Area and environmental heterogeneity could shape the hump-shaped pattern of species richness along elevation gradient

Abstract

Background Numerous studies have been conducted on species richness patterns along elevation gradients in temperate, tropical and sub-tropical mountains. However, few studies have been done to evaluate the combined effect of area and environmental heterogeneity (abiotic and biotic) on species richness. Numerous ecological studies have also failed to quantify environmental heterogeneity which we have done in this research. In this research, we studied the impact of area on environmental heterogeneity on species richness by considering the climate factors, annual mean temperature (AMT), annual mean precipitation (AMP), annual total solar radiation (ATSR), and Soil factors, soil organic carbon (SOC), Soil total nitrogen (STN), Soil extractable phosphorous (SEP), and Soil extractable potassium (SEK).Results Our analysis showed that species richness had a skewed hump-shaped pattern, with the highest species richness being at mid-elevation. The results also showed that climate factors had a strong positive correlation with species richness in relation to area as compared to soil factors. We also found that soil factors could be used to explain the species richness when combined rather than being interpreted individually. This study has showed that area could have profound effect on environmental heterogeneity therefore shaping species richness pattern along the elevation gradient in Mount Kenya.Conclusion The hump shaped species richness pattern can be due to the Ecophysiological constraints for example, low temperatures as elevation increases. The high species richness at the mid-elevation is because this zone has a large land area and also acts as transition zone between the extremes of the upper elevation range and lower elevation and species from either side can coexist since the environmental conditions are on the lower and higher limits for the existence of these plant species.