Type of Document Master's Thesis Author Talley, Scotland Author's Email Address firstname.lastname@example.org URN etd-1111102-112243 Title Impacts of Vertebrate Herbivores and Hurricane Georges on Densities of Belowground Plant Material on Shallow Mudflats in the Active Mississippi River Delta Degree Master of Science (M.S.) Department Forestry, Wildlife, and Fisheries Advisory Committee
Advisor Name Title Robert H. Chabreck Committee Chair Charles E. Sasser Committee Member Robert G. Downer Committee Member Keywords
- nutria disturbance
Date of Defense 2002-10-25 Availability unrestricted AbstractDelta National Wildlife Refuge (DNWR) is located in the active Mississippi River Delta (MRD). Resource managers at DNWR are implementing a marsh creation program that consists of dredging crevasses (openings) in the natural or man-made levees of major distributaries to divert sediment rich waters in to open bays. The mudflats thus created are colonized by stands of delta duck-potato (Sagittaria platyphylla) and delta three-square (Schoenoplectus deltarum). These plant communities stabilize the mudflats and provide high quality habitat for wintering waterfowl and nutria. Two challenges for the maintenance of these plant communities is disturbance from tropical storms and intense winter grazing. Objectives for my study were to measure initial (fall) density of belowground biomass in tropical storm impact vs. non-impact years and quantify herbivore use of belowground biomass.
My study was conducted in 1998-2000 following disturbance by Hurricane Georges in September 1998. Exclosures were used to prevent all grazing or limit grazing to nutria only in two treatments. The third treatment was unrestricted grazing. Twelve replicates were distributed over four crevasse/mudflat complexes. Soil cores were collected in November, January, and March to assess production and use of belowground biomass. A mixed model (PROC MIXED, SAS 1996) was used to analyze treatment effects.
Production in November 1998 was less than in November 1999 in both communities. In March of 1999 and 2000, belowground biomass in no grazing treatments was different from open grazing and nutria only grazing treatments, but the open grazing and nutria only grazing treatments did not differ.
Disturbance from Hurricane Georges did reduce belowground production in 1998 and winter grazing further depleted belowground biomass, but belowground production in 1999 was greater than 1998. The productivity of these plant communities was capable of sustaining heavy reduction in belowground biomass, yet return to high levels of productivity in the following year.
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