Flood tolerance in wetland angiosperms: a comparison of invasive and noninvasive species

Abstract

We assessed the biomass production, biomass allocation patterns, height growth, and root airspace of seventeen wetland plant taxa, including two potentially invasive species, grown under high nutrient conditions and subjected to four hydrologic regimes: constant drawdown, cyclic flooding and drawdown, cyclic flooding and drought, and constant flooding for the duration of the experiment (∼10 weeks). We found that: (1) the potentially invasive reed canary grass ( Phalaris arundinacea) and broadleaf cattail ( Typha latifolia) responded to treatments similarly; both outgrew the other perennial species in all four hydrologic regimes; (2) Phalaris had the highest levels of root airspace of all the taxa; (3) the grasses and graminoids nearly always tolerated flooding better than the broadleaf forbs, perhaps in part due to greater quantities of root airspace; and (4) the species that were most sensitive to flooding are typically found in drier, groundwater-fed, and more nutrient-poor environments. We hypothesize that Phalaris and Typha, which are both tall and productive, should be competitive dominants under a variety of hydrologic conditions, at least where nutrients are abundant, as in urban and agricultural landscapes. Eight of the noninvasive taxa tolerated flooding but produced less biomass and/or were shorter or shorter-lived than Phalaris and Typha. Among the five taxa that were most sensitive to flooding were slow-growing habitat specialists; such species will likely experience declines in areas that become impounded or experience greater volumes of runoff.