Mountain meadows face particular challenges under climate change due to a dual threat: rising temperatures (faster than in lower altitudes) and the encroachment of warm-adapted species that increase competition. Through the process of “thermophilization”, species adapted to warmer conditions migrate from lower elevations to higher ones. However, cold-adapted highland specialists struggle to survive under warmer conditions. The study by Sylvia Haider (from the Leuphana Institute of Ecology), Carolin Schaub and Susanne Lachmuth investigates how warmer conditions caused by climate change might impact the species composition and ecological functioning of these valuable and biodiverse habitats.
An experiment bringing the mountain to the valley
To simulate the effects of rising temperatures, the researchers transplanted highland plant communities from the German Alps to warmer, lower-elevation regions. Over four years, the researchers analysed how the transplanted communities changed in terms of species composition, functional identity (characteristics like leaf traits and resource-use strategies) and diversity (a measure of the variety of functional traits within a community). Therefore, they asked questions such as: How do communities change under warmer conditions? Which species are “winners” and which are “losers”? And how does the immigration of warm-adapted species affect the functional identity and diversity of communities as well as ecosystem functions and processes?
What makes this approach unique is that entire plant communities were integrated into natural environments. This allowed the researchers to account for real interactions with local species and environmental influences, providing more realistic results than e.g. artificial warming chambers. Factors like competition with native plant species and the effects of natural soils were thus included.
What are the findings, and what do they mean?
The study measured functional morphological and biochemical leaf traits, enabling the calculation of community-weighted trait means, functional richness, and functional divergence. The focus on functional traits provided insights into how species interactions and resource-use strategies could shift in response to climate warming.
The findings highlight the dynamic yet vulnerable nature of alpine ecosystems. Within just four years, the transplanted communities underwent significant changes. These communities first gained species richness, attributed to the immigration of warm-adapted lowland species and the “lag phase” of highland specialists, meaning their delayed disappearance. Highland specialists initially resisted extinction through strategies like vegetative reproduction (e.g., via rhizomes).
Warm-adapted species, originating from lower regions, exhibited different “strategies”: they grow faster, absorb more nutrients, and compete stronger for light. Over time, this could threaten the survival of cold-adapted specialists, which rely on slow growth and efficient resource use. For instance, Poa alpina (alpine meadow-grass), present in nearly all transplanted plots in the first year, had nearly vanished by the fourth year.
Another striking result is the increasing similarity between the transplanted and lowland communities. The mountain thus loses part of its unique identity, becoming similar to the lowlands with regard to species composition.
A call to action for protecting montane and alpine ecosystems
Overall, the results confirm the stated hypotheses that climate warming leads to significant changes in species richness, composition, and functional traits in mountain meadow communities. Highland plants adapted to cold temperatures and nutrient-poor soils are at risk of disappearing due to climate change. These species are not only ecologically but also culturally important. The study emphasizes that alpine ecosystems worldwide face similar threats, emphazising the strong connection between climate change and biodiversity loss.
To preserve these valuable mountain ecosystems, targeted conservation measures are essential. These include reducing greenhouse gas emissions to mitigate the effects of climate change and developing strategies to protect and support the survival of sensitive highland specialists.
If you are interested in the study in more detail, you can find it here: https://onlinelibrary.wiley.com/doi/full/10.1111/jvs.13280
