As a consequence of current climatic changes communities at high latitudes and altitudes are experiencing a more rapid rise in temperatures than the global average. Climatic changes influence a number of ecosystem properties and processes both directly and indirectly (via for example driving shifts in plant community composition and biotic interactions). We utilize natural gradients in climate in mountain and arctic ecosystems, and experiments along these gradients where we manipulate abiotic factors and biotic interactions (plant-plant, and plant-herbivore), to address how climate and biotic interactions separately or interactively effect plant community properties and ecosystem functions. Specifically, we use 1) a site within a newly established global network of Warming And Removal experiments in Mountains (WARM) where warming by OTCs is crossed with dominant plant species removal at a high and low elevation, and 2) reindeer exclusion plots (≥15 yr of exclusion) across habitats and vegetation types in the Fennoscandian mountain range (61°N to 70°N).
Results/Conclusions
Early (year two following establishment) measurements from an Arctic WaRM site, show that the lower, warmer and more productive elevation has a greater gross primary production standardized at 600 PAR (GPP600) compared to the high elevation even after accounting for NDVI. Further, following two decades of reindeer exclusion we find no difference in NDVI, but a higher LAI especially in sites with a higher reindeer density. Our findings show overall positive plant responses to warmer temperatures, and point towards community differences in functional responses to warming at the landscape scale. Finally, while plant-herbivore interactions are clearly important for local and regional vegetation patterns these findings shed light on the role of large mammalian herbivores in influencing ongoing Arctic greening.