Distribution Pattern of Gymnosperms’ Richness in Nepal: Effect of Environmental Constrains along Elevational Gradients

Abstract

Understanding the pattern of species distribution and the underlying mechanism is essential for conservation planning. Several climatic variables determine the species diversity, and the dependency of species on climate motivates ecologists and bio-geographers to explain the richness patterns along with elevation and environmental correlates. We used interpolated elevational distribution data to examine the relative importance of climatic variables in determining the species richness pattern of 26 species of gymnosperms in the longest elevation gradients in the world. Thirteen environmental variables were divided into three predictors set representing each hypothesis model (energy-water, physical-tolerance, and climatic-seasonality); to explain the species richness pattern of gymnosperms along the elevational gradient. We performed generalized linear models and variation partitioning to evaluate the relevant role of environmental variables on species richness patterns. Our findings showed that the gymnosperms’ richness formed a hump-shaped distribution pattern. The individual effect of energy-water predictor set was identified as the primary determinant of species richness. While, the joint effects of energy-water and physical-tolerance predictors have explained highest variations in gymnosperm distribution. The multiple environmental indicators are essential drivers of species distribution and have direct implications in understanding the effect of climate change on the species richness pattern.

Energy–water and seasonal variations in climate underlie the spatial distribution patterns of gymnosperm species richness in China

“…A negative relationship between species richness and climatic seasonality has previously been reported (Gao & Liu, 2018;Kristiansen et al, 2011;Liu et al, 2017;Panda et al, 2017;Pandey et al, 2020;Shrestha et al, 2017), and our study supports the climate seasonality hypothesis. The MAT in China is between -25 and 25°C,…”

“…Thus, multiple modeling approaches could be most suitable for quantifying the contributions of various hypotheses toward spatial richness patterns. Moreover, there are studies that explain the species richness patterns of gymnosperms along environmental gradients in the Himalayas (Pandey et al, 2020;Subedi, Bhattarai, Perez, & Sah, 2019). Tian (2002), Ying, Chen, and Zhang (2004), Li, Shen, Ying, and Fang (2009), Jiang, Cheng, and Yin (2010), and Yang (2015) have also studied the distribution of gymnosperms in China, while the mechanism that determines richness patterns were not considered.…”

Contrasting Gymnosperm Diversity Across an Elevation Gradient in the Ecoregion of China: The Role of Temperature and Productivity

“…Temperature and water availability have a direct relationship with the pattern of species richness by accelerating the metabolic activities in plants (Pausas and Austin, 2001;Currie et al, 2004). Water availability and temperature have a different response to the species diversity; however, their combined effect determines the synergic mechanisms of plant species richness (Vetaas and Grytnes, 2002;Gao and Liu, 2018;Pandey et al, 2020b). Previous studies showed the positive quadratic (mid-elevation peak) relationship between species diversity and temperature and water availability along elevation gradients (Bhattarai and Vetaas, 2003;Kluge et al, 2017;Subedi et al, 2019;Pandey et al, 2020b).…”

“…Available studies suggested different patterns of EDG that can be summarized into four patterns of species richness-(i) decrease in species with increasing elevation, (ii) increase in species with increasing elevation, (iii) highest number of species at mid-elevation, forming a unimodal pattern, and (iv) less number of species at mid-elevation, creating a "U"-shaped pattern. Most researches have explained a significant role of EDG in defining the diversity patterns of plants (Rahbek, 1995;Lomolino, 2001;Bhattarai and Vetaas, 2003;Bhattarai et al, 2004;Wang et al, 2007;Gao et al, 2017;Kluge et al, 2017;Gao and Liu, 2018;Subedi et al, 2019;Pandey et al, 2020b). Lomolino (2001) reviewed and summarized the studies linking the elevational distribution of species richness, and identified the further need for comparing the richness patterns and the factors that determine EDG.…”

“…Water availability and temperature have a different response to the species diversity; however, their combined effect determines the synergic mechanisms of plant species richness (Vetaas and Grytnes, 2002;Gao and Liu, 2018;Pandey et al, 2020b). Previous studies showed the positive quadratic (mid-elevation peak) relationship between species diversity and temperature and water availability along elevation gradients (Bhattarai and Vetaas, 2003;Kluge et al, 2017;Subedi et al, 2019;Pandey et al, 2020b). However, the correlation between species richness, temperature, and water availability varies from region to region.…”