Environmental correlates of understory plant diversity and distribution in a temperate climate-change refugium
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Aim
Regional climate-change refugia – areas where abiotic conditions related to hydrology and topography sustain unique plant communities despite an otherwise unsuitable regional macroclimate – have been essential for maintaining biodiversity through past climatic transitions. At fine spatial scales, regional refugia can also contain microrefugia, where canopy structure and topography strongly buffer understory microclimate. We tested whether such microrefugia structure understory plant communities within a regional climate-change refugium, where sheltered, groundwater-fed canyons have sustained a biogeographically distinctive flora since the Last Glacial Maximum.
Location
Temperate forest in the North American Great Plains, Nebraska, USA.
Methods
In a 20.2-ha forest inventory plot spanning a sharp topographic gradient, we quantified diversity, composition, and distributions and of understory woody and herbaceous plants across seven functional groups along fine-scale topographic, light, and soil moisture gradients.
Results
Woody species density and richness were significantly higher within sheltered microrefugia in canyon bottoms and on forested slopes and strongly decreased with increasing canopy openness, whereas C 4 grass richness was highest along the exposed, high-light forest-prairie ecotone, reflecting divergent functional group responses to microclimate buffering. Soil moisture structured richness across functional groups: woody plant and C 3 grass richness peaked at moisture extremes, sedge richness at intermediate moisture variability, and C 4 grass richness declined with increasing moisture variability. Both woody and herbaceous understory plants showed strong variation in composition with topography; in particular, woody seedlings and graminoids exhibited strong species turnover with increasing elevation.
Main Conclusions
These results demonstrate that topographically driven microrefugia support disproportionate understory biodiversity and suggest that protecting both regional refugia and finer-scale microrefugia will be critical for conserving plant communities, including species documented exclusively in microrefugia, as macroclimate continues to change.
Article activity feed
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Environmental correlates of understory plant diversity and distribution in a temperate climate-change refugium https://www.biorxiv.org/content/10.64898/2026.10.02.756313v1
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Environmental correlates of understory plant diversity and distribution in a temperate climate-change refugium https://www.biorxiv.org/content/10.64898/2026.10.02.756313v1
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