Nonlinear vegetation phenology shifts over northern China during 1982-2006

The response of vegetation phenology change to climate change effects in the Northern China has been reported in the past several decades. Phenological change is a critical understanding in terrestrial carbon cycling. This study aims to investigate linear and nonlinear change trends and nonlinear response change trends in climate in vegetation phenology over Northern China in the last three decades. We analyzed the vegetation phenology over the Northern China by the new released Global Inventory Modeling and Mapping Studies (GIMMS) Normalized Difference Vegetation Index (NDVIg) dataset from 1982 to 2006.Results show that based on linear method, we can found that SOS was gradually advanced, EOS gradually delayed, and then LOS gradually lengthened. But on the basis of nonlinear method, phenological trends in the SOS, EOS and LOS are not continuous, we can found extended LOS with advanced SOS and delayed EOS before the turning point (TP) of spring SOS and autumn EOS trends and shortened LOS with delayed SOS and advanced EOS after the turning point (TP) of spring SOS and autumn EOS trends.