Seed germination of a rare gypsum-associated species, Arctomecon californica (Papaveraceae), in the Mojave Desert

摘要

Persistence of rare species associated with unique soil habitats is uncertain with commonly accelerating threats such as habitat loss, fragmentation, and rapid environmental change and limited availability of critical life-history information, such as seed dormancy and germination. Exemplifying rare species of unique habitats in arid environments, Arctomecon californica Torr. & Frem. (Las Vegas bearpoppy) is endemic to gypsic- (calcium sulfate dihydrate) and calcic- (calcium carbonate) soil landscapes in the Mojave Desert of southern Nevada and northwestern Arizona, USA. We examined seed dormancy and germination of A. californica using integrated field and laboratory experiments assessing whether (i) field conditioning could enhance laboratory seed germination; (ii) sulfuric acid, as a potential constituent of gypsum soil water, could break dormancy; and (iii) different temperature regimes could affect germination. Our study demonstrates three findings pertaining to A. californica germination: the promotive effect of low temperature exposure, or more specifically single to multiple cold stratification (cold-wet) events; the potential initial enhancing role of sulfuric acid on the cold stratification process, which diminishes with prolonged cold stratification exposure; and the relative ineffectiveness of a one-season field conditioning treatment on A. californica germination, suggesting that longer cold stratification events, within season or over multiple seasons, are required to trigger germination. For land managers, the efficacy of cold stratification as a dormancy break has potential to inform A. californica conservation management within suitable habitat and support restoration applications such as in breaking dormancy before seeding and propagating plants.