Characteristics and soil anti-erodibility effects of mulberry forest lands at different altitudes of water-level fluctuation zone of the Three Gorges Reservoir

Due to periodic wet and dry processes, water-level fluctuation zone of the reservoir area is typically ecologically fragile. It is therefore important for protection of the eco-environments of reservoir areas to control soil and water loss in such specifically fragile zones. Mulberry forest plots were selected in the water-level fluctuation zone of the Three Gorges Reservoir in September 2012 at four altitudes (165 m, 170 m, 175 m and 180 m), with no flooding at the 180 m altitude. Soil physio-chemical characteristics, anti-erodibility and the driving factors of mulberry forest lands at different altitudes were studied. The aim of the study was to explore soil anti-erodibility effect of mulberry forests at different altitudes. The study further provides scientific basis for controlling soil and water loss in the reservoir area. Results suggested that soil anti-erodibility indexes for the 0-20 cm soil layer of mulberry forest lands at different altitudes were greatly different, and were in the order of 180 m (38.22%) > 170 m (23.09%) > 165 m (18.4%) > 175 m (10.5%). Soil anti-erodibility index was greater for unsubmerged area than submerged areas. For the same altitude, soil anti- erodibility index of the 0 10 cm layer was higher than that of the 10 20 cm layer. Fifteen indicators of soil anti-erodibility were optimized to 3 principal components ― F₁, F₂ and F₃. The comprehensive evaluation model of soil anti-erodibility index was F = 0.655F₁ + 0.236F₂ + 0.109F₃. Based on the comprehensive model evaluation, soil anti-erodibility was ranked as 180 m > 170 m > 165 m > 175 m. Correlation analysis showed that soil anti-erodibility index had significant positive correlation (P < 0.01) with soil clay content and greater-than 0.25 mm water stable aggregate content, with respectively correlation coefficients of 0.878 and 0.732. A significant positive correlation was observed between soil anti-erodibility index and organic matter content, with a correlation coefficient of 0.689. There was no significant correlation between soil anti-erodibility index and sand or silt content. It was concluded that soil clay, greater-than 0.25 mm water stable aggregate and organic matter were the key factors influencing soil anti-erodibility in the water-level fluctuation zone of the Three Gorges Reservoir area.