Turkey Lakes Watershed Study reference list: 1991

Element deposition in litter fall was measured monthly for 5 years. Temporal and spatial distributions are examined. Results show little risk of leaching losses of base cations from foliage in response to acidic precipitation.

Four types of litter traps are compared over three growing season, the traps having two rim heights, (0.25 and 1.0 m) and two surface areas (.25 and 1 m²). Height and surface areas affected the mass of litter trapped, and in general it was found that small traps near the ground should be avoided. From six to fourteen traps of each type were required to give representative sampling over three seasons, and over one season the number of traps needed increased.

Data are presented showing that the most abundant element in the standing crop biomass was Ca, followed by N > K > Mg > S > P. In the annual litterfall, over a three year period, the most abundant element was N. Data are also presented on total organic matter and elements in the forest floor, and the replenishment of leached bases by litterfall is discussed.

Ion movements are monitored in 20 feeder streams draining small basins in the TLW to assess their contribution to the main aquatic system, and to estimate ecosystem changes. Nitrogen output is less than input in 4 of 5 watersheds. In all cases but one, SO₄ input and output is nearly in balance in four basins. Chemical variability between streams in a watershed can be large, and some areas are sensitive to increased H⁺ load.

During 1981, element concentrations in throughfall, precipitation and stemflow were measured in a sugar maple stand at TLW; growing and dormant seasons were compared. Throughfall was the main source for the transfer of elements to the soil, while stemflow contributed only 1-10% of the total. Throughfall was richer in bases and SO₄-S during the growing season. The role of H⁺ in promoting base leaching from the forest canopy is discussed.

Annual fluxes of SO₄ through the forest canopy and podzolic soil at TLW in central Canada decreased in response to reductions in atmospheric SO₄ deposition. Despite these reductions, there was no additional release of previously adsorbed SO₄ from the soil. In the absence of changes in NO₃ cycling, changes in SO₄ alone can reduce base leaching from the TLW soil. Controlling emissions to reduce SO₄ inputs to forested watersheds will reduce SO₄ leaching from podzolic soils similar to those examined in the TLW.

Paper reviews current knowledge on the relationship between atmospheric acid deposition and element fluxes in major Eastern North American forest types, with TLW as a reference. Atmospheric N input is insignificant compared with ecosystem concentrations, and the N cycle is maintained. Sulphate concentrations are 70% of the total base cation concentrations in soil waters and atmospheric input of SO₄-S contributes significantly to the loss of K⁺, Ca²⁺, Mg²⁺, and Na⁺. A reduction in sulphur emissions should reduce cation losses.

Biomass and production of the fish community was estimated in 19 small lakes from four watersheds. Nineteen species of fish were counted, with 4.5 species per lake, although >75% of each lake's population was confined to <3 species. Production was found to be related in equal measure to fish biomass, average fish size, and ANC.

Report is an interpretation of data gathered through the ECE International Co-operative Programme for the monitoring of long-range transboundary air pollution. Data from Europe, the U.K., U.S.A., and Canada are presented. The Canadian data are from Nova Scotia, Quebec, and the Turkey Lakes. Sulphate levels have been declining in most countries, while nitrate is increasing in Norway and Sweden. Models developed can be used to predict future changes and map critical loads, and will be increasingly useful as the data-base grows.

The effects of acidification on wildlife in an aquatic environment include increased exposure to methyl-Hg for piscivores. Insectivores are at low risk from exposure to toxic metals. Of more importance is the decrease in available dietary Ca, as low pH leads to the extinction of molluscs and crustacaeans. Lack of Ca is also known to affect egg-laying and egg-shell integrity in birds and the growth of hatchling birds and some mammals. Herbivores may risk higher exposure to Al, Pb and Cd as some macrophytes accumulate high concentrations of these metals under acidic conditions. The review includes information from the Ranger Lake area of Algoma, near the TLW.