Global functional shifts in trees driven by alien naturalization and native extinction.

Area of Science:

• Ecology
• Biodiversity science
• Conservation biology

Background:

• Human activities are altering global tree diversity through extinctions and the spread of non-native species.
• These changes have significant implications for ecosystem structure, function, and stability.
• Understanding the traits and environmental niches of different tree species is crucial for predicting future ecological shifts.

Purpose of the Study:

• To analyze the functional traits and environmental niches of 31,001 tree species globally.
• To compare naturalized, threatened, and non-threatened species to identify patterns in diversity.
• To project future changes in tree communities under intensified extinction and naturalization scenarios.

Main Methods:

• Analysis of functional traits and environmental niches for over 31,000 tree species worldwide.
• Comparative analysis of naturalized, threatened, and non-threatened species.
• Modeling future shifts in tree communities based on projected extinction and naturalization rates.

Main Results:

• Future tree-rich ecosystems are predicted to be dominated by fast-growing, resource-acquisitive species.
• Slow-growing, conservative species face higher extinction risks.
• Naturalized species exhibit broader functional and environmental niches, thriving in colder, variable climates, while threatened species are specialized to warm, stable, nutrient-rich environments.

Conclusions:

• Projected naturalizations may increase local functional diversity but could decrease long-term ecosystem stability due to acquisitive strategies.
• Extinctions are expected to contract functional and environmental trait spaces, particularly in variable climates.
• There is an accelerating global trend towards faster-growing tree communities, necessitating conservation of slow-growing species and management of acquisitive ones to mitigate impacts on carbon storage and biodiversity.