Turkey Lakes Research Articles

Drought induced pulses of [formula omitted] from a Canadian shield wetland: use of δ 34S and δ 18O in [formula omitted] to determine sources of sulfur

Following summer drought periods, pulses of elevated SO 4 2 - concentrations are frequently observed in streams draining forested catchments that contain wetlands. Delays in the recovery of freshwater streams and lakes in eastern Canada from historically high levels of acidic precipitation have been partially ascribed to these periodic pulses of SO 4 2 - . Climate in eastern Canada has also changed within the last 25 a, with a documented increase in summer dryness and duration of droughts. In small forested catchments in the Turkey Lakes Watershed (TLW), SO 4 2 - concentrations in streams draining wetlands can be elevated by up to a factor of 7 during post-drought discharge events compared to the annual average. Two neighbouring catchments, one with a series of cascading wetlands and one without any wetlands, were selected for comparison. Stable S and O isotope ratios were analyzed in samples of bulk precipitation, streams, and groundwaters to examine sources of SO 4 2 - in post-drought pulses. δ 34 S – SO 4 2 - in the streams and groundwaters show that SO 4 2 - is retained in the wetland via SO 4 2 - reduction and stored in the upper peat profile. Nitrate is elevated in soil and groundwaters at TLW due to high rates of nitrification in forest soils and the presence of NO 3 - can be used to identify piezometers unaffected by SO 4 2 - reduction. δ 18 O – SO 4 2 - shows that higher concentrations of SO 4 2 - in deeper groundwater are likely due to oxidation of organic S and not a geologic source of reduced S. Following drought, the low δ 34 S – SO 4 2 - in streams is consistent with wetland retention by SO 4 2 - reduction and much lower than SO 4 2 - released by weathering in deep glacial till and bedrock. High SO 4 2 - groundwaters and geologic sources do not contribute to the SO 4 2 - pulses in streams. Isotopic patterns over 6 a were similar. Pulses of SO 4 2 - in the wetland catchments following drought are a result of the oxidation of S previously reduced and stored in the wetland.

Infiltration and soil water mixing on forested and harvested slopes during spring snowmelt, Turkey Lakes Watershed, central Ontario

Forest harvesting increases snow accumulation and water delivery to the soil surface relative to undisturbed forest; however, implications of these changes for water infiltration and storage in the soil profile are not well known. These processes were studied using a combined hydrometric and isotopic tracer approach in a harvested area and adjacent hardwood forest stand on a slope at the Turkey Lakes Watershed (TLW) in central Ontario. The slope had a mean gradient of 0.29 and a 0.5–1 m thick ablation till layer overlying compacted basal till. Pre-melt snow accumulation and daily water inputs in the harvested area and forest were measured during the 2000 and 2001 snowmelts. Soil water content in the ablation till was monitored at harvested and forest soil pits using time domain reflectometry. Isotopic signatures of input and soil water at the pits were sampled throughout melt. Total water inputs to the harvested soil surface exceeded that in the forest: 280 mm in the harvested area vs. 212 mm in the forest in 2000 and 526 mm in the harvested area vs. 409 mm in the forest in 2001. Near-surface soil water content, relative saturation of the ablation till and duration of soil saturation at 0.2 m depth were also greater in the harvested area compared to the forest for both years. Despite the absence of between-pit differences in soil properties influencing infiltration into the profile, a thinner ablation till layer at the harvested area pits would have contributed to greater soil saturation at 0.2 m depth in the harvested area. Greater soil wetness in the harvested area appeared to restrict mixing between inputs and pre-melt soil water relative to conditions in the forest during the 2000 melt, leading to longer water residence times at depth in the ablation till. This was partly supported by results from the 2001 melt. We suggest that harvesting of hardwoods on slopes in TLW may promote increased subsurface flow above the basal till contact and saturation overland flow during spring snowmelt, with implications for point-scale soil water chemistry as well as the quantity and quality of slope runoff to receiving streams.

Effect of storage on the isotopic composition of nitrate in bulk precipitation.

Stable isotopic analysis of atmospheric nitrate is increasingly employed to study nitrate sources and transformations in forested catchments. Large volumes have typically been required for delta18O and delta15N analysis of nitrate in precipitation due to relatively low nitrate concentrations. Having bulk collectors accumulate precipitation over an extended time period allows for collection of the required volume as well as reducing the total number of analyses needed to determine the isotopic composition of mean annual nitrate deposition. However, unfiltered precipitation left in collectors might be subject to microbial reactions that can alter the isotopic signature of nitrate in the sample. Precipitation obtained from the Turkey Lakes Watershed was incubated under conditions designed to mimic unfiltered storage in bulk precipitation collectors and monitored for changes in nitrate concentration, delta15N, and delta18O. Results of this experiment indicated that no detectable nitrate production or assimilation occurred in the samples during a two-week incubation period and that atmospheric nitrate isotopic ratios were preserved. The ability to collect unfiltered precipitation samples for an extended duration without alteration of nitrate isotope ratios is particularly useful at remote study sites where daily retrieval of samples may not be feasible.

On the limnology of Salda Lake, a large and deep soda lake in southwestern Turkey: future management proposals

Abstract The limnological characteristics of Salda Lake, a deep, soda and highly alkaline lake in the Lake District of southwestern Turkey, are presented. Physical and chemical variables indicate that the lake is composed of hydrochemically different water layers formed by groundwater sources located on the floor of the lake. Phytoplankton and zooplankton are characterized by a limited number of species and low dominance reflecting the extreme conditions of the lake. Hydromagnesite stromatolites occur all around the lake margins. The lake is threatened by falling water levels and organic pollution. Recommendations for the conservation of the lake are presented. Copyright © 2004 John Wiley & Sons, Ltd.

Abundance and Seasonal Variations of Cladoceran and Copepod Fauna of Kesikköprü Dam Lake in Turkey

Bu araştırmada, Bala Tarım İşletmesinde yetiştirilen GOı x GOı, Akkaraman ve Akkaraman x GOı kuzularının, doğumdan itibaren 6 aylık yaşa kadar olan dönemde; canlı ağırlık, cidago yüksekliği, göğüs derinliği, göğüs çevresi ve vücut uzunluğu özelliklerine ilişkin büyüme eğrilerinin tahmin edilmesi ve söz konusu parametrelerin erken seleksiyon kriteri olarak kullanılıp kullanılamayacağının tespiti amaçlanmıştır Bu amaçla üzerinde durulan özellikler için 130 baş Goı x Got, 101 baş Akkaraman ve 109 baş Ak x GD1 kuzuda doğumdan itibaren 6 aylık yaşa kadar birer aylık ara İlgili özelliklerin tartı ve ölçümler yapılmıştır. Üzerinde durulan özelliklere etki yapacağı düşünülen cinsiyet ve doğum tipi gibi makro çevre faktörleri standardize edilerek etkileri giderilmiştir Daha sonra canlı ağırlık ve vücut ölçülerinin zamana göre değişimini belirleyebilmek amacı İle Logistic büyüme modeli kullanılmış, elde edilen sonuçlar GD1x Go,, Akkaraman ve Ak x G01 kuzularında canlı ağırlık ve değişik vücut ölçülerindeki değişimleri tanımlamak için Logistic büyüme modelinin uygun olduğunu göstermiştir.

Cryptic wetlands: integrating hidden wetlands in regression models of the export of dissolved organic carbon from forested landscapes

AbstractThis study examines the relationship between wetlands hidden beneath the forest canopy (‘cryptic wetlands’) and dissolved organic carbon (DOC) export to streams and lakes in forested ecosystems. In the Turkey Lakes Watershed (TLW), located in the Algoma Highlands of central Ontario, Canada, there is substantial natural variation in average annual DOC export (kgC ha−1 year−1), ranging from 11·4 to 31·5 kgC ha−1 year−1 in catchments with no apparent wetlands. We hypothesized that the natural variation in DOC export was related to cryptic wetlands. Cryptic wetlands were derived manually from geographic coordinates that were surveyed with a differential global positioning system, and automatically from identification of topographic depressions and flat slopes (<1·5° ) within a digital elevation model (DEM) in a geographic information system. For the TLW catchments, which are characterized by shallow soils over bedrock, a significant correlation (r2 ≥ 0·9, p < 0·001) between manual and automated methods was observed for scales up to 50 m when a light detection and ranging DEM was used for the topographic analysis. Regression models indicated that cryptic wetlands (%) explained the majority of the natural variation in DOC export (kgC ha−1 year−1), with r2 = 0·88 (p < 0·001) for the model based on the manually derived wetlands and r2 = 0·85 (p < 0·001) for the model based on the automatically derived wetlands. The strength and significance of the automatically derived wetlands (%) versus DOC export (kgC ha−1 year−1) regression model diminished when other sources of DEMs were used. This study emphasizes the importance of including cryptic wetlands in predictive models of DOC export, particularly in catchments where the topography includes depressions and flat areas but no apparent wetlands. Copyright © 2003 John Wiley & Sons, Ltd.

Ecological Risk Analysis for Biotope Potantiality of Gala Lake in Turkey

Ecological Risk Analysis for Biotope Potantiality of Gala Lake in Turkey

Three-dimensional mapping of light transmittance and foliage distribution using lidar

The horizontal and vertical distributions of light transmittance were evaluated as a function of foliage distribution using lidar (light detection and ranging) observations for a sugar maple (Acer saccharum) stand in the Turkey Lakes Watershed. Along the vertical profile of vegetation, horizontal slices of probability of light transmittance were derived from an Optech ALTM 1225 instrument's return pulses (two discrete, 15-cm diameter returns) using indicator kriging. These predictions were compared with (i) below canopy (1-cm spatial resolution) transect measurements of the fraction of photosynthetically active radiation (FPAR) and (ii) measurements of tree height. A first-order trend was initally removed from the lidar returns. The vertical distribution of vegetation height was then sliced into nine percentiles and indicator variograms were fitted to them. Variogram parameters were found to vary as a function of foliage height above ground. In this paper, we show that the relationship between ground measurements of FPAR and kriged estimates of vegetation cover becomes stronger and tighter at coarser spatial resolutions. Three-dimensional maps of foliage distribution were computed as stacks of the percentile probability surfaces. These probability surfaces showed correspondence with individual tree-based observations and provided a much more detailed characterization of quasi-continuous foliage distribution. These results suggest that discrete-return lidar provides a promising technology to capture variations of foliage characteristics in forests to support the development of functional linkages between biophysical and ecological studies.

Lidar remote sensing of biophysical properties of tolerant northern hardwood forests

Previous forest research using time-of-flight lidar data has primarily focused on forest ecosystems with conifers as the predominant tree type. In this study, small-footprint time-of-flight lidar data were used to estimate biophysical properties of tolerant hardwood forests composed predominantly of mature sugar maple (Acer saccharum Marsh.) and yellow birch (Betula alleghaniensis Britton) in the Turkey Lakes Watershed (TLW) near Sault Ste. Marie, Ontario. Ground reference data were collected during the first two weeks of July 2000 for 49 circular sample plots, each 0.04 ha (or 400 m2) in area. Lidar data were acquired on 24 August 2000 using an Optech ALTM 1225 (Optech Incorporated, Toronto, Ont.). Ten biophysical forest metrics were derived for each plot: (1) maximum tree height (hmax), (2) Lorey's mean tree height (hLorey), (3) mean diameter at breast height (DBH), (4) total basal area (BA), (5) percent canopy openness (CO%), (6) leaf area index (LAI), (7) ellipsoidal crown closure (CC), (8) total aboveground biomass (BIO), (9) total wood volume (VOL), and (10) stem density (SD). Likewise, three laser height metrics were derived for each plot: (1) maximum laser height (Lhmax), (2) mean laser height (Lhmean), and (3) mean laser height calculated from lidar returns filtered based on a threshold applied to the intensity return values (LhIR). The results demonstrate that for each forest with a given stand structure, there exists one or more laser height metrics derived from lidar data that are capable of providing an estimate of various biophysical properties. Lhmax was the best estimator of hmax (r2 = 0.79) and hLorey (r2 = 0.87); LhIR was the best estimator of BA (r2 = 0.85), BIO (r2 = 0.85), and VOL (r2 = 0.87); and Lhmean was the best estimator of CC (r2 = 0.89), DBH (r2 = 0.63), CO% (r2 = 0.76), LAI (r2 = 0.80), and SD (r2 = 0.86). The results illustrate the potential for laser height metrics to estimate (i) plot heights and stem densities, (ii) aboveground biomass and volume, and (iii) canopy-related measures.

The effects of drying and re-wetting and increased temperature on sulphate release from upland and wetland material

In central Ontario, elevated SO 4 concentrations and export have been measured in both upland and wetland-draining catchments following summer droughts, although the source of excess SO 4 is unclear. The objective of this study was to determine the effects of drying and re-wetting and temperature, respectively, on the release of SO 4 from the primary S pools in wetlands ( Sphagnum and peat) and uplands (forest floor and mineral soil), using material collected from the PC1 catchment in Haliburton County, and from catchment S50 in the Turkey Lakes Watershed. Peat exhibited the most marked response to drying of the four materials considered, and within 24 h of re-wetting dried peat from both catchments released 3–4 times more SO 4 (50–67 mg kg −1 S-SO 4) than continuously moist peat (16 mg kg −1 S-SO 4), although temperature had only a marginal effect on SO 4 concentrations. There was no immediate response of Sphagnum to either drying or temperature, although S-SO 4 concentrations in Sphagnum tended to increase over the 30-day (d) incubation. There was a small but immediate increase in S-SO 4 concentrations in forest floor material (LFH) from both catchments within the first 24 h of incubation, which was greatest in treatments that were dried and/or incubated at a higher temperature. In contrast, neither temperature nor drying appeared to affect SO 4 release from mineral soil collected from either site. Results of laboratory incubations suggest that increases in SO 4 concentration that have been reported in wetland-draining streams immediately following summer dry periods may be quantitatively explained by drying and re-wetting of peat rather than increased mineralization in Sphagnum. Similarly, the higher SO 4 concentrations that have been measured in upland streams following summer droughts may in part be due to enhanced SO 4 release from the forest floor following drying and re-wetting. In contrast, while the mineral soil constitutes a large pool of total S, it does not appear to be responsive to changes in moisture or temperature in the short-term (<30 d) and therefore likely does not contribute to reported climate-related temporal variations in stream SO 4.

Trace Metal Levels In Surficial Sediments Of Lake Manyas, TURKEY AND TRIBUTARY RIVERS

Some trace element contents of surficial sediment samples from sampling stations in Lake Manyas (Bird Lake) in Turkey and its tributary rivers have been analyzed by flame atomic absorbtion spectroscopy. The mean levels (μgg −1 dry weight) of Mn, Fe, Cu, Pb, Ni, and Zn for five sampling stations in the first season (March 1996) and for eight sampling stations in the second season (May 1996) have been listed. The results have been compared with the values given in the literature. A comparison with the available benchmark sediment quality criteria and toxicity guideline values has also been made. The results in the light of those comparisons suggest that a pollution problem especially with respect to Cu, Pb, Zn and Ni exists at several stations which are effected by municipal and industrial effluents and at the middle of the lake.

Interpreting stable-isotope records from freshwater snail-shell carbonate: a Holocene case study from Lake Gölhisar, Turkey

The oxygen and carbon stable-isotope ratios from fossil snail shells within a small intramontane lake in southwest Turkey are used to highlight the potential, and problems, of using freshwater snail carbonate as a palaeoenvironmental proxy. Two species (Gyraulus piscinarum and Valvata cristata) yielded different isotope ratios at the same sampling intervals, probably due to differences in water-isotope composition between different microhabitats. Isotope ratios from a number of individual shells from the same sampling intervals (representing 7–25 years), show large ranges (up to 8‰ for 18O) for each species. Only by analysis of a significant number of species-specific shells (5) from each sampling interval can a true understanding of environmental change be obtained. Averages of the data provide an insight into longer-term climatic variation while the ranges provide an estimate of short-term (decadal) environmental variability.

Topographic Controls of Nitrogen, Sulfur, and Carbon Transport from a Tolerant Hardwood Hillslope

The lateral down-slope movement of water, NO3 -, NH4 +, SO4 2-, H+ and DOC through an ablation till was examined from 1987 to 1990 for a one hectaresoil catena on a steep hillslope with uniform forest cover at the Turkey Lakes Watershed (TLW), Ontario, Canada. Natural variation in the export of nutrients from the soil profile via soil water to Little Turkey Lake was assessed in relation to nutrient distribution in soil at different topographic positions.Subsurface throughflow exhibited dramatic differences in nutrientconcentrations and fluxes with slope position, largely reflectingthat of the soil horizons through which the water passed. GreaterNO3 -, SO4 2-, and DOC concentrations in subsurface water in the upper, well-drained hillslope were a reflection of enrichment by contact with more acidic, more developed podzols, and more favorable soil physical and biological conditions for NO3 - retention in solution.Nutrient inputs to the lake were strongly influenced by increaseddown-slope transport of water, and increased SO4 2-, N, and C retention in wetter, less-developed podzolic soils that characterize lower slope positions. An understanding of water movement and soil development variation withtopographic position was required to accurately estimate nutrient budgets for steep slopes at TLW.

AN IMPORTANT DIMENSION OF POOR QUALITY: COST INCREASING (An Appraisal in Term of The Forest Tree Seedling Production)

This study have been carried out for determining the solution between the cost and quality in connection with production of forest tree seedling in Egirdir Forest Nursery Enterprise, Turkey's Lakes Distinct. The findings obtained from the study are given below: (1) It is determined that the seedling standards with TS 2265 / March 1976 code number is approved more confirmable than the standards with TS 2265 / February 1988 from stand points of both competition power and success of production forest tree as it is a proper quality criteria and in confirmity with Europe Union norms. (2) As a result of inappropriate growing techniques has been practised in the forest nursery enterprise, the fixed cost per seedling has increased depending on the increasing the rate of discard seedlings. (3) The situation stated here, indicates the necessity for giving more importance to put a proper management into practice and to establish a new unit to pay more attention for production seedling with good quality in the state-owned forest nursery enterprises of Turkey. (4) The existing accounting systems in determining the seedling cost and quality of costs are insufficient. Due to these mentions, it is necessary to attach importance to the cost and management accounting systems and take urgent measure for new structural arrangements and put them into effects. Keywords: Forest Nursery Enterprise, Forest Tree Seedling Production, Quality Management, Cost of Poor Quality, Seedling Standards.

Foreword. The Turkey Lakes Watershed Study After Two Decades

Foreword. The Turkey Lakes Watershed Study After Two Decades

Trends in Water Chemistry in a Maple Forest on a Steep Slope

Year-to-year variation in SO42-,NO3-, Ca2+, K+, and Mg2+concentrations in forest floor and mineral soil percolatefrom a forested, podzolic soil at the Turkey Lakes Watershedon the Precambrian Shield was assessed for monotonic trendsbetween 1986 and 1995. Our objective was to examine howrapidly ion concentrations in soil percolate equilibratedafter stabilization of SO42- concentrations inprecipitation. Significant negative trends were detected inmonthly Ca2+, and Mg2+ concentrations in forestfloor and SO42-, Ca2+, and Mg2+ inmineral soil percolate during the 10-year-period. Thedecline in Ca2+ and Mg2+ was greater than annualdecreases in SO42- and NO3- in forestfloor percolate and proportional to the reduction inSO42- in mineral soil percolate. Response ofmineral soil percolate to a 15 μmolc L-1SO42- decrease in wet-only precipitation between1985 and 1986 was a gradual decline in SO42-concentration through 1995. The five-year meanSO42- concentration in bulk precipitation, forestfloor percolate, and mineral soil percolate decreased 8, 9and 18 μmolc L-1 from 1986–90 to 1991–95.Microbial (mineralization of organic S) and sorption(release from and/or retention in the pool of insolubleSO42-) processes in the soil were logicalexplanations for the observed changes in SO42- inmineral soil percolate.

Distribution of Diatoms in a Forested Stream Containing a Series of Interconnected Lakes

We explored the spatial variation in diatom communities withinthe Turkey Lakes Watershed (TLW). The TLW is a single watershed in an old growth sugar maple forest that contains an alternatingseries of stream and lake embayments. Near the outlet of each lake, we sampled pools and riffles to determine abundance and diversity of diatom communities along this hydrologic system. Diatom diversity, measured by Shannon-Weaver Index, richness andevenness, increased steadily downstream before eventually decreasing near the watershed outlet. Canonical CorrespondenceAnalysis indicated that diatom genera were correlated with streamchemistry. Upper reaches were the least productive, characterizedby lower pH ( 7), lower N:P (71:1 to 90:1, dominated by simple forms of N, e.g., nitrate-N), and high mean relative abundances of Cymbella spp. and Brachysira spp. Achnanthesminutissima (Kutz.) Hustedt, the most abundant species, and Navicula spp., Nitzschia spp., Gomphonema spp., and Frustrulia spp. were represented at all stream sites. Thisstudy revealed that within the TLW, a hydrologic system of the same stream order, the diatom community was influenced by a nutrient gradient, where the stream and its intervening lakes contributed to a shift from acidic, inorganic N-poor upper reaches to a circum-neutral, inorganic N-richer outlet. By imparting genera-specific stresses, stream flow (i.e. pools vs. riffles) further shaped the diatom community.

Characterizing the Spatial Pattern of Soil Carbon and Nitrogen Pools in the Turkey Lakes Watershed: A Comparison of Regression Techniques

There is considerable spatial heterogeneity in organic carbon (C), total nitrogen (N), and potentially mineralizable nitrogen (PMN) pools in the soils of the Turkey Lakes Watershed. We hypothesized that topography regulates the spatial pattern of these pools through a combination of static factors (slope, aspect and elevation), which influence radiation, temperature andmoisture conditions, and dynamic factors (catenary position,profile and planar curvature), which influence the transport ofmaterials downslope. We used multiple linear regression (MLR)and tree regression (TR) models as exploratory techniques todetermine if there was a topographic basis for the spatialpattern of the C, N and PMN pools. The MLR and TR modelspredicted similar integrated totals (i.e., within 5% of eachother) but dissimilar spatial patterns of the pools. For thecombined litter, fibric and hemic layer, the MLR models explaineda significant portion of the variance (R2 = 0.38, 0.23 and0.28 for C, N and PMN, respectively), however, the residuals werelarge and biased (the smallest contents were over-predicted andthe largest contents were under-predicted). The TR models (9-branch), in contrast, explained a greater portion of the variance (R2 = 0.75, 0.67 and 0.62 for C, N and PMN, respectively) and the residuals were smaller and unbiased. Based on our sampling strategy, the models suggested that static factors were most important in predicting the spatial pattern of the nutrient pools. However, a nested sampling strategy that included scales where both static (among hillslopes) and dynamic (within hillslope) factors result in a systematic variation in soil nutrient pools may have improvedthe predictive ability of the models.

Relation of Lake Acidification and Recovery to Fish, Common Loon and Common Merganser Occurrence in Algoma Lakes

Models are needed that predict both spatial and temporal improvements to ecosystems following reductions of acidifying emissions that produce `acid rain'. Logistic regression models were developed for the occurrence of fish and two fish-eatingbirds, common loons (Gavia immer) and common mergansers(Mergus merganser), using monitoring data collected onlakes across Ontario. These models were applied in the Algomaregion, including the Turkey Lakes Watershed (TLW). Using theWaterfowl Acidification Response Modeling System (WARMS), severalSO2 emission reduction scenarios were simulated, i.e. thosecontributing to measured 1982–1986 sulphate deposition levels, 1994levels (corresponding to full implementation of Canadian SO2emission reductions as stipulated in the 1991 Canada/U.S. AirQuality Agreement), 2010 levels (1994 plus full U.S. reductions),and both a 50% and a 75% further reduction beyond 2010 levels. Some habitat improvements in Algoma were predicted under the 2010scenario for all biota, but substantial increases in habitatquality, especially for mergansers, would occur only under further reductions. The TLW showed little change in chemistry orbiota, while lakes near the Montreal River were predicted toimprove substantially.

Temporal Trends in Water Chemistry in the Turkey Lakes Watershed Ontario, Canada, 1982-1999

The Turkey Lakes Watershed (TLW) was established in 1980 as asite for study of the ecosystem effects of acidic deposition, andsince then there has been ∼40% reduction in North AmericanSO2 emissions. Monitoring records for bulk deposition,shallow and deep ground water, two headwater streams and two lakeoutflows have been tested to identify statistically significantmonotonic trends. The TLW appears to be responding to decliningacidifying emissions because the most prevalent chemical trendacross sample types/stations was decreasing SO42-. Increasing pH was detected in four of the seven data sets, butonly the H+ decrease in bulk deposition was of a magnitudeto be an important ionic compensation for the SO42-decline. There is little evidence of acidification recovery inTLW waters however. Increasing alkalinity was found only in theoutflow of the penultimate lake of the basin, and in fact, deepground water and the other lake outflow had decreasing alkalinitytrends (i.e., continuing acidification). For the surface waterstations, the greater part of the ionic compensation fordeclining SO42- was decreasing base cations, and as aresult, these waters are probably becoming more dilute with time,although only the headwater streams exhibited decliningconductivity. Five of seven data sets had increasing dissolvedorganic carbon concentrations. Increasing NO3- wasimportant in ground waters. Drought has strongly influencedtrends and delayed recovery by mobilizing S stored in catchmentwetlands and/or soils.