黄土高原作物产量及水土流失地形分异模拟

退耕坡地是近年来黄土高原整治生态环境和控制水土流失的有效措施。基于WIN_YIELD 软件， 以延安燕沟流域为例，利用2005 年延安站的逐日气象数据和燕沟流域地貌、土壤及土地利用等资料， 模拟分析了不同地形高程、坡度和坡向条件下不同作物产量及水土流失的分异特征。结果表明： 在黄土高原， 地形坡度是影响作物产量、径流和泥沙的重要因素， 地形高程和坡向的影响普遍较微弱； 地形坡度越大， 作物产量越低， 高粱和玉米在坡度为25^o 时的产量模拟值分别较0^o 时下降15.44%和14.32%， 大豆、绿豆和马铃薯的下降幅度依次为5.26%、4.67%和3.84%； 产生径流和泥沙随地形坡度的增大而增大， 在坡度20^o左右存在一个高值区间； 不同作物的水土保持效益由高到低依次为大豆、绿豆(豆类)、马铃薯、玉米和高粱； 坡度小于5^o的坡耕地可以不进行梯田改造， 坡度大于15^o 的坡耕地应及早实现退耕还林还草。

Topographic Differentiation Simulation of Crop Yield and Soil and Water Loss on the Loess Plateau

De-farming slope farmland has been an effective measure in recent years for the improvement of the eco-environment and the mitigation of soil and water loss on the Loess Plateau. This paper, taking the Yangou Basin as a case study and using day-by-day meteorological data of Yan'an station in 2005, simulated and analyzed the quantitative relation between crop yield, soil and water loss and topographic condition with the aid of WIN-YIELD software. Results show that: 1) Topographic gradient has important influence on crop yield. The bigger the gradient is, the lower the crop yield. Yields of sorghum and corn decrease by 15.44% and 14.32% respectively at 25o in comparison to the case of 0o. In addition, yields of soya, bean and potato decrease slightly by 5.26% , 4.67% and 3.84% , respectively. The influences of topographic height and slope aspect on crop yield are slight. 2) Under the same topographic condition, different crops' runoff and soil loss show obvious disparity. The benefit of soil and water conservation from high to low ranks soya, bean, potato, corn and sorghum. Topographic gradient has important influence on soil and water loss. In general, the changing trend is that the soil and water loss aggregates with the increase of gradient, and the maximal amount occurs around 20o. The influence of topographic height is slight. Topographic aspect has a certain effect, and the fundamental characteristic is that values are higher at the aspect of south than north. 3) Topographic gradients of 5o and 15o are two important thresholds. The characteristics about soil and water loss with the variation of topographic gradients show that: the slope farmland with gradients less than 5o could remain unchanged, and the slope farmland more than 15o should be de-farmed as early as possible.