Seed germination responses to salinity for three rare wetland plants of spring-fed arid systems

Spring-fed wetlands within arid systems host unique species of plants, many of which are threatened due to the vulnerability of these ecosystems. Increased salinity and drier hydrologic regimes due to anthropogenic activities threaten these systems. Furthermore, limited knowledge regarding key life history traits of species jeopardize the restoration and management of their rare plants. Here, we evaluated key aspects of the seed ecophysiology of three rare plants of the Southwestern United States: Helianthus paradoxus (Pecos sunflower), Cirsium wrightii (Wright's marsh thistle), and Agalinis calycina (Leoncita false-foxglove). We examined seed dormancy break under controlled conditions and evaluated the effects of field-derived salinity gradients on seed dormancy break and germination. Seeds of C. wrightii were nondormant at dispersal, germination was high (>70%) under all treatments and was not affected by the tested salinities. Germination in H. paradoxus was high (>70%) following cold stratification, but increasing salinities reduced germination. A. calycina seeds required cold stratification, but germination was low (<50%) under all tested treatments and increasing salinities during incubation had the greatest negative effects in this species. Our findings contribute to the restoration of rare wetland plants within spring-fed arid marshes susceptible to groundwater declines and human-induced salinization.