Background and aims

Understanding the eco-evolutionary processes that govern leaf elemental composition in subtropical regions with diverse forest landscapes remains a challenge. Here, we investigated the phylogenetic and environmental regulation of leaf elemental composition in subtropical forests.

Methods

We sampled surface soils and leaves from herbs, ferns, deciduous woody species, and evergreen woody species across four forest landscapes (montane, valley, karst, and island forests) in the subtropical Lijiang River basin. We used phylogenetic comparative methods to identify regulators of leaf elemental composition.

Results

Leaf elemental concentrations varied significantly among growth forms, with evergreen woody species presenting the highest leaf C concentration relative to N, P, and K. Apart from C, leaf elemental concentrations also showed significant variations across forest landscapes; for instance, karst forest species exhibited the highest leaf Ca and Mg concentrations but the lowest leaf P concentration, reflecting pronounced P deficiency and enhanced supply of Ca and Mg. Phylogenetic signal, indicating phylogenetic conservatism, was significantly detected in leaf C, K, Ca, and Mg concentrations. Evolutionary model comparisons suggested that stabilizing selection towards multiple optima for growth forms best explained variation in leaf C concentration, while stabilizing selection towards multiple optima for each growth form within a specific landscape emerged as the dominant process for leaf N, P, K, Ca, and Mg concentrations.

Conclusions

Our study highlights the critical roles of leaf elemental conservatism and stabilizing selection towards multiple optima for growth forms within and across forest landscapes in regulating leaf elemental composition in subtropical region.

中文翻译：

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多元森林景观亚热带流域叶片元素组成的调控

 背景和目标

了解在森林景观多样的亚热带地区控制叶片元素组成的生态进化过程仍然是一个挑战。在这里，我们研究了亚热带森林叶片元素组成的系统发育和环境调控。

 方法

我们在亚热带漓江流域的四种森林景观（山地、山谷、喀斯特和岛屿森林）中对草本、蕨类植物、落叶木本物种和常绿木本物种的表层土壤和树叶进行了采样。我们使用系统发育比较方法来确定叶片元素组成的调节因子。

 结果

叶元素浓度因生长形式而异，常绿木本物种的叶 C 浓度相对于 N、P 和 K 最高。除 C 外，叶元素浓度在森林景观中也表现出显着差异;例如，喀斯特森林物种的叶片 Ca 和 Mg 浓度最高，但叶片 P 浓度最低，反映了明显的 P 缺乏和 Ca 和 Mg 供应的增加。系统发育信号表明系统发育保守性，在叶片 C、K、Ca 和 Mg 浓度中显著检测到。进化模型比较表明，稳定选择向生长形式的多种最佳选择最能解释叶 C 浓度的变化，同时稳定选择特定景观中每种生长形式的多种最佳选择成为叶片 N、P、K、Ca 和 Mg 浓度的主要过程。

 结论

我们的研究强调了叶元素保守性和稳定选择在调节亚热带地区叶元素组成中的关键作用。