Evaluating impacts of climate change on net ecosystem productivity (NEP) of global different forest types based on an individual tree-based model FORCCHN and remote sensing

摘要

Accurately assessing the NEP of global forest ecosystem is indispensable to adjusting the global carbon balance for climate change. In this study, an improved individual-based forest ecosystem carbon budget model (FORCCHN) and remote sensing outputs were applied to investigate the impacts of climate change on the NEP of global different forest types from 1982 to 2011. The contributions of carbon sinks in different forest types to carbon sinks in global forest ecosystems were explored. The global forests were categorized into five ecological types according to their habitats and generic characteristics: deciduous coniferous forest (DCF), evergreen coniferous forest (ECF), evergreen coniferous deciduous broad-leaved mixed forest (ECDBMF), deciduous broad-leaved forest (DBF) and evergreen broad-leaved forest (EBF). The results showed that globally, the forest ecosystems represented a huge carbon sink and that the total carbon uptakes per unit area per year for EBF, ECF, DBF, DCF and ECDBMF forests from 1982 to 2011 were 0.388 kgC m(-2).yr(-1), 0.116 kgC m(-2).yr(-1), 0.082 kgC m(-2).yr(-1), 0.048 kgC m(-2).yr(-1) and 0.044 kgC m(-2).yr(-1), respectively. Inter-annual variability in global NEP per unit area per year among different forest types clearly existed. From 1982 to 2011, especially, the NEP increased in the EBF and ECF forests globally, but decreased in DBF forests. Moreover, there were no significant changes in the NEP of DCF and ECDBMF forests. The carbon sink areas varied among the 5 global forest types. For the DCF forest, central Asia, northern Europe and central North America were the main carbon sink regions. Central Asia, northern Europe and central North America were the main carbon sink regions for the ECF forest. For the ECDBMF forest, the carbon sink regions were mainly concentrated in northern and central Asia. The carbon sink regions for the DBF forest were mainly concentrated in southern Asia, southern Europe and mid-eastern North America. The carbon sink regions for the EBF forest were mainly concentrated in northern and central South America, southern Africa and southern Asia. Finally, the individual contributions of the NEP of each of forest type to global forest's NEP were calculated. The contributions of NEP for the EBF, ECF, DBF, DCF and ECDBMF forests to the total NEP of global forests were 57.19%, 17.07%, 12.17%, 7.10% and 6.47%, respectively. Our findings highlight that, over the past three decades, the EBF, ECF and DBF forests have been the main contributors to the increases in net ecosystem productivity of global forests.