中国农田生态系统水分利用效率的格局与成因

1980—2009年间,中国农业区域年降水总量和年蒸散总量间的差额明显增大,农田水分需求增加,水分利用效率(WUE)是研究水分平衡的关键基础,因此综述WUE时空特征及其驱动机理,能够为不同农业区农田水分供需平衡管理提供理论支持。已有研究表明,中国农田生态系统WUE具有明显的时空差异,空间上总体呈现北高南低、东高西低的特征,时间上,北方农田WUE呈增加趋势,而南方地区相反;降水、气温、辐射等环境因子主要通过蒸散和总初级生产力的动态变化间接影响WUE,作物自身结构和遗传因素主要通过影响冠层和根系水、碳交换能力直接决定WUE的大小,而合理的栽培、灌溉及施肥方式能够提高降水的利用率、减少灌溉水损耗、改善群体光合性能,从而提高WUE。结合WUE的时空特征和变异机理,提高作物吸水特性、降低灌溉水损耗对于北方地区农田WUE的提高具有重要意义,而协调降水的季节分配、减少蒸散量和地表径流量是改善南方地区农田WUE的关键手段。

Pattern of Agroecosystem Water Use Efficiency and Its Formation Causes in China

Water use efficiency (WUE) is the basis in water balance research, and the review of spatialtemporal characteristics and drive mechanism of WUE could provide reference for co-ordination management of water supply and demand in different farmlands. The previous study showed that WUE in China had significant spatial-temporal difference, which was generally higher in the north than that in the south and higher in the east than that in the west. In time distribution, WUE in northern farmland showed an increasing trend and that in south China showed a decreasing trend. The precipitation, temperature and radiation indirect affected WUE through the influence on evapotranspiration and total primary productivity, plant structure and genetic factor mainly affected WUE thorough its influence on canopy, root water and carbon exchange capacity, the rational cultivation, irrigation and fertilization could increase WUE of precipitation, decrease the loss of irrigation water, improve the photosynthetic property, and then increase WUE. Considering the spatialtemporal characteristics and variation mechanism of WUE, increasing the water absorption characteristics of crop and reducing irrigation water loss are preferable ways to improve WUE in north China, while coordinating seasonal distribution of precipitation and reducing evapotranspiration and surface runoff are efficient approaches to promote WUE in south China.