The average chain length(ACL),carbon preference index(CPI),and hydrogen isotope composition(δ^(2)H)of long-chain n-alkanes in sediments have been used to retrieve information about the paleoclimate.Despite their impo...The average chain length(ACL),carbon preference index(CPI),and hydrogen isotope composition(δ^(2)H)of long-chain n-alkanes in sediments have been used to retrieve information about the paleoclimate.Despite their importance as in-between media from leaves to sediments,n-alkanes of surface soils have not been systematically analyzed at large scale.Such an investigation of the spatial variation of n-alkane properties in soil and their dependence on climatic and botanic(e.g.,vegetation type)factors could provide a rationale for a better estimation of the past environment.We synthesized the patterns andδ^(2)H of long-chain n-alkanes in soil(δ^(2)H_(n-alkanes))with regard to vegetation types(cropland,grassland,shrubland,and woodland)and environmental factors using data from peer-reviewed papers.Our results showed that the ACL and CPI of soil C_(27)–C_(33) n-alkanes were not suitable indicators for differentiating vegetation types at large scale;instead,ACL significantly correlated with water conditions such as mean annual precipitation(MAP)and Palmer drought severity index(PDSI),and CPI significantly correlated with temperature without significant influence of vegetation type.The variation(i.e.,standard deviation)of fractionation between theδ^(2)H values in annual precipitation and in soil n-alkanes(ε_(rain-soil))was smaller than that reported in leaves;therefore,soils were better suited to quantifying the general growing conditions of plants at a certain site.The fractionationε_(rain-soil)correlated with climatic conditions as described by the PDSI and relative humidity(RH).This correlation agreed with the change in leaf water enrichment with changing RH taken from the literature and was independent of the vegetation type at large scale.This meta-analysis may provide useful information for the variations of the patterns andδ^(2)H_(n-alkanes) values in surface soils.展开更多
Background:C4 plants have increased substantially during the past several decades in the grasslands of the Mongolian Plateau due to regional warming.Here,we explore how the patterns of abundances of C4 annuals and C4 ...Background:C4 plants have increased substantially during the past several decades in the grasslands of the Mongolian Plateau due to regional warming.Here,we explore how the patterns of abundances of C4 annuals and C4 perennials change over space and time.Methods:A total of 280 sites with C4 plants were surveyed in four types of grasslands in 9 years.The relative biomasses of C4 plants(PC4),C4 annuals(PA4),and C4 perennials(PP4)were calculated.Structural equation modeling was used to analyze the drivers of changes in PA4 and PP4.Results:At the regional scale,PA4 on average was 11%(±19%,SD)and PP4 was 13%(±19%,SD).Spatially,C4 annuals dominated the C4 communities within an east–west belt region along 44°N and tended to spread toward northern latitudes(about 0.5°)and higher altitudes in the east mountainous areas.The abundance of C4 annuals decreased,while that of C4 perennials increased.The patterns of C4 annuals and C4 perennials were mainly controlled by temperature,growing season precipitation,and dynamics between the two life forms.Conclusions:C4 annuals exhibited competitive advantages in normal and wet years,while C4 perennials had competitive advantages in dry years.Grazing as a main human disturbance increased C4 annuals,but had no significant effect on C4 perennials.展开更多
基金supported by the National Natural Science Foundation of China(Nos.41803008 and 31901090)Sichuan Science and Technology Program,China(No.2020YJ0170)Everest Scientific Research Project of Chengdu University of Technology,China(No.800002020ZF11410)。
文摘The average chain length(ACL),carbon preference index(CPI),and hydrogen isotope composition(δ^(2)H)of long-chain n-alkanes in sediments have been used to retrieve information about the paleoclimate.Despite their importance as in-between media from leaves to sediments,n-alkanes of surface soils have not been systematically analyzed at large scale.Such an investigation of the spatial variation of n-alkane properties in soil and their dependence on climatic and botanic(e.g.,vegetation type)factors could provide a rationale for a better estimation of the past environment.We synthesized the patterns andδ^(2)H of long-chain n-alkanes in soil(δ^(2)H_(n-alkanes))with regard to vegetation types(cropland,grassland,shrubland,and woodland)and environmental factors using data from peer-reviewed papers.Our results showed that the ACL and CPI of soil C_(27)–C_(33) n-alkanes were not suitable indicators for differentiating vegetation types at large scale;instead,ACL significantly correlated with water conditions such as mean annual precipitation(MAP)and Palmer drought severity index(PDSI),and CPI significantly correlated with temperature without significant influence of vegetation type.The variation(i.e.,standard deviation)of fractionation between theδ^(2)H values in annual precipitation and in soil n-alkanes(ε_(rain-soil))was smaller than that reported in leaves;therefore,soils were better suited to quantifying the general growing conditions of plants at a certain site.The fractionationε_(rain-soil)correlated with climatic conditions as described by the PDSI and relative humidity(RH).This correlation agreed with the change in leaf water enrichment with changing RH taken from the literature and was independent of the vegetation type at large scale.This meta-analysis may provide useful information for the variations of the patterns andδ^(2)H_(n-alkanes) values in surface soils.
基金This work was supported by the National Natural Science Foundation of China(31971465,31822006,31770503,41807108)National Basic Research Program of China(2016YFC0500601,2016YFC0500700)+1 种基金Youth Innovation Promotion Association CAS(201832,2020199)the Key Research Program from CAS(KFZD-SW-305-002).
基金supported by the DFG within the DFG research group 536(MAGIM)the National Natural Science Foundation of China(31630010 and 31320103916).
文摘Background:C4 plants have increased substantially during the past several decades in the grasslands of the Mongolian Plateau due to regional warming.Here,we explore how the patterns of abundances of C4 annuals and C4 perennials change over space and time.Methods:A total of 280 sites with C4 plants were surveyed in four types of grasslands in 9 years.The relative biomasses of C4 plants(PC4),C4 annuals(PA4),and C4 perennials(PP4)were calculated.Structural equation modeling was used to analyze the drivers of changes in PA4 and PP4.Results:At the regional scale,PA4 on average was 11%(±19%,SD)and PP4 was 13%(±19%,SD).Spatially,C4 annuals dominated the C4 communities within an east–west belt region along 44°N and tended to spread toward northern latitudes(about 0.5°)and higher altitudes in the east mountainous areas.The abundance of C4 annuals decreased,while that of C4 perennials increased.The patterns of C4 annuals and C4 perennials were mainly controlled by temperature,growing season precipitation,and dynamics between the two life forms.Conclusions:C4 annuals exhibited competitive advantages in normal and wet years,while C4 perennials had competitive advantages in dry years.Grazing as a main human disturbance increased C4 annuals,but had no significant effect on C4 perennials.
