湘西慈利县不同石漠化程度下土壤理化性质特征

Soil physical and chemical properties of different rock desertification degrees in Cili county of Xiangxi

【目的】研究湘西慈利县不同石漠化程度下土壤的理化性质特征,探明不同石漠化演替阶段土壤的主要限制因子,为湘西石漠化的生态恢复和综合治理提供理论依据。【方法】设置5个石漠化强度等级,每个等级设置3块标准样地,选择13项土壤理化指标,结合冗余分析(RDA)、主成分分析等分析方法,探讨不同石漠化程度及其剖面深度下土壤理化性质变异特征及其关键限制因子。【结果】1)慈利县石漠化土壤的物理性质在不同石漠化程度间存在差异性显著,土壤容重随石漠化程度加深而增大,土壤总孔隙度、毛管孔隙度、非毛管孔隙度、饱和持水量、毛管持水量和田间持水量则随石漠化程度加深而减小。2)石漠化土壤化学性质在不同石漠化程度间存在显著性差异,随石漠化程度加深,土壤TK(Total kalium)、TP(Total phosphorus)和SOM(Soil organic matter)含量逐渐降低,土壤TK(Total kalium)、AP(Available phosphorus)和AK(Available kalium)含量则先下降再上升后下降。3)慈利县石漠化土壤的理化性质在不同土壤深度间亦存在显著性差异,除土壤容重随着土壤深度增加而增大外,其他各项指标均呈下降趋势;土壤物理和化学性质之间相关性显著,RDA结果表明相关系数分别为0.997和0.973;随着土壤深度增加,钾元素和氮元素与土壤容重的相关性变得不显著,对石漠化地区肥力变化的响应更敏感,磷元素与饱和持水量、毛管持水量和田间持水量相关性变得显著。4)从澧水流域上游至下游石漠化程度先改善后加深,PCA土壤质量评价结果表明,土壤质量从优到劣依次为岩泊渡镇、甘堰乡、南山坪乡、零阳镇、苗市镇,与石漠化程度相对应。【结论】土壤理化性质在不同石漠化程度间基本具有显著性差异,物理性质呈阶段性下降,化学性质岩石聚集效应明显;在不同土壤深度间也基本具有显著性差异,土壤物理和化学性质之间相关性显著;石漠化程度在澧水流域从上游至下游先改善后加深,样地石漠化评价基本遵循石漠化演替的空间分布规律。

【Objective】To study the physical and chemical properties of soil under different rocky desertification degrees in Cili county,western Hunan,and to find out the main limiting factors of soil in different rocky desertification succession stages,so as to provide theoretical basis for ecological restoration and comprehensive control of rocky desertification in western Hunan.【Method】Five rocky desertification intensity grades were set,each grade was set with three standard sample plots,and 13 soil physical and chemical indexes were selected.Redundancy analysis(RDA)and principal component analysis were used to explore the variation characteristics and key limiting factors of soil physical and chemical properties under different rocky desertification degrees and profile depths.【Result】1)The physical properties of rocky desertification soil in Cili county have significant differences among different rocky desertification degrees.Soil bulk density increases with the deepening of rocky desertification,while soil total porosity,capillary porosity,non-capillary porosity,saturated water capacity,capillary water capacity and field water capacity decrease with the deepening of rocky desertification;2)There are significant differences in chemical properties of rocky desertification soil among different degrees of rocky desertification.With the deepening of rocky desertification,the contents of TN,TP and SOM in soil gradually decrease,while the contents of TK,AP and AK in soil first decrease,then increase and then decrease;3)The physical and chemical properties of rocky desertification soil in Cili county also have significant differences among different soil depths,except that the soil bulk density increases with the increase of soil depth,all other indexes show a downward trend.There is a significant correlation between soil physical and chemical properties,and RDA results show that the correlation coefficients are 0.997 and 0.973,respectively.With the increase of soil depth,the correlation between potassium and nitrogen and soil bulk density becomes insignificant,but more sensitive to the change of fertility in rocky desertification areas.The correlation between phosphorus and saturated water capacity,capillary water capacity and field water capacity becomes significant;4)From the upper reaches to the lower reaches of Lishui River Basin,the degree of rocky desertification first improved and then deepened.PCA soil quality evaluation results showed that the order of soil quality from superior to inferior was Yanbodu town,Ganyan township,Nanshanping township,Lingyang town and Miaoshi town,which corresponded to the degree of rocky desertification.【Conclusion】There are significant differences in soil physical and chemical properties among different degrees of rocky desertification,with physical properties decreasing in stages and chemical properties having obvious rock aggregation effect.There are also significant differences among different soil depths,and there is a significant correlation between soil physical and chemical properties.The degree of rocky desertification improved first and then deepened from upstream to downstream in Lishui River Basin,and the evaluation of rocky desertification in sample plots basically followed the spatial distribution law of rocky desertification succession.