Tree species diversity increases with conspecific negative density dependence across an elevation gradient.

Area of Science:

• Ecology
• Forest Science
• Biotic Interactions

Background:

• Elevational gradients influence species diversity, potentially mediated by biotic interactions.
• Conspecific density dependence (CSDD) describes how the negative effects of individuals of the same species impact survival and growth.
• Limited evidence exists on how CSDD varies with elevation.

Discussion:

• This study analyzed 40 years of tree survival and growth data from 23 old-growth temperate forest stands along a 1,000-m elevation gradient.
• CSDD on survival of small-to-intermediate trees was negative in lower, warmer, more humid, and diverse stands.
• CSDD on survival was less negative at higher elevations and neutral for larger trees, while CSDD on growth was negative across all sizes and elevations.

Key Insights:

• CSDD on tree survival varies significantly with elevation, impacting smaller trees more than larger ones.
• Negative CSDD on growth was observed across all tree sizes and elevations, indicating consistent self-limiting effects.
• Findings highlight distinct biotic interactions shaping forest dynamics across environmental gradients.

Outlook:

• Further research can explore the specific mechanisms driving CSDD variation with elevation, such as microclimate and resource availability.
• Understanding these biotic interactions is crucial for predicting forest responses to climate change and for conservation strategies.
• Investigating CSDD in different forest types and biomes will broaden our understanding of ecological dynamics.