Alpages Volants (2016 - 2026)

Responses of alpine meadows to a warming world

Team involved : BIOM
Platform involved : AAEM, PASTIS
Main contact person : Tamara Münkemüller (LECA, CNRS)
Funding sources : DiPEE, FREE, ZAA & LECA internal funding

Predicting the response of ecological communities to changing climate has emerged as one of the most important goals for ecology. Past research has shown that climate can directly affect species’ demographic performance by altering their phenology and functional traits, but can also indirectly affect them by changing interactions with competitors, consumers, and mutualists. More recent work suggests that among the most important determinants of how plant and soil communities respond to future conditions will be the novel interactions that emerge with the asynchronous responses of aboveground and belowground communities to climate change. However, the timeline of the different responses of plant and soil communities, the resulting novel interactions and feedbacks and, ultimately, the emerging dynamics of community assembly and ecosystem functioning remain largely unknown.

Addressing these challenges requires a holistic approach that simultaneously explores responses of plant and soil communities as well as ecosystem functioning. A well-suited study case are Alpine meadows in mountain environments with their steep climatic gradients and considerably changing compositions of phenologies, traits and species over short distances.

Summary : AlpagesVolants aims at better understanding and predicting (A) the early transient dynamics of coupled plant-soil communities in alpine meadows as a response to warming climate ; and (B) the dynamic mechanisms limiting the often strikingly-sharp ranges of plants in mountain environments.

The overall approach to address these research questions centers around the transplant experiment AlpagesVolants. The experiment was installed in the French Alps close to the Jardin du Lautaret in 2016 in a joint effort of LECA and Jardin du Lautaret. Community turfs (10 turfs of 4m2) were transplanted 500m downslope (and upslope) between an alpine site close to the Galibier pass and a sub-alpine site close to the Lautaret pass, subjecting them to a 3-degree increase (decrease) in temperature and a change in the snow regime. Control turfs have been transplanted from sub-alpine to sub-alpine conditions (10 turfs of 1m2) and from alpine to alpine conditions (10 turfs of 1m2). Each of the transplanted community turfs consists of the above- and below-ground parts of meadow communities and 20-25cm of their associated soil and soil communities. Since 2017 we observe in these plots attributes of plant communities (e.g. NDVI and plant phenology, plant community composition and plot specific plant traits), soil communities (e.g. community composition via environmental metabarcoding, extracellular enzymatic activity, qPCR), and attributes of soil functions (e.g. N, C, litter decomposition).

First results :

AlpagesVolants answers to two main blocks of questions around : (A) Transient dynamics triggered by climate warming and (B) drivers of species range limits.

Part A – Multi-trophic, multi-facet & interdependent responses to climate warming and resulting transient dynamics
Climate warming affects plant communities, soil communities and their ecosystem functions. Warming effects can be either direct or indirect and mediated via plant-soil feedbacks and/or functioning-diversity feedbacks. So far, we know little about the transient dynamics triggered by warming and the different timelines and feedbacks of responses from plants, soil microbes and ecosystem functions.
In order to better understand potential feedbacks, we added in parts of the transplanted communities treatments to simulate (in addition to the warming of the communities) the invasion of climate-adapted sub-alpine species and/or climate-adapted sub-alpine soils and their communities.

With the long-term monitoring of the experiment we aim at :
– Capturing the transient dynamics and asynchronous timelines of responses of different diversity compartments (e.g. plants, soil fungi, bacteria), their different facets (e.g. phenology, traits, species composition) and ecosystem functions (e.g. nitrogen and carbon cycle, enzymatic activities) to climate warming
– Better understanding the feedbacks within and between different diversity compartments and ecosystem functions
– Providing a proof-of-concept to highlight the importance of such an experiment

Part B – Disentangling drivers of range limits of sub-alpine species at different life stages
Very steep environmental gradients at the landscape scale are reflected in distinct plant communities over very short distances. Over these short distances and climatic gradients, dispersal and environmental filtering are often not sufficient to explain range limits of certain species, i.e. the presence of some species in sub-alpine conditions but not in very close alpine conditions. Competition has been suggested as a major force at upper range limits. However, testing for the importance of competition requires moving around not only the focal species but also its competitors. Here, we use AlpagesVolants. We add in parts of the uphill transplanted communities and the alpine as well as sub-alpine control communities four sub-alpine species that do not naturally occur in the alpine site.

With the long-term monitoring of the experiment we aim at answering the following questions :
– How do different facets of the sub-alpine background community (phenology, traits, species composition of plants and soil composition and functioning) respond to the transplantation beyond the range limit ?
– What is the relative importance of dispersal, environmental filtering and competition for limiting the ranges of the four focal species ?
– Are there differences between different “life stages” (establishment from seeds, establishment of transplanted adult individual, phenology, performance) ?

Partners :

LECA - CNRS - Université Grenoble Alpes - Université Savoie Mont Blanc (Laboratoire d’Écologie Alpine)
– Tamara Münkemüller
– Amélie Saillard
– Ludovic Gielly
– Billur Bektaş
– Wilfried Thuiller
– Julien Renaud
– Maya Guéguen
– Arnaud Foulquier