中国北方草原对气候干旱的响应

草原生长动态受气候条件的影响和制约,在很大程度上取决于水分条件.为了较好阐明草原生长与干旱气候关系,利用表征草原生长变化的NDVI(Normalized Difference Vegetation Index)指数和表征干旱的SPI(Standardized Precipitation Index)指数研究了荒漠草原、典型草原、草甸草原与干旱气候的线性关系,表明荒漠草原的生长动态受季节性干旱影响很大,短期、中长期和长期干旱对荒漠草原影响较小.典型草原对季节性干旱响应较强,而对短期、中长期和长期的干旱响应较弱.草甸草原对季节性和长期干旱响应较强.并且草原对降雨量的响应具有时滞效应,水分盈亏对草原的影响是累积效应.利用基于虚拟变量的回归模型和简单回归模型模拟了草原NDVI对SPI指数的响应关系,基于虚拟变量的回归模型显示出对草原NDVI与SPI关系的较优拟合度.表明了草原生长动态对干旱气候响应具有季节性效应.

Grassland response to drought in northern China

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.