Climate Change Vulnerability Of Forests In Eastern China

The vulnerability of forest ecosystem to climate change has gradually become one of the current research hotspots in ecological studies in the context of recent years’ global climate change.As one of the most important functions of ecosystems,forest productivity is often used as an indicator of vulnerability.Due to the large uncertainty in the estimation of forest productivity,this study first investigated the sampling method on how to use tree-rings to accurately estimate forest productivity.Then,the vulnerability of typical forest communities to recent climate changes in eastern China were evaluated based on reliable productivity time series,and the effects of climate,forest structure and species diversity on vulnerability were also analyzed.In addition,an ecosystem vulnerability assessment method based on climate exposure,vegetation stability and vegetation productivity was proposed,which was then used to evaluate the vulnerability of forest ecosystems in eastern China under past and future climate change using MC2 ecosystem process model.The main conclusions include:(1)It was found that ca.100%,40%,20% and 10% of individuals should be sampled from the 1/4largest to the 1/4 smallest trees,respectively,to ensure an accurate estimation of stand productivity history.The optimum sampling design was highly related with the distribution of productivity and biomass across diameter classes of the plots,and changed significantly along the climate gradient.Sampling designs inferred from models based on the biomass ratio in each diameter class by each plot and climate indices could estimate stand productivity history satisfactorily.It was also showed that previous sampling methods to estimate forest productivity may incur large uncertainties,and these data should be viewed with caution.(2)Assessment base on the probability of change in net primary productivity of typical forest communities showed that,the vulnerability of forest productivity for major forest communities in eastern China has shown regular changes along the latitude and longitude,with a spatial pattern that high in northeast and low in southwest.Climatic conditions,species diversity and stand structure all had significant effects on the vulnerability of forest communities,but climate and diversity played the major role while the effects of stand structure were relatively low.There is no significant difference in the vulnerability of forest productivity between succession stages,but the main influencing factors were different.The results of variance decomposition showed that,the vulnerability of early-and midsuccession forests were more affected by species diversity(explained 13% and 15% of the variances,respectively),while late-succession forests were more affected by climatic conditions(explained 40.6%of variances).The explanatory power of stand structure at all succession stages was relatively low(0.04%-0.63%),but its interaction with climate and diversity had certain impacts(0.01%-12.63%).Therefore,specific measures should be taken for forests at different succession stages to cope with the adverse impacts of climate change on forest productivity.(3)By following the concept of vulnerability proposed by IPCC,this study used a “moisture index”that comprehensively characterizes water and heat conditions to reflect the climate exposure of the ecosystem.An indicator named “vegetation stability” that combined the shift of vegetation types and vegetation intactness was also proposed,and together with the vegetation productivity as the measure of sensitivity and adaptation ability.Based on this method,a comprehensive assessment of the historical and future vulnerability of forests in eastern China to climate change was carried out,with the used of MC2 dynamic vegetation model.The results showed that,the vulnerability of forests in eastern China to climate exposure during the historical period was generally high in the north and low in the south.The vegetation stability was mainly affected by the natural vegetation intactness,but the vegetation type has not changed significantly.Vegetation productivity has also remained relatively stable.The overall vulnerability of the forests was generally low before the significant warming in the early 1980 s,but the subsequent warming in the past four decades has caused more than half of the area to be medium or higher vulnerable,and most were located in higher latitude areas.Under the scenario of continuous warming in the future,the vulnerability of the terrestrial ecosystem’s climate exposure will further increase,and vegetation will generally move significantly to higher latitudes,while the vegetation productivity in most areas will increase,and the overall vulnerability of forests will generally develop into a more vulnerable end.This study firstly explored the method of accurate measurement of forest productivity on the community scale,and used simulation to provide a reliable method for accurately estimating the time series of forest productivity for climate change assessment.Then using forest productivity,which is the core ecosystem function,as an indicator and evaluated the climate change vulnerability of forest productivity for the forests in eastern China.It was found that vulnerability of forest productivity was mainly affected by climate and species diversity.In addition,this study built a new vulnerability assessment framework,and conducted a systematic assessment of the history and future climate change vulnerability of forests in eastern China.The results of this study can not only provide useful methods and valuable decision-making references for current forest management and ecosystem protection in China,but also have important significance for the formulation of relevant policies in the future as the global climate may continue to warm.