Temporal variability and nestedness in California grassland species composition

Area of Science:

• Ecology
• Community Ecology
• Environmental Science

Background:

• Nestedness is a common spatial pattern where species-poor communities are subsets of species-rich ones.
• Temporal nestedness, examining this pattern across time, is less studied but crucial for understanding species coexistence.
• Interannual environmental variation can influence community composition and nestedness patterns.

Purpose of the Study:

• To investigate temporal nestedness in plant communities using long-term data.
• To determine if environmental variation drives temporal nestedness in California grasslands.
• To explore implications for species coexistence and community assembly.

Main Methods:

• Analysis of eight years of plant occurrence data from 71 California grassland sites.
• Statistical examination of nested distribution patterns across temporal scales.
• Correlation of species richness with interannual environmental conditions (e.g., rainfall, temperature).

Main Results:

• Strong signals of temporal nestedness were detected, indicating most species favor similar conditions.
• Favorable environmental years facilitated the expansion of grasses and forbs into new areas.
• Peak species richness for native and exotic annuals occurred after cool, wet years following hot, dry periods.

Conclusions:

• Interannual environmental variation can drive temporal nestedness in plant communities.
• The absence of specialists for poor-quality years promotes nested subset formation over time.
• This pattern has significant implications for species coexistence and ecological community dynamics.