土壤养分对亚热带天然林物种分布的影响

Effects of soil nutrients on species distribution in a subtropical natural forest

了解亚热带天然林土壤养分对物种分布的影响,确定不同土壤养分梯度下的指示种,对评价森林土壤肥力和管理森林资源具有重要意义。对康禾自然保护区样地胸径1 cm以上的植被进行每木调查,采集每个小样方的表层土壤,通过Spearman R.分析和多响应置换过程分析发现,影响康禾自然保护区样地物种分布的主要土壤养分元素是全氮、全钾和土壤有机质;样地中含量较低的全磷与物种分布呈极显著正相关,含量偏高的全钾与物种多度和均匀度指数呈极显著正相关,物种多样性指数与土壤有机质呈显著负相关,含量处于中等水平的全氮对物种分布影响不显著,在典范对应分析取得的结果中也得到了验证;对各土壤养分元素的指示种分析结果发现,全磷的指示种最多,而全氮和碱解氮没有达标的指示种。这些结果表明,全磷、全钾及土壤有机质是天然林植物种类组成与分布的限制因子,与南方砖红壤缺磷和有机质的状况相吻合;而氮素并不缺乏,不成为天然林植物物种组成和分布的限制因子,可能与氮沉降对氮素的持续补充有关。

Understanding the influence of soil nutrient on species distribution and determining species indicators in the subtropical natural forest have great signiifcance for evaluating forest soil fertility and managing forest resources. A permanent sampling plot of 6 hm2 was set up in Kanghe Nature Reserve for the census of woody plants≥ 1cm and surface soil sample collection. Through Spearman R. analysis and Multi-response permutation procedures （MRPP） analysis, the major soil factors affecting species distribution were detected, they were： total nitrogen, total potassium, and soil organic matter. Total phosphorus, which was low in content, had a very signiifcant positive correlation with species distribution, while total potassium, which was relatively high in content, had a very signiifcant positive correlation with species abundance and evenness index. The species diversity index had a significant negative correlation with soil organic matter, but was not signiifcantly related to total nitrogen, which was not in deifciency, Canonical Correspondence Analysis （CCA） yielded similar results. The analysis on indicator species based on soil nutrient gradients revealed that total phosphorus had the largest number of indicator species, whereas no significant indicator species was found for total nitrogen and available nitrogen gradients. These results demonstrated that total phosphorus, total potassium, and soil organic matter were the limiting factors for plant species composition and distribution in the subtropical natural forest, which was associated with the deficiency of phosphorus and organic matter in lateritic soil in south China; Nitrogen was not a limiting factor for plant species composition and distribution for its richness in subtropical natural forest, which might be associated with the continuous addition of nitrogen element from nitrogen deposition.