Impacts of slope aspects on altitudinal species richness and species composition of Narapani-Masina landscape, Arghakhanchi, West Nepal

This study aimed to find out the roles of altitude, slope aspect, and soil factors in species richness in the Narapani-Masina landscape, Arghakhanchi, Nepal. We surveyed forest plant communities by sampling 192 statistically representative 10 × 10 m sample plots from 64 sites representing all 100 elevation bands of 4 slope aspects (East, South, West, and North) of the landscape. We considered the species present in all plots of each 100 m contour elevation of four aspects as species richness of that elevation band. We collected the soil sample from 10 × 10 × 10 cm plot of 10 cm below the ground level at four corners of plant sampled plots to estimate the soil nutrients in a laboratory. We estimated the correlation, regression, Tukey post hoc test, PerMANOVA, and canonical correspondence analysis to show the relationship between environment and response variables. We found a significant negative relationship between species richness and altitude and soil nitrogen. The species richness showed a unimodal structure with elevation. The slope aspect showed a significant effect on species composition, but not on species richness. This study concludes that the increasing trend of soil N, P, and K with altitude showed a negative relation with species richness