Relationship between plant functional and taxonomic diversity with soil carbon storage in Nazluchay mountain rangelands, West Azerbaijan

This study was conducted to investigate the efficiency of taxonomic and functional diversity indices in explaining the amount of soil carbon storage of rangelands in the Nazluchay mountain area, Urmia province. For this purpose, soil and vegetation samples from nearly homogeneous map units were collected to calculate the amount of carbon stored in the soil as well as taxonomic and functional diversity. Climatic data were also recorded. The results of the study showed that there is no significant relationship between taxonomic diversity and soil carbon indicate. The results of the hierarchical regression showed the soil storage carbon has a significant linear relationship with silt characteristics, soil bulk density, modified aspect, CWMleaf length functional diversity index (as a representative of mass ratio hypothesis) and Feve and MFAD indicators (As a representative of the niche complementarity hypothesis). The resulting model has a coefficient of determination of 0.6. All parameters except soil bulk density have a positive relationship with carbon storage and in terms of standard regression coefficients, MFAD and CWMleaf length parameters with coefficients of 1.2 and 0.2 have the highest and least role in explaining soil carbon, respectively. In examining the hypotheses of how diversity affects the soil carbon, both the hypotheses of ecological niche complementarity and the hypothesis of mass ratio, are governing in the ecosystem of soil ecosystem storage, but the hypothesis of ecological niche complementarity plays a major role in relation to other hypotheses due to the high standard coefficients in explaining carbon. Based on the results, soil storage carbon increases based on increasing the frequency of long-leafed species, increasing functional evenness (uniform abundant distribution of species in the space of functional traits) and ultimately increasing the diversity of functional groups. In general, neglection of biodiversity reduction and weakening its condition will reduce soil carbon storage capacity.