老哈河流域地表植被覆盖对干旱的响应

Vegetation response to meteorological drought in Laohahe Basin

在原有的帕尔默旱度模式中嵌套双源蒸散发能力计算模型和混合产流模型,采用老哈河流域内及周边的15个气象站资料修正模型参数,构建可用于变化环境下植被-干旱响应关系分析并适用于我国北方地区的机理性旱度模式,计算研究区域各栅格逐月的帕尔默干旱指标,通过分析和建立归一化植被指数与帕尔默干旱指标的关系来定量评价老哈河流域不同植被类型归一化植被指数对气象干旱的响应.研究结果表明:(a)在植被生长期的开始和结束阶段,干旱对植被的影响较小;在植被生长期的中间月份,干旱对植被影响较大,其中6月份是研究流域植被的水分敏感期.(b)不同的植被类型受干旱影响的程度不同,干旱对灌丛和草地的影响大于对林地的影响.(c)带虚拟变量的回归模型能够合理地描述季节性的影响,模型的模拟精度较高,因此在考虑季节影响的情况下归一化植被指数可以用于干旱监测.

Based on the Palmer drought severity model,a physically-based drought severity model,which can be applied to assessment of the vegetation response to meteorological drought in a changing environment and is applicable to semi-arid regions in northern China,was established using the two-source PET model and hybrid runoff model.The model parameters were modified using the data from 15 meteorological stations in the Laohahe Basin from 1957 to 2008.The monthly PDSI value of each grid cell in the study area was calculated,and the correlation analysis and regression analysis of monthly NDVI and PDSI were conducted to quantitatively evaluate the responses of different types of vegetation to drought.The results show the following：（a） The effect of drought on vegetation was limited in the beginning and end of the growth period,and the drought influenced the vegetation remarkably in the middle of the growth period,during which the moisture-sensitive period appeared in June.（b） The responses of different types of vegetation to drought were different.The effect of drought on woodland was less than that on grassland and shrubland.（c） The high goodness-of-fit of the NDVI and PDSI correlation using the regression model with dummy variables indicated that NDVI is a good indicator of moisture conditions and can be used for detecting and monitoring drought with consideration of seasonal effects.