Hydraulic Strategies Modulate Forest Productivity Responses to Hotter Droughts.

Area of Science:

• Ecology
• Climate Change Science
• Forestry

Background:

• Climate change increases extreme events, threatening global forest productivity and carbon cycle regulation.
• Forest responses to compound events like hotter droughts are influenced by species' functional traits and diversity.
• Existing research often overlooks drought duration and frequency, focusing primarily on intensity.

Purpose of the Study:

• To assess the long-term effects of hotter drought intensity, frequency, and duration on forest productivity.
• To evaluate how functional identity and diversity modulate forest productivity responses to drought.
• To understand the implications for forest carbon mitigation potential under climate change.

Main Methods:

• Analysis of forest productivity data from 1985-2018 in a Mediterranean region.
• Integration of LiDAR, multispectral imagery, and forest inventory records from 748 plots.
• Application of generalized linear mixed models to assess drought impacts and trait-mediated responses.

Main Results:

• The negative impact of increased vapor pressure deficit and drought dimensions on forest productivity has intensified over time.
• Forests with higher functional diversity and moderately conservative species exhibited smaller productivity declines during extreme droughts.
• Highly conservative species-dominated forests showed increasingly negative productivity responses, potentially due to prolonged stomatal closure and carbon starvation.

Conclusions:

• Hotter droughts have a progressively negative and intensifying impact on Mediterranean forest productivity.
• Functional diversity and identity, particularly traits like cavitation resistance, stabilize forest productivity under drought stress.
• Incorporating these stabilizing roles is crucial for accurate modeling of long-term climate change impacts on forest carbon mitigation.