Department of Biology, Virginia Commonwealth University, Richmond, Virginia, 23284, USA.
Department of Biology and Ecology Center, Utah State University, Logan, Utah, 84322, USA.
Am J Bot. 2020 Jun;107(6):886-894. doi: 10.1002/ajb2.1483. Epub 2020 Jun 4.
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.
云对生态系统结构和功能有着深远的影响。然而，直接监测云和它们对生物群的影响是具有挑战性的，尤其是在偏远和地形复杂的热带云雾林中。我们认为，气候与植物群落的分类和功能组成之间的已知关系可以提供云底高度的特征，从而为偏远的热带云雾林提供快速且具有成本效益的评估。
为了检测云底高度，我们比较了以云形成为主导的生态系统中草本和木本植物群落的物种周转率和功能特征值。我们测量了土壤和空气温度、土壤养分浓度和细胞外酶活性。我们假设木本和草本植物将为云底高度提供特征，这可以从分类组成和植物功能的突然变化中得到证明。
我们证明了在海拔高度上，无论是木本还是草本物种，其分类组成和关键功能特征的群落加权平均值（比叶面积）都发生了突然变化，这与我们的预测一致。然而，与木本植物相比，草本植物的分类和功能变化在海拔 100 米的高度上突然发生。在草本植物的分类和功能变化较大的地方，土壤温度突然下降。包括土壤生物地球化学在内的其他环境变量并不能解释我们观察到的木本植物群落的突然变化。
我们提供了证据表明，基于特征的方法可用于估计云底高度。我们概述了如何使用这种方法来区分云底高度的上升和不同生长形式的环境要求。
