Soil and tree-ring chemistry response to liming in a sugar maple stand

An evaluation of the impact of dolomitic lime [CaMg(CO3)2] on soils (five years after treatment) and sapwood chemistry (after four growing seasons) was realized for a Ca-deficient sugar maple stand at the lake Clair watershed. The effect on humus chemistry was significant: exchangeable Mg and Ca, effective acidity (EA), base saturation (BSe), pH, and effective cation exchange capacity (CECe) significantly increased, while exchangeable Fe significantly decreased. In the B horizon, liming increased exchangeable Ca, Mg, and Mn concentrations while decreasing other acid cations. No significant temporal trends in element concentrations in tree rings could be detected, although the lime treatment significantly changed the average xylem Mg and Mn concentrations as well as the average Mg/Mn and Ca/Mn ratios of the sapwood. The absence of temporal trends in rings from the last 20 yr implied a significant re-equilibration of elements through the sapwood. Significant relationships were found between averaged xylem Ca/Mn and Mg/Mn ratios and exchangeable humus Ca, Mg, Mn, Al, Fe, and H+ concentration, EA, CECe, and BSe, suggesting that the average xylem Ca/Mn and Mg/Mn ratios are strong indicators of the soil acid-base status.     

Sulphate, Nitrogen and Base Cation Budgets at 21 Forested Catchments in Canada, the United States and Europe

To assess the concern over declining base cation levels in forest soils caused by acid deposition, input-output budgets (1990s average) for sulphate (SO₄), inorganic nitrogen (NO₃-N; NH₄-N), calcium (Ca), magnesium (Mg) and potassium (K) were synthesised for 21 forested catchments from 17 regions in Canada, the United States and Europe. Trend analysis was conducted on monthly ion concentrations in deposition and runoff when more than 9 years of data were available (14 regions, 17 sites). Annual average SO₄ deposition during the 1990s ranged between 7.3 and 28.4 kg ha⁻¹ per year, and inorganic nitrogen (N) deposition was between 2.8 and 13.8 kg ha⁻¹ per year, of which 41–67% was nitrate (NO₃-N). Over the period of record, SO₄ concentration in deposition decreased in 13/14 (13 out of 14 total) regions and SO₄ in runoff decreased at 14/17 catchments. In contrast, NO₃-N concentrations in deposition decreased in only 1/14 regions, while NH₄-N concentration patterns varied; increasing at 3/14 regions and decreasing at 2/14 regions. Nitrate concentrations in runoff decreased at 4/17 catchments and increased at only 1 site, whereas runoff levels of NH₄-N increased at 5/17 catchments. Decreasing trends in deposition were also recorded for Ca, Mg, and K at many of the catchments and on an equivalent basis, accounted for up to 131% (median 22%) of the decrease in acid anion deposition. Base cation concentrations in streams generally declined over time, with significant decreases in Ca, Mg and K occurring at 8, 9 and 7 of 17 sites respectively, which accounted for up to 133% (median 48%) of the decrease in acid anion concentration. Sulphate export exceeded input at 18/21 catchments, likely due to dry deposition and/or internal sources. The majority of N in deposition (31–100%; median 94%) was retained in the catchments, although there was a tendency for greater NO₃-N leaching at sites receiving higher (<7 kg ha^-1 per year) bulk inorganic N deposition. Mass balance calculations show that export of Ca and Mg in runoff exceeds input at all 21 catchments, but K export only exceeds input at 16/21 sites. Estimates of base cation weathering were available for 18 sites. When included in the mass balance calculation, Ca, Mg and K exports exceeded inputs at 14, 10 and 2 sites respectively. Annual Ca and Mg losses represent appreciable proportions of the current exchangeable soil Ca and Mg pools, although losses at some of the sites likely occur from weathering reactions beneath the rooting zone and there is considerable uncertainty associated with mineral weathering estimates. Critical loads for sulphur (S) and N, using a critical base cation to aluminium ratio of 10 in soil solution, are currently exceeded at 7 of the 18 sites with base cation weathering estimates. Despite reductions in SO₄ and H⁺ deposition, mass balance estimates indicate that acid deposition continues to acidify soils in many regions with losses of Ca and Mg of primary concern. The U.S. Government's right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged. The Canadian Crown reserves the right to retain a non-exclusive, royalty free licence in and to any copyright.     

Soil response to a 3-year increase in temperature and nitrogen deposition measured in a mature boreal forest using ion-exchange membranes

The projected increase in atmospheric N deposition and air/soil temperature will likely affect soil nutrient dynamics in boreal ecosystems. The potential effects of these changes on soil ion fluxes were studied in a mature balsam fir stand (Abies balsamea [L.] Mill) in Quebec, Canada that was subjected to 3 years of experimentally increased soil temperature (+4 °C) and increased inorganic N concentration in artificial precipitation (three times the current N concentrations using NH₄NO₃). Soil element fluxes (NO₃, NH₄, PO₄, K, Ca, Mg, SO₄, Al, and Fe) in the organic and upper mineral horizons were monitored using buried ion-exchange membranes (PRS? probes). While N additions did not affect soil element fluxes, 3 years of soil warming increased the cumulative fluxes of K, Mg, and SO₄ in the forest floor by 43, 44, and 79 %, respectively, and Mg, SO₄, and Al in the mineral horizon by 29, 66, and 23 %, respectively. We attribute these changes to increased rates of soil organic matter decomposition. Significant interactions of the heating treatment with time were observed for most elements although no clear seasonal patterns emerged. The increase in soil K and Mg in heated plots resulted in a significant but small K increase in balsam fir foliage while no change was observed for Mg. A 6–15 % decrease in foliar Ca content with soil warming could be related to the increase in soil-available Al in heated plots, as Al can interfere with the root uptake of Ca.     

Cadmium concentrations in tissues of willow ptarmigan (Lagopus lagopus) and rock ptarmigan (Lagopus muta) in Nunavik, Northern Québec

Willow and rock ptarmigan were obtained from Northern Québec. Willow ptarmigan were found to have mean cadmium concentrations of 179.7 microg/g (dw) in the kidneys and 25.8 microg/g (dw) in the liver; these levels were three times higher than those found in the rock ptarmigan. The cadmium levels in the ptarmigan were below the threshold above which adverse effects can be observed in birds. The difference between the two ptarmigan species in cadmium content is explained by the diet. A comparison of their diet showed that willow, which stores cadmium, is an important food resource for willow ptarmigan but not for rock ptarmigan. Because there is limited information available on the consumption of ptarmigan kidneys and liver by the Inuit, and the fact that this is a traditional way of life and provides nutritional benefits to the Inuit population, no consumption guidelines are proposed.     

A simple and fast screening test to detect soils polluted by lead

Lead pollution is an environmental priority. The evaluation of contaminated soils was often based on the results of the toxicity characteristic leaching procedure (TCLP) or the synthetic precipitation leaching procedure (SPLP). This paper presents a simple and fast screening test to detect soil contaminated by lead. The test is based on the chemistry of the stomach (Cl- concentration, pH 2, T = 37 degrees C) and simulates the incidental oral ingestion of soil by young children. The gastric juice simulation test (GJST) and the TCLP were applied to six size fractions from five soils. The GJST solubilized more Pb (up to 169 mg/l) than the TCLP especially for the smallest size fraction. Particle size had less effect on the TCLP. The percentage of lead released with the GJST, was most significant for the <63 microm size fraction and varied from 18 to 74% of the total lead content. Lead leached during the TCLP as a function of the total lead content showed poor linear regression coefficient (R) values for soils <250 microm. R values were significant for all size fractions with the GJST. The pH of approximately 5 in the TCLP limits the solubilization of lead in the small size fractions. The five soils exceeded the toxicity threshold of 10 microgPb/dl of blood for a significant fraction of children between 0 and 36 months using the EPA's IEUBK model (Integrated Exposure Uptake Biokinetic). But the TCLP did not detect lead contamination in two of these five soils. The GJST proved to be a better estimator of lead bioaccessibility in the gastrointestinal tract.     

Critical Loads and Exceedances of Acid Deposition and Associated Forest Growth in the Northern Hardwood and BorealConiferous Forests in Québec,Canada

We used the Québec forest monitoring network (`Réseaud'Étude et de Surveillance des Écosystèmes Forestiers' or RESEF)along with its atmospheric monitoring stations to assess criticalS and N loads and their combined soil acidification exceedancesfor natural ecosystems of the northern hardwood and borealconiferous forests in Québec, Canada. Critical loads (CL) forforest soil acidification were calculated using the simple mass-balance (SMB) approach and with the steady-state PROFILE model.Atmospheric deposition rates for water, S, N, Ca, Mg, Na, and K,for the years 1989–1993, and detailed, plot-specific forest andsoil characteristics were used as input. The SMB model alsorequired information regarding nutrient uptake and storage in theaboveground woody biomass. The CL calculations indicated that,from the 31 RESEF plots, 18 received atmospheric acidic inputs inexcess of their CL (55 and 61% of the hardwood and coniferousplots, respectively). The range of CL exceedance varied from 60to 470 eq ha^-1 yr^-1 for the hardwood stands, and from 10to 590 eq ha^-1 yr^-1 for the coniferous stands. The standswith CL exceedance were mainly located in the western and centralpart of the province. Stand growth associated with exceedanceclass of acidity was determined using the RESEF plots along withselected permanent forest survey plots having similar sitecharacteristics, but for which longer growth records wereavailable. We found a significant negative correlation betweenforest growth rates and critical soil acidification exceedancefor both the northern hardwood and the boreal conifer sites.Specifically, plots with critical load exceedances were found tohave a growth reduction of about 30% during the 1974–1982 andthe 1972–1990 measurement (plots with no soil acidificationexceedance served as a control). While this correlation is notnecessarily causal, it is nevertheless consistent with theexpectation that increased losses of soil base cations on accountof increased soil acidification should and could lead todeteriorating forest health conditions.     

Basal area growth of sugar maple in relation to acid deposition,stand health,and soil nutrients

Previous studies have shown in noncalcareous soils that acid deposition may have increased soil leaching of basic cations above the input rate from soil weathering and atmospheric depositions. This phenomenon may have increased soil acidity levels, and, as a consequence, may have reduced the availability of these essential nutrients for forest growth. Fourteen plots of the Forest Ecosystem Research and Monitoring Network in Québec were used to examine the relation between post-industrial growth trends of sugar maple (Acer saccharum Marsh.) and acid deposition (N and S), stand decline rate, and soil exchangeable nutrient concentrations. Atmospheric N and S deposition and soil exchangeable acidity were positively associated with stand decline rate, and negatively with the average tree basal area increment trend. The growth rate reduction reached on average 17% in declining stands compared with healthy ones. The results showed a significant sugar maple growth rate reduction since 1960 on acid soils. The appearance of the forest decline phenomenon in Québec can be attributed, at least partially, to soil acidification and acid deposition levels.     

Impact of nutrient removal through harvesting on the sustainability of the boreal forest

The cycling of base cations (K, Ca, Mg, and Na) was investigated in a boreal balsam fir forest (the Lake Laflamme Watershed) between 1999 and 2005. Base cation budgets were calculated for the soil rooting zone that included atmospheric deposition and soil leaching losses, two scenarios of tree uptake (whole-tree and stem-only harvesting), and three scenarios of mineral weathering, leading to six different scenarios. In every scenario there was a net accumulation of Mg within the soil exchangeable reservoir, while Ca accumulated in four scenarios. Potassium was lost in five of the six scenarios. Contrary to Ca and Mg, immobilization of K within tree biomass (69 mol x ha(-1) x yr(-1)) was the main pathway of K losses from the soil exchangeable reservoir, being five times higher than losses via soil leaching (14 mol x ha(-1) x yr(-1)). The amounts of K contained within the aboveground biomass and the exchangeable soil reservoir were 3.3 kmol/ha and 4.2 kmol/ha, respectively. Whole-tree harvesting may thus remove 44% of the K that is readily available for cycling in the short term, making this forest sensitive to commercial forestry operations. Similar values of annual K uptake as well as a similar distribution of K between tree biomass and soil exchangeable reservoirs at 14 other coniferous sites, distributed throughout the boreal forest of Quebec, suggest that the Lake Laflamme Watershed results can be extrapolated to a much larger area. Stem-only harvesting, which would reduce K exports due to biomass removal by 60%, should be used for these types of forest.     

Effects of Clear-Cutting and Plant Competition Control Methods on Carabid (Coleoptera: Carabidae) Assemblages in Northwestern Ontario

Total captures, species richness, diversity, and assemblages of adult carabids (Coleoptera: Carabidae) in a boreal mixed-wood ecosystem study were compared among unharvested, and clear-cut plots untreated or treated with herbicides (Vision® and Release®), mechanical treatments (brush saw and Silvana Selective). Carabids were sampled using unbaited pitfall traps for one growing season 7 and 9 years after clear-cutting, in the second growing season after competition control was applied. A total of 5032 individuals representing 30 species were collected between June 1 and September 25, 1995. Total catches were not affected by the harvest or the conifer release alternatives applied. Species richness and diversity increased following conifer release alternatives. Ten species showed habitat preferences after treatment whereas the remaining 20 species were not significantly affected by treatment.     

Assessing and selecting interventions for river water quality improvement within the context of population growth and urbanization: a case study of the Cau River basin in Vietnam

In this study, a multi-criteria methodology is proposed to identify and prioritize interventions for water quality improvement with the aid of computer simulation models. The methodology can be used to elaborate and compare future socio-economic development scenarios to select the best interventions based on three criteria: (1) ideas of experts and stakeholders about the importance of scenarios, (2) impacts of each scenario on surface water quality in watershed, and (3) benefit–cost analysis for each scenario. A score is computed for each scenario based on a weighted sum technique which enables to take into consideration different level of importance for the three criteria. The methodology is applied to Cau River basin in Vietnam, with the aid of a computer tool, to assess interventions for river water quality improvement within the context of population growth and urbanization. The results show that fast future population growth in upstream has significant impacts. In 2020, an increase of 116 % of the population in Bac Kan town can lead to an increase of 120 and 135 % in BOD₅ and NH₄ ⁺ median concentrations, respectively, with the implementation of a treatment plant for 10,000 people in Bac Kan town. Therefore, the increase of the domestic wastewater treatment plant’s capacity in Bac Kan town, at least twice as the projection of local government, is necessary. These results will help decision makers to select the best interventions for Cau River basin management.