Abstract
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.
Highlights
Conservation of biological diversity has become a core concern for forest management during last decades
39 woody species were recorded in this study (Appendix 1)
diversity of woody species (DIV) decreased from lowland forest (LoF) to Midaltitude forest (MiF), leveled up in montane forest (MoF) (Figure 2A and 2B)
Summary
Conservation of biological diversity has become a core concern for forest management during last decades. Abiotic factors and biotic trade-offs determine biodiversity and affect functioning of forest systems (Scherer-Lorenzen et al 2005). Habitat loss, biological invasions, environmental pollution, land use/land cover changes and human exploitation are among the most important influencing factors for biological diversity. These factors and their impacts on biological diversity; especially within forest ecosystems, are well represented in ecological literature (e.g., Clark and Covey 2012; Khaledian et al 2012; Mantyka-Pringle et al 2012).
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