| Loess Plateau is one of the most seriously degraded regions in China, where the problem of soil and water loss has been paid highly attention by the state. Since 1999, the state government implemented the policy of returning farmland to forest (grass) on a large scale, which caused dramatic changes on land cover types and landscape characteristics, and also altered the soil hydrological and anti-erosion properties on abandoned slope cropland. The experiment is conducted at the site of the Fangta small watershed in the hilly-gully Loess Plateau region, in which we selected the 21 samples of natural restoration community (Artemisia scoparia community, Stipa bungeana communitiey, Bothriochloa ischaemun community, Artemisia gmelinii+Stipa bungeana community, Artemisia gmelinii+Stipa grandis community, Artemisia gmelinii+Artemisia giraldii communitiey and Sophora viciifolia community, each community has three samples), three artificial Robinia psendoacacia and three artificial Caragana intermedia samples, with three bare slopeland as comparison. We intended to analyze the soil hydrological and anti-erosion properties on abandoned slope cropland, to screen the key factors that could influence these properties, and to discuss the relationship between the two properties by investigating, sampling and analyzing the vegetation and the soils. The main results were as follows:(1) With the succession of natural restoration community, soil natural water content, capillary porosity, total porosity, maximum suction capacity, saturated water holding capacity, and soil steady infiltration rate showed an increasing trend while bulk density showed a decreasing trend, so the soil hydrological property improved constantly. Soil natural water ratio, density, capillary porosity, total porosity, maximum suction capacity, saturated water holding capacity and soil steady infiltration rate of Robinia psendoacacia forest and Caragana intermedia forest in the surface layer were higher than that of annual herbaceous communities and grass communities, lower than that of perennial Artemisia communities and shrub community, while soil bulk density was less than the annual herbaceous community, which indicated that the soil hydrological property of Robinia pseudoacacia forest and Caragana intermedia forest was better than that of the annual herbaceous community and grass communities, worse than that of the perennial Artemisia communities and shrub community.(2) With the succession of natural restoration community, the content of soil clay silt, organic matter,>0.25 mm and> 5 mm aggregates and water-stable big aggregates showed an increasing trend, while fractal dimension of soil aggregate structure and damage percent of soil aggregate structure showed a decreasing trend, and indicated soil aggregate structure improved. And the root biomass, root biomass table area and root length density of soil in fibrous roots (d<1mm) increased, which improved the soil consolidation. So from the annual herbaceous communities to Artemisia grass communities and to shrub community, the soil anti-erosion property increased. The content of soil organic matter,>0.25 mm and>5 mm aggregates and water-stable big aggregates of Robinia pseudoacacia forest and Caragana intermedia forest were higher than those of annual herbaceous community and lower than those of perennial Artemisia grass communities and shrub community, soil aggregate fractal structure dimension and soil structure damage rate were lower than those of annual herbaceous community and higher than those of perennial Artemisia grass community and shrub community, and the root biomass, root surface area, root length density of the soil in fibrous roots (d<1mm) were higher than those of annual herbaceous community and lower than those of perennial Artemisia grass community and shrub community, leading to the soil anti-erosion property of Robinia pseudoacacia forest and Caragana intermedia forest was stronger than that of the annual herbaceous community, weaker than that of the Artemisia grass community and shrub community.(3) Soil hydrological property in the 0-10 cm soil layer could be characterized by soil steady infiltration rate, wilting water content and field to water, while soil anti-erosion property could be characterized by>5 mm water stable aggregate content, organic matter content and root length density (d<1mm). Soil hydrological property in the 10-20 cm soil layer could be characterized by soil wilting containing water, field to content and capillary porosity, while soil anti-erosion property could be characterized by>5 mm water stable aggregate content, silt content and>0.25 mm water stable aggregate content. The wilting moisture content showed a significant positive correlation with clay content, and showed an extremely significant positive correlation with silt content,>0.25 mm water stable aggregates and root biomass (d<1mm), but showed an extremely significant negative correlation with sand content and root length (d<1mm). Field water holding capacity showed an extremely significant positive correlation with clay content, silt content, and root biomass (d<1mm), but showed an extremely significant negative correlation with sand content. In the meantime time,> 5 mm water stable aggregate content had a significant function relationship with soil bulk density, capillary porosity, total porosity, maximum suction capacity and saturated water storage in the 0-10 cm soil layer, which also showed the multiple regression equation extremely significant correlation with capillary porosity and the maximum suction capacity. Therefore, soil-erosion and soil hydrological properties were closely related:... |
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