Soil Water Holding Capacities And Infiltration Characteristics Of Vegetation Restoration Models In Dry-hot Valley Of Jinshajiang River Basin

Dry-hot valley is a special ecosystem of southwest china. Because of natural, historical and man-induced reasons, the ecosystem degraded seriously which results in soil and water loss and large vegetation restoration diffculties. Therefore, three vegetation restoration models (Leucaena, Tamarindus indica+Paspalum notatum Flugge; Heteropogon contortus) of Yuanmou Dry-hot Valley, Yunnan Province were selected with bare land as control. By using field test, laboratory analysis and computer simulation, soil properties, soil water holding capacities and infiltration characteristics of above models were studied. The main results are as follows:(1) Soil bulk density, total porosity, capillary porosity, non-capillary porosity and the organic matter content of three models were all showed as Tamarindus indica +Paspalum notatum Flugge>Leucaena>Heteropogon contortus. Compared withthe bare land, soil physical and chemical properties of three models indicated that vegetation coverage had improved soil texture to a different extent, and the upper, improvement effect the better.(2) Tamarindus indica +Paspalum notatum Flugge, Leucaena had better soil water-holding capacity . Soil saturated water storage, water-holding capacity in non-capillary porosity, water-holding capacity in non-capillary porosity were all shown as Tamarindus indica +Paspalum notatum Flugge> Leucaena> Heteropogon contortus. The improvement function that each model plays on soil non-capillary porosity water-holding capacity was greater than on soil capillary porosity water-holding capacity.(3) As the depth increased, the soil saturated hydraulic conductivity of three models decreased. The upper was shown as Tamarindus indica +Paspalum notatum Flugge(2.37mm min^-1>Leucaena (1.02mm min^-1)>Heteropogon contortus(0.85mm min^-1), while the bottom was shown as Tamarindus indica +Paspalum notatum Flugge(1.69mm min^-1) > Heteropogon contortus(0.69mm min^-1) > Leucaena. (0.58mm min^-1). Analysises had indicated that there was a very significant negative linear correlation between soil bulk density and soil saturated hydraulic conductivity, while total porosity, capillary porosity and non-capillary porosity had a very significant positive linear correlation with it. Non-capillary porosity had a bigger influence than others.(4) Infiltration eigenvalues of three models was shown as initial infiltration rate > average infiltration rate > stable infiltration rate, and they had no obvious relationship with seasons. The longest time to reach stable infiltration stage was 42min(appeared in Leucaena), while the shortest was 20min(appeared in bare land). The biggest cumulative infiltration was 326.2mm(appeared in Tamarindus indica + Paspalum notatum Flugge), while the smallest was 41.6mm(appeared in bare land). Principal component analysis showed that inspite of dry season or rainy season, permeability of different models both presented as Tamarindus indica -hPaspalum notatum Flugge>Heteropogon contortus>Leucaena>bare land.(5) Analysises had showed that permeability of different models had a significant positive linear correlation with total porosity, non-capillary porosity and the organic matter content, and a significant negative linear correlation with soil bulk density. Based on the analysises dominant factor equations were established.(6) Simulations of soil infiltration processes were done on the different models. The results showed that fitting precision were shown as General empirical model > Kostiakov model > Philip model >Horton model. Error analysis indicated that values calculated by the General empirical model was most similar to the measured values on the attenuation stage, and its fitting results were more closed to the measured values than the Kostiakov model. These improved that General empirical model was the best model to describe the soil infiltration processes of this area.