Data from: Trait‐based signatures of cloud base height in a tropical cloud forest

Clouds have profound consequences for ecosystem structure and function. Yet, the direct monitoring of clouds and their effects on biota is challenging especially in remote and topographically complex tropical cloud forests. We argue that known relationships between climate and the taxonomic and functional composition of plant communities may provide a fingerprint of cloud base height, thus providing a rapid and cost-effective assessment in remote tropical cloud forests. To detect cloud base height, we compared species turnover and functional trait values among herbaceous and woody plant communities in an ecosystem dominated by cloud formation. We measured soil and air temperature, soil nutrient concentrations, and extracellular enzyme activity. We hypothesized that woody and herbaceous plants would provide signatures of cloud base height, as evidenced by abrupt shifts in both taxonomic composition and plant function. We demonstrated abrupt changes in taxonomic composition and the community-weighted mean of a key functional trait, specific leaf area, across elevation for both woody and herbaceous species, consistent with our predictions. However, abrupt taxonomic and functional changes occurred 100 m higher in elevation for herbaceous plants compared to woody ones. Soil temperature abruptly decreased where herbaceous taxonomic and functional turnover was high. Other environmental variables including soil biogeochemistry did not explain the abrupt change observed for woody plant communities. We provide evidence that a trait-based approach can be used to estimate cloud base height. We outline how rises in cloud base height and differential environmental requirements between growth forms can be distinguished using this approach.

云对生态系统的结构与功能具有深远影响。然而，直接监测云系及其对生物群的影响颇具挑战，尤其是在偏远且地形复杂的热带云雾林（tropical cloud forests）中。我们主张，气候与植物群落分类学、功能组成之间的既定关联，可作为云底高度的指纹标识，进而为偏远热带云雾林提供一种快速且高性价比的评估方案。为探明云底高度，我们在以云形成为主导的生态系统中，对比了草本与木本植物群落的物种周转（species turnover）及功能性状数值。我们测定了土壤与空气温度、土壤养分浓度以及胞外酶活性（extracellular enzyme activity）。我们提出假说：木本与草本植物均可反映云底高度的特征信号，具体表现为分类学组成与植物功能均出现突变式转变。研究结果证实，无论木本还是草本植物，其分类学组成以及关键功能性状——比叶面积（specific leaf area）的群落加权均值，均随海拔梯度发生突变，这与我们的预测一致。不过，相较于木本植物，草本植物的分类学与功能突变发生在海拔高出100米的位置。土壤温度在草本分类学与功能周转剧烈的区域出现骤降。其余环境变量（包括土壤生物地球化学特征）均无法解释木本植物群落观测到的突变现象。本研究证实，基于功能性状的研究方法可用于估算云底高度。我们还阐述了如何通过该方法，区分云底高度上升与不同生长型植物间的环境需求差异。