干旱对灌溉和雨养农田生态系统生产力的影响对比分析

灌溉是农作物应对干旱等极端气候条件的有效调节机制，在全球气候变化的背景下，未来干旱等极端气候事件发生的频率和严重程度预估会增加，定量分析灌溉和雨养条件下干旱对农田生态系统农作物生长的影响有助于更好地评估人类应对极端气候事件对生态系统的消极影响的能力，为制定合理有效的生态系统保护措施提供依据。以中国北方干旱区为研究区，基于标准化降水蒸散指数产品和MODIS增强型植被指数以及总初级生产力产品，利用MK趋势分析，皮尔逊相关分析和一元线性回归分析研究了2000~2014年间中国北方干旱区农田生态系统干旱、植被指数以及总初级生产力的发展趋势，分析了中国北方旱区农作物对干旱的响应的滞后时间，在相应的滞后时间下对比分析了灌溉农田和雨养农田农作物受干旱影响的差异。研究结果显示：在2000~2014年间北方旱区农田生态系统64.10%的区域呈现干旱减轻的趋势、75.78%和81.87%的区域呈现植被指数增加和总初级生产力增加的趋势，其中64.82%的植被指数增加和68.34%总初级生产力增加的区域伴随着干旱的减轻。除半干旱区雨养农田植被指数对干旱的响应的滞后时间为2个月外，其余滞后时间均为1个月。在滞后时间下，去趋势干旱指数与植被指数异常及总初级生产力异常均呈现显著的正相关关系。相对于雨养农田来说，灌溉分别缓解了32.22%和29.42%北方旱区干旱对农作物植被指数和总初级生产力的消极影响，且在干旱区的缓解程度要高于半干旱区。定量分析了干旱对灌溉和雨养农田生态系统GPP和EVI的影响差异，为评估灌溉抵抗干旱气候对植被生态系统的影响研究提供了参考。

Comparative Analysis of the Impact of Drought on the Crop Productivity of Irrigated and Rain-fed Farmland Ecosystems

Irrigation is an effective regulation mechanism for crops to response to extreme climatic conditions such as drought. Due to global climate change， the frequency and severity of extreme weather events such as drought are expected to increase in the future， quantitative analysis of the impact of drought on crop growth of farmland ecosystem under irrigation and rain-fed conditions will help to better assess the ability of human beings to cope with the negative impact of extreme climate events on the ecosystem， and provide a basis for formulating reasonable and effective ecosystem protection measures. The dry lands on northern China is taken as the study area. Based on Standardized Precipitation Evapotranspiration Index （SPEI） products and Enhanced Vegetation Index （EVI）， Gross Primary Productivity （GPP） products provided by MODIS， this paper analyzes the trends of drought and EVI， GPP of farmland ecosystems in the study area from 2000 to 2014 by using MK trend analysis and explores the lag time of crop productivity response to drought by using Pearson correlation coefficient. Then， the effects of drought on EVI and GPP of farmland ecosystem under the corresponding time lag are analyzed by using linear regression analysis and the differences in the effects of drought on EVI and GPP of irrigated farmland and rain-fed farmland are further compared. Study results indicate during 2000~2014， 64.10% of the study area showed a trend of drought alleviation， and 75.78% and 81.87% of the study area showed a trend of increased EVI and GPP， of which 64.82%， 68.34% of the areas with an increase in EVI， GPP were accompanied by drought alleviation. Expect for the lag time of rain-fed crop EVI in semiarid dry land response to drought was 2 months， all the rest lag time was 1 month. Based on the lag time， the SPEI and EVI， GPP showed a significant positive correlation. Compared to rain-fed farmlands， irrigation alleviated the negative effects of drought on EVI and GPP by 32.22% and 29.42%. The degree of mitigation in arid area is overall higher than that in semi-arid area. This study quantifies the differences of the impact of drought on the GPP and EVI of irrigated and rain fed farmland ecosystems， which provides a reference for the study of the impact of irrigation resistance on vegetation ecosystems.