Woody species diversity and forest structure from lowland to montane forest in Hyrcanian forest ecoregion

Abstract

Alborz Mountains host Caspian Hyrcanian forest ecoregion along the northern slopes and forest steppe ecoregion in highlands. Hyrcanian forest covers the southeastern part of Caucasus biodiversity hotspot and is of great biogeographic importance. Altitudinal pattern and correlation between woody species biodiversity (DIV), forest structure ((stem density (DEN), mean basal area (MBA) and mean height class (MHC)) and disturbance (DIS) were explored along 2,400 m altitudinal gradient in Hyrcanian relict forest, Central Alborz Mountains. Vegetation changes from lowland forest (LoF) to midaltitude forest (MiF) and montane forest (MoF) in this area. The altitudinal gradient was divided into twelve 200 m elevational belts. Point centered quarter method (PCQM) with 96 sampling points and 83 vegetation samples by plot method (PM) were used to record field data. Shannon-Wiener index and Pearson coefficient were used for diversity and correlation analysis. The results showed that DEN decreased linearly, MBA and MHC showed relatively hump shaped and DIS showed a reverse hump shaped pattern of change along altitudinal gradient. Woody species diversity decreased non-steadily from LoF to MoF. Transitional vegetations of Carpinus-Fagus and Fagus-Quercus represented higher diversity of woody taxa compared to adjacent homogenous communities. Significant correlation was observed between altitude and all parameters: DEN with MBA, DIS and DIV; MBA with DIS; MHC with DIS along with DIV; and DIS with DIV at the study area scale. Surprisingly, correlation between studied parameters differed within each vegetation type. Altitude probably acts as a proxy for human and environmental driving forces in this area. Stability of warm and wet condition, season length, soil depth along with forest accessibility probably influences the altitudinal pattern of the studied parameters. Disturbance affects forest structure and consequently diversity; especially in lowlands. The obtained results recommend using both forest biodiversity and mensuration data in management process of forest ecosystems.

Climatic stress drives plant functional diversity in the Alborz Mountains, Iran

“…We found that uncorrected functional diversity (FRic and Rao's Q) decreased with altitude which means that the vegetation became less functionally rich and less functionally dissimilar. This observation confirms findings of other studies who found a linear decreasing pattern in functional diversity along altitude for small mammals (e.g., Du et al, ), vascular plants (e.g., Jafari, Zarre, & Alavipanah, ; Lee, Chun, & Cho, ) or lichens (Bässler et al, ). However, functional diversity can be strongly correlated with species richness simply due to the fact that a larger species pool allows for a larger set of functional traits (Mason et al, ; Petchey et al, ).…”

Comparative study of floristic diversity along altitude in the northern slope of the central Alborz Mountains, Iran

“…In Iran, the studies related to vegetation structure as well as the flora mainly focused on forests (e.g. Jafari and Akhani 2008;Siadati et al 2010;Jafari et al 2013;Naqinezhad et al 2015;Gholizadeh et al 2017), while few studies were conducted in the regions above 2000 m (e.g. Akhani et al 2013;Mahdavi et al 2013;Noroozi et al 2011;Moradi et al 2017).…”

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

“…In order to analyze the variation in the composition of functional traits along the elevation gradient, principal coordinate analysis (PCoA -Gower 1966) was applied on a pairwise belt-to-belt dissimilarity matrix based on Gower's coefficients (because of the categorical nature of the dataset -Gower 1971) using the PAST software package (Hammer et al 2001). UPGMA clustering method using the Gower's coefficient matrix was adopted to re-test the PCoA results.…”