The Carbon Isotope Composition of Epiphytes Depends Not Only on Their Layers, Life Forms, and Taxonomical Groups but Also on the Carbon and Nitrogen Indicators of Host Trees

The carbon isotopic composition of plant tissues is a diagnostic feature of a number of physiological and ecological processes. The most important of which is the type of photosynthesis. In epiphytes, two peaks of delta 13C values are known to correspond to C3 and CAM photosynthesis and some variants of transitional forms between them. But the diagnosis of delta 13C may not be limited to the type of photosynthesis. This makes it necessary to study trends in the distribution of delta 13C in a broader ecological context. In this study, we present trends in the distribution of delta 13C epiphytes and other structurally dependent plants and their relationship with other isotopic and elemental parameters (delta 15N, C%, N%, and C/N) and with life forms of epiphytes, taxonomic or vertical groups in crowns (synusia), and the parameters of the trees themselves. In all communities except for the moss forest, delta 13C in epiphyte leaves was significantly higher (less negative) than in phorophyte leaves. In general, delta 13C in epiphytes in mountain communities (pine forest and moss forest) was more negative than in other communities due to the absence of succulents with CAM. delta 13C in the leaves of all epiphytes was negatively related to the percentage of carbon and delta 15N in the leaves of the phorophyte. When considering the Gaussian distributions of delta 13C with the method of modeling mixtures, we observe the unimodal, bimodal, and trimodal nature of the distribution.