Aims Boreal larch(Larix gmelinii)forests in Northeast China have been widely disturbed since the 1987 conflagration;however,its long-term effects on the forest carbon(C)cycling have not been explored.The objective of ...Aims Boreal larch(Larix gmelinii)forests in Northeast China have been widely disturbed since the 1987 conflagration;however,its long-term effects on the forest carbon(C)cycling have not been explored.The objective of this study thus was to quantify the effects of fire severity and post-fire reforestation on C pools and the changes of these forests.Methods Sixteen permanent plots have been set in two types of larch stands(L.gmelinii-grass,LG;and L.gmelinii-Rhododendron dahurica,LR)with three levels of fire severity(unburned,low-severity and high-severity but replanted),at 1987 burned sites in Daxing’anling,northeastern China,to repeatedly measure ecosystem C pools in 1998 and 2014.C components were partitioned into vegetation(foliage,branch,stem and roots),soil and detritus(standing and fallen woody debris and litter).The fire effects on post-fire C dynamics were examined by comparing the differences of C pools and changes between the two field investigations caused by fire severity.Important Findings During the study period,unburned mature stands were C sinks(105 g C m^(−2) year^(−1) for LG,and 190 g C m^(−2) year^(−1) for LR),whereas the low-severity stands were C-neutral(−4 and 15 g C m^(−2) year^(−1) for LG and LR,respectively).The high-severity burned but reforested stands were C sinks,among which,however,magnitudes(88 and 16 g C m^(−2) year^(−1) for LG and LR,respectively)were smaller than those of the two unburned stands.Detritus C pools decreased significantly(with a loss ranging from 26 to 38 g C m^(−2) year^(−1))in the burned stands during recent restoration.Soil organic C pools increased slightly in the unmanaged stands(unburned and lowseverity,with accumulation rates ranging from 4 to 35 g C m^(−2) year^(−1)),but decreased for the high-severity replanted stands(loss rates of 28 and 36 g C m^(−2) year^(−1) for LG and LR,respectively).These results indicate that fire severity has a dynamic post-fire effect on both C pools and distributions of the boreal larch forests,and that effective reforestation practice accelerates forest C sequestration.展开更多
Aims There are different components of carbon(C)pools in a natural forest ecosystem:biomass,soil,litter and woody debris.We asked how these pools changed with elevation in one of China’s ecologically important forest...Aims There are different components of carbon(C)pools in a natural forest ecosystem:biomass,soil,litter and woody debris.We asked how these pools changed with elevation in one of China’s ecologically important forest ecosystem,i.e.beech(Fagus L.,Fagaceae)forests,and what were the underlying driving factors of such variation.Methods The four C pools in nine beech forests were investigated along an elevational gradient(1095–1930 m)on Mt.Fanjingshan in Guizhou Province,Southwest China.Variance partitioning was used to explore the relative effects of stand age,climate and other factors on C storage.In addition,we compared the four C pools to other beech forests in Guizhou Province and worldwide.Important Findings The total C pools of beech forest ecosystems ranged from 190.5 to 504.3 Mg C ha^(–1),mainly attributed to biomass C(accounting for 33.7–73.9%)and soil C(accounting for 23.9–65.5%).No more than 4%of ecosystem C pools were stored in woody debris(0.05–3.1%)and litter(0.2–0.7%).Ecosystem C storage increased significantly with elevation,where both the biomass and woody debris C pools increased with elevation,while those of litter and soil exhibited no such trend.For the Guizhou beech forests,climate and stand age were found to be key drivers of the elevational patterns of ecosystem and biomass C storage,while for beech forests globally,stand age was the most important predictor.Compared to beech forests worldwide,beech forests in Guizhou Province displayed a relatively higher biomass C accumulation rate,which may be explained by a much higher precipitation in this area.The present study provides basic data for understanding the C budgets of Chinese beech forests and their possible roles in regional C cycling and emphasizes the general importance of stand age and climate on C accumulation.展开更多
Aims Soil respiration is one of the most important components in the car-bon(c)cycle in terrestrial ecosystems.to investigate the contribution of each component of c cycle to the total soil c efflux,we quantified the ...Aims Soil respiration is one of the most important components in the car-bon(c)cycle in terrestrial ecosystems.to investigate the contribution of each component of c cycle to the total soil c efflux,we quantified the rates of litter,root,and other mineral soil respiration from 2012 to 2014 in the primary and secondary tropical mountain rain forests in Hainan Island,china.Methods the seasonal dynamics of soil(Rs),non-litter(RNL)and non-root(RNR)respiration rates were measured using an automatic chamber system(Li-8100).Litter removal and root removal treatments were used to assess the contribution of litter and roots to belowground c production.We estimated the annual c efflux of each compo-nent of soil respiration in primary and secondary forests using a temperature-based exponential model and analyzed the impact of each component in each forest type.Important Findingsthe annual total soil c efflux was significantly higher in the primary rain forest(1567±205 g c m^(−2)yr^(−1))than that in the secondary forest(1300±70 g c m^(−2)yr^(−1),P<0.05).the litter,root,and mineral soils contributed 22%(349±185 g c m^(−2)yr^(−1)),38%(589±100 g c m^(−2)yr^(−1)),and 40%(628±128 g c m^(−2)yr^(−1))to the total soil c efflux in primary rain forest,respectively.In secondary forest,these three components contributed 11%(148±35 g c m^(−2)yr^(−1)),45%(572±259 g c m^(−2)yr^(−1)),and 44%(580±226 g c m^(−2)yr^(−1)),respectively.the temperature sensitivity(Q10)of Rs(2.70±0.14)in the primary forest was significantly higher than that in the secondary forest(2.34±0.12),with the Q10 values for respiration decreasing in the order of RNR>Rs>RNL.these results show that the difference in litter respiration between primary and secondary forest caused the major difference in annual soil respiration efflux between these two forest types.In addition,the litter respiration is more sensitive to the soil temperature than the other soil respiration components.展开更多
Grasslands in the Qinghai–Tibet Plateau play an important role in preserving ecological security and high biodiversity in this region.However,the distribution of the composition and structure of plant community and t...Grasslands in the Qinghai–Tibet Plateau play an important role in preserving ecological security and high biodiversity in this region.However,the distribution of the composition and structure of plant community and the mechanism by which it maintains itself in this region are still poorly understood.Here,we designed 195 grassland plots in 39 grassland sites along an approximately 1700 m elevation gradient on the Northeastern Qinghai–Tibet Plateau.We found that the grassland community height decreased significantly with increasing elevation,whereas community coverage did not significantly change.With increasing elevation,plant species richness(αdiversity)increased significantly,but the community variability(βdiversity)decreased significantly.The constrained clustering analysis suggested that theα-andβ-diversity in the grasslands transformed gradually with elevation,and that three discontinuous points(based on community structure)were observed at elevation of 3640,4252 and 4333 m.Structural equation modeling(SEM)indicated that the increase in precipitation and the decrease in temperature significantly positively influencedαdiversity,which was negatively correlated withβdiversity.These results demonstrate a quantitative-to-qualitative change in the community composition and structure along this elevational gradient on the Qinghai–Tibet Plateau.展开更多
基金National Natural Science Foundation of China(31321061,31330012)National Basic Research Program of China on Global Change(2014CB954001)+2 种基金National Key Technology Research and Development Program of the Ministry of Science and Technology of China(2011BAD37B01)Chinese Academy of Sciences(XDA05050000)Program for Changjiang Scholars and Innovative Research Team in University(IRT1054).
文摘Aims Boreal larch(Larix gmelinii)forests in Northeast China have been widely disturbed since the 1987 conflagration;however,its long-term effects on the forest carbon(C)cycling have not been explored.The objective of this study thus was to quantify the effects of fire severity and post-fire reforestation on C pools and the changes of these forests.Methods Sixteen permanent plots have been set in two types of larch stands(L.gmelinii-grass,LG;and L.gmelinii-Rhododendron dahurica,LR)with three levels of fire severity(unburned,low-severity and high-severity but replanted),at 1987 burned sites in Daxing’anling,northeastern China,to repeatedly measure ecosystem C pools in 1998 and 2014.C components were partitioned into vegetation(foliage,branch,stem and roots),soil and detritus(standing and fallen woody debris and litter).The fire effects on post-fire C dynamics were examined by comparing the differences of C pools and changes between the two field investigations caused by fire severity.Important Findings During the study period,unburned mature stands were C sinks(105 g C m^(−2) year^(−1) for LG,and 190 g C m^(−2) year^(−1) for LR),whereas the low-severity stands were C-neutral(−4 and 15 g C m^(−2) year^(−1) for LG and LR,respectively).The high-severity burned but reforested stands were C sinks,among which,however,magnitudes(88 and 16 g C m^(−2) year^(−1) for LG and LR,respectively)were smaller than those of the two unburned stands.Detritus C pools decreased significantly(with a loss ranging from 26 to 38 g C m^(−2) year^(−1))in the burned stands during recent restoration.Soil organic C pools increased slightly in the unmanaged stands(unburned and lowseverity,with accumulation rates ranging from 4 to 35 g C m^(−2) year^(−1)),but decreased for the high-severity replanted stands(loss rates of 28 and 36 g C m^(−2) year^(−1) for LG and LR,respectively).These results indicate that fire severity has a dynamic post-fire effect on both C pools and distributions of the boreal larch forests,and that effective reforestation practice accelerates forest C sequestration.
基金supported by the National Key Research and Development Program of China(grant no.2017YFA0605101)Ministry of Science and Technology of China(grant no.2015FY210200)National Natural Science Foundation of China(grant nos.31700374,31621091).
文摘Aims There are different components of carbon(C)pools in a natural forest ecosystem:biomass,soil,litter and woody debris.We asked how these pools changed with elevation in one of China’s ecologically important forest ecosystem,i.e.beech(Fagus L.,Fagaceae)forests,and what were the underlying driving factors of such variation.Methods The four C pools in nine beech forests were investigated along an elevational gradient(1095–1930 m)on Mt.Fanjingshan in Guizhou Province,Southwest China.Variance partitioning was used to explore the relative effects of stand age,climate and other factors on C storage.In addition,we compared the four C pools to other beech forests in Guizhou Province and worldwide.Important Findings The total C pools of beech forest ecosystems ranged from 190.5 to 504.3 Mg C ha^(–1),mainly attributed to biomass C(accounting for 33.7–73.9%)and soil C(accounting for 23.9–65.5%).No more than 4%of ecosystem C pools were stored in woody debris(0.05–3.1%)and litter(0.2–0.7%).Ecosystem C storage increased significantly with elevation,where both the biomass and woody debris C pools increased with elevation,while those of litter and soil exhibited no such trend.For the Guizhou beech forests,climate and stand age were found to be key drivers of the elevational patterns of ecosystem and biomass C storage,while for beech forests globally,stand age was the most important predictor.Compared to beech forests worldwide,beech forests in Guizhou Province displayed a relatively higher biomass C accumulation rate,which may be explained by a much higher precipitation in this area.The present study provides basic data for understanding the C budgets of Chinese beech forests and their possible roles in regional C cycling and emphasizes the general importance of stand age and climate on C accumulation.
基金National Natural Science Foundation of China(31321061,31330012)National Basic Research Program of China on Global Change(2014CB954001).
文摘Aims Soil respiration is one of the most important components in the car-bon(c)cycle in terrestrial ecosystems.to investigate the contribution of each component of c cycle to the total soil c efflux,we quantified the rates of litter,root,and other mineral soil respiration from 2012 to 2014 in the primary and secondary tropical mountain rain forests in Hainan Island,china.Methods the seasonal dynamics of soil(Rs),non-litter(RNL)and non-root(RNR)respiration rates were measured using an automatic chamber system(Li-8100).Litter removal and root removal treatments were used to assess the contribution of litter and roots to belowground c production.We estimated the annual c efflux of each compo-nent of soil respiration in primary and secondary forests using a temperature-based exponential model and analyzed the impact of each component in each forest type.Important Findingsthe annual total soil c efflux was significantly higher in the primary rain forest(1567±205 g c m^(−2)yr^(−1))than that in the secondary forest(1300±70 g c m^(−2)yr^(−1),P<0.05).the litter,root,and mineral soils contributed 22%(349±185 g c m^(−2)yr^(−1)),38%(589±100 g c m^(−2)yr^(−1)),and 40%(628±128 g c m^(−2)yr^(−1))to the total soil c efflux in primary rain forest,respectively.In secondary forest,these three components contributed 11%(148±35 g c m^(−2)yr^(−1)),45%(572±259 g c m^(−2)yr^(−1)),and 44%(580±226 g c m^(−2)yr^(−1)),respectively.the temperature sensitivity(Q10)of Rs(2.70±0.14)in the primary forest was significantly higher than that in the secondary forest(2.34±0.12),with the Q10 values for respiration decreasing in the order of RNR>Rs>RNL.these results show that the difference in litter respiration between primary and secondary forest caused the major difference in annual soil respiration efflux between these two forest types.In addition,the litter respiration is more sensitive to the soil temperature than the other soil respiration components.
基金National Natural Science Foundation of China(31901172)Science and Technology Project of Qinghai Provincial Department of Transportation(2019-07).
文摘Grasslands in the Qinghai–Tibet Plateau play an important role in preserving ecological security and high biodiversity in this region.However,the distribution of the composition and structure of plant community and the mechanism by which it maintains itself in this region are still poorly understood.Here,we designed 195 grassland plots in 39 grassland sites along an approximately 1700 m elevation gradient on the Northeastern Qinghai–Tibet Plateau.We found that the grassland community height decreased significantly with increasing elevation,whereas community coverage did not significantly change.With increasing elevation,plant species richness(αdiversity)increased significantly,but the community variability(βdiversity)decreased significantly.The constrained clustering analysis suggested that theα-andβ-diversity in the grasslands transformed gradually with elevation,and that three discontinuous points(based on community structure)were observed at elevation of 3640,4252 and 4333 m.Structural equation modeling(SEM)indicated that the increase in precipitation and the decrease in temperature significantly positively influencedαdiversity,which was negatively correlated withβdiversity.These results demonstrate a quantitative-to-qualitative change in the community composition and structure along this elevational gradient on the Qinghai–Tibet Plateau.
