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Impaired soil quality due to compaction and organic matter removal following forest harvesting and mechanical site preparation is of concern, especially on calcareous soils which are believed to be particularly sensitive to disturbance. This study set out to determine the effects of organic matter removal and compaction on soil quality and seedling productivity on calcareous soils of a localized disturbance landscape (2.25 m 2 ). Here we report ten year post-establishment results of Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco) and lodgepole pine ( Pinus contorta var . latifolia Engelm.) seedlings across four sites in southern British Columbia, Canada with eight treatment levels incorporating different quantities of organic matter removal and soil compaction. Pine seedlings suffered high rates of mortality when planted in deposits across all sites while Douglas-fir seedling mortality was high when planted in compacted undisturbed treatments at two sites and in deposits on the remaining sites. Douglas-fir volume was greatest on the deposit treatment regardless of site but grew significantly better on the non-calcareous site. Pine seedlings outgrew Douglas-fir seedlings and, after ten years, seedlings were largest on a mildly calcareous site. Seedling growth was generally found to be negatively affected by calcareous soils and compaction; however, the specificity of results, in terms of species and site interaction and changing response as the seedlings aged, reinforced the importance of treatment effects on soil quality and forest productivity across the entire length of a stand rotation.

Increased interest in biomass harvesting for bioenergetic applications has raised questions regarding the potential ecological consequences on forest biodiversity. Here we evaluate the initial changes in the abundance, species richness and community composition of rove (Staphylinidae) and ground beetles (Carabidae), immediately following 1) stem-only harvesting (SOH), in which logging debris (i.e., tree tops and branches) are retained on site, and 2) whole-tree harvesting (WTH), in which stems, tops and branches are removed in mature balsam fir stands in Quebec, Canada. Beetles were collected throughout the summer of 2011, one year following harvesting, using pitfall traps. Overall catch rates were greater in uncut forest (Control) than either stem-only or whole-tree harvested sites. Catch rates in WTH were greater than SOH sites. Uncut stands were characterized primarily by five species: Atheta capsularis, A. klagesi, A. strigosula, Tachinus fumipennis/frigidus complex (Staphylinidae) and to a lesser extent to Pterostichus punctatissimus (Carabidae). Increased catch rates in WTH sites, where post-harvest biomass was less, were attributable to increased catches of rove beetles Pseudopsis subulata, Quedius labradorensis and to a lesser extent Gabrius brevipennis. We were able to characterize differences in beetle assemblages between harvested and non-harvested plots as well as differences between whole tree (WTH) and stem only (SOH) harvested sites where logging residues had been removed or left following harvest. However, the overall assemblage response was largely a recapitulation of the responses of several abundant species.

Growth rates of young conifers can be poor on disturbed sites dominated by Kalmia angustifolia L. Hence, a conifer revegetation trial was established on a Kalmia -dominated site to evaluate the effects of various silvicultural options and planted species on selected soil organic layer characteristics. Larix laricina (Du Roi) K. Koch, Pinus banksiana Lamb., and Picea mariana (Mill.) BSP seedlings were planted in plots with or without Kalmia control with herbicides. The effect of fertilizer amendment was also assessed. Seventeen years postplanting, organic layer fertility indicators suggest that soil fertility improved after Kalmia control and conifer reestablishment, especially if nitrogen (N) – phosphorus – potassium fertilizer was also applied. When Kalmia was controlled, aerobically mineralizable N and exchangeable sodium concentrations were increased; fertilizer addition to herbicided plots also increased exchangeable potassium and calcium concentrations, and cation exchange capacity compared with untreated control plots. Conifer height, diameter, and canopy closure were Larix > Pinus > Picea. Kalmia cover in control plots was 87%; Kalmia reinvasion in herbicided plots achieved 40%–43% cover but did not differ among the conifer species. Principal component analysis indicated that aerobically mineralizable N and total N were positively correlated with canopy closure. Our results suggest that increases in organic-layer fertility were related to increased conifer size resulting from Kalmia control.

Salal (Gaultheria shallon Pursh), which is widely used for floral greenery, is an important non-timber forest product (NTFP) from the coastal forests of the Pacific Northwest of North America. However, there are no known studies on the impacts of commercial salal harvesting on subsequent growth. A study was therefore initiated to quantify the growth of salal 1 year after commercial harvesting, and to compare this with growth of unharvested salal. The amount of biomass removed from shrubs through commercial harvesting (131 g m−2) was the same as the amount of annual growth in adjacent undisturbed plots (135 g m−2). One year later, the amount of regrowth in previously harvested plots (144 g m−2) was greater than the amount of new growth in adjacent undisturbed plots (111 g m−2). As there was little difference in the weight per current stem, the increased biomass after commercial harvesting was attributed to the observed increase in stem number (60 stems m−2) as compared to undisturbed salal (50 stems m−2). Our study does not incorporate either repeated annual harvesting or variable harvesting intensities, both of which have been anecdotally reported to affect levels of re-growth and therefore sustainability.

Seedling growth is often hampered on sites dominated by Kalmia angustifolia. In June 2000, a trial was established on a clear-cut site in Quebec, Canada, with a high cover of Kalmia and Vaccinium species. The objectives were to evaluate how soil scarification and fertilization at the time of planting influence early growth and establishment of black spruce [Picea mariana (Mill.) BSP] and jack pine (Pinus banksiana Lamb.) seedlings. During the first 2 years, scarification reduced Kalmia cover three-fold and doubled the distance from seedlings to the nearest Kalmia stem. Scarification did not increase soil-extractable NH4-N concentration, and reduced soil potassium, calcium and magnesium. Scarification had no effect on seedling water stress. Seedling growth improved and foliar nutrient concentrations were generally higher in scarified plots than in unscarified control plots. No differences were observed between single- and double-pass scarification for any variables except for ground-level stem diameter of ...

To determine the nature of the negative influence of Kalmia angustifolia L. on black spruce (Picea mariana (Mill.) BSP) seedling growth and foliar nutrient concentrations, the effect of proximity to Kalmia on spruce seedlings was studied on two Kalmia-dominated sites of contrasting soil characteristics in central Newfoundland. Spruce seedlings and the soil at the base of their stems were sampled, and spruce leader length and foliar N and P concentration, as well as various physicochemical soil characteristics, were determined. Path analysis was used to determine the strength of direct and indirect relationships among variables hypothesized to be causally linked. Path diagrams were generated based on current knowledge of nutrient cycling in boreal ecosystems and mechanisms previously hypothesized to account for the influence of Kalmia on black spruce. On the wetter and richer site, proximity to Kalmia was associated with reduced spruce growth and humus extractable NH4-N, suggesting nutrient competition. On the drier and poorer site, results were consistent with a direct negative effect of Kalmia on the N nutrition of spruce. On both sites, we also found evidence for a direct effect of Kalmia on spruce growth that is consistent with allelopathic effects on spruce function.

The effects of litter quality and climate on decomposition rates of plant tissues were examined using percent mass remaining (MR) data of 10 foliar litter types and 1 wood type during 6 years exposure at 18 upland forest sites across Canada. Litter-quality variables used included initial nutrient contents (N, P, S, K, Ca, Mg) and carbon fractions (determined by proximate analysis and 13C nuclear magnetic resonance spectroscopy). Climate variables used included mean annual temperature; total, summer, and winter precipitation; and potential evaptranspiration. A single-exponential decay model with intercept was fit using the natural logarithm of 0- to 6-year percent MR data (LNMR) for all 198 type by site combinations. Model fit was good for most sites and types (r2 = 0.64–0.98), although poorest for cold sites with low-quality materials. Multiple regression of model slope (Kf) and intercept (A) terms demonstrated the importance of temperature, summer precipitation, and the acid-unhydrolyzable residue to N ratio (AUR/N) (r2 = 0.65) for Kf, and winter precipitation and several litter-quality variables including AUR/N for A (r2 = 0.60). Comparison of observed versus predicted LNMR for the best overall combined models were good (r2 = 0.75–0.80), although showed some bias, likely because of other site- and type-specific factors as predictions using 198 equations accounted for more variance (r2 = 0.95) and showed no bias.

Mechanisms responsible for conifer growth “check” on cutovers invaded by Kalmia angustifolia L. in central Newfoundland were studied by examining effects of added Kalmia and balsam fir ( Abies balsamea (L.) Mill) condensed tannins on black spruce humus N dynamics and microbial community development over 10 weeks using microcosms. Because of the silvicultural implications, interactions of tannins with fertiliser N, applied as (NH 4 ) 2 SO 4 , were also studied. Both tannin types significantly reduced NH + 4 –N leaching, whereas only Kalmia tannins reduced NO − 3 –N leaching, and then only from non-fertilised humus. Tannins did not significantly affect mineral N leaching from fertilised humus. Fertiliser N increased gross N mineralisation rates such that the increase in actively cycling N was many times greater than the increase in N leaching due to fertiliser N addition. Gross N mineralisation rates were higher in fertilised humus amended with tannins, suggesting possible toxicity of tannins on microbes at high N concentrations. Recovery of added tannins in leachate and in post-treatment humus samples was low. Net anaerobic N mineralisation decreased with tannin additions but increased with fertiliser N additions. There were few significant treatment effects on microbial properties derived from humus respirometry. Microbial biomass and basal respiration rates of all treatments declined by 30 and 37% respectively, indicating a general loss of available C during the experiment. The ratio of C mic -to-N mineralised as well as the nutrient deficiency index was lowest in humus amended with Kalmia tannins, suggesting higher microbial N deficiency in this treatment. Utilisation rates of various C sources by microbial communities showed distinctive patterns between pre-treatment and post-treatment humus samples, but did not reveal distinctive patterns among different treatments. Overall, results suggested that (1) condensed tannins decreased mineral N cycling abiotically by binding to and sequestering organic N sources, (2) fertiliser N counteracted negative effects of condensed tannins on humus N cycling, (3) microbial communities were N limited, which prevented abundant leaching of fertiliser N while maintaining fertiliser N in an active pool, and (4) the physiology and functional diversity of soil heterotrophic communities were controlled by C availability but were unaffected by tannin or fertiliser N additions. Further work is needed to determine the ecological importance of Kalmia tannins, relative to tannins produced by other plants, in reducing humus N availability on spruce cutovers.

The effects of conventional stem-only and whole-tree harvesting on nutrient losses in biomass removal and in leachate fluxes over a 3-yr period after cutting three white birch stands in central Newfoundland were determined. Losses of nutrients in biomass were proportionately greater with more intensive harvesting as tree components with higher nutrient concentrations (branches, foliage) were removed. Stem-only harvesting removed 126, 9, 51, 126 and 23 kg ha–1 of N, P, K, Ca and Mg in biomass, respectively. Whole-tree harvesting led to a 19% increase in biomass removal as compared to stem-only harvesting, but nutrient removals with whole-tree harvesting increased by 127% for N, 138% for P, 151% for K, 72% for Ca and 90% for Mg. Nutrient losses in deep percolation of soil solution during the first 3 yr after harvesting were generally greater following stem-only than whole-tree harvesting. This may be the result of increased leaching from slash, increased mineralization beneath slash, and retardation by slash of the successional vegetation that could act as a nutrient sink. In the first 3 yr following harvesting, leaching losses after whole-tree harvesting were 4, 0.2, 8, 23 and 7 kg ha–1 of N, P, K, Ca and Mg, respectively, as compared with 9, 0.1, 7, 28 and 9 kg ha–1 of N, P, K, Ca and Mg after stem-only harvesting. Nutrient losses in leachate were generally small compared to losses in biomass removal. Key words: Intensive harvesting; slash; nutrient budget; sustainable site productivity; Betula papyrifera (Marsh.)

The influence of NPK-fertilizer on decomposition of litter layers and deposited logging residues (brash) on a clearfelled Sitka spruce stand was followed during two years by zero-tension lysimetry and litterbags. Root development of second rotation planted trees on this peaty gley soil are restricted to the litter layers (LFH) and without fertilizer are dependent on its decomposition for release of nutrients. A comparison of fertilized and control plots showed few site differences and similar hydrological properties.