不同入侵程度下飞机草对喀斯特地区土壤理化性质的影响

外来生物入侵威胁着全球的生物多样性和生态系统的功能，研究外来入侵植物对土壤理化性质的影响有助于理解外来入侵植物的入侵机制。以广西喀斯特地区飞机草（Chromolaena odorata）入侵生境为研究对象，比较分析了不同飞机草入侵程度下（对照、轻度入侵、中度入侵、重度入侵）土壤物理和化学指标变化特征。结果表明：随着飞机草的入侵程度加重，土壤容重显著增加，轻度入侵、中度入侵和重度入侵生境下土壤容重分别比对照增加了10.3%、16.7%、22.3%，土壤非毛管孔隙度、总孔隙度和土壤含水量显著降低，土壤毛管孔隙度无显著变化；飞机草入侵对土壤pH值无显著影响，随着入侵程度加重，土壤速效磷和速效钾的含量显著升高，在重度入侵生境下土壤速效磷和速效钾含量分别比对照增加了4.3倍、3.8倍，土壤全氮和有机质含量显著降低。飞机草入侵显著改变了土壤理化性状，导致喀斯特地区土壤物理结构退化，生态系统水土保持能力下降，同时飞机草通过改变土壤养分循环提高了土壤可直接利用养分的水平，创造对自身有利的土壤环境，进而促进其生长和扩散。

Effects of different invasion degrees of Chromolaena odorata on physical and chemical properties of soil in karst areas

Invasion of alien species threatens the global biodiversity and ecosystem functions. Studying the effects of alien invasive plants on soil physical and chemical properties is helpful to understand the invasion mechanism of alien plants. In this study, the characteristics of soil physical and chemical indexes under different invasion degrees (control, mild invasion, moderate invasion, and heavy invasion) of Chromolaena odorata in karst area of Guangxi were compared and analyzed. The results showed that soil bulk density increased significantly with the invasion of C. odorata. Compared with the control, the soil bulk density increased by 10.3%, 16.7% and 22.3% respectively in light invasion, moderate invasion and heavy invasion habitats, while soil non capillary porosity, total porosity and soil water content decreased significantly, and soil capillary porosity had no significant change. C. odorata invasion had no significant effect onsoil pH value. The contents of soil available P and K increased significantly with the increase of invasion degree. Compared with the control, the contents of soil available P and K increased by 4.3 times and 3.8 times in heavy invasion habitat, respectively. The contents of soil total N and organic matter decreased significantly. The invasion of C. odorata significantly changed the soil physical and chemical properties, resulting in the degradation of soil physical structure and the decline of soil and water conservation capacity of ecosystem in karst area. Meanwhile, the invasion of C. odorata improved the level of soil available nutrients by changing the soil nutrient cycle, created favorable soil environment for itself, and then promoted its growth and spread.