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Inter-specific variation in salinity effects on germination in Pacific Northwest tidal wetland plants
Janousek, Chris AND C. Folger. Inter-specific variation in salinity effects on germination in Pacific Northwest tidal wetland plants. AQUATIC BOTANY. Elsevier Science Ltd, New York, NY, 111:104-111, (2013).
Salinity is an important stressor for vascular plants in coastal wetlands and may affect rates of seed germination. In a lab experiment with thirteen Oregon wetland species, we demonstrated inter-specific variability in germination responses to salinities ranging from freshwater to 20 ppt. Two species, pickleweed (Sarcocornia perennis) and Douglas’ aster (Symphyotrichum subspicatum), were relatively insensitive to mesohaline conditions, but most other species had reduced germination rates and slower root or shoot growth by 10 or 20 ppt. A number of species, including the common plants Agrostis stolonifera and Juncus balticus ssp. ater, occurred in wetlands with soil salinities greater than the apparent salinity tolerance of seedlings. This mismatch between adult and seedling sensitivity to salinity highlights the potential importance of windows of low salinity for successful seed germination in the field. Increased salinization of coastal estuaries (e.g., due to sea-level rise) may affect seedling germination and change plant composition in tidal wetlands of the Pacific Northwest.
Environmental stressors such as salinity may affect plant germination and early growth, eventually impacting the distribution and abundance of more mature individuals. In a lab study we evaluated germination sensitivity to salinity in 13 tidal wetland species found in the Pacific Northwest and then compared germination responses with the distributions of established plants along a soil salinity gradient. For two species we also tested whether seeds from wetlands with different salinity regimes varied in their tolerance of higher salinity. All species examined, except Sarcocornia perennis and Symphyotrichum subspicatum, showed maximum germination and seedling lengths under fresh to oligohaline (0-5 ppt) conditions. Other species, including those commonly distributed in more saline wetland soils as adults, had reduced germination at salinities ≥10 ppt. Sensitivity to elevated salinity in Triglochin maritima and Hordeum brachyantherum did not differ markedly between sampled populations. Our results show a mismatch between germination sensitivity and adult tolerance for about half of the species tested. The temporal or spatial occurrence of low salinity may lead to optimal germination rates in these species. Future increases in estuarine salinity, perhaps in response to sea-level rise or reduced precipitation in coastal areas, may change germination in marsh species and thereby shift plant composition.