长白山东坡植被指数变化及其对气候变化的响应

Variation of vegetation index in response to climate change on the eastern slope of Changbai Mountain, Northeast China

长白山地处温带针阔混交林的中心地带,对气候变化较为敏感.因此,探讨长白山区落叶松(Larix olgensis)树轮宽度和森林归一化植被指数(NDVI)与气候因子的关系,对于了解全球气候变暖背景下陆地生态系统的响应具有重要意义.以长白山自然保护区东坡为研究地点,利用东坡落叶松树轮宽度指数和选取1982-2006年UMD GIMMS NDVI数据及天池气候数据,在分析树轮宽度及NDVI与气候因子关系的基础上,重点探讨长白山东坡落叶松径向生长与NDVI之间的关系,并利用多元回归分析建立落叶松树轮指数与气候因子及年生物量生长量与NDVI的模拟回归方程.结果显示:(1)1957年以来该区温度呈极显著上升趋势,冬季升温最为显著,降水呈微弱下降趋势.(2)1982-2006年年均、夏季和生长季NDVI均呈缓慢下降趋势.(3)长白落叶松年表特征分析表明其生长对气候敏感,适用于进行年轮气候学分析.(4)NDVI与月平均温度相关性较强,且多以正相关为主,与月降水量多为负相关性.(5)落叶松径向生长受当年生长季的气候因子的影响强于上年,但是显著相关的月份略有差异,并且降水的影响要优于温度.(6)落叶松树轮宽度和年生物量生长量与NDVI以负相关为主,生长季NDVI与树轮年表相关性较差,而非生长季NDVI与年表相关性较好.(7)林分单位面积地上生物量为240.72 t/hm2,2009年林分生物量生长量约为2.91 t hm-2 a-1,即每公顷每年固碳约1.46 t,表明该地区老龄落叶松林仍具有较强的固碳能力.综上所述,在长白山地区,长时间序列的年轮宽度数据并不能很好地反映NDVI的长时期变化,利用树轮宽度指数重建该区NDVI有待进一步研究.

Changbai Mountain is located in the heartland of the temperate coniferous and broadleaved mixed forest, which issensitive to climate change. Studying how the tree-ring width of Larix olgensis and forest NDVI in the Changbai Mountain are related to climatic factors could lead to better understanding of the responses of the terrestrial ecosystem in the background of global climate warming. In this work, the tree-ring width index ofL. olgensis in the eastern slope of Changbai Mountain, UMD GIMMS NDVI from 1982 to 2006, and the weather data of Tianchi were selected to analyze the relationships between the tree- ring width and NDVI and climatic factors, and to find out the relationship between radial growth of L. olgensis and NDVI in the eastern slope of Changbai Mountain. The simulated regression equations of the tree-ring index ofL. olgensis and climatic factors, of biomass increment and NDVI, were established by multiple regression analytical method. The results were as follows： 1. Since 1957, the temperature of the region studied was in a highly significant rising trend, with winter temperatures changing most remarkably; but precipitation was in a weak downward trend. 2. From 1982 to 2006, NDVI of annual average, summer, and growing season decreased slowly. 3. The analysis of chronology characteristics of L. olgensis in Changbai Mountain showed that growth ofL. olgensis was sensitive to the climate, thus applicable for ring climate analysis. 4. NDV1 was strongly related to monthly average temperature with a positive correlation, but was negatively related to monthly precipitation. 5. Radial growth ofL. olgensis was more strongly influenced by climatic factors in the growing season of the current year than that of the previous year, with different period of significant correlation, and higher impact of precipitation than temperature. 6.The tree-ring width and biomass increment ofL. olgensis were mainly negatively correlated with NDVI. NDVI in the growing season was poorly correlated to tree-ring chronology, but NDVI outside growing season was well correlated to the chronology. 7. The stand aboveground biomass was 240.72 t/hm2 per unit area now, and the stand biomass increment was about 2.91 thm2 a-1 in 2009, which means about 1.46 t carbon sequestration per hectare per year. It indicated that forest of old Larix olgensis in the region still had a strong capacity of carbon sequestration. In summary, ring width data of long time is not adequate to reflect the variation trend of NDVI in the Changbai Mountain. Further study on the regional NDVI redevelopment is needed.