Trait-based responses to cessation of nutrient enrichment in a tundra plant community

Abstract

AbstractPlant communities worldwide show varied responses to nutrient enrichment—including shifts in species identity, decreased diversity, and changes in functional trait composition—but the factors determining community recovery after the cessation of nutrient addition remain uncertain. We manipulated nutrient levels in a tundra community for 6 years of nutrient addition followed by 8 years of recovery. We examined how community recovery was mediated by traits related to plant resource-use strategy and plant ability to modify their environment. Overall, we observed persistent effects of fertilization on plant communities. We found that plants with fast-growing traits, including higher specific leaf area, taller stature and lower foliar C:N, were more likely to show a persistent increase in fertilized plots than control plots, maintaining significantly higher cover in fertilized plots 8 years after cessation of fertilization. Additionally, although graminoids responded most strongly to the initial fertilization treatment, forb species were more vulnerable to fertilization effects in the long-term, showing persistent decline and no recovery in 8 years. Finally, these persistent fertilization effects were accompanied by modified environmental conditions, including persistent increases in litter depth and soil phosphorous and lower soil C:N. Our results demonstrate the potential for lasting effects of nutrient enrichment in nutrient-limited systems and identify species traits related to rapid growth and nutrient-use efficiency as the main predictors of the persistence of nutrient enrichment effects. These findings highlight the usefulness of trait-based approach for understanding the persistent feedbacks of nutrient enrichment, plant dynamics, and niche construction via litter and nutrient build-up.