Response of wetland plant species to hydrologic conditions

Abstract

Understanding hydrologic requirements of native and introduced species is critical to sustaining native plant communities in wetlands of disturbed landscapes. We examined plant assemblages, and 31 of the most common species comprising them, from emergent wetlands in an urbanizing area of the Pacific Northwest, USA, in relation to in situ, fine-scale hydrology. Percent cover by plant species was estimated in 2208 1-m 2 plots across 43 sites, with water depth at time of vegetation sampling measured in 432 plots. Three years of bi-weekly hydrologic data from each of the 43 sites were used to estimate mean surface water level and mean absolute difference (MAD) in surface water level for every plot. Nine assemblages of plant species that co-occur in the field were identified using TWINSPAN. The assemblage richest in native species occurred under intermediate hydrologic conditions and was bracketed by pasture grass dominated assemblages at drier conditions with low water level variability, and Phalaris arundinacea L. assemblages with higher mean water levels and variability. Results suggest minor changes in average water levels ($10 cm) or in variability (±2 cm in MAD) could promote a shift from assemblages dominated by natives to those dominated by invasive or alien taxa. Canonical correspondence analysis segregated the species into four groups related to hydrologic gradients. Each species response group was typified by taxa with similar optima for a given environmental variable, with each group related to a characteristic suite of hydrologic conditions. The most common species (P. arundinacea, Juncus effusus L., and Typha latifolia L.), each representing a different response group, exhibited unique responses in occurrence/abundance in relation to water level variability, but were abundant over a wide range of water depth. The realized niches of other species in each response group were more restricted, with peaks in cover confined to narrower ranges of water depth and variability.

Vascular plant species richness on wetland remnants is determined by both area and habitat heterogeneity

“…Calibration is an effective method to estimate the water condition, including soil moisture, soil pF value, groundwater level and surface water, and it has been used widely and successfully in applied plant ecology (e.g., ter Braak and Gremmen 1987;Goslee et al 1997;Schaffers and Sýkora 2000;Magee and Kentula 2005). Moreover, the species indicator values calibrated with field measurement data should achieve better statistic estimation (Diekmann 2003).…”

A Paleoecological Perspective on Wetland Restoration

“…However, as noted by Cairns and Heckman (1996) this immediately raises the question as to what frame of reference or benchmark does one use to establish the pre-disturbance condition? Moreover, others have demonstrated that restoring an ecosystem to a prescribed composition is difficult because the assumption of predictable community assembly is often not valid and restoration can result in unpredictable outcomes (Gwin et al 1999;Magee et al 1999;Zedler 2000;Magee and Kentula 2005). Such results led Hilderbrand et al (2005) to go so far as to declare such prescriptive restoration approaches to be a so-called restoration myth (i.e., their "Carbon Copy" myth) in that creating or restoring an ecosystem that is a copy of an idealized state with a single endpoint is at odds with the dynamic nature of ecosystems.…”

Temporal variation of over‐bank flooding of Wei River and its impact on a riparian wetland in Xi'an, China

“…Recent studies have showed that temporal surface connectivity plays a critical role in sustaining integrity and biodiversity of riparian wetland ecosystems and potentially influences functions of riverfloodplain ecosystems (Kingsford, 2000;Mitsch and Gosselink, 2000). Surface connectivity can regulate wetland soil, moisture and nutrients (Fennessy and Mitsch, 2001) and control plant community composition and distribution (Rea and Ganf, 1994;Bledsoe and Shear, 2000;Pettit et al, 2001;Robertson et al, 2001;Leyer, 2005;Magee and Kentula, 2005). It may also affect wetland biogeochemical processes (Hamilton et al, 1995;Tockner et al, 1999;Pringle, 2001;Fink and Mitsch, 2007), improve diversity of various vertebrate and invertebrate groups , and influence primary production in riparian wetlands (Robertson et al, 2001).…”