| Due to the complexity of topography, human activities and other factors, the hill-gully Loess Plateau region is one of the most serious soil erosion area in China. Vegetation restoration is an effective measure for soil and water conservation in the Loess Plateau region. In the study, different plant communities on different abandoned slope cropland in typical watersheds of Ansai County were selected as the research object. The annual soil erosion intensity in 2012-2015 was constantly monitored by erosion pin method, and the characteristics of soil erosion of different plant communities at presentwere analyzed combining with the investagating of charicteristics of rainfall and plant communities. The main results as follows:(1) The rainfall amounts of 2012, 2013 and 2014 were 480.2, 880.2 and 672.5mm, respectively.Compared to the mean rainfall 457.3mm of 1971-2015, it was suggested that the years of 2012, 2013 and 2014 were normal flow year, high flow year and high flow year respectively, which were larger than 457.3mm which was the mean rainfall amounts of 1971-2015. The rainfall amounts of 2015 was 310.2mm, belonged to low flow year, less than the mean value over the years.The order of monthly rainfall amounts was July>August>September>June>May>October which was same asthe annual mean value of 1971-2015. And the order of days of monthly rainfall was September>August>July>June>May>October, it was different with the annual mean value of 1971-2015 which was August>July>September>June>May>October. Coefficients of variation of monthly rainfall amounts and days were 43.7-118.7% and 32.3-37.7%, respectively. The maximum rainfall amounts and days occurred in July. The order of contribution rate of rainfall in different levelsto total rainfall was moderate rain>heavy rain>light rain>rainstorm, different with the annual mean value order of 1971-2015 which was moderate rain> light rain>heavy rain>light rain>rainstorm. The order of rainfall times was light rain> moderate rain>heavy rain>rainstorm, which was the same asthe annual mean value of 1971-2015.(2) There were 91 species belonged to 32 families(71 genera). The number of species of Compositae, Gramineae and Leguminosae accounted for 57.14% of the total number of species. The number of species of herb community was slightly greater than both tree and shrub communities. The numbers of families and genera under tree and shrub were slightly bigger than that of herb community. Richness index, diversity index and evenness index had no significant difference in different communities. The coverage of different communities was 20.1%-70.0%. In general, the regularity of coverage was shrub community>tree community>herb community. The above-ground biomass of herb community was 26.4-126.7 g/m2; the above-ground biomass of shrub community was 182.6-257.3 g/m2; the above-ground biomass under tree community was 35.5-72.0 g/m2.(3) Annual soil erosion intensity of different plant communities was between 878.1 and 5099.7 t/(km2?a). In general, annual soil erosion intensities of artificial Robinia psendoacacia community and shrub community were the greatest and the least, respectively. With the increase of returning time and the development of succession stage, the annual soil erosion intensity of herb community was decreased. The average annual soil erosion intensity of shurb communities and artificial Populus forest was 1228.1-2521.8 t/(km2?a); the average annual soil erosion intensity of artificial Robinia psendoacacia forest reached 3874.99 t/(km2?a) and it belonged to middle intensity erosion.(4) There was a significant positive correlation between annual rainfall and annual soil erosion intensity in Artemisia gmelinii community, Hippophae rhamnoides community and Robinia psendoacacia community. The relationship between annual heavy rainfall and annual soil erosion intensity was a significant positive correlation in Artemisia gmelinii community, Stipa bungeana community, Caragana intermedia community and Bothriochloa ischaemun community. The relationship between annual rainstorm and annual soil erosion intensity also was a significant positive correlation inArtemisia giraldii community. Heavy rain and rainstorm played an important role in soil erosion in Hippophae rhamnoides community and Robinia psendoacacia community. The relationship between slope and annual soil erosion intensity was a significant power function relation in herb community, shrub community and tree community. There was a negative exponential function relation between coverage and annual soil erosion intensity in herb community, shrub community and tree community. Critical effective coverage of different communities was between 27.0% and 87.9%. The critical effective coverage increased with the increase of annual precipitation. |
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