石羊河上游地区树轮年表与NDVI关系分析

在石羊河上游地区选择4个样点，采集160余根青海云杉样芯，经过固定、打磨、交叉定年和测量等工作，建立研究区的树轮宽度年表。利用美国NASA戈达德航天中心的GIMMS/NDVI数据，建立研究区1982-2006年逐月标准化植被指数（NDVI）序列。发现研究区NDVI年内变化为单峰型，5-8月为生长季，年际间变化则有波动减少的趋势。经过相关性分析后发现，树轮年表与非生长季（上一年9月到当年4月）降水呈显著正相关，非生长季WTBX]NDVIWTBZ]与非生长季的降水呈较明显负相关。分析NDVI与年表关系后发现，生长季WTBX]NDVIWTBZ]与树轮年表相关性较差，而非生长季NDVI与年表相关性较好且为负相关（r=-0.667，p<0.01）。

Analysis on the Correlation between NDVI and Tree-ring Width Chronologies in the Upper Reaches of the Shiyang River

In this study 160 tree cores were collected from Picea crassifolia in the upper reaches of the Shiyang River.After mounted,polished,cross-dated and measured,the tree-ring width chronologies in the study area were developed.The monthly normalized difference vegetation index(NDVI)for the period from January 1982 to December 2006 was created using the GIMMS/NDVI data with the 8 km×8 km resolution from the NASA Goddard Space Flight Center.It was found that the annual NDVI curves were unimodal,the main growth season lasted from May to August,and the annual change of NDVI during the period of 1982-2006 was decreased in a fluctuation way.The relationships among tree-ring width index,NDVI and climatic data were analyzed.The results showed that both tree-ring width index and NDVI were strongly affected by precipitation during the period during non-growth period from September to next April,there was a significant positive correlation between tree-ring width index and precipitation during this period,but a significant negative correlation between NDVI and precipitation.The correlation between NDVI and tree-ring width index in plant growth season was poor,but there was a good negative correlation between them in non-growth season(r=-0.667,p<0.01).