北京东灵山辽东栎林树木生长对气候要素的响应特征

根据北京东灵山辽东栎(Quercus wutaishanica)的年轮宽度资料,分析了该地区树木生长在1951—2010年时段对气候要素的响应特征。相关分析表明,夏季干旱胁迫是限制东灵山辽东栎树木生长的最为重要的气候要素,主要体现在与夏季(7—9月)温度的负相关关系和夏季降雨(7月)的正相关关系,另外春季(5月)温度对树木生长也有一定的限制性影响;年表与生长季节干旱指数普遍呈正相关关系,进一步证实了干旱胁迫对树木生长的限制性作用。滑动相关分析表明,年表与夏季温度负相关关系及与夏季降雨的正相关关系在近期趋于增强,这表明夏季干旱胁迫对树木生长影响作用有不断加强的趋势。辽东栎林是北京东灵山温带落叶阔叶林的优势群落,在暖干化气候不断发展背景下,辽东栎林生长的干旱胁迫效应将更加突出,对北京东灵山地区森林的生产力及固碳能力产生负面影响。

Tree-ring growth responses of Liaodong Oak (Quercus wutaishanica) to climate in the Beijing Dongling Mountain of China

Based on tree-ring width data of Quercus wutaishanica forest in Beijing Dongling Mountain, we detected response sensitivity of radial growth to local climate variables during the overlap period (1951-2010) between tree ring and climate data. Correlation analysis indicated that yearly growth was strongly correlated with summer temperature (from July to September) and precipitation (July), indicating summer drought stress was the major constraint for tree growth. Tree radial growth was also positively correlated with growing season (from April to October) Palmer Drought Severity Index (PDSI), further confirming high sensitivity of tree growth to moisture condition. Additionally, climate condition in spring had a partial influence on tree growth, representing the significantly negative correlation with May temperature. Moving correlation analysis revealed that the relationship between tree rings and summer temperature (negative) and precipitation (positive) has become strengthened in the recent years. This predominantly show that the influence of summer drought stress on radial growth becomes more evident recently. Climate change models predict higher temperatures and increasing drought stress in the study area. The elevated dry climate will increasingly threaten Q. wutaishanica forest growth, allowing a downward trend in Net Primary Production (NPP), and the weakened ability of terrestrial carbon sink of local forests should be expected.