Potential Future Studies

In addition to the Wood River Wetland, other drained wetlands in the upper Klamath River basin are being restored through changes in water-level management (Agency Lake Ranch) or reconnecting the wetlands by removing dikes (for example, at TNC Williamson River Delta Preserve). Restoration of these wetlands presents unique opportunities to gain knowledge about how drained wetlands respond to various management strategies. The wetland character and history that govern the content and relative decomposition of the organic content of the soils, along with variables that control biogeochemical processes, determines to a large extent how a wetland responds to flooding or other changes in water-level management.

Comparing Managed Wetlands

Functioning wetlands support healthy vegetation that take up and store nutrients and carbon, trap sediment, and generally improve downstream water quality. Active wetlands process nutrients through removal of nitrogen by plant uptake and denitrification and removal of phosphorus from uptake and precipitation into insoluble forms along with iron and other minerals. Each process requires a specific suite of conditions dictated by the local hydrology, soil type, and plant or bacterial assemblage. Future studies of managed wetlands around Agency and Upper Klamath Lakes could examine how current and future water-level management affects soil conditions, plant assemblage structure, biogeochemical processing, and nutrient losses/storage over time. Additional monitoring of DO, pH, SC, and nutrients and additional flux studies in different types of wetlands could provide additional feedback to refine adaptive management strategies.

Plant Physiology Studies

Vegetation surveys indicate a continuing trend toward more obligate wetland plant species and a decrease or stabilization in the proportion of weedy, upland, or edge species (Bureau of Land Management, 2006). Enhanced production of emergent wetland species might be achieved by targeting water levels to specific concentrations of nutrients or dissolved salts. The high SC (as much as 2,500 µS/cm) and temperature (33.4°C) in the South Unit during summer could exceed the tolerance for seed germination of target plant species. The high DOC color in water effectively absorbs light wavelengths utilized during photosynthesis. As a result, light extinction depths were generally shallow (35–70 cm), which indicates that light probably limits photosynthesis in much of the open-water areas. Such light limitation might also decrease successful germination of dormant wetland plant seeds. Future studies could determine the light requirements for seed germination to promote recruitment and stimulate plant biomass, thereby increasing nutrient uptake and build plant biomass. Understanding individual plant preferences and tolerances for dissolved salts, nutrients, and light, for example, could accelerate wetland restoration by optimizing growth or mitigating unfavorable conditions.

Potential Effects of Dissolved Organic Carbon Export from Restored Wetlands

Potential inhibitory effects of DOC on Aphanizomenon flos-aquae—Decomposition of peat soils in the Wood River Wetland resulted in as much as 270 mg/L DOC in surface water (table 8). Certain types of DOC may inhibit or interfere with the growth of blue-green algae such as Aphanizomenon flos-aquae (AFA) (Geiger, 2001). If future management includes pumping high-DOC water into Agency Lake, monitoring the abundance and health of the AFA could verify potential interactive effects. Alternatively, as a result of wetland draining, export of DOC and bioavailable N and P may have enriched the lake with excess carbon and nutrients that stimulated heterotrophic activity and enriched the lake sediments with organic matter. This scenario may have contributed to the current condition of near complete dominance by AFA in Upper Klamath and Agency Lakes.