Summer dormancy, drought survival and functional resource acquisition strategies in California perennial grasses.
Evidence suggests drought severity is increasing due to climate change, but strategies promoting severe drought survival in perennial grasses have been seldom explored. This is particularly true of summer dormancy, an adaptation common in summer-dry Mediterranean-type climates. In addition, though theory predicts superior drought survival results in lower potential productivity, studies rarely measure both drought survival and growth under optimal conditions.



Physiological and functional ecological approaches were integrated to quantify interspecific variation in foliar and root traits in a suite of eight California perennial grass species. In a glasshouse experiment, summer dormancy, foliar functional trait variation, and seasonal growth and phenology under non-limiting water conditions and dehydration tolerance under progressive drought were quantified. In a second glasshouse study, root functional traits were quantified under non-limiting water conditions in rhizotrons.



Summer dormancy was associated with higher dehydration tolerance, and negatively associated with traits conferring dehydration avoidance. Species with greater summer dormancy were characterized by greater springtime productivity, earlier reproduction, and a shallow and fine root system, which are indicative of dehydration escape. Summer dormancy was associated with an acquisitive, competitive functional strategy in spring, and a conservative strategy in summer.



Both the escape and acquisitive springtime strategies observed in summer dormant perennial taxa are typically associated with annual grasses. California grasslands were once dominated by perennial species, but have been overtaken by non-native Mediterranean annual grasses, which are expected to be further favoured by climate change. Owing to functional similarity with these exotic annuals, it is suggested that native summer dormant taxa may play an important ecological role in the future of both natural and restored California grasslands.
Department of Plant Sciences, University of California, Davis, CA 95616, USA jbalachowski@ucdavis.edu.
Jennifer A
JA
Balachowski
INRA USC 1338, CEFE UMR 5175, CNRS, Université de Montpellier, Université Paul-Valéry Montpellier, EPHE, 1919 Route de Mende, 34293 Montpellier cedex, France.
Pauline M
PM
Bristiel
INRA USC 1338, CEFE UMR 5175, CNRS, Université de Montpellier, Université Paul-Valéry Montpellier, EPHE, 1919 Route de Mende, 34293 Montpellier cedex, France.
Florence A
FA
Volaire
D000222:Adaptation, Physiological; D002140:California; D055864:Droughts; D065948:Grassland; D010641:Phenotype; D057445:Plant Dormancy / Q000502:physiology*; D018517:Plant Roots / Q000502:physiology; D006109:Poaceae / Q000502:physiology*; D012621:Seasons; D014867:Water / Q000502:physiology
D014867:Water
California grasslands; Poaceae; dehydration avoidance; dehydration tolerance; drought escape; functional traits; perennial grasses; root traits; summer dormancy