Grassland response to drought in northern China
中国北方草原对气候干旱的响应

Dynamic variation of grassland growth is influenced and restricted by climatic conditions.However,it mainly depends on moisture condition.To clarify preferably relations between grassland growth and drought,we adopted NDVI(Normalized Difference Vegetation Index) representing variation of grassland growth and SPI(Standardized Precipitation Index) characterizing drought to study linear relations between desert,type,meadow steppe and drought.The results showed that seasonal drought had great influence on dynamics of desert steppe growth,whereas,short-term,medium-term and long-term drought had little influence.Dynamics of typical steppe growth showed a strong response to seasonal drought,a lower response to short-term,medium-term and long-term drought.Dynamics of meadow steppe growth indicated clearly a strong response to seasonal drought and long-term drought.It was found to have lag effects of precipitation on grassland,cumulative effects of abundance and lack of moisture on grassland.Simulated response relation grassland NDVI to SPI by regression model containing dummy variables and simple regression model respectively,goodness of fit occurred in regression model with dummy variables.It was concluded that dynamic variation of grassland growth response to drought had seasonal effects.