Influence of environmental factors on tree species diversity and composition in the Indian western Himalaya

Shinny Thakur,Vikram S Negi,Rupesh Dhyani,I.D Bhatt,A.K Yadava

doi:10.1016/j.foreco.2021.119746

Abstract

Understanding patterns in forest communities and its driving factors play a critical role in ecological studies. In view of this, present study attempts to understand the role of environmental and anthropogenic factors towards shaping species diversity and composition along the altitudinal gradient (700–3800 m asl) in Indian western Himalaya. A total of 51 tree species (28 families) were recorded; Pinaceae (5) and Fagaceae (5) were the species rich families. α-diversity indices i.e., Margalef's richness index (R), Shannon index (Hʹ) and Simpson index showed a humped shaped distribution, whereas Evenness index (E) showed an inverted humped shaped distribution along the altitude range. Based on non-metric dimensional scaling (NMDS), four different community types were identified. Redundancy analysis (RDA) revealed a strong relationship of tree species composition with environmental (41.73% variation) and anthropogenic factors (17.35% variation). RDA further indicated that the bulk density (BD), disturbance index (DI), mean diurnal temperature range (Bio2) and solar radiation (SR) are significantly associated with sub-tropical (below 1200 m) and lower temperate forest (1200–1700 m) types. Likewise, soil organic carbon (SOC), precipitation of the driest quarter (Bio17) and pH were significantly associated with upper temperate (1700–2900 m), and subalpine forest composition (>2900 m). Both NMDS classification and RDA ordination clearly demonstrate spatial variability in composition of tree community and environmental properties.

Highlights

The importance of mountains for biodiversity and sustaining ecosystem services, has been recognized for long in the aftermath of Rio Earth Summit (1992) when Chapter 13 Agenda 21 (1992) established mountains as an important habitat that support all forms of living organisms (UN 1992)
Species diversity, increased with an increase in species richness i.e., the level of species diversity depended on the richness of species composition
The results revealed, subtropical and lower temperate forests were significantly (p

Summary

Introduction

The importance of mountains for biodiversity and sustaining ecosystem services, has been recognized for long in the aftermath of Rio Earth Summit (1992) when Chapter 13 Agenda 21 (1992) established mountains as an important habitat that support all forms of living organisms (UN 1992). The Himalaya has been recognized as one of the globally important biodiversity hotspots that encompasses world's most diverse montane environment, characterized by high diversity of both plant communities and species (Kala et al, 2002; Oommen and Shanker, 2005; Rawal et al 2013; Boscutti et al, 2018; Negi et al 2019). Indian Himalayan Region (IHR) represents a large part of Himalayan Biodiversity Hotspot, where richness, representativeness, and uniqueness of biodiversity components (at gene, species and ecosystem levels) are well recognized (Rawal et al 2013). The composition of forest community and distribution of plant species in the region is the refection of environmental gradients (Chawla et al, 2008; Chian et al, 2016; Gómez-Díaz et al, 2017; Ahmad et al, 2020). Studies have demonstrated that anthropogenic activities are responsible to change the species richness, diversity, and distribution patterns, and subsequently influence the edaphic and environmental conditions (Ahmad et al, 2018; Wang et al, 2019)

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