黄土区渭北旱塬苹果基地对区域水循环的影响

通过对苹果地、农田和其他塬面主要土地利用方式的比较研究，发现苹果地土壤入渗速率大、降雨产流率低和存在生物利用型土壤干层。这些水文学性质将增强土壤－植物－大气间垂直水分交换，削弱降雨转化为地表径流和地下水的比例，最终影响区域地表和地下水资源的数量。另外土壤干层的出现还削弱了土壤水库对年际和季节性干旱的调节作用，导致苹果产量随降雨量的自然变化呈现较大波动。

Effect of Apple Base on Regional Water Cycle in Weibei Upland of the Loess Plateau

Weibei Upland in southern part of Loess Plateau is a commercial apple base where the increase of apple planting area has seriously affected the regional water cycle. This paper studies the effects of different land use patterns on hydrological parameters. The main results are as following: (1) The initial and steady rates of infiltration in apple orchard were higher than those in grassland, naked land and farmland. Their initial rates of infiltration were 0 823 cm/min , 0 215 cm/min, 0 534 cm/min and 0 586 cm/min respectively. Their steady rates of infiltration were 0 45 cm/min, 0 038 cm/min, 0 191 cm/min and 0 155 cm/min respectively. (2) No runoff in apple orchard was produced in the 8 events of observed natural rainfalls, but it was produced in winter wheat, corn and alfalfa plots where runoff coefficients reached 2 39%, 1 58% and 0 31% respectively. (3) The transpiration of apple trees was very strong, leading to gradual depletion of the ascendant soil moisture. The average soil water contents of 3~9 meters soil profile in Changwu plots with apple trees of 14 and 32 years old were 11 77% and 11 59% and in Luochuan plots with those of 15 and 28 years old, 11 7% and 11 59% respectively. They are closing to 9 0% of wilting moisture of Changwu soil and 8 6% of wilting moisture of Luochuan soil. The pathway of rainfall percolating to groundwater was shut down by dry soil profile.