作 者 ：孙智辉,刘志超,雷延鹏,曹雪梅
期 刊 ：生态学报 2010年 30卷 2期 页码：533~540
Keywords:vegetation, normalized difference vegetation index （NDVI）, climate, the hilly and gully region of northern Yan’an,
摘 要 ：利用GIMMS和SPOT两种归一化植被指数（NDVI）数据和气候资料，分析延安北部丘陵沟壑区1982—2007年植被覆盖的历史演变及其与气候因子的关系。结果表明: (1) 延安北部丘陵沟壑区植被覆盖状况26a来尽管有波动起伏，但是整体在持续转好，年平均NDVI增加了14.2%。夏季的NDVI值最高、波动起伏最大，其次是秋季，春、秋季的NDVI年际变化具有明显的上升趋势。各季NDVI与年NDVI均有相关关系，春、秋季NDVI与年NDVI相关显著。NDVI年内变化曲线为单峰型，春季NDVI缓慢增加，秋季NDVI降低速度比较快。(2)年平均NDVI与年温度相关不明显，夏、秋、冬三季NDVI与同期温度相关也不明显，只有春季平均NDVI与该季温度相关显著。3—4月份温度对植被的影响呈正相关，温度越高，返青生长越快；初夏6—7月份，温度对植被生长有滞后影响，前期温度与后期NDVI为负相关。降水量是引起NDVI年际波动的影响因子之一，年降水量与当年7月和9月份NDVI相关，决定了一年植被最为旺盛时的好坏。月降水量对NDVI影响具有滞后性，上年9月份降水影响翌年4—6月份的NDVI，6月和7月份NDVI受当月和前期降水影响。 (3) 1999年以来，延安北部丘陵沟壑区植被覆盖快速上升，除与降水增多有关外，非气候因素中生态保护和环境建设等人为措施，如植树造林、封山禁牧等封育措施是导致植被显著增加的重要原因。
Abstract:The GIMMS and SPOT, which are the Normalized Difference Vegetation Index (NDVI), are utilized to analyze the historical evolution of the vegetation cover in Hilly and Gully Region of Northern Yan′an from 1982 to 2007 and relationship with climate factors. The results show that (1) The vegetation cover status is getting better continuously, although there were undulations in vegetation cover over past 26a in this region, and the averaged annual NDVI increased by 14.2%. The NDVI in summer is of maximum value and remarkable undulation, the NDVI value in autumn is next, while NDVI in spring and autumn has distinguished uptrend. NDVI values in each season are related with annual NDVI, and correlations of spring and autumn NDVI with annual NDVI are significant. The annual variation of NDVI is single peak type, while the spring NDVI increased slowly, the autumn NDVI decreased more rapidly. (2) There was no obvious correlation between annual average NDVI and annual temperature, and also poor correlation of NDVI in summer, autumn and winter with temperature in the same phase, only the NDVI in spring was correlated significantly with spring temperature. The impacts of temperature in March and April on vegetation are positive, the higher the temperature is, the faster the growth after returning-green stage of vegetation is. The temperature in June and July has negative lag influence on vegetation growth. The precipitation is one of the key factors influencing variation of NDVI, annual precipitation is related with NDVI values in July and September, which determines good or bad vegetation. The effect of monthly precipitation on the NDVI has hysteresis characteristic, the precipitation in preceding September affects the NDVI in April to June in next year, the monthly and previous precipitation affect the NDVI in June and July. (3) The vegetation cover has increased rapidly in Hilly Gully Region of Northern Yan′an since 1999, which maybe associated with increasing precipitation, and also with some non-climate factors by adaptive strategies in ecological conservation and environment protection, such as afforestation, mountain enclosure and fenced grassland.
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