Investigating the relation of functional diversity and biomass of plant communities in the central Zagross

Functional diversity is directly related to ecosystem services, biomass contains most of them such as food, conservation, tourism and pollination. This study attempted to test such assumptions as (i) The existence of close relationship between plant production and the community-weighted mean trait values (CWM), as expected from the “production ratio hypothesis” (ii) existence of close relationship between Rao’s functional diversity index with plant production according to “Tilmann hypothesis of diversity” to predict plant production and to find the best relation between plant production with environmental factors in the wooded rangeland of central Zagros. The results showed that among value of CWM, the most R² was related to functional diversity index of weighted mean of leaf index equal to %37. Also the amount of this index for Rao’s functional diversity index was %18 showing that this index only is able to explain about 18 percent of plant production variations. The most community-weighted mean values showed increasing trend with increasing plant production. It was observed that a combination of abiotic factors, Functional diversity (FDQ) and CWM index including of rainfall, temperature, CWM-ME, CWM-Long Leaf, and CWM-Height variables explains about 76% of plant production variations and can be regarded as the most appropriate model to forecast plant production. The results indicate the functional identity of plant community as proposed by Grime is the main driver of ecosystem function compared to niche complementrity hypothesis.