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

Chhaya M Werner,Anu Eskelinen,Maria Tuomi

doi:10.1007/s00442-021-05064-w

Abstract

Plant 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.

Highlights

Nutrient enrichment has been implicated as a driver of biodiversity loss and compositional change for plant communities globally (Bobbink et al 2010; Harpole et al 2016; Payne et al 2017)
We examined whether the effects of nutrient enrichment persisted 8 years after the cessation of the nutrient addition treatment by comparing the pretreatment communities to communities 14 years after the experiment was established or whether the communities had returned to the pretreatment stage
We found that species with traits associated with resource acquisitiveness were more likely to have persistent increases in fertilized plots than control plots

Summary

Introduction

Nutrient enrichment has been implicated as a driver of biodiversity loss and compositional change for plant communities globally (Bobbink et al 2010; Harpole et al 2016; Payne et al 2017). Theoretical predictions and field data indicate that in nutrient-enriched conditions, traits that allow plants to take advantage of increased resources are those associated with higher competitive ability for light in resource-rich conditions by promoting fast growth (Reich 2014). These “resource-acquisitive” traits include high relative growth rate, high specific leaf area, high leaf N and P concentrations (Westoby et al 2003; Adler et al 2013; Reich 2014), and taller stature, which is associated with higher competitive ability for light (Fargione and Tilman 2002; Hautier et al 2009). Despite the great potential of traits for predicting various community processes, their role as predictors of species’ persistence in previously nutrient-enriched conditions has yet to be addressed

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Conclusion