Influence of Different Densities of Robinia pseudoacacia Forest on Soil Moisture in Loess Region of Western Shanxi Province
On the basis of investigation on Robinia pseudoacacia forestlands in Caijiachuan watershed in loess region of western Shanxi province, R.pseudoacacia forestlands with the densities of 1 400 trees/hm2 and 2 200 trees/hm2 were selected to represent low and high density R.pseudoacacia forests of this region respectively, with the bare land as a control sample plot.Based on the located observation of soil moisture at 0-150 cm soil layer of sample plots, soil moisture condition and its' spatio-temporal changes in forestlands with different densities of R.pseudoacacia were studied, and the effects of rainfall on compensation and rehabilitation of soil moisture in R.pseudoacacia forestlands were investigated by measuring the deficit and compensation degree of soil water storage.The results showed that: (1) The annually average soil water storage of low density R.pseudoacacia forestland was 7.49 mm higher than that of high density R.pseudoacacia forestland, and the period of low density R.pseudoacacia forestland in which soil water storage reached the optimal water storage was 60 days longer than that of high density R.pseudoacacia forestland;(2) in vertical direction of soil profile, there was no significant difference between soil moisture consumption of low and high R.pseudoacacia forestlands at 30-150 cm soil layer, while high density R.pseudoacacia forest consumed more soil water than low density R.pseudoacacia forest at the surface layer of soil (0-30 cm);(3) in consideration of rehabilitation of soil moisture and rainfall compensation depth under different rainfall intensities, it was found out that soil water deficit in high density R.pseudoacacia forestland was relatively greater and natural rainfall wasn't sufficient to compensate the soil moisture;however, soil moisture in low density R.pseudoacacia forestland could recover to high level after raining.On the whole,the soil moisture condition of low density R.pseudoacacia forestland was better.Therefore it is suggested that the planting density of R.pseudoacacia forestland in the study area should be less than 1 400 trees/hm2.
loess region of western Shanxi provinceRobinia pseudoacaciasoil water storagedeficit degree of soil water storagecompensation degree of soil water storage
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