青藏高原高寒草地植被指数变化与地表温度的相互关系

为了解脆弱的高原生态环境对升温过程的响应,利用1982-2006年国家标准地面气象站地表温度和GIMMS-NDVI数据集,探讨了青藏高原高寒草地植被指数和地表温度的变化特征及其相互关系.结果表明:1982-2006年,高寒草地NDVI、地表温度整体均呈现增加趋势,年均NDVI、生长季NDVI、年最大NDVI(NDVImax)与年均地表温度、生长季地表温度的上升趋势分别为0.007(10a)-1、0.011(10a)-1、0.007(10a)-1与0.60℃·(10a)-1、0.43℃·(10a)-1;NDVImax与地表温度显著相关的地区达70.49%.但是高原地形、气候、水文环境的空间差异性导致高寒草地NDVI与地表温度的相关关系十分复杂.NDVImax与年均地表温度的相关性最为显著;在返青期和枯萎期,NDVI与地表温度均为显著正相关.不同的植被覆盖条件下,NDVI对地表温度的响应不同:植被覆盖差以及退化严重的地区,NDVImax与地表温度呈负相关性;反之,NDVImax与地表温度主要表现为正相关.

Relationship between vegetation index and ground surface temperature on the Tibetan Plateau alpine grassland

To improve the understanding on response mechanism of the vulnerable ecological system on the Tibetan Plateau to the climatic change, relationship between alpine grassland vegetation index and ground surface temperature from 1982 to 2006 is investigated over the Tibetan Plateau. The data resources are ground surface temperature (GST) data from meteorological stations and relative cell NDVI values quoted from the GIMMS NDVI database. Employing regression analysis method, correlations between alpine grassland'' NDVI and GST by various time-scale and the annual changes both of them are focused on. The results show that both of alpine grassland NDVI and GST showed positive trend from 1982 to 2006 overall the plateau. The trend of annual mean NDVI, NDVI in growing season, maximum NDVI and annual mean GST, GST in growing season were 0.007, 0.011, 0.007 per decade and 0.60, 0.43 degrees Celsius per decade, respectively. The area of maximum NDVI associated with GST accounted for 70.49%. However, spacial heterogeneity in topography, climatic condition and hydrological condition led the complexity in the impact of GST to the growth of grass. The correlation between maximum NDVI and annual mean GST was found to be most significant; in reviving and withering period, NDVI and GST were significantly positively correlated. The correlation of the maximum NDVI to the GST clearly depended on bio-coverage:they briefly negative correlated for poor vegetation cover or degrading regions; but positive for the good vegetation cover.