| Low hilly is widely distributed in the middle and lower reaches region of Yangtze River, with an area of the region's land area accounts for around 60%. Low hilly areas are basically in the periphery of combining agriculture and forestry, it has a large population density, and complex and diverse site conditions, tending to happen waterpower erosion, inevitably leads to soil degradation and non-point source pollution, which is an important origin of sedimentation and pollution in the Yangtze River water system and the main fountainhead of soil erosion in the middle and lower reaches of Yangtze River. Master the basic law of soil erosion on yellow soil slope surface in this region through the scientific experiments, which is the key prerequisite of bringing forward comprehensive management pattern of the soil erosion in low hilly region of Yangtze River.At present, the domestic and international researches have been related more to the characteristics of slope loess erosion in hilly-gully region of the loess altiplano, the mechanism and prediction models of soil erosion in the south purple soil and the red soil hilly region, but for the soil erosion of yellow soil low hilly in Yangtze River Basin, study more limit to management countermeasures and mode discussing, etc..Through a typical field plots trial, especially the studies that explore the erosion law through comparing simulated rainfall on the slope with the terrace still comparatively lack. In this study, the trial area is Xiangbizui small watershed in Xishui County of Hubei Province, it selects the masson pine natural forest, five-year artificial economic forest+ equally configured ridge hedgerows (including peach+daylily, chestnut+lily, bamboo+lily, plum +lily), peanut agricultural land and other existing vegetation restoration mode, sets the abandoned land that de-farming in five years as a control, carries through the vegetation and soil survey of the typical plot, and field artificial simulated rainfall experiments, combines with the observation data that surface soil erosion of each vegetation restoration pattern, probes into the characteristic of runoff and sand yield process on surface and the law of soil erosion caused by rainfall erosion on yellow soil slope surface in low hilly of the middle reaches of the Yangtze River, analyzes and compares the soil and water conservation function of each restoration mode, in order to lay the foundation for putting forward appropriate vegetation restoration measures and comprehensive treatment pattern of yellow soil region in low hilly of the middle reaches of the Yangtze River. The main findings are as follows:(1) The survey result of vegetation community characteristics shows that, masson pine natural forest pattern has a complex vegetation spatial structure, in which shrub layer coverage,evenness index J are respectively 99.7%,0.890, herb layer richness index R=3.950, the three indexes are higher than the other vegetation restoration mode, and peanut crop lands coverage,60.1%,is minimum. In the artificial vegetation restoration mode, the chestnut+daylily pattern has the highest coverage,98.6%, the rest indexes are not obvious advantage; Plum+daylily pattern s R, H value of the highest, respectively 3.960 and 2.342, D, J value also at a high level; Peanut crop land in all indexes are lower than other modes; The D, J value of Abandoned land (control) mode is the highest, respectively 0.861,0.804, coverage and the R value are only higher than the peanut crop land.(2) Soil survey result display, the primary physical properties of all vegetation restoration patterns have small differences, the main chemical properties are complex, the difference is comparatively obvious, the soil nutrients have visible surface aggregation phenomenon. The analyze result by integrating various physical and chemical indexes show that soil condition of the masson pine natural forests is best, soil permeability coefficient, organic matter, total nitrogen, total phosphorus, available phosphorus and potassium content have a distinct advantage, followed by chestnut+daylily, and peach+daylily, plum+daylily, bamboo+daylily are similar with the abandoned land (control) mode, peanut crop land is the worst.(3) The field of artificial simulated rainfall tests shows that, under the premise of some conditions(water and heat status, soil, small terrain, and so on) are comparatively consistent, the terrace's effect of soil and water conservation is markedly better than slope land's, the runoff and sand yield process of slope land is more complex; About blocking runoff and increasing infiltration forestland be clearly better than the agricultural land; The vegetation coverage, species diversity have a great impact on runoff and sand yield process on the land surface; The relevant polynomial correlativity equation of cumulative runoff, sand yield and rainfall duration of each simulated rainfall meet"Y= ax~2+bx+c (a>0) "form.(4) The observation data of field run-off plots shows that, the initial yield duration of abandoned land (control),peach+daylily and masson pine that in a simultaneous observation under a continuous natural rainfall is increase in turn; The runoff and sand yields on surface are manifest as masson pine< peach+daylily< abandoned land (control) mode; The change that surface soil nutrient content before and after of rain nutrient content data in the runoff water indicate that soil nutrient has been gradual losing with the runoff process, but did not show obvious loss law.Use the abandoned land (control) mode as a reference, the compare result of surface runoff and soil erosion amount of all vegetation restoration patterns in three observation period shows that, the reduction rate of surface runoff and soil erosion is the largest, of the most obvious capacity that water storage and soil conservation, the capacity that water storage and soil conservation of the artificial vegetation restoration patterns magnitude as:chestnut+daylily> peach+daylily> bamboo +daylily>plum+daylily, they all exceed the abandoned land (control) mode.(5) Judging from the soil and water conservation function of vegetation, due to the adverse influence of vegetation coverage, soil fertility and other aspects, combined with observation data of field run-off plots to analysis, the function that water, soil and fertilizer conservation of the abandoned land (control) mode comparatively not good, lower than the other six vegetation restoration patterns diverse degrees.The soil and water conservation function of masson pine pattern is the first in all vegetation restoration patterns lie on the obvious advantages on community characteristics of vegetation, soil physical and chemical properties and other aspects. Compare with the abandoned land (control) mode, its reduction rate of surface runoff is about 40%, reduction rate of soil erosion is high to 80%. The water and soil conservation function that natural forest modes which masson pine forest as the representative is very significant.The analyse that vegetation community characteristics, soil physical and chemical properties and observation data which from the field run-off plots show that, the soil and water conservation function of peach+daylily mode is weaker than chestnut+daylily mode in the artificial vegetation restoration patterns, has little advantage compared with the rest modes. Compare with the abandoned land (control) mode, its reduction rate of surface runoff is around 20%, reduction rate of soil erosion is about 80%. The water and soil conservation function that economic forest+ridge hedgerows modes which peach+daylily as the representative has a gap compare with that of natural forest modes, and making sure its regional popularization sense only also through actual inspection of economic, ecological, social and other indexes.The analyse that vegetation community characteristics, soil physical and chemical properties and data from the field of artificial simulated rainfall tests show that, the surface initial runoff duration of peanut crop land is short, the initial losses are less, about blocking runoff and increasing infiltration it be clearly weaker than the forest land. The water and soil conservation function that crop land modes which peanut land as the representative has a distinct gap compare with that of the masson pine natural forest,chestnut forest land and other vegetation restoration patterns.
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