly(p<0.05)positively correlated with the soil recalcitrance index,total nitrogen,and available nitrogen contents but was significantly(p<0.01)negatively correlated with soil pH.Conclusions:Our results demonstrate that SOC has lower turnover rates in old-growth forests,accompanied by higher soil chemical recalcitrance,nitrogen status,and lower soil pH.This finding helps to elucidate the mechanism underlying C sequestration in old-growth forest soils,and emphasizes the important value of old-growth forests among global C sinks.
基金the Strategic Priority Research Program-Climate Change:Carbon Budget and Relevant Issues of the Chinese Academy of Sciences(XDA05050205)National Basic Research Program of China(2009CB421101)+1 种基金National Natural Science Foundation of China(NSFC-31400415)Guangdong Provincial Natural Science Foundation of China(8351065005000001),the Dinghushan Forest Ecosystem Research Station.
文摘Aims The aim of this study was to investigate the effects of precipitation changes on soil organic carbon(SOC)fractions in subtropical forests where the precipitation pattern has been altered for decades.Methods We conducted field manipulations of precipitation,including ambient precipitation as a control(CK),double precipitation(DP)and no precipitation(NP),for 3 years in three forests with different stand ages(broadleaf forest[BF],mixed forest[MF]and pine forest[PF])in subtropical China.At the end of the experiment,soil samples were collected to assay SOC content,readily oxidizable organic carbon(ROC)and non-readily oxidizable organic carbon(NROC),as well as soil microbial biomass carbon(MBC),pH and total nitrogen content.Samples from the forest floors were also collected to analyze carbon(C)functional groups(i.e.alkyl C,aromatic C,O-alkyl C and carbonyl C).Furthermore,fine root biomass was measured periodically throughout the experiment.Important Findings Among the forests,ROC content did not exhibit any notable differences,while NROC content increased significantly with the stand age.This finding implied that the SOC accumulation observed in these forests resulted from the accumulation of NROC in the soil,a mechanism for SOC accumulation in the mature forests of southern China.Moreover,NP treatment led to significant reductions in both ROC and NROC content and therefore reduced the total SOC content in all of the studied forests.Such decreases may be due to the lower plant-derived C inputs(C quantity)and to the changes in SOC components(C quality)indicated by C functional groups analyses under NP treatment.DP treatment in all the forests also tended to decrease the SOC content,although the decreases were not statistically significant with the exception of SOC and ROC content in PF.This finding indicated that soils in MF and in BF may be more resistant to precipitation increases,possibly due to less water limitations under natural conditions in the two forests.Our results therefore highlight the different responses of SOC and its fractions to precipitation changes among the forests and suggest that further studies are needed to improve our understanding of SOC dynamics in such an important C sink region.
基金supported by the National Natural Science Foundation of China(31961143023,31670453)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA23080302)+2 种基金the National Key Research and Development Program of China(2021YFF0703905)the Chinese Ecosystem Research Network(CERN)the Dinghushan Forest Ecosystem Positioning Research Station of the National Science and Technology Infrastructure Platform and the Operation Service Project of the National Scientific Observation and Research Field Station of the Dinghushan Forest Ecosystem of Guangdong,the Ministry of Science and Technology of the People’s Republic of China.
基金the National Natural Science Foundation of China(31770491,31270499 and 41430529)Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(GML2019ZD0408)the Youth Innovation Promotion Association,CAS and Natural Science Foundation of Guangdong Province of China(2019A1515011486)。
文摘The mutual interdependence of plants and arbuscular mycorrhizal fungi(AMF)is important in carbon and mineral nutrient exchange.However,an understanding of how AMF community assemblies vary in different forests and the underlying factors regulating AMF diversity in native tropical forests is largely unknown.We explored the AMF community assembly and the underlying factors regulating AMF diversity in a young(YF)and an old-growth forest(OF)in a tropical area.The results showed that a total of 53 AMF phylogroups(virtual taxa,VTs)were detected,38±1 in the OF and 34±1 in the YF through high-throughput sequencing of 18S rDNA,and AMF community composition was significantly different between the two forests.A structural equation model showed that the forest traits indirectly influenced AMF diversity via the plant community,soil properties and microbes,which explained 44.2%of the total observed variation in AMF diversity.Plant diversity and biomass were the strongest predictors of AMF diversity,indicating that AMF diversity was dominantly regulated by biotic factors at our study sites.Our study indicated that forest community traits have a predictable effect on the AMF community;plant community traits and soil properties are particularly important for determining AMF diversity in tropical forests.
