滇南喀斯特地区灌木群落和人工林土壤元素化学计量特征

在云南喀斯特地区,为提升退化灌木群落的生态系统服务功能,营造了不同树种的人工林分。这些人工林分如何影响土壤化学性质还未得到充分认识。以云南泸西县灌木群落及三种常见人工林(云南松(Pinus yunnanensis)、赤杨(Alnus japonica)和侧柏(Platycladus orientalis))土壤为研究对象探讨喀斯特地区在人工林建造后土壤的13种元素全量、可利用性含量和化学计量学特征变异格局,为喀斯特石漠化治理提供理论依据。结果表明,1)基于判别分析,四种群落土壤化学计量特征可以显著区分。土壤Fe、P、K、Mn全量及交换性Ca、交换性Mg和NH_4~+-N对区分四种群落土壤贡献最大。2)四种群落之间相比,侧柏林土壤C、N、S、Na全量和NO_3~--N含量均低于其他三种群落,土壤肥力较低;赤杨林铵态氮含量最高;云南松林有效Fe、有效Cu含量/N、C素具有显著相关性,占所有元素对数的38.5%,说明该地土壤元素积累的相互依赖性。与灌木群落相比,人工林土壤元素全量和可利用性含量相关性比例均更高。这些研究结果对今后基于适地适树人工林营造、生态系统服务功能提升和经营利用,均具有重要指导意义。

Characteristics of soil stoichiometry in native shrub and plantation communities in karst regions of Yunnan province

The natural forest vegetation degraded to shrub-dominated plant communities in karst areas of Yunnan province, due to the geological conditions and long-term human disturbance. Plantation stands of different tree species have been established to raise ecosystem services across Yunnan province, such the karst shrub areas, during the last three decades. In this context, the elemental compositions of original soils could be influenced to a certain extent. In this study, we measured the total and available element concentrations of 13 elements (C, N, S, P, K, Ca, Mg, Na, Fe, Al, Cu, Zn, and Mn), and summarised the stoichiometric traits of soils in the shrub, Pinus yunnanensis, Alnus japonica, and Platycladus orientalis stands in Luxi county, Yunnan province. The results showed that firstly, soil stoichiometric traits of four communities were significantly distinguished based on canonical discriminant analysis. Furthermore, soil total Fe, P, K, Mn concentrations, and available Ca, Mg, and NH₄⁺-N concentrations, contributed to the differences the most. Secondly, cypress stands showed lower total C, N, S, Na and NO₃^--N concentrations compared with the other three communities, suggesting that the soil fertility was reduced. The soil NH₄⁺-N concentration was higher in alder stands compared with the other communities; the soil available Fe and Cu concentrations were highest in the Yunnan pine stand. Furthermore, there were also significant differences of C/N and C/K ratios among the four stands. Thirdly, based on a correlation analysis of the 13 elements and the pH value, 35 pair-elements showed a significant correlation, accounting for 38.5% of all elements, suggesting that there was strong inter-dependence accumulation of soil elements in these karst areas. Compared with the shrub community, the significant correlations between the total elements and available elements in plantation stands were higher. Our results have important implications for plantation establishment and management to increase ecosystem services in such karst areas.