-Impact of multiple environmental factors on species abundance in various forest layers using an integrative modeling approach

Abstract

It was hypothesized that multiple environmental factors influence distribution and abundance of plant species in different vegetation layers of the forest ecosystem=. Here, we have assessed plant diversity, abundance and its relationship with multiple factors through an integrative modeling approach. To substantiate or negate our hypothesis, Quadrat quantitative ecological methods were carried out for the sampling of vegetation in Humid Forest Ecosystem of the Western Himalayas. Rectangular plots of 100 m, 50 m and 1 m were established for trees, shrubs and herb species, respectively. All the edaphic, topographic, climatic and disturbance factors were determined using different standard procedures and protocols. We have applied multiple linear regression and structural equation models using R-Software on most abundant plant species each from trees, shrubs and herbs. Preliminary, integrative modeling showed that the species abundance is significantly associated with a set of soil nutrients (physio-chemical variables), topography (aspect, slope, elevation) and disturbance factors (anthropogenic and grazing pressure). The species dominance effects were synchronously influenced (p˂0.025) by the soil physical characters (sand, silt and clay), canopy and regeneration potentials compared to other factors. Our results provide bases to understand the underlying mechanisms of species abundance and its importance of the forest ecosystem in the western Himalayas. This work concludes that ecological diversity is overall the result of multiple factors but climatic, topographic, anthropogenic and grazing pressures primarily shape the diversity and functioning in a forest ecosystem. Additionally, we found a clear pattern that variations in edaphic factors cause the abundance of certain species over others.