桂西北喀斯特地区不同土地利用类型土壤抗蚀性研究

土壤抗蚀性是反映土壤抵抗侵蚀能力的重要参数之一,是土壤侵蚀研究的重要内容。本文选取土壤有机质、水稳性团聚体、团聚体结构破坏率、团聚状况、团聚度、分散率和<0.05 mm粉黏粒含量等7个指标,通过单因素方差分析及主成分分析,探讨了桂西北喀斯特地区5种不同土地利用类型土壤抗蚀性的差异。结果表明:原生林和次生林土壤有机质含量显著(P<0.05)高于撂荒地、坡耕地和人工林,撂荒地土壤有机质含量较坡耕地和人工林高,但差异不显著。原生林、次生林及撂荒地土壤>0.25 mm水稳性团聚体总量及团聚状况显著高于坡耕地及人工林,但其土壤团聚体结构破坏率及分散率显著低于坡耕地;人工林土壤团聚体结构破坏率显著高于次生林,但与原生林、撂荒地和坡耕地差异不显著;人工林土壤分散率则与坡耕地类似,显著低于原生林、次生林及撂荒地;原生林、次生林土壤团聚度与撂荒地、坡耕地差异不显著,但显著高于人工林;次生林、撂荒地及人工林<0.05 mm粉黏粒含量与原生林、坡耕地差异不显著,但坡耕地土壤<0.05 mm粉黏粒含量显著高于原生林。由主成分分析综合评分得到土壤抗蚀性强弱顺序为:原生林>次生林>撂荒地>坡耕地>人工林。因此,喀斯特地区人为干扰严重降低了土壤的抗蚀性,耕地通过撂荒方式能够提高土壤抗蚀性。

Anti-soil erodibility of different land use types in Northwest Guangxi Karst Regions

Anti-soil erosion index is critical for analyzing soil erosion. In this paper, 7 indices (including soil organic matter, water stable aggregate, structural damage rate, re-aggregation situation/degree, dispersion rate and <0.05 mm silt/clay content) were selected to analyze anti-soil erosion degrees of 5 different land use types via both ANOVA and principal component methods in Northwest Guangxi karst regions. The results showed that soil organic matter contents in original and secondary forestlands were significantly higher (P < 0.05) than those in fallow lands, slope farmlands and artificial forestlands. Fallow lands had higher but insignificant soil organic matter content than slope farmlands and artificial forestlands. Amounts of soil >0.25 mm water stable aggregates and re-aggregation situation/degree in original forestlands, secondary forestlands and fallow lands were significantly higher than those in slope farmlands and artificial forestlands. However, slope farmlands had significantly higher structural damage rate and dispersion rate than other land use types. Structural damage rate of artificial forestlands was significantly higher than that of secondary forestlands, but similar to those of original forestlands, fallow lands and slope farmlands. Dispersion rate of artificial forestlands was similar to that of slope farmlands, but significantly lower than those of original forestlands, secondary forestlands and fallow lands. Re-aggregation degrees of original and secondary forestlands were similar to those of fallow lands and slope farmlands, but significant higher than that of artificial forestlands. The <0.05 mm silt/clay contents of secondary forestlands, fallow lands and artificial forestlands were similar to those of original forestlands and farmlands. However, original forestlands had a significantly lower <0.05 mm silt/clay content than slope farmlands. The order of anti-soil erosion degree of 5 land use types obtained by principal component analysis was: original forestland > secondary forestland > fallow land > slope farmland > artificial forestland. It was therefore concluded that human disturbances in karst regions severely weakened soil anti-erodibility, which could be improved by leaving farmlands to fallow.