Water-limited environments affect the association between functional diversity and forest productivity

Area of Science:

• Ecology
• Forest Science
• Biodiversity Research

Background:

• Biodiversity-ecosystem function (BEF) relationships are contingent on environmental conditions, complicating predictions of future forest responses.
• Understanding shifts in BEF relationships across environmental gradients is vital for predicting forest dynamics under climate change.

Purpose of the Study:

• To investigate how water limitation shapes forest functional composition and diversity.
• To determine the relationship between tree functional traits, diversity, and forest annual increment.
• To compare how functional diversity influences forest increment across Mediterranean and temperate climates.

Main Methods:

• Compiled data on five key functional traits for 78%-90% of Italian National Forest Inventory tree species.
• Analyzed the influence of a water limitation gradient on functional composition and diversity.
• Assessed the roles of mass ratio and niche complementarity in linking tree diversity to forest annual increment.

Main Results:

• Forest functional composition shifted towards conservative traits under higher water limitation.
• Functional diversity responses varied by trait and climate region; temperate forests showed increased functional diversity with water limitation.
• Tree diversity positively correlated with forest annual increment through mass ratio and niche complementarity effects.

Conclusions:

• Biodiversity mediates forest annual increment under water stress by enhancing species interactions and resource use complementarity.
• Niche complementarity effects were stronger in Mediterranean forests than temperate ones.
• Conserving functional diversity is essential for maintaining forest productivity amidst increasing drought.