Abstract

The spatial-temporal variation characteristics of vegetation activity and its climate response patterns are of great significance in deepening our understanding of regional vegetation degradation and climate change trends. The re-sponse of vegetation to climate factors varies spatially due to its heterogeneity. Moreover, there may be lag periods before climate factors affect vegetation. In this paper, we studied the responses of vegetation to climate factors at an ecosystem-dependent scale. GIMMS NDVI3g data were collected to indicate vegetation activity. Pure pixels with a single vegetation type were extracted to reduce the influence of the raw NDVI data. Then, a stepwise regression meth-od 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 heterogeneity. The response of vegetation activity to most climate factors showed a lag, especially the response to precipitation. Generally, there was no correlation between vegetation coverage and precipitation at the start of the growing season. Moreover, for most vegetation, the correlation between vegetation activity and precipita-tion increased to a peak and then decreased during the growing season. 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 vegetation type and growth stage. These findings could contribute to a better understanding of the drivers and mechanisms of vegeta-tion degradation on the Tibetan Plateau.