Light and warming drive forest understorey community development in different environments.

Area of Science:

• Ecology
• Global Change Biology
• Plant Ecology

Background:

• Chronic global change drivers (climate change, nitrogen deposition) and pulse disturbances (ecosystem management) impact plant communities.
• Land-use legacies can further influence community responses to environmental changes.
• Disentangling these drivers is crucial for predicting future plant community trajectories.

Purpose of the Study:

• To investigate the relative importance of warming, light addition, and nitrogen enrichment on temperate forest herbaceous plant communities.
• To assess the role of land-use legacies (ancient vs. post-agricultural forest soils) in community responses to global change.
• To evaluate the contribution of intraspecific trait variation (ITV) to community functional trait changes.

Main Methods:

• A multifactor global change experiment using 384 mesocosms with five-species herbaceous communities.
• Soils were sourced from ancient and post-agricultural European forests.
• Treatments included warming, light addition, and nitrogen enrichment, with measurements of plant height, specific leaf area (SLA), and species cover over three seasons.

Main Results:

• Increased light availability and warming significantly altered species composition, leading to taller herbaceous communities.
• Nitrogen enrichment and land-use history had limited effects on overall community height.
• Intraspecific trait variation was important for understanding community-level specific leaf area responses, particularly under nutrient enrichment in low-light conditions.

Conclusions:

• Warming and altered light availability are key drivers of forest herb community shifts, promoting taller growth.
• Intraspecific trait variation significantly influences functional trait responses, especially leaf morphology under nutrient stress.
• Land-use legacies had a minimal impact, possibly due to the experimental removal of dispersal limitation.