Vegetation phenology is an important parameter in models of global vegetation and land surfaces, as the accuracy of these simulations depends strongly on the description of the canopy status. Temperate forests represe...Vegetation phenology is an important parameter in models of global vegetation and land surfaces, as the accuracy of these simulations depends strongly on the description of the canopy status. Temperate forests represent one of the major types of vegetation at mid-high latitudes in the Northern Hemisphere and act as a globally important carbon sink. Thus, a better understanding of the phenological variables of temperate forests will improve the accuracy of vegetation models and estimates of regional carbon fluxes. In this work, we explored the possibility of using digital camera images to monitor phenology at species and community scales of a temperate forest in northeastern China, and used the greenness index derived from these digital images to optimize phenological model parameters. The results show that at the species scale, the onset dates of phenological phases （Korean pine, Mongolian oak） derived from the images are close to those from field observations （error 〈 3d）. At the community scale the time series data accurately reflected the observed canopy status （A^2=0.9） simulated using the phenological model, especially in autumn. The phenological model was derived from simple meteorological data and environmental factors optimized using the greenness index. These simulations provide a powerful means of analyzing environmental factors that control the phenology of temperate forests. The results indicate that digital images can be used to obtain accurate phenologicai data and provide reference data to validate remote-sensing phenological data. In addition, we propose a new method to accurately track phenological phases in land-surface models and reduce uncertainty in spatial carbon flux simulations.展开更多
Afforestation projects were applied in the Poyang Lake Basin of China at the beginning of 1980s. The large-scale plantation may dramatically influence the changes in carbon storage of forests in this basin. Therefore,...Afforestation projects were applied in the Poyang Lake Basin of China at the beginning of 1980s. The large-scale plantation may dramatically influence the changes in carbon storage of forests in this basin. Therefore, climate-induced variations in the carbon balance of the Poyang Lake Basin＇s forests may play an important role in the carbon cycle of China. However, we have little understanding of their long-term behavior, especially the future trend of carbon sink/source patterns under climate change and rising atmospheric CQ. The annual carbon budget of the Poyang Lake Basin＇s forests during 1981-2050 was estimated by using the Integrated Terrestrial Ecosystem Carbon-budget model （InTEC） coupled with projected climate change simulated by Regional Integrated Environmental Model System （RIEMS 2.0）. During 1981-2000, the rapid increment of annual NPP in this basin was possible due to large plantation. Soil organic carbon storage （0-30cm） of forests generally decreased by 1.0% per year at the beginning of plantation. Moreover, forests in this basin converted from carbon source in 1980s to carbon sink in 1990s. By 2040-2050, total carbon stocks of forest ecosystems will increase by 0.78Pg C, compared to recent years （2001-2010）. Under future climate and CQ concentration in AIB scenario, NEP of forests in Poyang Lake Basin lean to keep relative stable （20-30Tg C y-i） because of old forests except for some years induced by extreme droughts. Our results also showed that prediction of NEP of forests in Poyang Lake Basin was controlled by water limitation; in contrast, temperature was the main factor on inter- annual variability of NPP.展开更多
基金supported by"Strategic Priority Research Program"of the Chinese Academy of Sciences(Grant No.XDA05050600)National Natural Science Foundation of China(Grant No.41071251)National Program on Key Basic Research Project(973 Program,No.2010CB833504)
文摘Vegetation phenology is an important parameter in models of global vegetation and land surfaces, as the accuracy of these simulations depends strongly on the description of the canopy status. Temperate forests represent one of the major types of vegetation at mid-high latitudes in the Northern Hemisphere and act as a globally important carbon sink. Thus, a better understanding of the phenological variables of temperate forests will improve the accuracy of vegetation models and estimates of regional carbon fluxes. In this work, we explored the possibility of using digital camera images to monitor phenology at species and community scales of a temperate forest in northeastern China, and used the greenness index derived from these digital images to optimize phenological model parameters. The results show that at the species scale, the onset dates of phenological phases （Korean pine, Mongolian oak） derived from the images are close to those from field observations （error 〈 3d）. At the community scale the time series data accurately reflected the observed canopy status （A^2=0.9） simulated using the phenological model, especially in autumn. The phenological model was derived from simple meteorological data and environmental factors optimized using the greenness index. These simulations provide a powerful means of analyzing environmental factors that control the phenology of temperate forests. The results indicate that digital images can be used to obtain accurate phenologicai data and provide reference data to validate remote-sensing phenological data. In addition, we propose a new method to accurately track phenological phases in land-surface models and reduce uncertainty in spatial carbon flux simulations.
基金the State Key Basic Research Development Project (Grant No.2010CB833503)the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No.KZCX2-YW-QN301)
文摘Afforestation projects were applied in the Poyang Lake Basin of China at the beginning of 1980s. The large-scale plantation may dramatically influence the changes in carbon storage of forests in this basin. Therefore, climate-induced variations in the carbon balance of the Poyang Lake Basin＇s forests may play an important role in the carbon cycle of China. However, we have little understanding of their long-term behavior, especially the future trend of carbon sink/source patterns under climate change and rising atmospheric CQ. The annual carbon budget of the Poyang Lake Basin＇s forests during 1981-2050 was estimated by using the Integrated Terrestrial Ecosystem Carbon-budget model （InTEC） coupled with projected climate change simulated by Regional Integrated Environmental Model System （RIEMS 2.0）. During 1981-2000, the rapid increment of annual NPP in this basin was possible due to large plantation. Soil organic carbon storage （0-30cm） of forests generally decreased by 1.0% per year at the beginning of plantation. Moreover, forests in this basin converted from carbon source in 1980s to carbon sink in 1990s. By 2040-2050, total carbon stocks of forest ecosystems will increase by 0.78Pg C, compared to recent years （2001-2010）. Under future climate and CQ concentration in AIB scenario, NEP of forests in Poyang Lake Basin lean to keep relative stable （20-30Tg C y-i） because of old forests except for some years induced by extreme droughts. Our results also showed that prediction of NEP of forests in Poyang Lake Basin was controlled by water limitation; in contrast, temperature was the main factor on inter- annual variability of NPP.
