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Plant responses to increased inundation and salt exposure: interactive effects on tidal marsh productivity
Citation:
Janousek, Chris AND C. Mayo. Plant responses to increased inundation and salt exposure: interactive effects on tidal marsh productivity. Plant Ecology. Springer Netherlands, , Netherlands, 214:917-928, (2013).
Impact/Purpose:
Climate change may increase stressors for plants in estuarine wetlands as they are exposed to greater submergence and higher salinity. In a field experiment conducted in three wetlands in central Oregon, we found that increasing inundation lowered biomass production in all seven species that we investigated. Plants transplanted to more saline sites also tended to have lower biomass. The degree of change in productivity under different inundation or salinity conditions varied by species, but even a species commonly found at lower tidal elevations had reduced productivity. Plants also exhibited changes in the ratio of above-ground to below-ground productivity. Generally, greater inundation induced plants to shift relatively more productivity to the shoots. Our results have implications for how tidal wetlands may change if salinity and inundation increase in coastal estuaries. Less production in future tidal wetlands may impact accretion or other ecosystem functions and services.
Description:
Flooding and high salinity generally induce physiological stress in wetland vascular plants which may increase in intensity with sea-level rise (SLR). We tested the effects of these factors on seedling growth in a transplant experiment in a macrotidal estuary in the Pacific Northwest. Seven common wetland species were grown at mean higher high water (MHHW, a typical mid-marsh elevation), and at 25 and 50 cm below MHHW in oligohaline, mesohaline, and polyhaline marshes. Increased flooding reduced shoot and root growth in all species, including those typically found at middle or lower tidal elevations. It also generally disproportionately reduced root biomass. For more sensitive species, biomass declined by >50 % at only 25 cm below MHHW at the oligohaline site. Plant growth was also strongly reduced under polyhaline conditions relative to the less saline sites. By combining inundation and salinity time-series measurements we estimated a salt exposure index for each site by elevation treatment. Higher values of the index were associated with lower root and shoot biomass for all species and a relatively greater loss of below-ground than above-ground production in most species. Our results suggest that inundation and salinity stress individually and (often) interactively reduce productivity across a suite of common marsh species. As relative SLR increases the intensity of stress on coastal marsh plants, negative effects on biomass may occur across a range of species and especially on below-ground production.