Plant community nutrient levels and soil biogeochemical responses to sixty-plus years of brown lemming exclusion in Utqiaġvik, Alaska

Small mammal herbivores are crucial drivers of Arctic ecosystem functions, but responses to herbivory depend on context such as land cover and study length. We examined the long-term effects (more than sixty years) of small mammal exclusion across three land cover classes near Utqiaġvik, Alaska, on community plant nutrient content and belowground biogeochemical processes. Due to large responses in bryophyte cover, we also examined the importance of including nonvascular data into Arctic plant nutrient studies. Community-weighted mean (CWM) foliar phosphorous concentrations were higher in dry exclosure plots, whereas foliar carbon concentrations were lower in dry and moist exclosure plots but showed no responses to herbivore exclusion in wet plots. Additionally, N:P and C:P were lower due to long-term herbivore exclusion in dry land cover. When nonvascular plant data were included, foliar nitrogen and phosphorus concentrations were lower in exclosures than in grazed plots in wet land cover. We found no significant effects of long-term herbivore exclusion on soil biogeochemical properties. Our results underscore the importance of small mammals as drivers of Arctic plant community nutrient levels with potential consequences for ecosystem functions, especially over decadal timescales. We also contribute significant evidence for the importance of including nonvascular plants in community-weighted plant nutrient analyses.