Turkey Lakes Watershed Study reference list: 2007

07-01 J. Spoelstra, S.L.Schiff, P.W. Hazlett, D.S. Jeffries, R.G. Semkin. The isotopic composition of nitrate produced from nitrification in a hardwood forest floor. Geochim. Cosmochim. Acta 71, 3757-3771, 2007.

Summary: Three lysimeters were installed at the TLW in order to measure the isotopic composition of microbial nitrate produced in-situ in forest soils. Microbial nitrate in the forest floor was depleted in 15N relative to that exported in groundwater and headwater streams. It was hypothesized that 15N -depleted forest floor substrate is not detected in groundwater because of immobilization in the mineral soil and mixing with nitrate generated in the mineral soil. The current methods of calculating the d18O of microbial nitrate are shown to give a reasonable value for nitrate from nitrification at the TLW.a

07-02 Burniston*, D.A., W.J.M. Strachan, J.T. Hoff, F. Wania. Changes in surface area and concentrations of semivolatile organic contaminants in aging snow. Environ. Sci. Technol. 41, 4932-4937, 2007. (*Contact D.S. Jeffries for correspondance).

Summary: Five snowpacks at the TLW were sampled during the winter of 1999/2000 to measure specific snow surface area and concentrations of OCPs and PCBs. Fresh snow was compared with aged snow samples, which lost half the initial surface area during aging. OCPs and PCBs were lost at the same rate except when snow aged at a colder temperature. The contaminants concentrations increased in snowpacks aged during rising temperatures. While surface area decreases clearly contribute to the loss of semivolatile organic compounds from metamorphosing snowpacks, other confounding factors play a role in determining concentration changes, in particular in wet snow.

07-03 Keller*, W. Implications of climate warming for Boreal Shield lakes: a review and synthesis. Environ. Rev. 15, 99-112, 2007. (*Contact D.S. Jeffries for correspondance).

Summary: This is a review of the complex effects of climate warming on lakes of the Boreal Shield, including those at the TLW site. One such effect is the re-acidification of lakes following a drought, during which stored sulphur from atmospheric deposition becomes oxidized causing many physical and chemical changes. Biological interactions are difficult to predict, and more studies and modelling that consider stressor effects are needed.

07-04 Monteith*, D.T., J.L. Stoddard, C.D. Evans, H.A. de Wit, M. Forsius, T. Høgåsen, A. Wilander, B.L. Skjelkvåle, D.S. Jeffries, J. Vuorenmaa, B. Keller, J. Kopácek, and J. Vesely. Dissolved organic carbon trends resulting from changes in atmospheric deposition chemistry. Nature 450, 537-540 + append., 2007. (*Contact D.S. Jeffries for correspondance).

Summary: The TLW is among 522 lakes and streams in North America and Northern Europe for which modelled time series data explains rising DOC levels in terms of changes in deposition chemistry and acid sensitivity of catchments. DOC concentrations have increased in proportion to decreases in anthropogenic sulphur and sea-salt deposition. Changes in organic acidity have buffered acid deposition and the rise in DOC is linked to recovery from acidification. Increased export of DOC to the oceans may be a result of increasing solubility of organic matter.

07-05 Jeffries, D.S., F.D. Beall, N.W. Foster, P.W. Hazlett, S.L. Schiff, R.G. Semkin, J. Spoelstra. How is the Turkey Lakes Watershed (central Ontario, Canada) responding to declining sulphur inputs? Environment Canada Water Science and Technology Directorate Contribution No. 05-373, 10 pp, 2007.

Summary: This paper assesses the recovery of the TLW ecosystem in response to SO2 emissions reductions in North America over the past 25 years. SO4 deposition has declined in proportion to emissions reductions in most streams, but stream acidity has not recovered as expected, in part as a result of declining base cation concentrations. Episodic events resulted in 10-fold increases in SO4 concentrations, and isotope studies reveal that re-oxidation of organic S was the primary source. Sulphur in wetland soils is released in the period following a drought. Daily and weekly monitoring of meteorological and atmospheric deposition continue at the TLW.

07-06 Clair, T.A., J. Aherne, I.F. Dennis, M. Gilliss, S. Couture, D. McNicol, R. Weeber, P.J. Dillon, W. Keller, D.S. Jeffries, S. Page, K. Timoffee, B.J. Cosby. Past and future changes to acidified eastern Canadian lakes: a geochemical modelling approach. Applied Geochemistry 22, 1189-1195, 2007.

Summary: A model for acidification of groundwater in catchments (MAGIC) was applied to characterize the past and future chemistry of aquatic systems in eastern Canada. The TLW is one of the long-term monitoring sites among 500 lake sites used in the analysis. The model predicts that by 2030 ANC levels will be acceptable at more than 90% of the lakes in the Algoma area, but current emission controls will not be sufficient to improve ANC and pH levels in all parts of Canada.

07-07 Pink*, M., M.G. Fox and T.C. Pratt.  Numerical and behavioural response of cyprinids to the introduction of predatory brook trout in two oligotrophic lakes in northern Ontario.  Ecology of Freshwater Fish 16, 238-249, 2007. (*Contact D.S. Jeffries for correspondance).

Summary: >Four of the lakes in the TLW were part of a study conducted in 2003 and 2004 in which brook trout were added to Batchawana Lake North to examine the response of cyprinid prey species.  No changes in abundance or habitat use patterns were observed among the cyprinids.  The only consistent response by the prey fish was increased shoaling. Since predator-prey responses are difficult to predict in small-scale experiments, further whole-lake studies are needed.

07-08 Pink*, M., T.C. Pratt, M.G. Fox.  Use of underwater visual distance sampling for estimating habitat-specific population density.  North American Journal of Fisheries Management 27, 246-255, 2007. (*Contact D.S. Jeffries for correspondance).

Summary: Two methods of sampling fish population density were compared in 5 Ontario lakes, including 4 at the TLW.  It was found that underwater visual distance sampling compares closely with the traditional mark-recapture techniques.  Further, it has the advantage of being less intrusive, is able to determine age-0 fish abundance as well as school size and other information not obtained by mark-recapture.

07-09 Sanford, S. E., I.F. Creed, C.L. Tague, F.D. Beall and J.M. Buttle. Scale-dependence of natural variability of flow regimes in a forested landscape. Water Resources Research 43 W08414, doi:10.1029/2006WR0052998, 2007.

Summary: This research determined relationships between natural variability in the flow regime and basin scale. A hydrologic model was used to characterize natural flow regimes of basins in the TLW using the range of variability approach. A 30-year simulated flow record wasused to calculate natural variability. Flow variability under wetter conditions was similar across all basins, regardless of scale. Flow variability under drier conditions was scale-dependent, as smaller basins were more variable than larger basins. Indices describing near-streamriparian areas within a basin, median basin residence time and basin curvature were significantly related to flow variability under drier conditions. These findings present a potential management template for establishing reference conditions of basin disturbance.

07-10 Fairweather, T.A. Tracking the alternative fates of nitrogen in forested catchments. MSc. Thesis, Department of Biology, University of Western Ontario, London.  70pp, 2 appendices, 2007.

Summary: N2O efflux to the atmosphere and N export to streams (nitrate, ammonium, dissolved organic nitrogen and N2O) were measured during the 2006-2007 non-growing season (November- April) in upland (C35) and wetland (C38) catchments at the TLW. Gaseous N2O efflux did not differ between upland soils in the two catchments or between upland and wetland soils in the catchment with the wetland. While concentrations of dissolved N2O discharged to surface waters were higher in the wetland catchment than in the upland catchment, when dissolved N2O fluxes were included in N export estimates, this did not account for the difference in N export between the two catchments.

07-11 Webster, K.L. Topographic controls on carbon dioxide efflux from forest soils. PhD. Thesis, Department of Biology and Environmental Science, University of Western Ontario, London.  129pp, 2 appendices, 2007.

Summary: Heterogeneity in topographic features at the TLW were defined using a fuzzy classification scheme and stochastic depression analysis. These features became the fundamental unit for describing patterns in soil carbon pools and, monitoring and modelling its atmospheric fate in C38. The distribution of soil carbon along hillslopes differed. Soil respiration (Rs) was higher in the ecotone than in upland or wetland portions of the catchment. A model that included soil temperature and soil moisture explained 57% of the variance in Rs. Inclusion of the soil carbon C:N explained an additional 15% of the variance. Combining this empirical relationship with the area of features provided catchment-aggregated effluxes of Rs.