Using China's ground observations,e.g.,forest inventory,grassland resource,agricultural statistics,climate,and satellite data,we estimate terrestrial vegetation carbon sinks for China's major biomes between 19...Using China's ground observations,e.g.,forest inventory,grassland resource,agricultural statistics,climate,and satellite data,we estimate terrestrial vegetation carbon sinks for China's major biomes between 1981 and 2000.The main results are in the following:(1)Forest area and forest biomass car-bon(C)stock increased from 116.5×10^(6) ha and 4.3 Pg C(1 Pg C=10^(15) g C)in the early 1980s to 142.8×10^(6) ha and 5.9 Pg C in the early 2000s,respectively.Forest biomass carbon density increased form 36.9 Mg C/ha(1 Mg C=10^(6) g C)to 41.0 Mg C/ha,with an annual carbon sequestration rate of 0.075 Pg C/a.Grassland,shrub,and crop biomass sequestrate carbon at annual rates of 0.007 Pg C/a,0.014―0.024 Pg C/a,and 0.0125―0.0143 Pg C/a,respectively.(2)The total terrestrial vegetation C sink in China is in a range of 0.096―0.106 Pg C/a between 1981 and 2000,accounting for 14.6%―16.1%of carbon dioxide(CO_(2))emitted by China's industry in the same period.In addition,soil carbon sink is estimated at 0.04―0.07 Pg C/a.Accordingly,carbon sequestration by China's terrestrial ecosystems(vegetation and soil)offsets 20.8%―26.8%of its industrial CO_(2) emission for the study period.(3)Considerable uncertainties exist in the present study,especially in the estimation of soil carbon sinks,and need further intensive investigation in the future.展开更多
Grassland covers approximately one-third of the area of China and plays an important role in the global terrestrial carbon(C) cycle.However,little is known about biomass C stocks and dynamics in these grasslands.Durin...Grassland covers approximately one-third of the area of China and plays an important role in the global terrestrial carbon(C) cycle.However,little is known about biomass C stocks and dynamics in these grasslands.During 2001-2005,we conducted five consecutive field sampling campaigns to investigate above-and below-ground biomass for northern China's grasslands.Using measurements obtained from 341 sampling sites,together with a NDVI(normalized difference vegetation index) time series dataset over 1982-2006,we examined changes in biomass C stock during the past 25 years.Our results showed that biomass C stock in northern China's grasslands was estimated at 557.5 Tg C(1 Tg=1012 g),with a mean density of 39.5 g C m-2 for above-ground biomass and 244.6 g C m-2 for below-ground biomass.An increasing rate of 0.2 Tg C yr-1 has been observed over the past 25 years,but grassland biomass has not experienced a significant change since the late 1980s.Seasonal rainfall(January-July) was the dominant factor driving temporal dynamics in biomass C stock;however,the responses of grassland biomass to climate variables differed among various grassland types.Biomass in arid grasslands(i.e.,desert steppe and typical steppe) was significantly associated with precipitation,while biomass in humid grasslands(i.e.,alpine meadow) was positively correlated with mean January-July temperatures.These results suggest that different grassland ecosystems in China may show diverse responses to future climate changes.展开更多
The knowledge of carbon(C) stock and its dynamics is crucial for understanding the role of grassland ecosystems in China's terrestrial C cycle.To date,a comprehensive assessment on C balance in China's grassla...The knowledge of carbon(C) stock and its dynamics is crucial for understanding the role of grassland ecosystems in China's terrestrial C cycle.To date,a comprehensive assessment on C balance in China's grasslands is still lacking.By reviewing published literature,this study aims to evaluate ecosystem C stocks(both vegetation biomass and soil organic C) and their changes in China's grasslands.Our results are summarized as follows:(1) biomass C density(C stock per area) of China's grasslands differed greatly among previous studies,ranging from 215.8 to 348.1 g C m-2 with an average of 300.2 g C m-2.Likewise,soil C density also varied greatly between 8.5 and 15.1 kg C m-2.In total,ecosystem C stock in China's grasslands was estimated at 29.1 Pg C.(2) Both the magnitude and direction of ecosystem C changes in China's grasslands differed greatly among previous studies.According to recent reports,neither biomass nor soil C stock in China's grasslands showed a significant change during the past 20 years,indicating that grassland ecosystems are C neutral.(3) Spatial patterns and temporal dynamics of grassland biomass were closely correlated with precipitation,while changes in soil C stocks exhibited close associations with soil moisture and soil texture.Human activities,such as livestock grazing and fencing could also affect ecosystem C dynamics in China's grasslands.展开更多
Above- and belowground biomasses of grasslands are important parameters for characterizing re- gional and global carbon cycles in grassland ecosystems. Compared with the relatively detailed in- formation for abovegrou...Above- and belowground biomasses of grasslands are important parameters for characterizing re- gional and global carbon cycles in grassland ecosystems. Compared with the relatively detailed in- formation for aboveground biomass (AGB), belowground biomass (BGB) is poorly reported at the re- gional scales. The present study, based on a total of 113 sampling sites in temperate grassland of the Inner Mongolia, investigated regional distribution patterns of AGB, BGB, vertical distribution of roots, and their relationships with environmental factors. AGB and BGB increased from the southwest to the northeast of the study region. The largest biomass occurred in meadow steppe, with mean AGB and BGB of 196.7 and 1385.2 g/m2, respectively; while the lowest biomass occurred in desert steppe, with an AGB of 56.6 g/m2 and a BGB of 301.0 g/m2. In addition, about 47% of root biomass was distributed in the top 10 cm soil. Further statistical analysis indicated that precipitation was the primary determinant factor in shaping these distribution patterns. Vertical distribution of roots was significantly affected by precipitation, while the effects of soil texture and grassland types were weak.展开更多
气候变化及其对植被净初级生产力的影响是全球变化研究的核心内容之一。基于空间化的CENTURY生物过程模型,分析1981-2010年内蒙古草地净初级生产力(NPP)的时空演变规律及其对关键气候因子的敏感性特征。结果表明:近30年内蒙古草地大部...气候变化及其对植被净初级生产力的影响是全球变化研究的核心内容之一。基于空间化的CENTURY生物过程模型,分析1981-2010年内蒙古草地净初级生产力(NPP)的时空演变规律及其对关键气候因子的敏感性特征。结果表明:近30年内蒙古草地大部分区域NPP呈下降态势但趋势并不显著,全区平均降速约为1.17 g C/m2?a;NPP年代际变化时空差异较大,1980s至1990s约69.65%的区域NPP下降,1990s至2000s NPP下降加剧,下降面积较前者扩大了17.50%;NPP对降水与温度的敏感性特征空间异质性较强,但总体上区域降水减少可能是近30年内蒙古草地NPP下降的主要因素,温度升高同样会导致草地NPP下降,但作用程度较小。展开更多
基金Supported by the National Natural Science Foundation of China(Grant Nos.90211016,40638039,40228001,and 40021101)the Key MOE Research Project(Grant No.306019)
文摘Using China's ground observations,e.g.,forest inventory,grassland resource,agricultural statistics,climate,and satellite data,we estimate terrestrial vegetation carbon sinks for China's major biomes between 1981 and 2000.The main results are in the following:(1)Forest area and forest biomass car-bon(C)stock increased from 116.5×10^(6) ha and 4.3 Pg C(1 Pg C=10^(15) g C)in the early 1980s to 142.8×10^(6) ha and 5.9 Pg C in the early 2000s,respectively.Forest biomass carbon density increased form 36.9 Mg C/ha(1 Mg C=10^(6) g C)to 41.0 Mg C/ha,with an annual carbon sequestration rate of 0.075 Pg C/a.Grassland,shrub,and crop biomass sequestrate carbon at annual rates of 0.007 Pg C/a,0.014―0.024 Pg C/a,and 0.0125―0.0143 Pg C/a,respectively.(2)The total terrestrial vegetation C sink in China is in a range of 0.096―0.106 Pg C/a between 1981 and 2000,accounting for 14.6%―16.1%of carbon dioxide(CO_(2))emitted by China's industry in the same period.In addition,soil carbon sink is estimated at 0.04―0.07 Pg C/a.Accordingly,carbon sequestration by China's terrestrial ecosystems(vegetation and soil)offsets 20.8%―26.8%of its industrial CO_(2) emission for the study period.(3)Considerable uncertainties exist in the present study,especially in the estimation of soil carbon sinks,and need further intensive investigation in the future.
基金supported by the National Natural Science Foundation of China (Grant Nos. 90711002 and 90211016)
文摘Grassland covers approximately one-third of the area of China and plays an important role in the global terrestrial carbon(C) cycle.However,little is known about biomass C stocks and dynamics in these grasslands.During 2001-2005,we conducted five consecutive field sampling campaigns to investigate above-and below-ground biomass for northern China's grasslands.Using measurements obtained from 341 sampling sites,together with a NDVI(normalized difference vegetation index) time series dataset over 1982-2006,we examined changes in biomass C stock during the past 25 years.Our results showed that biomass C stock in northern China's grasslands was estimated at 557.5 Tg C(1 Tg=1012 g),with a mean density of 39.5 g C m-2 for above-ground biomass and 244.6 g C m-2 for below-ground biomass.An increasing rate of 0.2 Tg C yr-1 has been observed over the past 25 years,but grassland biomass has not experienced a significant change since the late 1980s.Seasonal rainfall(January-July) was the dominant factor driving temporal dynamics in biomass C stock;however,the responses of grassland biomass to climate variables differed among various grassland types.Biomass in arid grasslands(i.e.,desert steppe and typical steppe) was significantly associated with precipitation,while biomass in humid grasslands(i.e.,alpine meadow) was positively correlated with mean January-July temperatures.These results suggest that different grassland ecosystems in China may show diverse responses to future climate changes.
文摘The knowledge of carbon(C) stock and its dynamics is crucial for understanding the role of grassland ecosystems in China's terrestrial C cycle.To date,a comprehensive assessment on C balance in China's grasslands is still lacking.By reviewing published literature,this study aims to evaluate ecosystem C stocks(both vegetation biomass and soil organic C) and their changes in China's grasslands.Our results are summarized as follows:(1) biomass C density(C stock per area) of China's grasslands differed greatly among previous studies,ranging from 215.8 to 348.1 g C m-2 with an average of 300.2 g C m-2.Likewise,soil C density also varied greatly between 8.5 and 15.1 kg C m-2.In total,ecosystem C stock in China's grasslands was estimated at 29.1 Pg C.(2) Both the magnitude and direction of ecosystem C changes in China's grasslands differed greatly among previous studies.According to recent reports,neither biomass nor soil C stock in China's grasslands showed a significant change during the past 20 years,indicating that grassland ecosystems are C neutral.(3) Spatial patterns and temporal dynamics of grassland biomass were closely correlated with precipitation,while changes in soil C stocks exhibited close associations with soil moisture and soil texture.Human activities,such as livestock grazing and fencing could also affect ecosystem C dynamics in China's grasslands.
基金Supported by the National Natural Science Fundation of China (Grant Nos. 90211016, 40021101 and 30700090)
文摘Above- and belowground biomasses of grasslands are important parameters for characterizing re- gional and global carbon cycles in grassland ecosystems. Compared with the relatively detailed in- formation for aboveground biomass (AGB), belowground biomass (BGB) is poorly reported at the re- gional scales. The present study, based on a total of 113 sampling sites in temperate grassland of the Inner Mongolia, investigated regional distribution patterns of AGB, BGB, vertical distribution of roots, and their relationships with environmental factors. AGB and BGB increased from the southwest to the northeast of the study region. The largest biomass occurred in meadow steppe, with mean AGB and BGB of 196.7 and 1385.2 g/m2, respectively; while the lowest biomass occurred in desert steppe, with an AGB of 56.6 g/m2 and a BGB of 301.0 g/m2. In addition, about 47% of root biomass was distributed in the top 10 cm soil. Further statistical analysis indicated that precipitation was the primary determinant factor in shaping these distribution patterns. Vertical distribution of roots was significantly affected by precipitation, while the effects of soil texture and grassland types were weak.
文摘气候变化及其对植被净初级生产力的影响是全球变化研究的核心内容之一。基于空间化的CENTURY生物过程模型,分析1981-2010年内蒙古草地净初级生产力(NPP)的时空演变规律及其对关键气候因子的敏感性特征。结果表明:近30年内蒙古草地大部分区域NPP呈下降态势但趋势并不显著,全区平均降速约为1.17 g C/m2?a;NPP年代际变化时空差异较大,1980s至1990s约69.65%的区域NPP下降,1990s至2000s NPP下降加剧,下降面积较前者扩大了17.50%;NPP对降水与温度的敏感性特征空间异质性较强,但总体上区域降水减少可能是近30年内蒙古草地NPP下降的主要因素,温度升高同样会导致草地NPP下降,但作用程度较小。
