Claude Camiré

Changes in nutrient availability and forest floor characteristics in relation to stand age and forest composition in the southern part of the boreal forest of northwestern Quebec

Abstract Changes in forest floor properties and nutrient availability along a boreal post-fire sere succession covering a time span of 231 years were assessed using soil analysis and exchange resins. A decline in pH (from 5.5 to 3.65), effective cation exchange capacity (CEC) (from 72.5 to 39.6 cmol(+)kg−1), exchangeable cation concentrations, as well as in Ca, Mg, K and PO4 concentrations on resin was observed. Contrary to what has been reported so far for boreal forests, NO3 and NH4 concentrations did not decrease in the course of succession. Ammonium concentrations remained constant while those of NO3 reached their highest values at age 27, decreased abruptly between ages 27 and 47, and started to increase in older stands. No correlation was found between NO3 availability and pH, P concentrations or C/N ratio. Interactive effects of stand age and stand composition on nutrient concentrations on resins were evaluated using path analysis. While it is not possible to fully disentangle the contribution of single factors, the results showed a positive effect of aspen on Ca concentrations. These results stressed the need to evaluate the long term impacts of successive rotations of softwood species coupled with the elimination of hardwood competition on the soil base status of plantations.

Changes in the forest floor of Canadian southern boreal forest after disturbance

. The concentrations and contents of organic matter and nutrients in organic deposits on the forest floor were estimated along a 231-yr chronosequence following fire at the southern limit of the boreal forest in eastern Canada. The sampling design was stratified to take into account the variability related to the presence of the principal tree species as well as to the presence of large gaps created by a recent spruce budworm (Choristoneura fumiferana) outbreak. The forest floor showed a steady accumulation of organic matter and total nutrients with time-since-fire and a 50 % decrease in the concentrations of available P and K, but not N (as determined by aerobic incubation). The increase in forest-floor weight was accompanied by an increased storage of available N, Ca and Mg. The availability of N and Ca was more strongly affected by tree species and gaps than by time-since-fire. A high N-availability was observed under Betula papyrifera and in gaps, while high a Ca-availability was found near Populus tremuloides and Thuja occidentalis. In old sites, the forest floor of gaps, created by a recent spruce budworm outbreak, had a necromass similar to that of a young forest, but the low concentrations of available P and K of an old forest.

Decomposition of roots of black alder and hybrid poplar in short-rotation plantings: Nitrogen and lignin control

The decomposition of the roots (0–2 mm, 2–5 mm and 5–10 mm) of black alder (Alnus glutinosa (L.) Gaertn.) and hybrid poplar (Populus nigra L. X Populus trichocarpa Torr & Gray) was followed over a 462-day period in pure and mixed plantings in southern Quebec. Small roots of alder had the highest initial concentrations of nitrogen and lignin, and lost 9 and 10% less mass than medium and large roots, respectively. Large roots of poplar had the highest lignin-to-nitrogen ratio and showed the smallest loss of mass over the total incubation period. Slow root decomposition of black alder and hybrid poplar was characterized by a greater proportion of initial root nitrogen immobilized per unit of carbon respired. Lignin concentration in roots of alder and poplar increased rapidly at the beginning of the incubation. Our results suggest that high levels of nitrogen in roots of alder could contribute in slowing the rate of decomposition by allowing the formation of nitrogen-lignin derivatives and low levels of nitrogen in roots of poplar may limit the growth of microorganisms and the rate of root decomposition. A multiple regression was developed using initial nitrogen, lignin concentration and the ratio of lignin to nitrogen to produce an index of the rate of root decomposition. The correlation between the index values and the percentage of residual root mass was significant (r=0.98, p<0.01).

Soil compaction induced by careful logging in the claybelt region of northwestern Quebec (Canada)

Soil compaction induced by forest harvesting operations can reduce site productivity. Intensity, extent and persistence of soil compaction were assessed on fine- to medium- and coarse-textured soils. Severe compaction took place in the wheel track section of the skid trails. On fine- to medium-textured soils, half of the effects on the 0- to 10-cm and 10- to 20-cm mineral soil bulk densities (+11 and +8%) and half of the changes in the 10-cm depth soil strength (+69%) occurred in the course of the first two skidding cycles (cycle of half impact). On coarse soils, half of the effect on the 0- to 10-cm bulk density (+11%) occurred during the first three passes. Cycles of half impact for soil strength were 9, 14, 7 and 6 for the 2.5-, 5-, 10-, and 20-cm depths and corresponded to increases of 235, 402, 157 and 103% respectively. Compaction was more limited between track sections of trails. Six to twelve years following clearcutting on fine- to medium-textured soils, 0- to 10-cm soil bulk density was less in ...

Nitrogen net mineralization and dynamics following whole-tree harvesting and winter windrowing on clayey sites of northwestern Quebec

Concerns over decreases in soil nitrogen reserves and productivity following the removal of logging residues (windrowing, shearblading and piling) have been raised by numerous researchers. Medium-term impacts of this practice on soil N reserves and availability and on indices of organic matter quality were assessed for balsam fire (Abies balsamea (L.) Mill.), white birch (Betula paperyfera Marsh.) and white spruce (Picea glauca (Moench) Voss) stands growing on dry to fresh clayey sites in northwestern Quebec, Canada. Unharvested control stands, whole-tree harvested cutovers and windrowed sites were compared. Fifteen years following harvesting and windrowing, forest floor Kjeldahl N concentrations and content and forest floor in situ net N mineralization rates (undisturbed closed top cores incubation) were affected by harvesting but not by windrowing. No differences in mineralization constant, potentially mineralizable N and cumulative mineralized N (526 day incubation period) were found between treatments, suggesting that treatment differences in field net N mineralization rates were the result of interactions between residual ecosystem structures such as forest floor, coarse woody debris and vegetation and meteorological conditions. If these trends persist over time, it could signal that, while whole-tree harvesting does not have a direct effect on soil organic matter quality, long-term impacts on N dynamics could result from changes in ecosystem structures. Slash removal following whole-tree harvesting did not have any additional negative impact.

Effect of soil K, Ca and Mg saturation and endomycorrhization on growth and nutrient uptake of sugar maple seedlings

Nutrient imbalances of declining sugar maple (Acer saccharum Marsh.) stands in southeastern Quebec have been associated with high exchangeable Mg levels in soils relative to soil K and Ca. A greenhouse experiment was set up to test the hypothesis that the equilibrium between soil exchangeable K, Ca, and Mg ions influences the growth and nutrient status of sugar maple seedlings. Also tested was whether endomycorrhization can alter nutrient acquisition under various soil exchangeable basic cations ratios. Treatments consisted of seven ratios of soil exchangeable K, Ca, and Mg making up a total base saturation of 58%, and a soil inoculation treatment with the endomycorrhizal fungus Glomus versiforme (control and inoculated), in a complete factorial design. Sugar maple seedlings were grown for 3 months in the treated soils. Plant shoot elongation rate, dry biomass and nutrient concentrations in foliage were influenced by the various ratios of soil cations. The predicted plant biomass and foliar K concentration were highest at a soil Ca saturation of 38%, a soil K saturation of 12%, and a soil Mg saturation of 8%. Potassium concentration in foliage was dependent on the level of Ca and Mg saturation in the soil when soil K saturation was close to 12%. Foliar Ca and Mg levels were more dependent on their corresponding levels in soil than foliar K. Colonization by G. versiforme did not influence seedling growth and macronutrient uptake. The results confirm that growth and nutrition of sugar maple are negatively affected by imbalances in exchangeable basic cations in soils.

Effects of two silvicultural practices on soil fauna abundance in a northern hardwood forest, Quebec, Canada

Soil fauna play a key role in soil fertility and productivity of forest ecosystems and represent an important base of terrestrial food chains. The impact of forest management on soil fauna should be considered when sustainable forest management and conservation of biodiversity are desired. We evaluated the impact of selective cutting and strip clearcutting on soil fauna abundance in a northern hardwood forest of the Lower Laurentians of Quebec. Twelve years after strip clearcutting, the abundance of carabid beetles (Coleoptera: Carabidae), collembolans (Hexapoda: Collembola) and snails (Stylommatophora: Sigmurethra) was greater in the strip clearcuts than the adjacent undisturbed strips. Snails and millipedes (Polydesmida: Polydesmidae) were more abundant in the selective cuts 6 to 8 yr after treatment. Spiders (Arachnida) were the only organism whose abundance was lower in the selective cuts than in the adjacent undisturbed forest . No significant negative effect of the silvicultural treatments was noted...

Application of leaf, soil, and tree ring chemistry to determine the nutritional status of sugar maple on sites of different levels of decline

Nutrient concentrations and D.R.I.S. indices of leaves, soil chemistry and dendrochronological changes of elemental concentrations in sugar maple (Acer saccharum Marsh.) were used to determine its nutritional status on three sites of contrasting levels of decline. We hypothesized that the ratio of Al to base cations in tree rings would increase more at the most severely declining site, and that the ratios of K+ to divalent cations (Ca2+ and Mg2+) would increase slower or decrease more rapidly over time than at the less severely declining sites. Forest health, based on percentage of foliage missing, and leaf K and Mg concentrations of the three sites were ranked as follows: Morgan Arboretum > Saint-Hippolyte > Entrelacs. Soil pH, Ca, Mg, E.C.E.C. and percentage of base saturation were highest at the Morgan Arboretum, and exchangeable Al in the organic horizon was highest at Entrelacs. Concentrations of K, Ca, Mg and Al, and ratios of these elements in wood were determined for each of the following periods: 1940–1956, 1957–1973 and 1974–1989. Variations in tree ring chemistry among sites were significant for K and Al and all elemental ratios except K:Mg. Al concentration and the ratios of Al to base cations in wood were all significantly higher at Entrelacs (7.0 vs 2.6 and 2.8 mg Al kg−1 for the other two sites, respectively). Weak relationships were generally observed between leaf and soil elemental concentrations, and wood elemental concentrations. The D.R.I.S. K index and soil exchangeable K and Al showed good concordance with wood concentrations. With the exception of Mg, Al and Al:Mg, the effect of period was significant for all other elements and ratios of elements. The most severely declining stand (Entrelacs) differed from the healthiest stand by decreasing K:Ca and increasing A1:K from the 1940–1956 to the 1957–1973 period.

Growth, nitrogen accumulation, and symbiotic dinitrogen fixation in pure and mixed plantings of hybrid poplar and black alder

SummaryGrowth and N accumulation were assessed in pure and mixed plantings (2 years old) of hybrid poplar and black alder in southern Québec. Symbiotic dinitrogen fixation was evaluated by natural15N dilution. Growth of hybrid poplar plants and N accumulation in their tissues increased with their decreasing contribution to species ratio whereas no differences among treatments were measured for black alder. Yield and N content per hectare of aboveground components increased with the proportion of black alder in the plantation. Symbiotic dinitrogen fixation was estimated at 68% of alder nitrogen in both pure and mixed treatments. The maximum rate of N-fixation was 53kg ha−1 yr−1 in pure alder plots. The amount of nitrogen accumulated in entire plants of black alder from symbiotic fixation could be sufficient to balance the N export in harvested stems and branches of short-rotation plantations containing at least 33% of alder.

Influence of remnant trees on nutrients and fallow biomass in slash and burn agroecosystems in Guinea

Three tree species are traditionally conserved in the traditional slash and burn agricultural system practiced for the production of upland rice (Oryza sativa Linn.) in the Fouta Djallon region of Guinea, i.e. (Parinari excelsa [Sabine], Parkia biglobosa [Jacq.) Benth.], Erythrophleum guinensis [G. Don.]). Sampling a chronosequence of fallow sites indicated that extractable P; exchangeable K, Ca and Mg; cation exchange capacity (CEC) and pH all decreased over the fallow period with patterns that differed with soil depth. Soils under the remnant Parinari excelsa and Parkia biglobosa trees had higher concentrations of organic C; total N; extractable P; exchangeable K, Ca and Mg; total P and Ca; and CEC than did the open microsites. Extractable P; exchangeable K, Ca and Mg; total P and Ca; and CEC were greater under Parinari excelsa than under Erythrophleum guinensis. Intensive measurements of a single mature fallow site showed that the foliar nutrient concentration of the large trees was not an accurate index of which microsite had the greatest accumulation of biomass and nutrients in the aboveground fallow vegetation. The biomass and the total amounts of N, P, K, Ca and Mg in the fallow vegetation were significantly greater for the Parinari excelsa and Parkia biglobosa microsites than for the open microsites. We conclude that although the nutrient status of the soils decreased over the 8-year fallow period, the microsites under the large trees were generally more fertile than the open microsites. However, there were important differences in the effects of the different tree species.