Heterogeneity-diversity relationships differ between and within trophic levels in temperate forests

Area of Science:

• Ecology
• Biodiversity Science
• Forest Ecology

Background:

• The habitat heterogeneity hypothesis suggests increased habitat complexity supports higher biodiversity.
• However, complex relationships exist, with some studies showing decreased richness at high heterogeneity due to stochastic extinctions.
• This indicates potential trade-offs and group-specific responses to different heterogeneity facets.

Purpose of the Study:

• To systematically investigate the multifaceted relationship between habitat heterogeneity and biodiversity.
• To test the habitat heterogeneity hypothesis across diverse species groups and multiple heterogeneity facets simultaneously.
• To identify which facets of habitat heterogeneity most strongly influence biodiversity patterns in temperate forests.

Main Methods:

• Decomposition of habitat heterogeneity into six key facets across approximately 500 temperate forest plots in Germany.
• Quantification of biodiversity for 12 distinct species groups (bats, birds, arthropods, fungi, lichens, plants) encompassing 2,600 species.
• Statistical analysis to determine the relationship between heterogeneity facets and species richness for each group.

Main Results:

• Heterogeneity in horizontal and vertical forest structure was the primary driver of most heterogeneity-diversity relationships (HDRs).
• Plant diversity, deadwood, and topographic heterogeneity also played significant roles, with relative importance varying even within trophic levels.
• While 53% of HDRs showed a monotonic increase (supporting the classical hypothesis), 21% were hump-shaped, and 25% decreased monotonically.

Conclusions:

• The study reveals that forest structure and plant diversity are key drivers of biodiversity.
• Habitat heterogeneity-diversity relationships are complex and vary significantly across species groups and facets of heterogeneity.
• No single, generalizable mechanism universally explains biodiversity patterns in response to habitat heterogeneity.