Study On Soil And Water Conservation Benefits Of Several US Introduced Grasses

Water and Soil are the fondmantal things for the survival and development of human.As important technical means for hunman beings to protect soil and water resources, and improve ecological environment, water and soil conservation has played an important role in the process of human pursuiting sustainable and coordinated economic and environmental development. With their large coverage and relatively rapid growth etc, grassess are playing important roles in water and soil conservation. the authors analyzed the imported 11 United States grasses combining the mathod of indoor artificial rainfall through laboratory analysis and applying the relevant analysis approach of gray system to preliminaryly study these grasses,and studied the relationships between slope\rainfall intensity and runoff\sediment yeild , the relationships between runoff \sediment yeild and runoff time .and contrasted the water and soil conservation benefit of the importanted grasses, which is of important significance on soil erosion control and ecological construction guidance.The conclusions are as follows:Planting grasses can cover the surface and reduces the erosion of precipitation on the ground surface quickly and effectively. Cultivation of fawn can better improve the soil and it's water and soil capacity, compared with other species, its performance is the best overall. Smoth Brome Grass have a better effect of improving soil and water conservation compared to other grasses,and it's performance turned out to be outstanding than other grassess, but when the slop is too big,its water and soil greater ability reduces,so we can planted this species in the area whose slope is relatively smaller. Tall Wheatgrass and Slender Wheatgrass has a lower ability on bearing great rainfall intensity, and it's unreasonable to plant the grass in a heavy rain or rainstorm area, Crested Wheatgrass has a strong performance in heavy rain area compared with other species of water-retention capacity, which can be planted in such areas.Relationship between runoff yeild \ sediment yeild and slope: under the slope of 10°,there was a power regression between rainfall intensity and sediment yeild ,and a logarithmic regression on the heigher slope of 15°and 20°, Namely, the sediment yeild on high slope increases faster then on the low slope ones. With low rainfall intensity of 60mm/h ,there was a Linear function between the slope and sediment yeild,and a power regression of heigher rainfall intensity of 90mm/h and 120mm/h,which means that runoff on high rainfall intensity increases faster then on the low ones.There was a power regression between runoff yeild and sediment yeild ,and the Correlation coefficient is 0.9456. It mesns that runoff yeild increased as the increasing of sediment yeild ,regardless of the rainfall intensity and slope circumstances.The relationship between runoff yeild and runoff time,and sediment yeild and runoff time are not that close.Generally, whether bare land or grassland, the runoff process are increase at the first, gradually reach it's first peak than stabilizing. Different rainfall intensity of the runoff process are significantly different, big runoff also means strong sediment yeild, the runoff process between different slope are obvious. Naked in the same circumsta nces, the runoff yeild of bare land is bigger than grass planting area during the dynamic prossess . in this dynamic process ,the grass planting area has a big runoff yeild than the bare land under the condition of higher rainfall intensity .The process of Sediment yeild is more complicated,it has a characteristics of"more than one Peak and one Valley", because the soil moisture and the cementing power is small, the soil particle is loose, the soil can easily be sputtered at first,and reach its first peak. And than with the extension of rainfall and the increasing of runoff yeild , and the increasing of the water erosion role,the second peak appeared . Since then, with the runoff yeild steadied gradually, the process of sediment yeild goes smoothly. In the Sediment and runoff process, the runoff yeild is related to the sediment yeild relativly, in the dynamic process Such characteristics and circumstances appears more obviously in the performance of bare land than it's appearing in the grass planted area.