Soil particle fractal dimension and soil moisture physical properties in different forest stands in hilly red soil region
JIA Jiang-Bao, GU Chu-Jun, ZHOU Feng, LIU Jing-Chao, BANG Chao-Yun
(1.Binzhou University, Shandong Provincial Key Laboratory of Eco-Environmental Science for Yellow River Delta, 256603,Binzhou,Shandong; 2.School of Bio-Chemical and Environmental Engineering, Nanjing Xiaozhuang University, 211171,Nanjing; 3.Fujian Changting Monitoring Station of Soil and Water Conservation, 366300,Changting, Fujian:China)
Abstract：Based on the theory of soil fractals and physical hydrology, we investigated soil particle size distribution (PSD), fractal dimension, soil water physical parameters and related affecting factors of four typical vegetations in hilly red soil region of Changding County, Fujian Province. Our aims are to explore the improving effect and the mechanism of the forest vegetation to soil fractal structure and soil moisture physical property. The results indicated that: 1) in hilly red soil region, the mass fraction sequence of soil particles among all kinds of forests was given as follows: coarse>fine sand and gravel particles>silt and clay. Forests could improve the contents of soil fine sand and silt and clay, compared with bare land, and the mixed forest has better improving effects than pure forest. 2)Vegetation restoration could decrease the soil bulk density and increase soil porosity. The sequence of soil total porosity and capillary porosity was given as follows: conifer-broadleaf forest land>arbor mixed with shrub land>conifer forest land>economic forest land>bare land. The soil saturated water content of conifer-broadleaf forest land, arbor mixed with shrub land, conifer forest land, and economic forest land was 1.20,1.16,1.14,1.10 times higher than that of bare land, respectively. The capacity of soil water storage in 0-20 cm soil layer was larger than that in 20-40 cm soil layer. 3)The sequence of soil fractal dimension was given as follows: conifer-broadleaf forest land>arbor mixed with shrub land>conifer forest land>economic forest land>bare land. Soil fractal dimension in 0-20 cm soil layer was larger than that in 20-40 cm. Fractal dimension had significantly positive correlation with soil silt and clay, total porosity, soil saturated water content and void ratio, and had negative correlation with the mass fraction of gravel, soil density. But there was no significant correlation with non-capillary porosity, non-capillary porosity water-holding content, and soil total absorption precipitation and effective precipitation. The soil of four typical forest stands were good structural soil with uneven coefficient in hilly red soil region. Mixed forest has better soil particle distribution, particularly, conifer-broadleaf forest soil. The improving effect of forest vegetation on soil fractal structure and soil moisture physical property was followed as this order: conifer-broadleaf forest land> arbor mixed with shrub land > conifer forest land > economic forest land. The fractal geometry mechanism of improved soil fractal structure and soil moisture property with forest communities was to increase the soil fractal dimension by raising the content of fine-grained soil particles, thereby improving aggregate structure, pore structure, soil texture uniformity and soil moisture physical property. The results of this study could provide reference for scientific selection and distribution of water conservation vegetation types in hilly red soil region.
2012, Vol. 10 
