Disjunct performance and distribution in the sedge Carex prasina

Area of Science:

• Ecology
• Plant Ecology
• Biogeography

Background:

• Understanding species distributions and predicting responses to environmental change requires knowledge of how abiotic factors influence them.
• Distinguishing environmental effects from other mechanisms like competition and dispersal limitation is crucial at landscape scales.

Purpose of the Study:

• To investigate the influence of environmental factors, specifically soil characteristics, on the distribution and performance of Carex prasina.
• To compare how the species' performance in controlled greenhouse conditions relates to its distribution patterns across a landscape.

Main Methods:

• A greenhouse experiment assessed Carex prasina performance on soils from various wetland habitats.
• Soil characteristics were analyzed to correlate with species performance (biomass, chlorophyll content) and landscape distribution (occurrence, abundance).
• Landscape-scale analysis examined the probability of occurrence and abundance across a 10-km² old-growth forest.

Main Results:

• In greenhouse experiments, Carex prasina biomass and chlorophyll content increased with soil organic matter (OM).
• Across the landscape, however, the species' occurrence and abundance decreased as soil OM increased.
• Carex prasina occurred on soils where its performance was reduced, not enhanced, indicating a disconnect between performance and distribution.

Conclusions:

• Species distribution is not solely determined by optimal environmental performance; other factors like competition or dispersal limitation can be more influential.
• The study cautions against assuming that a species' most abundant habitats are where it performs best.
• Carex prasina's distribution along edaphic gradients is not explained by its performance, highlighting the need to differentiate biotic and abiotic factors in shaping species distributions.