锡盟水土保持工作“八五”期间取得成效

1 针对地区特色,采取不同对策1991年,我盟多、兰、太18条小流域被列为“滦河上游”锡盟段国家重点治理区,经过5年时段的连续达标治理,到1994年底,全部完成国家下达的计划任务.共完成水保治理面积363.09 km^2,占计划任务的100.8%,年治理进度90km^2.其中国家投资251万元,地方匹配122.08万元.群众自筹(包括投劳折款)511.73万元.完成总面积中,多伦县完成160.59km^2,占计划任务的111.5%,太仆寺旗完成126.6km^2,占计划任务的87.9%,正兰旗完成75.84km^2,占计划任务的105.3%.

Nutrient Losses in Soils on Loess Plateau

The soil nutrient losses due to excessive soil loss on Loess Plateau were studied by means of runoff plotsand systematical determination of soil nutrients both in sediments and runoff.The results show that theamounts of nutrient losses depended on the amounts of erosion sediments. Along with sediment, 11-197 kgnitrogen/hectare and 9-174 kg phosphorus/hectare were lost, accounting for 92.46-99.47 percent of the totalamount of nitrogen loss and 99.85-99.99 percent of the total amount of phosphorns loss respectively. Thenutrient losses, very small in runoff, were mainly attributed to erosion of a few rainstorms during a year. Thenutrient level in sediment was mostly higher than that in the original soil. Planting grass evidently reducedthe losses of soil nutrients. The N level was lower in runoff than in rainfall so that the N loss from runoffconld be made up by rainfall. Fertilizer application to crops raised the nutrient level in runoff.

The Suitability of Using Leaf Area Index to Quantify Soil Loss under Vegetation Cover

Soil erosion by water under forest cover is a serious problem in southern China.A comparative study was carried out on the use of leaf area index(LAI) and vegetation fractional coverage(VFC) in quantifying soil loss under vegetation cover.Five types of vegetation with varied LAI and VFC under field conditions were exposed to two rainfall rates(40 mm h-1 and 54 mm h-1) using a portable rainfall simulator.Runoff rate,sediment concentration and soil loss rate were measured at relatively runoff stable state.Significant negative exponential relationship(p < 0.05,R2 = 0.83) and linear relationship(p < 0.05,R2 = 0.84) were obtained between LAI and sediment concentration,while no significant relationship existed between VFC and sediment concentration.The mechanism by which vegetation canopy prevents soil loss was by reducing rainfall kinetic energy and sediment concentration.LAI could better quantify such a role than VFC.However,neither LAI nor VFC could explain runoff rate or soil loss rate.Caution must be taken when using LAI to quantify the role of certain vegetation in soil and water conservation.

Study on Influence of Soil Erosion for Different Covered Patterns in Karst Slope of Sugarcane Planting Regions

Sugarcane production is mainly slope cultivation, so soil erosion was serious. The results showed that the different coverage methods have a higher production rate of 39.26%-41.22%, than the control treatment （blank） without covering, so yield-increasing effect was significant. As annual rainfall is around 1,250 mm and the control treatment（blank） without covering, the whole year of fertilizer runoff was 175 mm, the average soil content of runoff water was 2.22 g/L, and the total amount of soil loss was 3585.0 kg/ha. The treatment with farmer fertilization practice ＋ plastic film mulching annual runoff water was 153 mm, the average soil content of runoff water was 2.30 g/L, and the total soil loss of volume was 3183.0 kg/ha. The treatment with optimize fertilization ＋ plastic film mulching annual runoff water was 141mm, the average soil content of runoff water was 2.42 g/L, and the total amount of soil loss was 2958.0 kg/ha. Sugarcane leaves covered treatment runoff did not occur throughout the year. The coverage of treatment compared with the control treatment, runoff water reduction is in the range of 12.6-16.0%, is 15.8-23.8% reduction in the amount of runoff soil. Treatment with no fertilization nutrient N loss was 5.760 kg/ha, and P205 loss was 2.565 kg/ha in runoff water. Farmer fertilization treatments the nutrient N loss was 12.435 kg/ha, and the loss P205 was mulching treatment nutrient N loss was 7.755 kg/ha, and P205 loss was 3.960 kg/ha in water runoff. Optimizing fertilization ＋ plastic 3.540 kg/ha in runoff water.

Effect of Land Use on Soil Erosion and Nutrients in Dianchi Lake Watershed, China

Soil erosion and loss of soil nutrients have been a crucial environment threat in Southwest China. The land use and its impact on soil qualities continue to be highlighted. The present study was conducted to compare soil erosion under four land use types(i.e.,forestland, abandoned farmland, tillage, and grassland) and their effects on soil organic carbon(SOC), total nitrogen(TN) and total phosphorus(TP) in the Shuanglong catchment of the Dianchi Lake watershed, China. There were large variations in the erosion rate and the nutrient distributions across the four land use types. The erosion rates estimated by137 Cs averaged 2 133 t km-2year-1under tillage and abandoned farmland over the erosion rate of non-cultivated sites, and the grasslands showed a net deposition. For all sites, the nutrient contents basically decreased with the soil depth. Compared with tillage and abandoned farmland, grassland had the highest SOC and TN contents within 0–40 cm soil layer, followed by forestland. The significant correlations between137 Cs, SOC and TN were observed. The nutrient loss caused by erosion in tillage was the highest. These results suggested that grassland and forestland would be beneficial for SOC and TN sequestration over a long-term period because of their ability to reduce the loss of nutrients by soil erosion. Our study demonstrated that reduction of nutrient loss in the red soil area could be made through well-managed vegetation restoration measures.