三江源地区植被对水分胁迫条件的响应特征

Response of Vegetation to Water Stress in the Three-River Headwaters Region of China

水分胁迫条件是影响植被生长的重要因素之一.本文基于归一化植被指数（NDVI）和标准化降水蒸散指数（SPEI）,研究了三江源地区1983～2010年农田、草甸、阔叶林、针叶林和稀疏草原五种植被类型对于不同尺度SPEI的响应.结果表明,近28年来,三江源地区NDVI在年内差异显著,年均值基本稳定不变.中期和长期SPEI呈现微弱湿润化趋势.在非生长季节,短期SPEI和植被存在较强的负相关关系,说明植被对于干旱有一定的适应能力;而在生长季节,植被和长期SPEI存在正相关关系,说明水分盈亏对于植被的影响具有累积效应.三江源地区植被生长动态对于水分胁迫响应具有季节性和滞后性.SPEI对于不同植被类型的影响表现出一定差异性.

The water stress is one of the most important factors affecting vegetation growth. Based on the Normalized Difference Vegetation Index（NDVI） and Standardized Precipitation Evapotranspiration Index（SPEI）,the response of vegetation to water stress in the Three-River Headwaters Region was analyzed for five representative vegetation types. Results showed that inner annual variability in the NDVI showed significant seasonal differences,and the midterm and long-term SPEI had a humid trend. During the non-growing season,the short-term SPEI was strongly negative correlated with vegetation,indicating that vegetation had a certain adaptability to water stress. However,during the growing season,the long-term SPEI had a positive correlation with vegetation,indicating that the water surplus and deficiency had a cumulative effect on vegetation growth. Therefore,the response of vegetation growing dynamic to the water stress in the Three-River Headwaters Region had lag effect and seasonality. Differences existed in the effect of SPEI on different representative types of vegetation.