Turkey Lakes Watershed Study reference list: 2000

Hydrological processes were investigated through mathematical modeling of water quality. Using data from the Turkey Lakes Watershed, (January 1981 to December 1984), 4 watershed acidification models were applied to compute hydrogen ion, alkalinity and sulphate concentrations. The models TMWAM, ILWAS, ETD, and RAINS were used with the objective of deriving stochastic models to predict the probability of higher hydrogen ion concentration events due to snowmelt and rainfall in acid sensitive watersheds. The models need to be tested on long term data, and should include climatic scenarios.

Stream and soil water composition in two basins at the TLW during springmelt episodes of 1992-1996 were analyzed to determine snowmelt pathways and chemical response to episodic acidification. Dissolved SiO₂ and H⁺ in stream and shallow soil water were positively correlated at both sites, indicating a significant contribution by shallow soil water to both stream flow and chemistry during snowmelt.

Critical soil acidification rates determined at the TLW using steady-state mass balance modeling were found to be high (900 to 1400 eq ha^-1 yr^-1 depending on the forest harvesting regime). As a consequence, critical load exceedance is low. Weathering of TLW soils provides a buffer against acid inputs and natural acidification. The TLW appears to be near or at N saturation.

Sources of nitrogen exported at basins 31 and 47 (lowland and highland respectively) of the TLW were identified using isotopes of nitrogen and oxygen (the isotopic signature of microbially amended nitrogen is quite different from that of N in atmospheric deposition). At the TLW, nitrification of ammonium appears to be the dominant source of exported N, even during snowmelt.

A short summary of the TLW Study prepared as an introduction for the special volume published in Ecosystems.

Samples of the L-(Oi), F-(Oe) and H-(Oa) layers collected in 1981 and 1996 were analyzed to evaluate chemical changes. Total organic matter and element contents remained unchanged except N which increased significantly. On an areal basis there were significant increases in exchangeable Ca and Na and decreases in exchangeable NH₄ and SO₄. In spite of significant changes in atmospheric inputs, it appears that active biological processes serve to impart stability to the mineral composition of the forest floor.

This paper uses water quality data collected in small water bodies in the Algoma region, including the TLW to establish a sustainable, water quality survey protocol for the CWS (OR) LRTAP biomonitoring network by reducing the sampling intensity and/or frequency while maintaining a statistical trend detection capability.

Leeches collected in acid-sensitive lakes in Muskoka, Sudbury and Algoma (including the TLW) were examined to assess relationships between populations and certain chemical and physical characteristics of lakes. Thirteen species of leeches were trapped with species richness found to be high in lakes with high pH. Yet, leech occurrence, richness and abundance trends over a 9-year period in Sudbury area lakes showed no direct relationship to changes in lake chemistry suggesting that leeches are not suitable as direct indicators of chemical recovery from acidification.

This paper investigates atmospheric concentrations and deposition fluxes of major ions to the TLW between 1980 and 1996. Precipitation acidity did not decline, probably as a result of a base cation decline. In keeping with the lower SO₂ emissions in North America during this period, the 17-year mean annual total has declined by 35%, while the annual total deposition of oxidized nitrogen shows a net increase of 10% since the 1980's. This reflects a 10% increase in emissions. Wet deposition accounted for two-thirds of total atmospheric deposition of S and N, and dry deposition of oxidized N was 95% dominated by gaseous HNO₃ deposition, as opposed to particulate NO₃. Total deposition of S and N was high during the measurement period.

Haloacetic acids (HAAs) in surface waters and precipitation were measured across Canada, including precipitation from the TLW (Algoma) monitoring site. Daily precipitation levels varied from <10 to 2400 ng/l HAA depending on source trajectories, urban centers being major contributors of trifluoroacetic acid and the chloroacetic acids. Atmospheric transport and deposition distributes the contaminants to Canadian ecosystems.

The TLW was one of 12 study sites selected to test whether remote sensing can be used to determine stand-level forest condition. The BFCP project seeks to develop a forest condition rating system (FCR) to classify forest stand condition from healthy to stressed using the Compact Airborne Spectrographic Imager (CASI) with validation by traditional on-ground forest evaluation. The TLW Harvesting Impacts Project was the study site for which the influence of structural changes on spectral response was examined. The highest levels of variability were in shelterwood sections compared with the clearcut and control plots. The 1999 TLW Workshop.

The TLW is included in a review of recent progress in understanding hydrological processes in forest landscapes across Canada. A model used by Creed et al (TOPMODEL) describes flow processes in the TLW basin and postulates episodic N flushing leading to large stream N export. The harvesting project at TLW is listed with ten other forests as a site for monitoring potential impacts due to forest disturbance.