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Dryad

Contrasting changes in diversity

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Apr 12, 2024 version files 83.93 KB

Abstract

Questions: Climate change may have different effects on species richness depending on regional climates, soil types and the functional composition of local communities.  

Location: Subalpine belt of the Grandes Rousses (Alps) and Sancy mountain ranges (The Massif Central), France.

Methods: We compared changes in species richness in response to recent climate change in communities from two mountain ranges subjected to contrasting environmental conditions, with a more continental climate and drier soils in the Alps than in the Massif Central. Vegetation composition of 189 and 157 plots were assessed in 1997 and 2017-2018 in the Alps and 1988-1989 and 2022 in the Massif Central, respectively. Five species traits (height, lateral spread, leaf area, specific leaf area and leaf dry matter content) were measured on 108 and 144 species, respectively. Changes in vegetation composition and species richness along spatial environmental gradients were analysed with correspondence analyses at the Sancy site and canonical correspondence analysis at the Alpe d’Huez site. Changes in functional composition across sites with were analysed with principal component analysis. Changes in species richness with climate change were analysed with repeated-measure ANOVAs.

Results: In both mountain ranges summer temperatures increased and the hydric balance decreased over the past three decades, but snow cover duration decreased in the Alps only, whereas irradiance strongly increased in the Massif Central only. Functional composition was characterized by shorter and more conservative species in the Alps than in the Massif Central dominated by tall exploitative species. Species richness overall decreased with climate change by ca 10% in the Alps but overall increased by ca 10% in the Massif Central. Species richness decreased in the Alps likely because of increasing competition induced by dwarf shrub encroachment due to decreasing snow cover duration, whereas species richness increased in the Massif Central likely due to increasing irradiance in a very nebulous climate.

Conclusion: The opposite changes in species richness observed at the two mountain ranges with recent climate change were likely to be explained by their contrasting climate and soil conditions driving different functional compositions and diversity-environment relationships.