Climate, soil resources and microbial activity shape the distributions of mountain plants based on their functional traits

Camille Martinez‐Almoyna,Thierry Delahaye,Cédric Dentant,Wilfried Thuiller,Gabin Piton,Maxime Rome,The Orchamp Consortium ,Louise Boulangeat,Sylvain Abdulhak,Virgile Noble,Tamara Münkemüller,Jérôme Poulenard,Amélie Saillard,Julien Renaud,Arnaud Foulquier,Philippe Choler

doi:10.1111/ecog.05269

Abstract

While soil ecosystems undergo important modifications due to global change, the effect of soil properties on plant distributions is still poorly understood. Plant growth is not only controlled by soil physico‐chemistry but also by microbial activities through the decomposition of organic matter and the recycling of nutrients essential for plants. A growing body of evidence also suggests that plant functional traits modulate species’ response to environmental gradients. However, no study has yet contrasted the importance of soil physico‐chemistry, microbial activities and climate on plant species distributions, while accounting for how plant functional traits can influence species‐specific responses.Using hierarchical effects in a multi‐species distribution model, we investigate how four functional traits related to resource acquisition (plant height, leaf carbon to nitrogen ratio, leaf dry matter content and specific leaf area) modulate the response of 44 plant species to climatic variables, soil physico‐chemical properties and microbial decomposition activity (i.e. exoenzymatic activities) in the French Alps.Our hierarchical trait‐based model allowed to predict well 41 species according to the TSS statistic. In addition to climate, the combination of soil C/N, as a measure of organic matter quality, and exoenzymatic activity, as a measure of microbial decomposition activity, strongly improved predictions of plant distributions. Plant traits played an important role. In particular, species with conservative traits performed better under limiting nutrient conditions but were outcompeted by exploitative plants in more favorable environments.We demonstrate tight associations between microbial decomposition activity, plant functional traits associated to different resource acquisition strategies and plant distributions. This highlights the importance of plant–soil linkages for mountain plant distributions. These results are crucial for biodiversity modelling in a world where both climatic and soil systems are undergoing profound and rapid transformations.

Highlights

Human-induced global change alters climate, and soil properties and functioning (Rillig et al 2019)
Models accounting for functional traits were slightly better than the model accounting for the environment only
Understanding the mechanisms underlying plant distributions is a great challenge to anticipate the consequences of global changes on plant communities (Thuiller et al 2008)

Summary

Introduction

Human-induced global change alters climate, and soil properties and functioning (Rillig et al 2019). Climate and soil jointly influence plant species distributions through their effect on plant growth, survival and reproduction (Buri et al 2017). Favorable environmental conditions select for functional trait values related to an exploitative strategy (i.e. rapid nutrient acquisition and fast growth, Aerts 1999, Reich 2014). Plants with exploitative traits lead to a soil organic matter that is easier to decompose, which increases nutrient availability, and in return favors exploitative plants. Conservative plant traits induce low decomposability of soil organic matter, which slows down nutrient release in the soil, and selects plants with conservative trait values (Wardle and Bardgett 2002, Grigulis et al 2013, Legay et al 2016). It is well known that plants and soils are linked by feedback loops at local scales, the influence of plant–soil linkages on plant distributions is under-studied at large biogeographic scales

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