天坑森林植物叶-凋落物-土壤C、N、P生态化学计量特征

为探究广西乐业大石围天坑森林群落的C、N、P养分循环特征，比较了天坑内外森林群落的植物叶片-凋落物-土壤C、N、P含量及其化学计量比，采用相关性分析和冗余分析等统计方法研究其内在联系和相互影响。结果表明，与天坑外部森林相比，天坑内部森林植物叶片和凋落物呈现出C低N、P高，土壤为C、N低P高的格局。植物叶片C:N、C:P与凋落物C、N:P显著正相关，植物叶片C与土壤P显著负相关；天坑外部森林的植物叶片N、N:P与土壤N:P显著负相关，植物叶片C:N与土壤C、C:N显著正相关，说明天坑森林内部凋落物的C、P养分可能主要来源于植物叶片，而天坑外部森林的植物叶片C、N主要来自土壤。土壤C:N:P对植物叶、凋落物的C:N:P变化的解释率分别为90.7%和50.6%，其中土壤P对植物叶和凋落物的C:N:P计量特征变化的解释度最高，坑内生境植物对P含量变化更为敏感、坑外植物对于N含量变化更为敏感，表明天坑内部森林可能是P素受限位点、天坑外部森林是N素受限位点。喀斯特天坑内部森林和外部森林植物叶-凋落物-土壤的C:N:P的差异和联系，体现了天坑内外森林群落的养分循环特征和植物群落的适应性。

Characteristics of Carbon, Nitrogen and Phosphorus Stoichiometry of Leaf, Litter and Soil in the Karst Tiankeng Forest

In order to explore the nutrient cycling characteristics of C, N and P in Tiankeng forest communities in Dashiwei, Leye, Guangxi, the contents and stoichiometric ratios of C, N and P in plant leaf, litter and soil of forest communities inside and outside Tiankeng were compared, and their internal relationship and interaction were studied by using correlation analysis and redundancy analysis. The results showed that the leaf and litter of the forest inside Tiankeng showed a pattern of low C, low N and high P, and the soil was low C, low N and high P compared with the forests outside the Tiankeng. The C:N and C:P in leaf were significantly positively correlated with the C and N:P in litter, and C in leaf showed significantly negative correlation with P in soil. The N and N:P in leaf outside Tiankeng were significantly negative correlated with N:P in soil, and C:N in leaf was significantly positive correlated with C and C:N in soil, indicating that the C and P in litter inside Tiankeng forest might came from leaves, while C and N in leaf outside Tiankeng forests were mainly from soil. The explanation rates of soil C:N:P for the change of C:N:P of leaves and litter were 90.7% and 50.6%, respectively. The P had the highest explanation for the change of C:N:P of leaves and litter. Plants inside Tiankeng were more sensitive to the change of P content, while plants outside Tiankeng were more sensitive to the change of N content, which indicating that the forest inside Tiankeng might be the P-limited site, while the forest outside Tiankeng might be the N-limited site. The differences and associations of C:N:P in leaf-litter-soil of the forests inside and outside karst Tiankeng reflected the characteristics of nutrient cycling and the adaptation of plant community.