LEAF LITTER BREAKDOWN IN A RECENTLY IMPOUNDED RESERVOIR¹

Abstract

The impoundment of Richard B. Russell Lake resulted in the inundation of 3490 ha of forested area or 33 percent of the total area of the lake. Estimates of the total inundated leaf litter biomass were combined with a leaf litter decomposition study to determine the nutrient load and dissolved oxygen demand to the reservoir. Hickory leaf bags broke down most rapidly at the 3‐m and 28‐rn depths, followed by short‐needle pine, white oak, a hardwood litter mixture, beech, and red oak. Leaf bags incubated at the 3‐m depth exhibited significantly higher breakdown rates than those at the 28‐m depth for most leaf types, due to differences in dissolved oxygen and temperature. Respiration rates of litter were also higher at the 3‐m depth. Most leaf types accumulated nitrogen and phosphorus and lost organic carbon after an initial leaching period. Richard B. Russell Lake exhibited extensive anoxia and the buildup of total organic carbon, nitrogen, and phosphorus during summer stratification. Leaf litter breakdown accounted for 64 percent of the organic carbon increase but acted as a sink for nitrogen and phosphorus. The dissolved oxygen demand of the litter accounted for over 50 percent of the demand incurred in the lake.

State-of-the-art of reservoir limnology and water quality management

“…Effect of flooding grasslands: There are many laboratory studies which demonstrate the importance of plant nature (ferns, perennials, shrubs, trees) upon reservoir concentrations of organic matter, dissolved oxygen and nutrient salts due to differences in decomposition processes: Campbell et al (1975), Triska et al (1975), Howarth & Fischer (1976), Reed (1979), Therien et al (1982), Mouchet (1984), Crawford & Rozenberg (1984), Gunnison et al (1986) and James et al (1988). In studies of the food composition of insects from newly flooded tropical and temperate reservoirs Cherry & Guthrie (1975) and McLachlan (1977) conclude that the decline in benthic invertebrate biomass that takes place after filling is associated with a switch in their diet from terrestrial detritus to algal biomass which occurs when filling is completed.…”