Grazed vs the Ungrazed: Herbivory Effects on Leaf Nutrient Content and Chemical Defense

Abstract

Despite growing evidence of herbivory's influence on plant nutrient dynamics in the Arctic tundra, the short-term effects on leaf nutrient and phenolics contents across different tundra habitats and dominant plant species remain underexplored. This study enhances our understanding by analyzing the impacts of a 2-year herbivore exclusion (involving Svalbard reindeer and migratory geese) on leaf nutrient contents and phenolics, within three dominant tundra species—Bistorta vivipara, Dryas octopetala, and Salix polaris—and three habitat types: moss tundra, disturbed moss tundra, and dryas ridges. Our approach corrected for baseline nutrient levels for species-specific effects and accounted for differential Plant Functional Type (PFT) responses in the habitat-specific analysis. The results indicate generally weak and non-significant changes in leaf nutrient and phenolics contents to short-term herbivory exclusion. However, significant increases were observed in phenolic content in Bistorta vivipara and phosphorus content in Dryas octopetala. The disturbed moss tundra also showed a significant reduction in phosphorus content. Thereby, only one out of 18 habitat-level models and two out of 18 species-specific models showed significant changes. These findings suggest that Arctic tundra habitats exhibit relative resilience to short-term herbivory in terms of leaf nutrient and phenolic contents responses. Given the nuanced nature of these findings, further research is needed to fully elucidate the intricate interactions between herbivory, leaf nutrient and phenolic contents across the diverse Arctic tundra landscape.