Beyond leaf habit: generalities in plant function across 97 tropical dry forest tree species

Abstract Leaf habit has been hypothesized to define a linkage between the slow-fast plant economic spectrum and the drought resistance-avoidance trade-off in tropical forests (‘slow-safe versus fast-risky’). However, variation in hydraulic traits as a function of leaf habit has rarely been explored for a large number of species. We sampled leaf and branch functional traits of 97 tropical dry forest tree species from four sites to investigate whether patterns of trait variation varied consistently in relation to leaf habit along the ‘slow-safe versus fast-risky’ tradeoff. Leaf habit explained from 0 to 43.69 % of individual trait variation. We found that evergreen and semi-deciduous species differed in their location along the multivariate trait ordination when compared to deciduous species. While deciduous species showed consistent trait values, evergreen species trait values varied as a function of the site. Last, trait values varied in relation to the proportion of deciduous species in the plant community. We found that leaf habit describes the strategies that define drought avoidance and plant economics in tropical trees. However, leaf habit alone does not explain patterns of trait variation, which suggests that quantifying site-specific or species-specific uncertainty in trait variation as the way forward.摘要：叶习性（leaf habit）被假设为联结热带森林植物经济谱（plant economic spectrum）快慢维度与抗旱-避旱权衡（drought resistance-avoidance trade-off）关系的纽带，即“慢-安全”与“快-风险”策略二分法。然而，针对大量物种开展的、以叶习性为变量的水力性状（hydraulic traits）变异研究仍较为匮乏。本研究从4个样地采集了97种热带干旱林树木的叶片与枝条功能性状（functional traits），旨在探究性状变异模式是否沿“慢-安全”与“快-风险”权衡轴，随叶习性呈现出一致的变化规律。结果显示，叶习性可解释0至43.69%的单个性状变异。研究发现，与落叶树种相比，常绿与半落叶树种在多性状排序（multivariate trait ordination）轴上的分布位置存在显著差异。落叶树种的性状值表现出较高的一致性，而常绿树种的性状值则随样地发生显著变化。此外，性状值还与植物群落中落叶树种的占比密切相关。本研究证实，叶习性能够界定热带树木的避旱策略与植物经济策略类型。但仅依靠叶习性无法完全解释性状变异模式，这表明未来研究应量化样地特异性或物种特异性的性状变异不确定性。