Data from: Rooting depth and specific leaf area modify the impact of experimental drought duration on temperate grassland species

Due to climate change, temperate grasslands are being exposed to
increasingly severe droughts. Concurrently, land-use intensification is
altering grasslands’ functional composition by promoting fast-growing,
resource-acquisitive species with high specific leaf area (SLA). How SLA
affects the ability of grassland species to resist and recover from
increasingly severe droughts and if deep roots improve their drought
performance remains unclear. To investigate this, we established a common
garden field experiment including temperate grassland species with SLAs of
17.9–39.3 mm2g-1 and maximal rooting depths of 16–252 cm. After 1.5 years,
we simulated droughts for 0, 79, 134, 177 and 220 days. Drought effects on
plant performance increased with drought length, reducing the survival of
green tissue and annual biomass by up to ~50% across all 32 species
considered. As plant-available water remained in deep soil layers by the
end of all treatments, deep roots mitigated the negative effect of
increasing drought length on productivity in the later stage of drought
and favoured productivity after long drought. The low-to-high SLA trait
gradient among the 16 graminoid species seemed to represent alternative
survival strategies ranging from dehydration tolerance to dehydration
avoidance, rather than drought sensitivity. Variable drought responses
along the SLA gradient of forbs imply that multiple other traits are
related to drought resistance across evolutionarily distant species.
Synthesis: Our results suggest that deep roots are beneficial for
temperate grassland species subjected to longer periods without rainfall
when plant-available water is lacking in shallow soil layers but remaining
in deep soil layers. In the face of increasing drought severity, we thus
recommend (1) fostering deep-rooted species in intensive grasslands on
deep, productive soil and (2) directing further studies towards
identifying management practices that support deep rooting in semi-natural
grasslands.