Climate Change Affects Vegetation Differently on Siliceous and Calcareous Summits of the European Alps

Lena Nicklas,Andrea Lamprecht,Peter Unterluggauer,Christian Rixen,Pascal Vittoz,Klaus Steinbauer,Brigitta Erschbamer,Jean-Paul Theurillat,Martin Mallaun,Dietmar Moser,Andreas Gattringer,Sonja Wipf,Johannes Wessely,Janette Walde

doi:10.3389/fevo.2021.642309

Abstract

The alpine life zone is expected to undergo major changes with ongoing climate change. While an increase of plant species richness on mountain summits has generally been found, competitive displacement may result in the long term. Here, we explore how species richness and surface cover types (vascular plants, litter, bare ground, scree and rock) changed over time on different bedrocks on summits of the European Alps. We focus on how species richness and turnover (new and lost species) depended on the density of existing vegetation, namely vascular plant cover. We analyzed permanent plots (1 m × 1 m) in each cardinal direction on 24 summits (24 × 4 × 4), with always four summits distributed along elevation gradients in each of six regions (three siliceous, three calcareous) across the European Alps. Mean summer temperatures derived from downscaled climate data increased synchronously over the past 30 years in all six regions. During the investigated 14 years, vascular plant cover decreased on siliceous bedrock, coupled with an increase in litter, and it marginally increased on higher calcareous summits. Species richness showed a unimodal relationship with vascular plant cover. Richness increased over time on siliceous bedrock but slightly decreased on calcareous bedrock due to losses in plots with high plant cover. Our analyses suggest contrasting and complex processes on siliceous versus calcareous summits in the European Alps. The unimodal richness-cover relationship and species losses at high plant cover suggest competition as a driver for vegetation change on alpine summits.

Highlights

Alpine plants are highly sensitive to global warming (Kammer et al, 2007; Grytnes et al, 2014; Rixen and Wipf, 2017; Winkler et al, 2019)
Bare ground was significantly larger in calcareous regions (4.2 ± 0.6% mean ± standard error, see Table 3 for all mean values) than in siliceous regions (3.3 ± 0.5%; Table 2, Calcareous: p = 0.05)
The present study provides evidence that vegetation attributes such as species richness and species turnover, and the distribution of surface cover types generally differ between calcareous and siliceous summits and show contrasting changes over 14 years of climate warming on the micro-scale of 1 m × 1 m

Summary

Introduction

Alpine plants are highly sensitive to global warming (Kammer et al, 2007; Grytnes et al, 2014; Rixen and Wipf, 2017; Winkler et al, 2019). Since competitive species with a higher growth rate are benefiting from warming (Farrer et al, 2015; Winkler et al, 2019) it is expected that slow-growing, cold-adapted species are threatened by competitive displacement (Alexander et al, 2015) and/or physiological constraints (Larcher et al, 1998; Marcante et al, 2012, 2014; Lamprecht et al, 2018) over time. Recent studies in the Central Austrian Alps have already shown losses and decrease in cover of cold-adapted species from permanent plots (Lamprecht et al, 2018; Steinbauer et al, 2020). Species distribution models might overestimate losses, as extinctions are still rarely encountered in revisitation studies in the European Alps (Kulonen et al, 2018)

Results

Discussion

Conclusion