Science > Turkey Lakes Watershed Study

Turkey Lakes Watershed Study

Study Description:

In Ontario, the indirect effects of the atmospheric deposition of sulphate and nitrate on
acidification of soil and water from a sugar maple -yellow birch forest on the Precambrian Shield is being examined at the 10.5 km2 Turkey Lakes Watershed (TLW), located north of Sault Ste. Marie, Ontario. The watershed is the site of interdisciplinary research on impact of long-range transported air pollutants on the biology of forests, lakes and streams, and the recovery of terrestrial and aquatic ecosystems in response to reduced deposition of acidic pollutants (Morrison et al. 1999).

The TLW Study was organized as a joint initiative of Canadian Forest Service, Environment Canada and Department of Fisheries and Oceans. Since its inception in 1979, the study has attracted researchers from various universities, the Ontario government, and other federal government departments. The research strives to define the impact of acidic deposition on undeveloped aquatic and terrestrial terrain. It is highly integrated across disciplines and agencies and has contributed significantly the Government of Canada's policy related to transboundary air pollution. Approximately 220 scientific and technical publications have been produced. A third of these have included CFS authors. Research related to the watershed has been described at a large number of meetings and has attracted visitors from various countries.

Biogeochemical studies are evaluating the long-term impacts of ambient acidic deposition after 1980 on nutrient cycling and soil chemistry in the tolerant hardwood forest at the Turkey Lakes Watershed (TLW). To assess long-term effects of reductions in atmospheric S deposition on forest floor chemical composition, quantitative samplings of L-, F- and H- layers were conducted in 1981 and, again, in 1996. Forest floor total OM and element contents remained unchanged, with the exception of N, which increased significantly from 1981 to 1996. On an area basis, there were significant increases in exchangeable Ca2+and Na+ and decreases in exchangeable NH4+-N and SO42--S. There were no significant differences in average annual litterfall OM, N, Ca, Mg, S or Na inputs between 1980-85 and 1992-97. Efflux of cations from the forest floor reflected reduced throughput of SO42-. Overall, the results suggest that, in spite of atmospheric inputs, active biological processes, including litter input, fine root turnover, and tree nutrient uptake, serve to impart stability to the mineral composition of mature sugar maple forest floor (Morrison and Foster 2001).

Changes in mineral soil properties and the cycling of nutrients within the tolerant hardwood forest from the early 1980s to the late 1990s have been documented at three locations within the TLW. A continuous record on nutrient levels in soil water draining from the ablation till at TLW has been maintained from 1982 to 1997 at one location and from 1985 to the present at a second location. In particular, the focus has been to document the extent that ambient N and S deposition has reduced the rate of calcium and magnesium leaching from the soil when compared to leaching rates at higher levels of deposition in the 1970s and earlier. This study has provided some unique insights on N and S interaction in N-saturated soils. For example, recovery of base cation leaching from the soil due to acidic deposition can be delayed during recurring cycles of increasing nitrification in soil (Foster and Hazlett, in press).

In the review period a major synthesis was conducted of the temporal trends in biogeochemistry and biological production in atmospheric, terrestrial and aquatic systems at the TLW (Foster and Hazlett, in press). Detailed data on changes in tree growth and soil properties at TLW have been used to evaluate critical loads and exceedances of soil acidification for tolerant hardwood stands (Maoyeri et al. 2001). Acid rain has been shown to increase the cycling of potassium and sodium between the soil and the trees, more than the cycling of calcium and magnesium (Morrison and Foster 2001). Since 1997 the role of partial and complete forest and ground vegetation removal on the off-site movement of N and S and base cations have been examined.

In Ontario, studies have been undertaken in jack pine ecosystems to examine biophysical processes and controls governing site quality and net primary productivity, and their response to management impacts. The objectives were to determine the effects of harvesting intensity, organic matter removal, soil compaction, planting density and vegetation control on soil physical processes and microclimatic conditions, vegetation responses and biomass partitioning, and interactions between soil temperature, soil moisture, drainage, carbon sequestration and nutrient cycling (Bhatti et al. 2000; Fleming et al. ,submitted)

In Ontario, studies are underway to evaluate long-term environmental impacts of harvesting on sustainable site productivity in adult jack pine forest. Nutrient cycling data from jack pine forest is being collected to calibrate two models (similar data are being collected with respect to black spruce and tolerant hardwood forest as well). A simple, steady-state model will rate the susceptibility of a site to nutrient removals. A dynamic simulation model will assess the timing and magnitude of long-term environmental impacts associated with harvesting. An analysis of the five-year response of jack pine and competing vegetation to three levels of organic matter removal and one level of compaction at nine experimental sites has been completed (Fleming et al submitted), Tiveau, 2000). The steady-state model has been applied to four experimental sites in Ontario (Bhatti et al. 1998a), and thirteen additional sites across Canada (Bhatti et al 1998b). Post-harvest assessment of off-site nutrient transport after clearcutting in jack pine (seven years) and clearcutting and partial cutting in tolerant hardwoods (four years) has been completed

Additional work related to leaf area-productivity relationships, soil respiration and carbon cycling may be conducted on jack pine harvesting impacts study sites in northern Ontario. In addition, the scope of the pine research will be broadened to examine whether mineral fertilizer application, alone or in conjunction with residue additions, can be used to offset nutrient removals associated with intensive management (increased yield/nutrient removal, shorter rotations) and enhance biomass production in young stands. The goal is to develop recommendations and protocols for managing these coarse-textured, infertile soils in a sustainable manner using nutrient amelioration and residue management strategies.

References:

Bhatti, J.S.; Foster, N.W.; Oja, T. Moayeri, M.H.; Arp, P.A. 1998 Modelling potentially sustainable biomass productivity in jack pine forest stands. Can. J. Soil Sci. 78: 105-113.

Fleming, R.L.; Foster, N.W.; Hazlett, P.W.; Laporte, M.F.; Hogan, G.D.; Jeglum, J.K. Effects of harvest intensity and soil disturbance on carbon dynamics in a jack pine ecosystem. (submitted)

Foster, N.W.; P.W. Hazlett. Trends in water chemistry in a maple forest on a steep slope at the Turkey Lakes Watershed. Water, Air, Soil Pollution: Trends (in press).

Maoyeri, M.; Simpson, B.; Arp, P.; Foster, N. 2001. Evaluating critical soil acidification loads and exceedances for tolerant hardwood stands at Turkey Lakes, Ontario. Ecosystems 4: 555-567.

Morrison, I.K.; Foster, N.W. 2001. Fifteen-year change in forest floor organic and element content and cycling at the Turkey Lakes Watershed. Ecosystems 4/6: 545-554.

Morrison, I.K.; Cameron, D.A.; Foster, N.W.; Groot., A. 1999. Forest research at the Turkey Lakes Watershed. For. Chron. 75:3 p.395-399

Tiveau, D. 2000. Secondary vegetation succession on jack pine (Pinus banksiana) cutovers in northeastern Ontario. Swedish Univ. Agric. Sci., Dep. For. Ecol., M.Sc. Thesis.