# Rapid plant functional trait responses to warming, flooding, and herbivory in high-latitude coastal wetlands

## TL;DR

This study shows how plants in high-latitude wetlands quickly adjust their traits in response to climate change factors like warming, flooding, and herbivory.

## Contribution

The study reveals context-dependent and consistent trait responses to multiple climate drivers in high-latitude wetlands using a full-factorial experiment.

## Key findings

- Warming increased plant size in the Lowland wetland but not in the Upland wetland.
- Herbivory consistently reduced plant size and promoted acquisitive leaf traits across all species.
- Flooding had contrasting effects on leaf economics traits depending on wetland type and species.

## Abstract

Climate change is rapidly altering high-latitude coastal wetlands through increasing temperatures, more frequent flooding, and changing herbivore abundance and distribution. Examining plant functional trait responses to these drivers provides insight into how plant communities are shaped by climate change. We used a one-year full-factorial mesocosm experiment in coastal Alaska to assess immediate responses of two size-related traits (vegetative height and leaf area) and two leaf economics traits (specific leaf area [SLA] and leaf dry matter content [LDMC]) to warming, flooding, and goose herbivory in three dominant species across two wetland communities (Lowland and Upland) differing in landscape position. We sampled different sedges (Carex rariflora and Carex lyngbyei) and the same deciduous dwarf-shrub (Salix fuscescens) in the two wetlands. Warming increased plant size for the sedge (leaf area: + 15%) and the shrub (height: + 15%; leaf area: + 19%) in the Lowland wetland only. Flooding promoted acquisitive trait values for the Lowland sedge (SLA: + 8%; LDMC: − 6%) and conservative values for the Upland shrub (SLA: − 9%; LDMC: + 11%). The shrub thus showed clear wetland-specific responses to warming and flooding. Herbivory triggered coordinated responses across all three species, consistently decreasing size-related trait values (height: − 17–35%; leaf area: − 33–50%) and promoting acquisitive trait values (SLA: + 14–40%; LDMC: − 12–23%). Despite the absence of interactions, each driver contributed significantly to trait variation, underscoring the value of multifactorial approaches. The combination of consistent (herbivory) and context-dependent (flooding and warming) responses highlights the complexity of trait responses and improves predictions of rapid phenotypic adjustments in coastal high-latitude wetlands.

The online version contains supplementary material available at 10.1007/s00442-026-05876-8.