Optimizing physiological dormancy break of understudied cold desert perennials to improve seed-based restoration

Abstract

In degraded drylands, post-disturbance native plant community re-establishment is almost exclusively conducted using seeds. These restoration efforts are challenging, in large part as a result of a limited understanding of seed dormancy and germination traits. In this paper, we characterize these traits for four herbaceous perennials (Asteraceae) that are widely distributed and highly desired in the restoration of ecologically imperiled drylands of North America. We assess baseline germination and the effects of chemical stimulants across a suite of temperatures and quantify the influence of (1) cold stratification, (2) dry after-ripening, and (3) dry cold storage on germination.Three months of cold stratification achieved near-maximum dormancy alleviation for all species. Exposure to warmer temperatures following stratification increased germination further, reducing the required stratification length. Across all species, at least a third of seeds maintained at 3 ± 2 °C germinated, suggesting that in situ germination occurs in late winter or early spring. Changes in the thermal germination envelope were species-dependent, indicating different germination niches and strategies for population persistence. Dry after-ripening and cold storage improved germination, but responses were highly variable across species, temperature, and time. Chemical stimulants promoted germination in three species and may be an alternative to cold stratification or after-ripening.