Global change experiments in mountain ecosystems: A systematic review

Mountain ecosystems are particularly sensitive to global change and are therefore often used as early warning systems while providing essential ecosystem services. For this reason, researchers aim to understand how these ecosystems develop under climate change. While focus increased in the last decades, mainly due to manipulation experiments, our understanding of how these ecosystems respond to environmental changes remains fragmented. In this study we systematically reviewed 767 manipulation experiments on global change effects in mountain environments over the past three decades, analyzing 3082 ecological responses across different organizational levels. Temperature manipulation was the most common experiment type (45% of studies), showing strong effects on plant phenology, soil respiration, and nutrient cycling. Water availability significantly impacted productivity and carbon cycling, while nutrient manipulations altered community composition and biomass production. Plant responses dominated the research (71% of studies), showing species-specific adaptations to warming. Soil microbial communities exhibited significant responses to warming, affecting decomposition processes and nutrient availability. However, critical knowledge gaps remain. Experimental studies on adult trees in tropical and boreal regions are scarce, and animal responses, biotic interactions, and aquatic environments require more attention. Furthermore, most experiments (73%) were short-term, with a duration under 5 years and focused on single factors, limiting our understanding of long-term and interactive effects. A network of standardized experiments across mountain regions, combining different research methods and collaboration between research groups, could address these gaps.