Dystric Brunisol Research Articles

Rapid turnover of organic acids in a Dystric Brunisol under a spruce–lichen forest in northern Saskatchewan, Canada

Fujii, K., Morioka, K., Hangs, R., Funakawa, S., Kosaki, and Anderson, D. W. 2013. Rapid turnover of organic acids in a Dystric Brunisol under a spruce–lichen forest in northern Saskatchewan, Canada. Can. J. Soil Sci. 93: 295–304. Organic acids released by lichen play an important role in mineral weathering and podzolization in the Boreal–Tundra transition zone of Canada; however, importance of low-molecular-weight organic acids in the soil carbon (C) cycle in the black spruce–lichen forests remains unclear. We examined soil solution composition and mineralization kinetics of 14C-radiolabelled oxalate and citrate to quantify the C fluxes from organic acid mineralization in a Dystric Brunisol under a spruce–lichen forest in northern Saskatchewan. Oxalate concentration in soil solution was greatest in the lichen layer, while the high levels of citrate were observed in the lichen and organic (O) layers to the Ae horizon with the lowest sorption capacity. Oxalate and citrate were rapidly mineralized within the lichen and O layers and had short mean residence times (0.5 to 2.7 h). Substantial C fluxes due to citrate mineralization were observed both within the lichen and O layers, but oxalate mineralization led to C flux in the lichen layer only. The contribution of citrate and oxalate to microbial respiration was large (up to 57%) in the surface soil layers. Citrate was the dominant substrate for microbial respiration of the surface soil; however, it appears that oxalate could also be an important microbial substrate within the lichen layer, at least in summer months. We conclude that the exudation of low-molecular-weight organic acids by lichenous fungi, followed by their rapid mineralization, could play an important role in the C cycles of the sandy soils under spruce–lichen forest.

Brunisolic soils of Canada: Genesis, distribution, and classification

Smith, C. A. S., Webb, K. T., Kenney, E., Anderson, A. and Kroetsch, D. 2011. Brunisolic soils of Canada: Genesis, distribution, and classification. Can. J. Soil Sci. 91: 695–717. Brunisols are considered as moderately developed soils formed under forest cover. They have a wide range of physical and chemical properties and no single dominant pedogenic process drives the development of these soils. Brunisols are some of the more common soils in Canada, occupying over 1.2 million km2 of land, roughly equivalent to the area of Podzolic soils, and about half the area of the most common soil order in Canada, the Cryosols. Brunisols occur mainly within the boreal forest regions, but extend across the country with the exception of the Arctic and prairie regions. Within the zone of discontinuous permafrost they co-exist on landscapes with Cryosols. In humid regions of both eastern and western Canada they form a continuum of soil development with Podzolic soils. Within subhumid to semi-arid regions they often co-exist with Luvisolic soils, occurring on parent materials too coarse to enable Luvisolic soil formation. Brunisols equate closely to the Cambisol reference group in the World Reference Base taxonomic system and to several suborders of the Inceptisol order in Soil Taxonomy. Both Melanic and Sombric Brunisols are important agricultural soils in British Columbia, Ontario and the Maritime provinces. Eutric and Dystric Brunisols support commercial forest stands throughout the boreal forest and western cordillera of Canada.

Genesis of upland soils, Lewes Plateau, central Yukon. Part 1: soils formed on Pleistocene glacial deposits

Dampier, L., Sanborn, P., Smith, S., Bond, J. and Clague, J. J. 2011. Genesis of upland soils, Lewes Plateau, central Yukon. Part 1: soils formed on Pleistocene glacial deposits. Can. J. Soil Sci. 91: 563–578. We describe and interpret nine upland (>1000 m asl) Dystric Brunisols and one Humo-Ferric Podzol formed on till of the McConnell [Marine Isotope Stage (MIS) 2] and penultimate (MIS 4 or 6) glaciations on the Lewes Plateau of central Yukon Territory. Unlike soils formed on correlative glacial deposits at lower elevation in the nearby Tintina Trench, the soils on the Lewes Plateau display only weak age-related differences. Penultimate and McConnell soils have solum thicknesses of 50–75 cm and <50 cm, respectively, but other morphological and chemical properties do not differ between the two age groups. Smectite is present in the McConnell soils; it was previously reported only in soils formed on Early Pleistocene glacial deposits in central Yukon and was interpreted to reflect weathering and soil formation during warm interglaciations. Paleoclimatic interpretations of clay mineralogy in central Yukon may be confounded by differences in parent material provenance and should be reassessed. This study shows that field soil characteristics alone are insufficient to differentiate McConnell and penultimate glacial deposits in upland landscape positions on the Lewes Plateau.

Genesis of upland soils, Lewes Plateau, central Yukon. Part 1: Soils formed on Pleistocene glacial deposits

Dampier, L., Sanborn, P., Smith, S., Bond, J. and Clague, J. J. 2011. Genesis of upland soils, Lewes Plateau, central Yukon. Part 1: soils formed on Pleistocene glacial deposits. Can. J. Soil Sci. 91: 563-578. We describe and interpret nine upland (>1000 m asl) Dystric Brunisols and one Humo-Ferric Podzol formed on till of the McConnell [Marine Isotope Stage (MIS) 2] and penultimate (MIS 4 or 6) glaciations on the Lewes Plateau of central Yukon Territory. Unlike soils formed on correlative glacial deposits at lower elevation in the nearby Tintina Trench, the soils on the Lewes Plateau display only weak age-related differences. Penultimate and McConnell soils have solum thicknesses of 50-75 cm and <50 cm, respectively, but other morphological and chemical properties do not differ between the two age groups. Smectite is present in the McConnell soils; it was previously reported only in soils formed on Early Pleistocene glacial deposits in central Yukon and was interpreted to reflect weathering and soil form...

Mehlich 3 extractable nutrients as determined by near-infrared reflectance spectroscopy

Near-infrared reflectance spectroscopy (NIRS) is a cost-effective and environmentally friendly technique of soil analysis that is particularly advantageous in intensive soil sampling and soil nutrient management as well. This study evaluated the potential of NIRS for predicting P, K, Ca, Mg, Cu, Zn, Mn, Fe, and Al extracted by Mehlich 3. We used 150 air-dried samples collected from a 15-ha site dominated by Orthic Humic Gleysol and Gleyed Dystric Brunisol soils. Calibration equations were developed using modified partial least squares regression. The accuracy of NIRS prediction was evaluated using the coefficient of determination (R2), the ratio of performance deviation (RPD), and the ratio of error range (RER). Reliable calibrations were found for Ca, Cu, and Mg (R2 ≥ 0.7, RPD ≥ 1.75, and RER ≥ 8). Less-reliable calibrations were found for Al, Fe, K, Mn, P, and Zn (R2 &lt; 0.7, RPD &lt; 1.75, and RER &lt; 8). In the validation with independent samples, acceptable regression coefficients (i.e., 0.8 ≤ slope ≤ 1.2) were only found for Ca, Mg, and Mn. We presumed that the pH of the Mehlich 3 extractant (2.5 ± 0.1) may affect the solubility of most of these nutrients, regardless the soil texture and, consequently, the potential of NIRS to predict them. The more a nutrient was correlated to clay content, the more it was likely predictable by NIRS. The prediction models obtained for Al, Ca, Cu, Fe, K, Mg, and Mn could still be used for screening purposes in cases where high accuracy is not required. These NIRS prediction models should be validated across larger geographic areas of geological homogeneity. Key words: Soil analysis, Mehlich 3, near-infrared reflectance spectroscopy, calibration

Species and Spacing Effects of Northern Conifers on Forest Productivity and Soil Chemistry in a 50-Year-Old Common Garden Experiment

Species and Spacing Effects of Northern Conifers on Forest Productivity and Soil Chemistry in a 50-Year-Old Common Garden Experiment

Estimating nitrogen exports in response to forest vegetation, age and soil types in two coastal-forested watersheds in British Columbia

This study compared the variability in nitrogen (N) export as a function of (i) vegetation types, (ii) soil types, and (iii) both vegetation and soil types using the least square estimation method for two coastal-forested watersheds in southern Vancouver Island, British Columbia, Canada. Nitrogen exports estimated using both vegetation and soil types were found to be more accurate than those estimated by either vegetation or soil types alone. Results showed that forested wetlands had the highest N exports ranging from 0.16 to 0.98 kg ha −1 year −1 for ammonium-N (NH 4-N), from 0.27 to 2.95 kg ha −1 year −1 for nitrate-N (NO 3-N) and from 3.48 to 5.61 kg ha −1 year −1 for total N (TN). Young forests had the lowest N exports ranging from 0.03 to 0.74 kg ha −1 year −1 for NH 4-N, from 0.01 to 0.21 kg ha −1 year −1 for NO 3-N and from 0.57 to 1.03 kg ha −1 year −1 for TN. Duric Dystric Brunisols had the highest N exports, 2.78 kg ha −1 year −1of TN and Orthic Ferro-Humic Podzols had the lowest, 1.54 kg ha −1 year −1 of TN. A Hoerl curve described the response of N export rates to the change of forest ages well. Average TN export decreased from 4.00 kg ha −1 year −1 for forest regeneration to 0.75 kg ha −1 year −1 for young forests and then increased from 1.28 kg ha −1 year −1 for mature forests to 1.74 kg ha −1 year −1 for old-growth forests. Using watershed protection, as an example, that will eventually convert all the current forests into old-growth forests, an even area distribution of forest ages from regeneration to mature will reduce N export from forested lands to streams by up to 37% in Sooke Lake watershed.

Spatial and temporal trends in soil properties at a soil quality benchmark site in central Nova Scotia

In response to concerns over the widespread soil degradation occurring on Canada's agricultural lands, Agriculture and Agri-Food Canada established a network of benchmark sites to assess soil quality change by monitoring agronomically important soil properties. The Nova Scotia site was established in 1989 on Queens (Gleyed Brunisolic Gray Luvisols) and Debert (Gleyed Dystric Brunisols) soil series under a corn–forage rotation within the Annapolis–Minas Lowlands ecoregion. The objectives of the project were to quantify temporal changes in agronomically important soil properties and determine how the property values vary with the landscape and components of the soil map unit. A 20 × 25 m grid was used in 1990 and again in 1995 to sample soil from the Ap horizon and to locate saturated hydraulic conductivity and penetration resistance measurements. The samples were analyzed for pH, organic C, total N, and available P and K. The results indicate that over 5 yr, organic C, C:N ratio, available P, and saturated hydraulic conductivity declined by 7.9, 4.7, 12.5, and 53%, respectively. Significant differences in pH, organic C, total N, available K, penetration resistance and saturated hydraulic conductivity were associated with selected components of the soil map unit. Slope position had a minimal effect on soil properties except for available K where the highest levels were located on middle slope positions. Interactions between particle size and slope position were found, with soils with coarse-loamy sola on upper slope positions having the lowest pH. The results of this study also demonstrated the utility of the method for monitoring soil quality change and the importance of the soil map unit in interpreting the spatial and temporal differences in soil properties. Key words: Soil variability, soil monitoring, soil properties, soil map unit, spatial correlation

Long-term fertilization effects on soil carbon under permanent swards

In a long-term study with four rates each of fertilizer N, P, and K in factorial combination on timothy (Phleum pratense L.), soil C concentration in the 0- to 15-cm layer of an Orthic Dystric Brunisol in New Brunswick ranged from 25 to 37 g C kg−1 after 26 yr, and from 26 to 44 g C kg−1 after 35 yr. Soil C concentration was not related to the wide range of aboveground net productivity resulting from contrasted long-term fertilization treatments. Soil C concentration, however, was negatively correlated to soil pH. Key words:Phleum pratense L., timothy, carbon, fertilization

Effects of coarse-fragment content and size on soil erosion under simulated rainfall

Farmers have long considered coarse fragments a hindrance in potato production. Rock picking or crushing has become a routine operation. Using simulated rainfall events and runoff-erosion plots (1 m × 1 m), the effects of coarse-fragment content (0, 7, 15 and 25% by volume) and size (1.0–1.9, 1.9–5.1 and 5.1–7.6-cm diam) on runoff, infiltration and soil loss were evaluated on an Orthic Dystric Brunisol. Study objectives were to quantify the influence of coarse fragments on soil erosion and to convert these relationships into mathematical equations for use with existing models to predict soil loss. Although there were only marginal increases in infiltration and reductions in runoff attributable to increasing content and size of coarse fragments, the rate of soil loss from the control was higher than that from all other treatments. In general, the rate of soil loss decreased with increasing content and size of coarse fragments. The effects of content and size of coarse fragments on soil-loss reduction, either individually or in combination, were expressed mathematically with correlation coefficients greater than 0.82. The study also revealed that for a given volumetric coarse-fragment content, the percentage surface cover increased with increasing coarse-fragment size. This finding has important practical implications because most reporting of coarse fragments is done on the basis of volume rather than percentage surface cover. Key words: Rock content, rock size, rainfall simulator, infiltration, soil loss

Soil genesis on a chronosequence, Pinery Provincial Park, Ontario

Soils on a late Holocene dune chronosequence were studied along Lake Huron at Pinery Provincial Park, in southwestern Ontario. Progressive exposure of new materials, associated with declining lake levels, has allowed the development of soils in a sequential manner from the shoreline (approximately time zero) to about 2.3 km inland. Six soil pits were excavated and sampled in narrow depth increments along a transect ranging in estimated age from 100 to 4700 yr B.P. Chronofunctions were formulated based on pedogenic properties in order to evaluate the rates and pathways of soil genesis in southern Ontario. The soils graded from an Orthic Regosol near the shore to an Eluviated Dystric Brunisol to 2.3 km inland. The increasing thickness of the solum and darker chroma in the B horizons were the most obvious morphological indications of a progression in soil weathering. Linear chronofunctions of increasing total silt and clay contents with soil age suggest that physical breakdown of sand particles to silt and clay may be occurring. Total organic matter in the profiles increases logarithmically with soil age with a rapid increase in the first 2000 yr or so. The depth of CaCO3 leaching increased linearly with increasing soil age. Data indicate that mean annual precipitation may be the most important influence on the rates of carbonate weathering. Soil pH decreases linearly with soil age in the first 2900 yr. However, vegetative variations appear to influence the pH beyond 2900 yr of soil development. Depth to, and thickness of, the B horizons also increased linearly with soil age. Key words: CaCO3 weathering, solum thickness, clay accumulation, dune chronosequence

Short range variability of soil chemistry in three acid soils in Ontario, Canada

Abstract The objective of this study was to assess the efficacy of soil sampling and analysis methodologies used in Canada's Acid Rain National Early Warning System (ARNEWS). During July and August of 1992, twenty‐five soil pits were sampled and analyzed for available phosphorus (P); exchangeable potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), copper (Cu), manganese (Mn), zinc (Zn), aluminum (Al), sodium (Na), sulfate‐sulfur (SO4‐S), boron (B), and molybdenum (Mo); total nitrogen (N), P, K, Ca, Mg, Fe, Cu, Mn, Zn, Al, Na, sulfur (S), B, nickel (Ni), lead (Pb), and organic matter (O.M.); pH; and cation exchange capacity (C.E.C.) at three ARNEWS sites across Ontario. The soils were: i) a till‐derived Ferro‐Humic Podzol (Humic Haplorthod), ii) a Humo‐Ferric Podzol (Haplorthod) developed in coarse glaciofluvial sand, and iii) a Dystric Brunisol (Dystrochrept). The three sites were similar in chemical composition except for available P, exchangeable Ca, Mn, total Mn, O.M., and pH. Sample numbers calculated to achieve ±10% error with 95% confidence were much higher in mineral horizons than in forest‐floor horizons. Organic macro‐elements and pH were found to be the least variable parameters while micro‐elements were significantly more variable. Analyses are categorized into groups requiring similar numbers of samples. Other studies have found comparable levels of variability and their results are compared to coefficients of variation generated by the Ontario results. Variability within a pit was also observed and found to be less than that found across each 20‐ x 20‐m site but still very significant. Overall, the variability results from other studies appear to be applicable to Ontario acid soils for common analyses. Investigations observing micro‐elements, or which require high levels of accuracy, should incorporate pilot studies to ascertain the degree of variability for their location.

Effects of potato hilling on water runoff and soil erosion under simulated rainfall

The practice of planting potatoes (Solanum tuberosum) in rows and hilling the plants at some stage of growth has been universally adopted. Using a rainfall simulator and runoff-erosion plots (0.9 m wide × 1 m long), the effects of hilling on runoff, infiltration, and soil loss were examined on an Orthic Dystric Brunisol. Tests of the rainfall simulator revealed that variations in operating pressure (36.5–62.1 kPa) and soil slope conditions (0–15%) did not significantly (P &lt; 0.05) affect the intensity and spatial uniformity of the simulated rainfall. The potato hills studied were 90 cm apart with heights of approximately 25 cm, row-sideslopes of 35° and furrow widths of 10 cm, which are similar to those used in commercial production. Although not significantly different at P &lt; 0.05, the runoff rate from the hilled plots was approximately 20% higher than that from the unhilled plots. Hilling resulted in a significant reduction in infiltration rate (P &lt; 0.05). Average soil loss from the hilled plots was approximately four times higher than from the unhilled plots. For runoff rates below a critical value of 0.93 L min−1, the rate of soil loss correlated linearly with the runoff rate, whereas a non-linear exponential equation was generated for the entire range of runoff with r = 0.94. The increase in soil loss as a result of hilling was adequately predicted from row-sideslope gradients using an existing equation derived from erosion data obtained from fields having conditions similar to that of potato hills. Key words: Universal soil loss equation, slope steepness, cover and management factor, row-sideslope, spatial uniformity, infiltration

Copper and zinc sorption on some B horizons of Quebec soils

Abstract The sorption of Cu and Zn on soils, as a function of pH, is important to an understanding of their mobility in the soil solution and their availability for plant nutrition. Copper and Zn sorption as a function of the pH were measured for six B horizons of two Orthic Humic Gleysols, two Orthic Humo‐Ferric Podzols, one Orthic Dystric Brunisol and one Orthic Sombric Brunisol. The results show that: 1) for the same amount of metal in solution and the same pH, more Cu is sorbed than Zn and 2) there is a maximum of sorption at or just above pH 5.00 and a large decrease as pH decreases. During the pH‐dependent sorption of Cu and Zn on six B horizons of Quebec soils, it was found that ions were released into solution thus altering the charge generated by the soil at low pH and the sorption behavior of Cu and Zn. The solid phase most likely to control the level of ions in solution is believed to be the amorphous and oxide forms of Al and Fe. The dissolution of these metal oxide or hydrous oxide materials ...

A SOIL CHRONOSEQUENCE ON BEACH SANDS, VANCOUVER ISLAND, BRITISH COLUMBIA

A soil chronosequence near Cox Bay, on the west coast of Vancouver Island, British Columbia was investigated. Soils in the sequence have developed on sandy beach deposits, which are advancing toward the ocean at a rate of 0.26 m per year. Dendrochronology and geomorphology established surface ages ranging from 127 to 550 yr for seven selected pedons across these deposits. With soil age, there was progressive deepening and differentiation of genetic horizons, resulting in soil classification that ranged from an Orthic Dystric Brunisol at the youngest site (site 1) to an Orthic Humo Ferric Podzol at the oldest site (site 7). Organic matter increased from a maximum value for mineral horizons of 1.1% in the Bm of site 1 to 4.7% in the Ae of site 7. Oxalate-extractable Al in the uppermost B horizons of the soils increased from 0.12% at site 1 to 0.30% at site 6. Available Mg and K from the lowermost horizons sampled decreased from 35 and 25 mg kg−1 to 4 and 5 mg kg−1, respectively, when moving from sites 1 to 6. Accumulations of organic matter, Fe and Al, and losses of available Mg were plotted against soil age and yielded chronofunctions with exponential solutions. Key words: Soil chronosequence, soil genesis, Podzol development, chronofunctions

PEDOGENIC IMOGOLITE IN SANDY BRUNISOLS OF EASTERN ONTARIO

Imogolite that appears to have formed by weathering in the present soil (pedogenic imogolite) occurred in two well-drained Dystric Brunisols on fine sand materials in eastern Ontario. Imogolite was detected by electron microscopy and was most abundant in the fine clay fraction of the lower B horizons. Several characteristics of these two pedons considered to be favorable for the occurrence of imogolite are: low organic matter content in the sola; high ratio of (Alo-Alp)/Alp in the B horizons; the strong but not extremely acid soil reaction in the B horizons and the porous nature of the soils. The finding is consistent with the hypothesis that the downward movement and precipitation of inorganic amorphous forms of Al and Si is a major process in podzolization. It also demonstrates that the occurrence of imogolite is not restricted to Spodosols or Podzolic soils. Key words: Pedogenic imogolite, proto-imogolite allophane, Dystric Brunisols, Spodosols

EXTRACTABLE Fe, Al, Si AND C IN B HORIZONS OF PODZOLIC AND BRUNISOLIC SOILS FROM ONTARIO

To investigate the content of amorphous forms of Fe, Al and Si in podzolic soils, the B horizons from 54 Humo-Ferric Podzols and 24 Eluviated Dystric Brunisols were sampled in northern Ontario. Dithionite-citrate-bicarbonate (DCB) Fed and Ald, acid NH4-oxalate Feo, Alo and Sio, Na-pyrophosphate Fep, Alp and Cp and NaOH-tetraborate Fet and Alt were determined on all samples. Feo/Fed ratios averaged 0.87 and suggested that most of the extractable Fe was amorphous. Inorganically bound Fe and Al in pyrophosphate extracts were estimated by addition of NH4OH to the extracts. The amount of inorganically bound Fe, expressed as a percentage of that extracted by DCB, was calculated at 79 ± 23%, whereas the corresponding value for Al was 61 ± 20%. (Alo-Alp)/Sio atomic ratios, plus linear correlation analysis of (Alo-Alp) against Sio, suggested the presence of amorphous aluminosilicates with Al/Si ratios approaching 3. (Feorg + Alorg)/Cp ratios averaged 0.10, a figure near the value suggested by other authors for the maximum amount of Fe and Al bound to organic matter. (Cp/(Fep + Alp) atomic ratios did not appear to be useful in differentiating Podzolic from Brunisolic soils. Key words: Podzolic soils, chemical criteria, extractants

Long‐Term Phosphorus Sorption in a Brunisol in Response to Dosed‐Effluent Loading

AbstractPhosphorus sorption characteristics of a major soil in the Shawnigan Lake area of Vancouver Island were studied in response to periodic secondary effluent loading. Five soil columns 0.60 m long and 0.139 m in diam were prepared from the B horizon of the Shawnigan gravelly silt loam (classified as a Dystric Brunisol and Typic Dystrochrept according to the Canadian and U.S. Systems of soil classification, respectively). Water table level was maintained at the base of the two partially saturated columns (PSC). The other three columns (USC) remained unsaturated at all times and were subjected to a tension of 6.0 kPa. A single, daily dose of 1 L (∼6.6 cm) of secondary effluent was applied to all columns except on weekends and holidays.The effluent P was retained effectively by the USC columns initially, but broke through with time as in case of the PSC columns. The leachate P concentration reached an equilibrium value (EPC) after about 70 pore volumes of effluent had passed through the columns. The EPC changed only slightly beyond 70 pore volumes, but was a function of effluent P concentration and percolation rate. About 60 to 90% of added P was retained by the columns, even after 2.7 yr of leaching. Surface layers were the most effective renovators of effluent P; however, the total amount of P retained by the soil was dependent more on effluent percolation rate and leaching period, and less on water table level.

INCREASE IN NEUTRAL SALT EXTRACTABLE CATION EXCHANGE CAPACITY OF SOME ACID SOILS AS AFFECTED BY CaSO4 APPLICATIONS

The equilibration of acid soils, a Sombric Ferro-Humic Podzol (CSSC-2) from British Columbia, an Orthic Ferro-Humic Podzol (CSSC-19) from Quebec and two horizons of a Dystric Brunisol (SSD-330, SSD-331) from British Columbia, with CaSO4 solution demonstrated that SO4 ions reacted with components of these soils. These reactions increased soil pH, ion activity product (Al)(OH)3 and neutral salt extractable exchangeable cations. The increase in pH and ionic activity product (Al)(OH)3 were noticeable on a single equilibration; however, increase in neutral salt extractable cations was only observed after subsequent equilibrations. After three equilibrations, the sums of NaCl extractable cations were 6.56, 11.99, 5.62 and 4.31 meq/100 g for soil samples CSSC-2, CSSC-19, SSD-330 and SSD-331, respectively. The corresponding values for the unequilibrated soils were 5.20, 7.49, 4.30 and 2.50 meq/100 g. On further equilibration there was no increase in total extractable cations for sample CSSC-2; however, for the other three samples there were increases which became progressively smaller. The reaction of SO4 ions with aluminum hydroxy clay complexes seems to be the mechanism for the increase of negative sites. Key words: Cation exchange capacity, CaSO4, acid soils

ACTIVITE BIOLOGIQUE DANS LES SOLS DE SIX ECOSYSTEMES FORESTIERS DU QUEBEC MERIDIONAL

Dynamics of woody material degradation were studied in the soils of six forest ecosystems of meridional Quebec. This comparative study was performed measuring weight losses of wood samples, buried for long periods of time in the different horizons of each soil studied. In all cases, degradation was much faster close to the soil surface; thus a more or less marked decreasing vertical gradient was observed in the activity for most of the soils studied. The lengths of time necessary for half decomposition (50%) were calculated for the samples buried in each station. For the hardwood forests, values of about 1.7, 2.8 and 2.3 yr were obtained for half decomposition in the Melanic Brunisol, the Sombric Brunisol and the Dystric Brunisol, respectively. A value of 4.6 yr was calculated for the Minimal Humo-Ferric Podzol of the mixed forest to reach half decomposition. Similarly about 35 and more than 40 yr would be necessary for half decomposition of the samples in the Orthic Ferro-Humic Podzol and the Ortstein Ferro-Humic Podzol of the two coniferous forests, respectively. The influence of major environmental factors, such as climate, soil and vegetation on the dynamics of microbial and faunal soil communities is discussed.