亚热带山地森林木质藤本和共生树木枝条和叶片性状的分化

Divergences in stem and leaf traits between lianas and coexisting trees in a subtropical montane forest

因缺少性状的比较,我们对亚热带山地森林木质藤本和树木的与生态适应策略有关的功能性状变异格局仍知之甚少。本文通过研究中国西南亚热带山地森林中不同叶片习性的33种植物(7种落叶和4种常绿木质藤本、10种落叶和12种常绿树木)的13个性状的分化来填补此空白。研究结果表明,木质藤本的枝条木质部导管直径、理论导水率、比叶面积、叶片氮和磷含量显著高于树木,但其叶片干物质含量和氮磷比显著低于同域分布的树木,表明木质藤本采取获取的生态策略,具有更高效的枝条导水系统和生产力更强的叶片。与树木相比,木质藤本的导管直径变异更大,同时具有一些大导管和很多小导管,说明木质藤本具有较大的导管二型性。生长型解释了性状总变异的48.7%,叶片习性仅解释了3.8%的总变异,生长型和叶片习性之间没有显著的交互作用。此外,枝叶性状仅在树木中存在显著相关,木质藤本中不存在,表明亚热带木质藤本枝条的水力功能与叶片的性状是解耦的。上述结果表明,亚热带山地木质藤本和树木的枝条和叶片功能性状存在显著差异。加强对亚热带山地生态系统中木质藤本和树木生态策略差异机制的认识还需要深入研究。

Patterns in functional trait variation associated with the ecological strategies of lianas and trees in subtropical montane forests remain poorly understood due to lack of trait comparisons.Here,we filled this gap by investigating trait divergence between lianas and trees with different leaf habits for 13 traits of 33 species(7 deciduous and 4 evergreen liana species,and 10 deciduous and 12 evergreen tree species)in a subtropical montane forest in southwestern China.We found that lianas had significantly larger stem xylem vessel diameter,higher theoretical hydraulic conductivity,specific leaf area,leaf nitrogen,and phosphorus concentrations,but lower leaf dry-matter content and N/P ratio than sympatric trees,indicating that lianas employ an acquisitive ecological strategy,with a more efficient stem hydraulic system and more productive leaves.In contrast to trees,lianas exhibited a larger variation in vessel diameter,with a few wide and many narrow vessels in the xylem,indicating a greater vessel dimorphism.Growth form explained 48.7%of the total trait variation,while leaf habit only explained 3.8%of trait variation,without significant interaction between growth form and leaf habit.In addition,significant stem-leaf trait relationships were only found in trees,but not in lianas,indicating decoupling of stem hydraulic function and leaf traits in subtropical lianas.These results suggest that subtropical montane lianas and trees differ strikingly in stem and leaf functional traits.Further studies are warranted to strengthen our understanding of the mechanisms underlying the strong divergence in ecological strategies between lianas and trees in subtropical forest ecosystems.