Predictability of flood pulse driven assembly rules for restoration of a floodplain plant community

Abstract

Community assembly rules were formulated to evaluate the restoration of wet prairie along the periphery of the floodplain of the Kissimmee River in central Florida. Restoration of this plant community is expected to be driven by the reestablishment of flood pulse hydrology following the ongoing dechannelization of the river. Assembly rules were assessed with plant species composition and cover data from 15 permanent plots on the restored floodplain and 6 control plots on the channelized floodplain. These sites were sampled biannually from 1998 to 2010. Mean annual hydroperiods and depths confirmed that the frequency, duration and amplitude of post-restoration flood pulses at study sites were similar to historic reference locations. Elimination of pasture grasses (primarily Paspalum notatum Flüggé) following restoration of the flood pulse validated the hypothesized deletion rule for initial transformation of the wet prairie zone. Predicted increased dominance of obligate and facultative wetland species, a ''community addition rule'', also was confirmed. An index of weighted averages of wetland indicator taxa showed significant short-term responses to antecedent hydroperiods and depths, and a restoration trajectory for wetland plant species. As predicted, recruitment of wet prairie indicator species from the extant seed bank correlated with reestablishment of the flood pulse, but was greatest when inundation extended from the wet season into the dry season. Restoration of a wetland plant community did not result in the predicted increase in species richness and diversity. Colonization and expansion of the exotic grass, Hemarthria altissima (Poir.) Stapf & C.E. Hubb., disrupted community reassembly processes. By summer 2007, mean cover of this species and several other exotic grasses increased to 24%, and necessitated herbicide treatments. Assembly rules provided useful predictions for the initial restoration of wet prairie vegetation, but were eventually confounded by the spread of an exotic species that was new to the regional flora.

Large‐scale environmental flow results in mixed outcomes with short‐term benefits for a semi‐arid floodplain plant community

“…trees and large shrubs), but that these benefits take several years to eventuate (Cunningham et al., ). These longer‐term responses to watering have been reported in riparian systems worldwide (Nishihiro et al., ; Rood et al., ; Toth & van der Valk, ). Longer‐term studies are needed to elucidate the temporal scale over which different plant functional groups and taxa respond to environmental flows.…”

Variant restoration trajectories for wetland plant communities on a channelized floodplain

“…Historical contingencies from early disturbances, the potential for alternative endpoints, and the successional timeframe for soil development belie assumptions that provide the basis for several myths that have clouded the science and practice of restoration ecology (Hilderbrand et al ). Mixed responses to the ongoing Kissimmee River restoration effort, including progress (Toth & van der Valk ; Colangelo ; Koebel et al ; Toth ) and shortcomings (Toth ; Cheek et al ; Spencer & Bousquin ), indicate elements of restoration projects with broad, ecosystem scale goals (e.g. ecological integrity) will have inconsistent temporal trajectories that need to be considered in evaluation and adaptive management plans (Suding ).…”

Invasibility Drives Restoration of a Floodplain Plant Community

“…High turnover between the 2002 wet season and 2003 dry season followed the first prolonged flood pulse when mean wet season depths reached 23.3 ± 3.9 cm and coincided with peak colonization by plant species that were found in the seed bank of study plots (Toth and van der Valk ). After water levels receded, 30 seed bank species were found for the first time in these wet prairie plots during spring 2003, which was two times the number of new colonizations by seed bank species during other post‐restoration sampling periods and represented 25% of the total number of colonizations by seed bank species.…”

“…Plant species with the highest turnover frequencies (Table ) were primarily obligate or facultative wetland species, including some of those with the highest cover on the post‐restoration floodplain (Toth and van der Valk, ). Three of these species, Ptilimnium capillaceum , Diodea virginiana , and Polygonum punctatum , have annual life cycles, and most have short stature with associated vulnerability to submergence during high‐amplitude flood pulses.…”

“…antecedent depths) were used as metrics for quantifying the duration and amplitude of restored flood pulses. Toth and van der Valk () showed that post‐restoration hydroperiods and depths were not significantly different than that at reference sites on the historic floodplain.…”