Data from: The experimental manipulation of atmospheric drought: Teasing out the role of microclimate in biodiversity experiments

Climate change alters mean global surface temperatures, precipitation
regimes, and atmospheric moisture. Resultant drought affects the
composition and diversity of terrestrial ecosystems worldwide. To date,
there are no assessments of the combined impacts of reduced precipitation
and atmospheric drying on functional trait distributions of any species in
an outdoor experiment. Here, we examined whether soil and atmospheric
drought affect the functional traits of a focal grass
species (Poa secunda) growing in monoculture and
8-species grass communities in outdoor mesocosms. We focused on specific
leaf area (SLA), leaf area, stomatal density, root:shoot ratio, and fine
root:coarse root ratio responses. Leaf area and overall growth were
reduced with soil drying. Root:shoot ratio only increased for P. secunda
growing in monoculture under combined atmospheric and soil drought. Plant
energy allocation strategy (measured using principal components) differed
when P. secunda was grown in combined soil and
atmospheric drought conditions compared with soil drought alone. Given a
lack of outdoor manipulations of this kind, our results emphasize the
importance of atmospheric drying on functional trait responses more
broadly. We suggest that drought methods focused purely on soil water
inputs may be imprecisely predicting drought effects on other terrestrial
organisms as well (other plants, arthropods, and higher trophic levels).