气候变化对大兴安岭北部蒙古栎种群动态的影响

The Effect on Climate Change on Population Dynamics of Quercus mongolica in Notth Greater Xing'an Mountain

通过对气象因子和样地数据分析表明 ,2 0余年来大兴安岭北部气候趋于变暖 ,低海拔地带蒙古栎呈现明显的进展趋势 ,演替趋于以蒙古栎为优势种的阔叶林 ,海拔较高地带蒙古栎更新不良 ,演替趋于兴安落叶松和几种阔叶树的混生林。蒙古栎种群发展与干暖化具有一致性。在各类气象因子中 ,5月均低温是影响蒙古栎更新的决定性因子 ;由海拔升高引起的区域干燥度降低也是影响更新的重要因子 ,这也说明蒙古栎对冷湿生境的不适应性。

Northern forests play an important role in sustaining the balance of carbon dioxide(CO_2)in terrestrial ecosystems, the impact of climate change on spatial pattern and process of forest ecosystems, especially in high latitude forest area, has became an important ecological issue in world wide during past decade. With the increased atmospheric carbon dioxide (CO_2)and global climate change, forest stand structure and species composition in north forest ecosystem are effected from stand scale to landscape level, NPP over large area may be changing. The indication of global climate change which effects on forest ecosystem is the variation of distribution area of tree species, therefore many studies focus on this issue by means of ecological transect on landscape level. Quercus mongolica often coexists in old forests with korean pine( Pinus koraiensis )and broad-leaved in northeastern forests in China, it becomes a dominance in dry and warm site. Models and field studies show that extension of Quercus mongolica is one of indicators of climate drying and warming in the northeastern forest ecosystems in China. In this paper, we use ecological transect technique and select three typical forest plots to establish one transect from south to north with a gradient driven by temperature factors in northern Greater Xing'an mountain. The transect passes across the northern distribution edge of Quercus mongolica , where it is a sensitive species to reflect climate change. Each plot is 50m×50m(0.25hm 2)and is divided into 625 quadrates(2m×2m)for studying the composition of each species from seedling to canopy trees. The importance values for each species, i.e., Quercus mongolica, Larix gmelinii, Populus davidiana, Betula platyphlla, are calculated by means of relative density, relative frequency and relative prominence in each plot. We also use climate data, comparing with each plot data, to analysis the relationship between the changing trend of climate and the regeneration of Quercus mongolica in this area during past over twenty years.The results show that (1)According to climate factors, i.e., annual average temperature, annual average low temperature, annual accumulate temperature, it become warmer in north Greater Xing'an mountain for recent twenty years whether in south plot, Songling, middle plot, Xinlin, or in north plot, Tahe. The stand structure and species composition is changed by climate change.(2) Quercus mongolica , often existing in lower altitude, extends its distribution area and displays as higher importance value, from seedling to canopy trees, at the north plot Tahe. This means that Quercus mongolica as a dominant species in succession layer at local stand will replace original Larix gmelinii . In Xinlin plot with higher altitude, its regeneration is not good due to relatively low temperature. Larix gmelinii at this location has higher importance value and still is the dominant species mixed with some other broad-leaved. (3)With increased drying and warming of climate, from south plot to north plot, Quercus mongolica can succeed in regeneration and extends. Its regeneration has a close relation with climate factors, especially lower temperature in May in growth season, also with the decrease of aridity index caused by higher altitude. This shows the inelasticity of Quercus mongolica to cold and wet site.