Disappearing green: Shrubs decline and bryophytes increase with nine years of increased snow accumulation in the High Arctic

Abstract

Abstract Question How does increased snow depth affect plant community composition of High Arctic tundra, and can the Normalized Differential Vegetation Index ( NDVI ) detect induced changes? Location Adventdalen, Spitsbergen, Svalbard (78°10′ N, 16°04′ E). Methods We manipulated snow depth on the tundra using fences, resulting in Deep , Medium , and Ambient snow regimes. Increased snow led to warmer winter soil temperatures, a delayed onset of growing season and wetter conditions during the early growing season. Plant community composition of living and dead plant material was recorded after nine years. NDVI was measured at the plot level using a handheld sensor. Results Community composition and the abundance of typically dominant shrub species were substantially different in the Deep compared to the Ambient regime. Deep had lower cover of live shrubs ( Cassiope tetragona, Dryas octopetala and Salix polaris ) and Luzula confusa , and higher cover of dead shrubs ( Cassiope and Dryas ) compared to the other snow regimes. Bryophyte cover was highest in Medium . NDVI was positively correlated to the cover of living vascular plants and negatively correlated to cover of dead vascular plants. Accordingly, Deep snow regime had reduced NDVI , reflecting the contribution of dead Cassiope and Dryas . Conclusion Snow regime strongly influenced community composition in High Arctic plant communities. Enhanced snow regimes had more dead shrubs, reduced Luzula and increased bryophyte cover than ambient conditions. These differences were detectable by handheld NDVI sensors.