Alpine shrub growth follows bimodal seasonal patterns across biomes - unexpected environmental controls

Under climate change, cold-adapted alpine ecosystems are turning into hotspots of warming. However, the complexity of driving forces of growth, associated biomass gain and carbon storage of alpine shrubs is poorly understood. We monitored alpine growth mechanisms of six common shrub species across contrasting biomes, Mediterranean and tundra, using 257 dendrometers, recording stem diameter variability at high temporal resolution. Linking shrub growth to on-site environmental conditions, we modelled intra-annual growth patterns based on distributed lag non-linear models implemented with generalized additive models. We found pronounced bimodal growth patterns across biomes, and counterintuitively, within the cold-adapted biome, moisture, and within the drought-adapted biome, temperature was crucial, with unexpected consequences. In a warmer world, the Mediterranean alpine might experience strong vegetation shifts, biomass gain and greening, while the alpine tundra might see less changes in vegetation patterns, minor modifications of biomass stocks and rather browning. Generalized additive models reveal an unexpected environmental control in shrub growth across biomes.

Automated summary

Under climate change, the alpine ecosystems are becoming hotspots of warming. This study investigates the growth mechanisms of alpine shrubs and reveals the differences in growth patterns between different biomes. It finds that temperature and moisture play crucial roles in shaping shrub growth, with unexpected consequences. In a warmer world, the Mediterranean alpine may experience significant vegetation shifts and greening, while the alpine tundra may see minor changes and browning.