Abstract:

Aims: Mineral elements are important determinants of soil nutrients and are related to forest community composition and nutrient cycling. There is high terrain heterogeneity in karst seasonal rainforest local scale, but there is still lack of research on how terrain and other abiotic and biotic factors affect the spatial distribution of soil mineral elements in karst area.

Methods: In this study, we set up 100 litter fall traps along the elevation gradient in the 15 ha northern tropical karst seasonal rainforest dynamics plot in Nonggang, southwestern Guangxi, and conducted soil sampling at the litter fall trap sites. We tested soil samples for the content of mineral elements such as K, Ca, Mg. We performed quantitative analysis of the association between ecological factors and soil K, Ca, Mg in karst seasonal rainforests based on methods such as spatial regression models and variation partitioning.

Results: Soil K, Ca and Mg in the study area were all spatially autocorrelated, with Ca significantly positively correlated with elevation and convexity (P < 0.05), mainly clustered in the hilltop; K significantly positively correlated with topographic wetness index, mainly clustered in low-lying land; Mg showed clustering characteristics in the hillside. Variation partitioning shows that ecological factors drove the spatial distribution of soil K, Ca and Mg more than spatial structure. Elevation was the highest predictor variable among the individual ecological factors, and abiotic factors were higher than biotic factors in general, and species richness was the highest among biotic factors, while the aggregation of Mg elements was accompanied by a higher level of species richness.

Conclusion: In this study, the soil K, Ca and Mg in the 15 ha northern tropical karst seasonal rainforest dynamics plot in Nonggang have spatial autocorrelation, and the spatial distribution of the three soil elements was significantly different. In the karst seasonal rainforest in southwestern Guangxi, ecological factors such as altitude have a strong driving effect on the spatial distribution of soil K, Ca and Mg. However, in terms of the accuracy of the analysis results, adding more ecological factors and expanding soil sampling points may further enhance the interpretation of ecological factors and spatial variables on the spatial distribution of soil elements.

Key words: soil mineral elements, ecological factors, spatial regression model, variation partitioning, northern tropical karst seasonal rainforest