Gradient analysis of soil-plant interactions from the alpine-nival ecotone to the snowline on slopes of the Central Great Caucasus (Kazbegi Region, Georgia)

Tamar Jolokhava,Khatuna Gigauri,Otar Abdaladze,Zaal Kikvidze

doi:10.15407/ukrbotj78.03.163

Abstract

Alpine ecosystems are especially sensitive to climatic changes which affect the relationships among glaciers, snow, vegetation and soils. Our aim was to examine how the variation in the abiotic environment affected soil properties and plant species distribution at regional and local scales. We sampled soil and vegetation along two transects set on the opposite-facing slopes (North versus South), from the alpine-nival ecotone to the snowline (Central Great Caucasus, Kazbegi, Georgia). We measured also soil temperature and controlled for the slope inclination. Multivariate ordination methods were used to link abiotic factors, soil properties and plant species distribution along the gradients. We found that ordination models were better resolved when soil properties were used as environmental variables instead of abiotic ones such as elevation, inclination and slope aspect. Soil pH and plant available potassium were the best predictors of plant species distribution in these habitats. We conclude that the models that account for the role of soils as a mediator between the abiotic environment and vegetation can more accurately describe plant species distribution at local and regional scales: a potentially important amendment with implications for the monitoring of the effects of climate change on vegetation at least in high mountain systems.

Highlights

Soils are important medium which can connect vegetation patterns with ecological processes (Chapin et al, 1995; Dahlgren, 2006; Budzhak, Didukh, 2020)
In mountains, where discernible gradients were instrumental for studying plant species distributions (Lomolino, 2001; Körner, 2007), clear differences were documented in these distribution patterns between calcareous and siliceous soils (e.g., Michalet et al, 2002; see Tudela-Isanta et al, 2018 for the recent contribution); the importance of soil physical and chemical properties to plant life were emphasized (Tale, Ingole, 2015; Praeg et al, 2019)
The variation in the abiotic environment on large temporal and spatial scales is considered to be an excellent predictor of plant community composition (Huston, Huston, 1994), even though the inclusion of soil variables in the set of environmental variables improves predictive power of the models based on abiotic variation (Buri et al, 2020)

Summary

Introduction

Soils are important medium which can connect vegetation patterns with ecological processes (Chapin et al, 1995; Dahlgren, 2006; Budzhak, Didukh, 2020). In mountains, where discernible gradients were instrumental for studying plant species distributions (Lomolino, 2001; Körner, 2007), clear differences were documented in these distribution patterns between calcareous and siliceous soils (e.g., Michalet et al, 2002; see Tudela-Isanta et al, 2018 for the recent contribution); the importance of soil physical and chemical properties to plant life were emphasized (Tale, Ingole, 2015; Praeg et al, 2019). In the descriptions and analyses of vegetation on ecological gradients, soils are usually treated as a part of environment which participates in developing vegetation patterns through ecophysiological performance and microbiota (Körner, 2003; Molau et al, 2005; Devictor et al, 2010; Donhauser, Frey, 2018), and the feedback between vegetation and soil is rarely analysed in the context of species spatial distributions. A question arises as to whether an important knowledge can be gained by explicitly including the relations between, on the one hand, abiotic variables and soil, and, on the other hand, soil and plants, in the analyses? Addressing this question was the general goal of our study

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