Abstract

The spatial-temporal variation character-istics of vegetation activity and its cli-mate response patterns are of great sig-nificance in deepening our understand-ing of regional vegetation degradation and climate change trends. The response of vegetation to climate factors varies spatially due to its heterogeneity. More-over, there may be lag periods before climate factors affect vegetation. In this paper, we studied the responses of vege-tation to climate factors at an ecosystem-dependent scale. GIMMS NDVI3g data were collected to indicate vegetation activity. Pure pixels with a single vegeta-tion type were extracted to reduce the influence of the raw NDVI data. Then, a stepwise regression method was adopted to calculate the regression equation for NDVI and meteorological data with the consideration of effect lag times. In the results, the vegetation activity showed an overall increasing trend over the last 31 years, but there was strong spatial heter-ogeneity. The response of vegetation activity to most climate factors showed a lag, especially the response to precipita-tion. Generally, there was no correlation between vegetation coverage and precip-itation at the start of the growing season. Moreover, for most vegetation, the cor-relation between vegetation activity and precipitation increased to a peak and then decreased during the growing sea-son. In addition, there was no obvious lag period for the effect of the sunshine percentage on vegetation. The lag period of temperature varied on different vege-tation type and growth stage. These find-ings could contribute to a better under-standing of the drivers and mechanisms of vegetation degradation on the Tibetan Plateau.