喀斯特峰丛洼地植被演替过程中土壤养分的积累及影响因素

Soil nutrient accumulation and its affecting factors during vegetation succession in karst peak-cluster depressions of South China

以桂西北环江县典型喀斯特峰丛洼地为对象,利用空间代替时间的方法,于2009年分析了植被演替过程中表层土壤(0～15 cm)养分的变化及其主要控制因素.结果表明:随着植被正向演替(草地-灌丛-次生林-原生林),表层土壤的有机碳、全氮和全磷等含量显著增加,分别由演替初期(草地)的29.1、2.48和0.72 g.kg-1增加为演替后期(原生林)的73.9、8.10和1.6 g.kg-1.土壤阳离子交换量与有机碳和全氮密切相关,是喀斯特土壤C、N积累的主要控制因素;凋落物中的P含量、C/P和N/P是土壤全磷积累的主要控制因素,较高的凋落物P含量、N/P以及较低的C/P有利于土壤中P的积累;而坡度、坡向和裸岩率等地形因子对土壤养分的影响较小.

Taking the typical karst peak-cluster depressions in Huanjiang County of northwest Guangxi as the objects, and by using the method of replacing time with space, an analysis was made on the dynamic changes of top soil （0-15 cm） nutrients and their dominant controlling factors during the process of vegetation succession. With the positive succession of vegetation （herb-shrub-second- ary forest-primary forest）, the soil organic carbon （SOC）, total nitrogen （TN）, and total phosphorus （TP） contents increased significantly, with the soil SOC, TN, and TP increased from 29.1 g·kg-1 , 2.48 g · kg-1 , and 0.72 g·kg-1 in herb community to 73.9 g·kg-1 , 8.10 g·kg-1 , and 1.6 g·kg-1 in primary forest, respectively, which indicated that the positive succession of vegetation was helpful to the soil nutrient accumulation. The soil cation exchange capacity （CEC） had close relationships with the soil SOC and TN, being the primary controlling factor for the accumulation of the soil C and N. The litter P content, C/P ratio, and N/P ratio were the major factors controlling the P accumulation in the topsoil. The litters higher P content and N/P ratio and smaller C/P ratio were helpful for the P accumulation. Topographic indices （slope, aspect, and rock expo- sure ratio） had little effects on the soil nutrients.