广西喀斯特次生林地表碳库和养分库特征及季节动态

以自然保护区原生林为对照,调查了广西喀斯特区处于同一次生演替序列中的灌丛、藤刺灌丛、乔灌丛3个群落的地表凋落物存量,同时对凋落物层和土壤表层(0-5 cm)的有机碳,全氮、磷、钾等养分元素的含量、贮量状态及其雨季前后的变化进行了研究.结果表明:地表凋落物存量及有机碳、全氮贮量随演替阶段上升均呈增高趋势;除全磷外,土壤的有机碳和养分元素含量与凋落物层贮量相关性显著(p<0.05);雨季期间,凋落物迅速分解,地表凋落物的分解量要大于当季凋落量,并且次生林的凋落物分解与养分释放量显著高于原生林;雨季后,各群落有机碳和养分的凋落物层贮量以及土壤含量均有所降低.其中凋落物层贮量下降显著的是藤刺灌丛与乔灌丛.土壤养分含量则在灌丛与原生林阶段下降更为明显.在从灌丛向顶级群落演替的进程中,森林的自养能力可能存在一个先增高再降低的过程.

Carbon and Nutrient Pools and Their Seasonal Changes of Forest Floor in Secondary Forest in Karst region of Guangxi

Taking primary forest as contrast in Mulun natural reserve, we chose three secondary forests which represented different succession stages as shrub, vine-shrub and tree-shrub for studying their characteristics and seasonal dynamics of carbon and nutrients pools of forest floor in Karst region, Guangxi. After investigating the stocks of litters under forest, we analyzed organic carbon(OC), total nitrogen(TN), phosphor (TP) and potassium(TK) content of the litter layers and topsoi(O — 5 cm) in the end of February and August 2008. The results showed that: (1) Overall, the stocks of litters, OC and TN on forest floor increased as the succession going on; OC and nutrients content in topsoil had significant correlation with the stocks in litter layers except TP. (2) During the rainy season, the litters decomposed and released nutrients so fast that the decomposition amounts exceeded the input amounts; and the processes performed much faster in secondary forests than primary forest. (3) After rainy season, the stocks of OC and nutrients in litter layers decreased obviously in vine-shrub and tree-shrub, however the contents in topsoil showed more significant decrease in shrub and primary forest; it supposed that the self-sustaining ability of the secondary forests go upward and then downward as the succession progressing from shrub to climax stage.