Graduate Thesis Or Dissertation

 

Figure 7.jpg Público Deposited

https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/ff365958m

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Abstract
  • The need to preserve Oregon's estuaries has been expressed through the Land Conservation and Development Commission's Estuarine Resources Goal 16. The first use of the mitigation guideline set forth in this goal is in the Coos Bay estuary. The proposed North Bend Airport runway extension will fill 32 acres (13 ha) of tideland in Coos Bay. Mitigation of this fill is the breaching of the dikes in upper Joe Ney Slough near Charleston, Oregon, 6.5 miles (10.5 km) southeast of the airport site. Vegetation and elevation data were gathered in the diked portion of Joe Ney Slough, a control site, and an area of marsh adjacent to the proposed runway extension. Through comparsion of vegetation and elevation at the Joe Ney Slough and control sites, the historic and future pattern of salt marsh vegetation is interpreted. Thirteen plant communities are identified by cluster analysis of 682 vegetation samples from the Joe Ney Slough site: 1) Eleocharis- Agrostis alba, 2) Eleocharis-Juncus effusus var. pacificus-Jussiaea, 3) Juncus effusus var. gracilis-Lotus, 4) Oenanthe-Juncus effusus var. pacificus-Agrostis alba, 5) Carex lyngbyei, 6) Carex obnupta, 7) Agrostis alba-Potentilla, 8) Agrostis alba-Alopecurus-Potentilla, 9) Juncus balticus, 10) Holcus-Agrostis tenuis-Ranunculus, 11) Ranunculus, 12) Agrostis tenuis-Festuca arundinacea, 13) Festuca arundinacea- Agrostis tenuis. Total community biomass is mostly proportional to its areal extent. A vegetation and elevation map, both at a scale of 1 to 2,450, are presented. Seven plant communities are identified by cluster analysis of 66 vegetation samples from the control site: 1) Salicornia, 2) Carex lyngbyei, 3) Deschampsia-Juncus balticus-Triglochin, 4) Agrostis alba- Triglochin-Plantago, 5) Agrostis alba-Potentilla, 6) Juncus balticus- Agrostis alba-Potentilla-Festuca rubra, 7) Potentilla-Festuca rubra. Biomass data indicate that standing crop is higher in this natural marsh than in the diked area. A vegetation map of this site at a scale of 1 to 1,420 is presented. Analysis of 329 vegetation samples from the airport site identified a Salicornia community at elevations higher than 1.4 m above Mean Lower Low Water (MLLW). Upon dike breaching, 12.5 percent of the land area within the mitigation site can be expected to become mudflat. All but a few species present in this area today can be expected to disappear with reinstatement of estuarine waters. Salt marsh species associated with silty substrates are expected to become established between elevations of 1.4 and 2.4 m above MLLW.
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