| Soil water content plays a critical role in soil nutrient cycling, soil degradation,soil erosion prevention and vegetation rehabilitation.Therefore it is of great significance to study soil moisture properties of silvopastoral system in karst area.Based on the method of field investigation and laboratory analysis, this paper studied on the soil moisture characteristics of the silvopastoral system in karst area, and it mainly discussed from following aspects: the effect of forest-grass composite pattern with soil conditioner on soil water content, prediction of saturated hydraulic conductivity, the correlation analysis between soil physical and chemical properties and soil water content. Discussed from the following aspects:(1)After field investigation, we choosed the Chinese prickly ash and Pennisetum hydridum and control(wasteland) as the research object, and then analyzed the three modes of the soil water content, which were Chinese prickly ash + Pennisetum hydridum, Pennisetum hydridum and control. Compared with the wasteland, grassland(Pennisetum hydridum) and forest-grass land Inter as(Chinese prickly ash +Pennisetum hydridum) were benefit to improve soil water content,increased by2.81%~8.48% and7.84%~9.66%% respectively, and forest-grass composite pattern was better.In pot experiment, Paspalum thunbergii, Perennial ryegrass and Dolichos lablab L. were cultivated to research the effect of soil water content in differents soil conditioners and different forage.Results show that, the average soil water content of planting paspalum enhanced 6.21% ~ 9.94% and 8.67% ~ 21.97% respectively,compared with ryegrass and Dolichos lablab L. The soil capacity of holding water of paspalum was obviously higher than that of Dolichos lablab L..After adding the 5%straw carbon in soil, the average soil water content of planting paspalum, ryegrass and Dolichos lablab L. were increased by 46.34%~48.65%,45.44%~47.75%,38.29%~45.72 respectively compared with control.In conclusion, Paspalum and straw carbon is the best the collocation to improve the soil water moisture, it can be indicates from the result that selecting a suitable forage and soil conditioners is importance to improve the soil water content.(2)The saturated hydraulic conductivity was predicted by the soil transfer function model(HYPRES), and the infiltration and seepage characteristics of soil moisture could be reflected from it too. For the field investigation, grassland(Pennisetum hydridum) and forest-grass land Inter as( Chinese prickly ash +Pennisetum hydridum) were benefit to improve the soil saturated hydraulic conductivity, increased by 23.55% ~ 40.95% and 41.37% ~ 47.21% respectively compared with the control.In pot experiment,straw carbon processing Planting paspalum, ryegrass and Dolichos lablab L. Soil saturated hydraulic conductivity increased by 38.29%~45.72, 45.44%~47.75% and 46.34%~47.69% respectively compared with the control in straw carbon treatment, in terms of three kinds of forage grass, planting paspalum is the best, and it is remarkably higher than the Dolichos lablab L. at significance level P <0.01.(3)The change of soil water content is closely related to the physical and chemical properties of soil.The result of the correlation analysis from field investigation showed that the soil bulk density, capillary porosity, field water-holding capacity, water stable aggregates, clay content, sand content and the organic matter are well-associated with soil water content(r > 0.8). Compared with the control, the soil bulk density and sand content of the Pennisetum hydridum were reduced1.82% ~ 11.59% and 6.67% ~ 12.64% respectively, and both of them in Chinese prickly ash+Pennisetum hydridum were reduced 5.93% ~ 7.84% and 31.88% ~41.67% respectively, and the differences of soil bulk density were significant(P <0.01). In Chinese prickly ash+Pennisetum hydridum, the soil bulk density, capillary porosity, field water-holding capacity, water stable aggregates, clay content, sand content and organic matter were higher than that in wasteland. Compared with the control, the above measurement indicators in Pennisetum hydridum were reduced11.40%~20.36%, 4.44%~6.35%,4.55%~18.18%, 10.45%~15.44% and 14.35%~25.25% respectively, but in Chinese prickly ash+Pennisetum hydridum they were reduced 20.27~22.02%, 8.48%~9.49%, 30.33%~41.81%, 17.42%~21.57% and36.04% ~ 41.21% respectively. For pot experiment,the soil physical and chemical properties are in agreement with the results of field investigation.(4)Through correlation analysis in this paper,soil bulk density, porosity, texture,water stable aggregates, organic matter and other 7 representative indicators were selected to establish correlation model of the soil water content and soil physicochemical properties. Result showed that soil bulk density was significantly negatively correlated with soil water content, and it was the main influence factor of soil water content. Summing up the results of the pot experiment and field investigation, the soil bulk density is the common influencing factor, which provides the prediction direction for the reasonable collocation of vegetation in Karst area. |
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