Spatial heterogeneity increases diversity and stability in grassland bird communities

Area of Science:

• Ecology
• Conservation Biology
• Landscape Ecology

Background:

• Grasslands are dynamic ecosystems influenced by fire and herbivores.
• Human actions have led to grassland homogenization, reducing ecosystem function and biodiversity.
• Previous studies suggest restoring grassland heterogeneity can boost avian diversity, but optimal levels and impacts on stability are unclear.

Purpose of the Study:

• To investigate avian responses to interacting fire and grazing across varying levels of landscape heterogeneity.
• To determine the impact of different fire return intervals and patchiness on avian diversity and community stability.
• To assess the relationship between landscape-scale heterogeneity and fine-scale vegetation characteristics influencing bird communities.

Main Methods:

• Utilized a landscape-level experimental design with seven landscapes (430-980 ha) exhibiting a gradient of fire- and grazing-dependent heterogeneity.
• Manipulated fire return intervals (annual to four-year) and fire seasonality to create varying patchiness.
• Quantified avian community change using detrended correspondence analysis and related species responses to landscape and microhabitat features.

Main Results:

• Greater landscape heterogeneity significantly increased avian diversity and community stability over time.
• The most heterogeneous landscapes supported nearly four times greater bird community stability compared to the most homogenous ones.
• Species' presence and abundance were positively associated with increased heterogeneity, with finer-scale responses linked to litter cover and vegetation height.

Conclusions:

• Increased fire- and grazing-dependent heterogeneity enhances grassland bird diversity and stability at the landscape scale.
• Management strategies should focus on restoring disturbance processes to promote heterogeneity for grassland bird conservation.
• Restored heterogeneity can lead to fine-scale avian community variability but broad-scale stability and diversity.