摘要
本文讨论了长江上游水源区云南境内土壤侵蚀的范围、程度和保持状况。长江发源于中国西部的青藏高原,横贯大陆西东,全长6380km,其源头位于地壳活动和地质不稳定的高原区,流域区是以水稻生产为主的、土地利用程度较高的农业主产区,所以,土壤侵蚀极其严重;随着三峡大坝的修建,土壤侵蚀产生泥沙淤积将降低水库的使用效率等问题,致使土壤保持成为该区必不可少的措施之一,土壤侵蚀问题正越来越受到关注。文章回顾了云南省的土壤保持工作,并以东川、寻甸为例,阐明了云南省的区域土壤保持措施。在云南农业大学农场正在进行的径流区实验被用于评估不同土壤保持措施的效果。试验选择种植当地的主要作物玉米(Zea mays),采取传统的栽培方法,在三个不同的坡度上,沿等高线种植和顺坡向下垂直种植等处理进行,试验地条件与生产上的坡耕地一致。1993～1996年的研究结果表明:一般情况下,沿等高线种植的地区,土壤侵蚀率较低,采取这种措施,平均侵蚀率为顺坡向种植的0.69;秸秆覆盖和沿等高线种植是比较有效的土壤保持措施。
The scale and severity of soil erosion within the headwaters of the Yangtze River in Yunnan Province are discussed. The Yangtze River rises in the western uplands of the Qinghai-Tibet Plateau and traverses 6380 km through southern and central China. The headwaters are in tectonically active and geologically unstable uplands. The basin is also generally under intensive agricultural use, mainly for rice cultivation. Hence, erosion rates are high and of increasing concern, especially considering the construction of the Three Gorges (Sanxia) Dam in the middle section. Sedimentation within the proposed reservoir could impair its efficiency and therefore soil conservation must be an integral component of basin management. Soil conservation efforts in Yunnan are reviewed and the local-scale planned approach to soil conservation is illustrated, using Oongchuan and Xundian as case studies. An ongoing runoff plot study at Yunnan Agricultural University (Kunming) is used to evaluate the effectiveness of various soil conservation measures. Maize (Zea mays) cropping treatments, typically employed in local agronomic practices, are applied to 30 erosion plots at 3 different slope angles, cultivated both parallel and perpendicular to the contour, thus, simulating a range of agricultural conditions on arable slopes. Plot data from 1993-1996 suggest several suitable soil conservation measures. Erosion rates . were generally lower on plots where contour cultivation was used. The mean contour cultivation erosion rate was 0.69 of the mean downslope orientated cultivation rate. Straw mulch and contour cultivation seem particularly suitable soil conservation measures.
