Vascular epiphyte diversity and host tree architecture in two forest management types in the Himalaya

Abstract

Epiphytes are one of the most diversified plant life forms, whose species richness peaks in the tropics and subtropics. Here we examined vertical distribution metrics (i.e., number of epiphyte individuals and epiphyte species richness) of vascular epiphytes (i.e., orchids and ferns) on two dominant host trees (i.e., Schima wallichii (DC.) Korth. and Quercus lanata Sm.) in sub-tropical forests of Nepal. We sampled a total number of 72 host trees of Q. lanata and S. wallichii from two forest sites: a government protected national park forest and community managed forest. We applied generalized linear mixed models and Kruskal-Wallis rank sum tests to explain epiphyte diversity by tree architecture (i.e., diameter at breast height, tree height, crown size, number of forks, bark rugosity, bark pH and tree layer), host species and forest management types. After variable selection via multi-model inference technique, we found diameter at breast height to be the most powerful and significant explanatory variable for the number of epiphyte individuals and epiphyte species richness across host tree species, tree layers, and forest management types. Interestingly, epiphyte diversity was on average higher in the community managed forest than in the national park forest, on S. wallichii than on Q. lanata and particularly on the trunk below forks. We conclude that effective conservation of epiphyte diversity in the Nepal Himalaya requires conservation of old-growth host trees through community approaches. If large and old tree stands are maintained, community managed forests can host high diversity of vascular epiphytes and provide ecosystem goods to local people alike.