Effects of a pulsing hydroperiod on a created riparian river diversion wetland.

摘要

In this study, succession, hydroperiod, and water-quality dynamics are documented for a whole-ecosystem study involving a 3-ha created riparian wetland at the Schiermeier Olentangy River Wetland Research Park at The Ohio State University in Columbus, Ohio USA during 2003 through 2006. The effect of delivering influent water to the wetland as seasonal pulses or as a continuous steady flow on the hydroperiod, water chemistry, avian use, plant primary production, and plant community structure within the wetland was investigated. A simulation model was then developed using short-term measurements of river and wetland stage to predict long-term patterns of succession and plant development within the wetland. This wetland typically receives seven or eight natural flood pulses each year from the Olentangy River. Of 21 species planted in 1997, only Scirpus americanus and Juncus effusus remained as important macrophyte species during the study six to seven years after planting. Typha spp. (angustifolia and latifolia), colonized naturally and was the dominant macrophyte in most of the wetland during this study.; Mean nutrient reductions per flood pulse for nitrate-nitrite, total Kjeldahl nitrogen (TKN), soluble reactive phosphorus (SRP), and total phosphorus (TP) during 2003-2004 were 0.71 g-N m-2, 0.92 g-N m-2, 0.016 g-P m-2, and 0.08 g-P m-2 respectively. The annual reductions of N-NO3-, TN, P-SRP, and TP were 74%, 41%, 46%, and 31% by mass. A greater removal of NO3 - and TP occurred in the emergent marsh section of the wetland than the open water section. Conversely TKN increased through the emergent marsh and decreased through the open water. Overall, the oxbow design appeared to be successful in ecological terms and similar diversion wetlands are recommended for other locations to examine their function under different climates and hydroperiods.; While hydrologic pulses affect wetland function and may enhance productivity and contribute stability to ecosystems, the overall effects of these pulses on biogeo-chemical processes in riparian river diversion wetland ecosystems have not been clearly demonstrated experimentally at an ecosystem scale. The natural hydroperiod of the riparian wetland was varied in 2005; its natural flood pulses were removed and replaced with an artificial steady-flow supplied by submersed pumps. The wetland received 8 natural river pulses from April 2004--March 2005, then a steady flow of river water was pumped through the wetland from April 2005--March 2006. In 2004 the wetland received a total of 27 m3 m-2 yr-1 (cubic meters of influent water per square meter of wetland area per year) of inflow followed by 20 m3 m-2 yr-1 of inflow in the steady flow year 2005. The removal rate was higher for nitrate-nitrogen, total nitrogen, and total phosphorus during the year with flood-pulsing than during the steady-flow year. The only nutrient that did not have a difference in removal rate in the two years was soluble reactive phosphorus. There were differences in spatial dynamics of most of the nutrients in flood-pulsing and non-pulsing years and between wet and dry seasons in all years of the study. In all cases, however, total nitrogen concentrations in the wetland increased through the emergent marsh and then decreased across the open water basin.