Functional turnover from lowland to montane forests: evidence from the Hyrcanian forest in northern Iran

Abstract

Plant functional traits and functional diversity play key roles in ecosystem functioning. Exploring patterns of functional diversity is of great importance in the management process of forest ecosystems. Altitudinal pattern of plant functional diversity is poorly investigated in Hyrcanian relict forest, N Iran. We explored differences in trait composition between lowland and montane forest types. Altitudinal variation of plant functional traits along 2400 m altitudinal gradient was examined. In order to collect species and vegetation data, 67 vegetation sampling plots were placed along the altitudinal gradient. Eight plant functional traits; related to plant physiognomy, competitive ability and dispersal, were selected for 174 recorded vascular plants and weighted by importance-value of taxa. We used generalized linear model, principal coordinate analysis along with functional diversity metrics to investigate functional changes along the gradient. The importance of different traits such as chamaephyte life form, tiny leaves, dry indehiscent fruits and small seeds increase with altitude. In contrast, other traits including large leaves, taller plants, fleshy fruits, anemophily as well as medium to large seeds decrease with increasing elevation. Functional difference between lowland and montane forest vegetation is strongly supported in our results. Trait associations, different environmental parameters, disturbance type and especially altitude were concluded to be important predictors of functional changes. Vegetation type is a key determinant of functional patterns in temperate forests. We strongly recommend exploring and considering functional diversity in forest management practices.

Keywords

• Functional Diversity
• Gradient
• Hyrcanian Forest
• Multivariate Analysis
• Vegetation