Whole-tree Harvesting Research Articles

How Can Local Environmental Planning Affect Forest Soil Acidity? A Case Study in Stockholm, Sweden

The objective of this study is to assess how local planning can influence the acidity in the upper forest soil layer. Exceedance of soil acidity was determined by a steady-state mass balance model approach in relation to both present and future deposition. Future deposition scenarios were derived for Stockholm County based on transportation planning. Europe-wide scenarios were derived using the RAINS (Regional Air Pollution Information and Simulation) model. The deposition changes were assessed in relation to two different types of forest harvesting practices: whole-tree harvesting; and stem harvesting. The results demonstrate that local emission reductions combined with tree stem harvesting give the greatest remediation of soil acidity. This implies that forest soil acidity can be introduced as an indicator in local environmental planning.

Pile Movement and Nutrient Distribution in the Soil around Slash Piles Produced during Whole-tree Logging by a Yarder and a Processor

After mechanized whole-tree harvesting at a clear cutting site, using a cable yarding system and a processor, piles of slash remain at the landing areas near roads. This study examined the movement of slash piles and their effect on soil nutrients in the ground below the pile. The profile of one pile was measured for three years. In order to investigate nutrient concentrations, soil was sampled at two sites. The volume of the pile decreased by 6% per year. Piles placed on convex or uniform hillsides are stable, and have a low risk of sliding on a slope. Analysis of the water-soluble nutrients in the soil suggests that water carries nutrients from the pile into the soil up to ca. 7 m from the pile. There is a reduction in soil acidity, and rainwater flow from the pile adds several minerals to the soil, particularly Ca. Slash in a pile on a convex or uniform hillside does not have any impact on a forest, either positively or negatively. We should try to return slash to stands or utilize it as a biomass resource.

Molecular characterization of bacterial diversity in Lodgepole pine (Pinus contorta) rhizosphere soils from British Columbia forest soils differing in disturbance and geographic source

Rhizosphere bacteria from Lodgepole pine (Pinus contorta) seedlings were characterized from forest soils which differed in disturbance and geographic source. Soil disturbance treatments included whole-tree harvesting with and without heavy soil compaction and whole-tree harvesting with complete surface organic matter removal and heavy soil compaction from British Columbia (BC) Ministry of Forests Long-Term Soil Productivity installations in three biogeoclimatic subzones in central BC, Canada. Bacterial community members were characterized by DNA sequence analysis of 16S rRNA gene fragments following direct DNA isolation from soil, polymerase chain reaction amplification and cloning. Phylogenetic analyses revealed that 85% of 709 16S rDNA clones were classified as alpha-, beta-, gamma-, and delta-Proteobacteria, Actinobacteria, Cytophaga-Flexibacter-Bacteroides group, Acidobacterium, Verrucomicrobia, and candidate divisions OP10 and TM6. Members of the Proteobacteria and Acidobacterium represented 55% and 19% of the clone library, respectively, whereas the remaining bacterial divisions each comprised less than 4% of the clone library. One hundred and six 16S rDNA clones could not be classified into known bacterial divisions. No significant differences were detected for soil disturbance treatment or site effects on the proportions of 16S rDNA clones affiliated with Proteobacteria and Acidobacterium. Phylogenetic analyses revealed that it was common for 16S rRNA gene fragments from different soil disturbance treatments and geographic locations to be closely related.

Molecular characterization of bacterial diversity in Lodgepole pine ( Pinus contorta) rhizosphere soils from British Columbia forest soils differing in disturbance and geographic source

Rhizosphere bacteria from Lodgepole pine ( Pinus contorta) seedlings were characterized from forest soils which differed in disturbance and geographic source. Soil disturbance treatments included whole-tree harvesting with and without heavy soil compaction and whole-tree harvesting with complete surface organic matter removal and heavy soil compaction from British Columbia (BC) Ministry of Forests Long-Term Soil Productivity installations in three biogeoclimatic subzones in central BC, Canada. Bacterial community members were characterized by DNA sequence analysis of 16S rRNA gene fragments following direct DNA isolation from soil, polymerase chain reaction amplification and cloning. Phylogenetic analyses revealed that 85% of 709 16S rDNA clones were classified as α-, β-, γ-, and δ-Proteobacteria, Actinobacteria, Cytophaga- Flexibacter- Bacteroides group, Acidobacterium, Verrucomicrobia, and candidate divisions OP10 and TM6. Members of the Proteobacteria and Acidobacterium represented 55% and 19% of the clone library, respectively, whereas the remaining bacterial divisions each comprised less than 4% of the clone library. One hundred and six 16S rDNA clones could not be classified into known bacterial divisions. No significant differences were detected for soil disturbance treatment or site effects on the proportions of 16S rDNA clones affiliated with Proteobacteria and Acidobacterium. Phylogenetic analyses revealed that it was common for 16S rRNA gene fragments from different soil disturbance treatments and geographic locations to be closely related.

Effects of crushed wood ash on soil chemistry in young Norway spruce stands

The use of logging residues as a fuel in district heating plants has led to regular wood ash recycling to forest soil to prevent soil nutrient depletion. Wood ash with a low content of unburnt matter reacts with water and air in a so-called self-hardening process. Hardening of the ash is a way to reduce its reactivity and thus increase the time for its dissolution. In four field experiments, changes in soil chemistry were analyzed 6 years after application of hardened crushed wood ash to 8–10-year-old Norway spruce ( Picea abies (L.) Karst.) stands. The 0–5, 5–10 and 10–20 cm layers of the soil were sampled, including the disturbed humus layer. Logging residues were collected at the preceding harvest. At each site, hardened crushed wood ash of two types, Nymölla and Perstorp, was applied in a randomized block design ( n=4). The dose applied was 3 Mg ha −1. Exchangeable Ca, Mg, K and effective cation exchange capacity (CEC eff) on a per hectare basis in the 0–20 cm soil layers were significantly higher in wood ash-treated plots than in the control plots in analyses across all study sites. Total exchangeable acidity was significantly lower after wood ash application. There was a significant effect on pH in the 0–5 cm layer of the soil in three of the sites, where pH increased on average by 0.5 units in wood ash Perstorp-treated plots and by 0.7 units in wood ash Nymölla-treated plots compared to control plots. Further down in the soil profile, no differences were detected at any site. Wood ash application resulted in a higher level of base saturation (BS), especially in the 0–5 cm layer. BS increased on an average by 39 and 31% units in the 0–5 cm soil layer, and by 13 and 10% units in the 5–10 cm soil layer, in wood ash Nymölla- and Perstorp-treated plots, respectively, compared with the control. The results show that hardened wood ash recycling can compensate for base cations lost at whole-tree harvesting.

Survival, growth, and growth allocation of planted Scots pine trees after different levels of biomass removal in clear-felling

A great concern in forestry today is whether whole-tree harvesting influences site productivity and whether it is consistent with the principle of sustainable use of forest resources. To evaluate this a randomised field experiment established 24 years ago in Scots pine ( Pinus sylvestris L.) in southern Sweden was used. Treatments were conventional stem harvest (CH), whole-tree harvest (WTH), and branch and stem harvest (BSH). Seedling survival was unaffected by treatments. The total basal area over bark at breast height (1.3 m, m 2 ha −1) was significantly reduced following WTH from the 15th year after planting. Sample trees on CH plots produced 20% more wood biomass than WTH and BSH plots, while biomass produced within the crown was unaffected by treatment. Height growth was greater for sample trees on CH plots during the last year of measurement, while basal area and volume under bark were larger from the 12th year onwards when compared with the WTH treatment. BSH showed a decreased basal area growth under bark during the two 4-year-periods, 13–16 and 17–20 years after planting, and a decreased volume growth under bark from year 9 onwards in comparison with CH. Radial growth was increased for CH up to 3 m of the stems during the 9–12-year period and at 3 m during the 13–16-year period in comparison with the other two treatments. The implications of the results are discussed in terms of long-term site productivity and overall silvicultural outcome.

Restoration cutting as a management tool for regenerating Pinus banksiana after ice storm damage

In January 1998, an ice storm caused extensive and severe crown damage to the rare Pinus banksiana– P. rigida barrens in northeastern New York. These barrens contain some of the southernmost populations of P. banksiana and northernmost populations of P. rigida in the eastern US. Because P. banksiana showed particularly severe damage compared to P. rigida, and P. banksiana regeneration is absent or sparse in these stands, there is concern that P. banksiana importance may be dramatically reduced in severely damaged stands. In an attempt to reduce the risk of wildfire and to regenerate P. banksiana in such stands, restoration cuttings were completed in 1998 and 1999. Restoration cutting consisted of whole-tree harvesting (i.e. harvest of boles and attached branches) of nearly all standing trees, while branches and attached cones broken during the ice storm were left on-site as a seed source. In restoration cuttings, there were 23,400–39,800 P. banksiana seedlings/ha 2 years after harvesting, while few or no P. banksiana seedlings were observed in uncut damaged stands. P. banksiana seedling densities were several times as high in plots with evidence of soil scarification than in unscarified plots (54,000–63,600 and 12,100–30,300 P. banksiana seedlings/ha, respectively). Regeneration was positively related to cone density and negatively related to shrub and herbaceous species percent cover (e.g. R=0.30 and −0.55, respectively, for the 1999 cut), indicating the importance of even dispersal of cone-bearing slash and the reduction of competing vegetation. Restoration cutting can be used to regenerate P. banksiana in stands severely damaged by ice storms or other canopy disturbances (e.g. blowdown) if soils are adequately scarified and harvesting is conducted within a few years after canopy damage.

Modelling the influence of harvesting on Chinese boreal forest carbon dynamics

Chinese boreal forests, geographically distributed in the Daxinganling Mountains of northeastern China, are the most southern part of the global boreal forest biome. The dominant species is larch ( Larix gmelinii) with other major species including birch ( Betula platyphylla), pine ( Pinus sylvestris var. mongolica) and oak ( Quercus mongolica). In this study, the terrestrial ecosystem process model CENTURY 4.0 was used to investigate the influence of different harvest disturbance regimes on the carbon stocks and fluxes of Chinese boreal forest ecosystem relative to a natural disturbance regime. Managed disturbance regime scenarios examined include harvesting intensity (no biomass removal (NBR), conventional harvesting (CH) and whole tree harvesting (WTH)) and rotation length (from 30 to 400 years). Field data were assembled from three forest regions (Xinlin, Tahe and Mohe), representing the northern, middle and southern parts of the Chinese boreal forest, respectively. The results presented in this study indicate that biomass, litter and soil carbon stocks (averaged over a rotation period) can be elevated significantly by suppression of all disturbances (NBR scenario) but are lowest under the most intense harvest scenarios (WTH). Harvest rotation length had a significant influence on carbon stocks (biomass, litter and soil carbon); the lowest simulated carbon stocks were found with the shortest rotations, and relatively higher stocks under longer rotations. Net primary production (NPP) decreased with increasing harvest intensity or decreasing rotation length. Net ecosystem production (NEP) decreased with decreasing harvest intensity or decreasing rotation length. NPP and NEP reach maximum values at rotation lengths of about 200 and 100 years, respectively. Observations and simulated data for ecosystem carbon stocks (biomass, litter and soil carbon) and carbon fluxes (NPP and NEP) in the southern region were slightly higher than those in the mid- and northern regions. The high productivity and biomass of the Chinese boreal forests relative to those of Canada, USA and Russia, are likely due to their southerly location: warm temperature and adequate precipitation create good conditions for forest development and growth . Nevertheless, the long history of forest use by human has resulted in much of the boreal forest in China landscape being in less than a primary state.

Assessing the geochemical balance of managed boreal forests

Abstract A sustainable forest management system requires that a balance must be reached between ecosystem nutrient losses and gains in the course of a rotation. In order to determine the influence of stand characteristics (species composition, density, site potential productivity), method of forest harvesting (stem-only versus whole-tree) as well as rotation length on nutrient losses induced by biomass harvesting, a geochemical balance (nutrient inputs minus outputs) was computed from published information and forest inventory databases for the southern portion of the boreal forest of Quebec. Losses were compared with potential nutrient gains that varied according to soil types. We provided a tool for assessing the risk of having a negative nutrient budget (outputs>inputs) that forest managers can use with information that is already available to them. This exercise was conducted for five commercial tree species, namely paper birch (Betula papyrifera Marsh.), aspen (Populus tremuloides Michx.), balsam fir (Abies balsamea (L.) Mill.), jack pine (Pinus banksiana Lamb.), and black spruce (Picea mariana (Mill.) B.S.P.), grouped into four site indexes and three stand density classes. Strong differences in nutrient exportation in biomass appeared between stands of different compositions as well as between stands of the same species but of different classes of productivity or density. The most nutrient-demanding tree species were trembling aspen and balsam fir. As expected, whole-tree harvesting caused a greater drain on nutrient reserves than stem-only harvesting, but this effect varied strongly with tree species and was greatest for balsam fir and lowest for jack pine. Harvesting the forest before or after the age of financial maturity, which might be desirable under some circumstances, generally created a lesser nutrient drain but this was at the expense of biomass production. Aspen was an exception to this rule showing a greater nutrient drain for stands harvested prior to the age of financial maturity. Implications for the development of indicators of sustainable forestry and for future research are discussed.

Molecular characterization of bacterial diversity from British Columbia forest soils subjected to disturbance.

Bacteria from forest soils were characterized by DNA sequence analysis of cloned 16S rRNA gene fragments (16S clones). Surface organic matter and mineral soil samples from a British Columbia Ministry of Forests Long-Term Soil Productivity (LTSP) installation were collected during winter and summer from two disturbance treatments: whole-tree harvesting with no soil compaction (plot N) and whole-tree harvesting plus complete surface organic matter removal with heavy soil compaction (plot S). Phylogenetic analyses revealed that 87% of 580 16S clones were classified as Proteobacteria, Actinobacteria, Acidobacterium, Verrucomicrobia, Bacillus/Clostridium group, Cytophaga-Flexibacter-Bacteroides group, green nonsulfur bacteria, Planctomyces, and candidate divisions TM6 and OP10. Seventy-five 16S clones could not be classified into known bacterial divisions, and five 16S clones were related to chloroplast DNA. Members of Proteobacteria represented 46% of the clone library. A higher proportion of 16S clones affiliated with y-Proteobacteria were from plot N compared with plot S. 16S rRNA gene fragments amplified with Pseudomonas-specific primers and cloned (Ps clones) were examined from mineral-soil samples from plots N and S from three LTSP installations. A significantly greater proportion of sequenced Ps clones from plot N contained Pseudomonas 16S rRNA gene fragments compared with Ps clones from plot S.

Cultivation-dependent characterization of bacterial diversity from British Columbia forest soils subjected to disturbance.

Bacteria from forest surface organic matter and mineral soil horizons were cultivated using four methods and characterized by fatty acid methyl ester (FAME) analysis. Soil samples from a British Columbia Ministry of Forests Long-Term Soil Productivity (LTSP) installation were collected during winter and summer from two disturbance treatments (whole-tree harvesting with no soil compaction (plot N) and whole-tree harvesting plus complete surface organic matter removal with heavy soil compaction (plot S)) and from an unlogged reference plot (REF). Seventy-five percent of 1795 bacterial isolates were affiliated with 42 genera representing beta- and gamma-Proteobacteria, Actinobacteria, the Bacillus/Clostridium group, and the Cytophaga-Flexibacter-Bacteroides group. Approximately half of the culture collection represented genetic diversity confined to four bacterial genera: Pseudomonas, Bacillus, Paenibacillus, and Arthrobacter. A significantly higher proportion of bacterial isolates belonging to Actinobacteria, and the member genus Arthrobacter, were isolated from plot S soil samples compared with soil samples from plots N and REF. Twenty-five percent of bacterial isolates were not conclusively identified to genus with FAME analysis. Sherlock Tracker cluster analysis and partial 16S rRNA gene sequence analysis enabled classification of a subset of these isolates.

Productivity and Cost of Mechanized Whole-Tree Harvesting of Fast-Growing Eucalypt Stands

The performance of alternative equipment for the whole-tree harvesting of eucalypt stands was evaluated, using data from five different commercial operations. The study covered three machines for felling and bunching, two for extraction (skidding), and two for combined delimbing, debarking and chipping. Productivity and operating cost models were evaluated for each of the machines, in order to estimate the net harvesting costs under varying forest stand and site conditions. It was found that under easy terrain conditions (flat terrain, dry ground), trees should be felled by threewheeled feller-bunchers and extracted by front-end loaders, as this combination had the lowest harvesting costs. Due to mobility limitations, this equipment may have to be replaced by tracked feller-bunchers and conventional skidders in steep terrain and/or soft ground. It was estimated that the cost of using the wheeled feller-buncher and the front-end loader system ranged between 16–22$ per oven-dry-ton (odt), depending on tree size. If difficult terrain imposes a shift towards the second, more expensive combination, harvesting cost will increase by about 30% and may exceed 25 $/odt for an average tree weight less than 0.1 odt. Unit costs are inflated by 30% if the hog fuel is considered a by-product and the harvesting cost is charged entirely on the clean chip.

Effects of harvesting regimes on carbon and nitrogen dynamics of boreal forests in central Canada: a process model simulation

The effects of different harvesting intensities and rotation lengths on the long-term carbon (C) and nitrogen (N) dynamics of boreal forests in central Canada were simulated using the process-based ecosystem model century 4.0. Three harvesting intensities and four rotation lengths were investigated. Results suggest that intensive harvesting regimes (e.g. whole-tree harvesting (WTH)) would decrease total ecosystem C, soil C storage, and N availability, compared with conventional harvesting (CH). Harvested biomass would increase with increasing harvesting intensity. Net loss of forest productivity (indicated by above-ground biomass) would be higher in higher productivity stands in the low boreal ecoclimatic region. For a given harvesting intensity, total ecosystem C stock and N availability would be highest with long rotations (120 years) and reduced under shorter rotations (60 and 30 year). Extremely short rotations (i.e. 30 year) would reduce boreal forest productivity by as much as 65%. Longer rotations and less intensive harvesting could increase C sequestration about 36–40% in the boreal forest region of central Canada.

Stand and site productivity response following whole-tree harvesting in early thinnings of Norway spruce ( Picea abies (L.) Karst.)

Two field experiments were established on nutrient poor, sandy soils in Klosterheden National Forest and in Mangehøje Forest Plantation in western Denmark to quantify the effect on site productivity of whole-tree harvesting in early thinnings of Norway spruce. The growth response following biomass removal was investigated for four treatments: (1) no thinning (NT), (2) whole-tree harvesting in which the felled trees were removed immediately after thinning (WTH green), (3) whole-tree harvesting in which the felled trees were left to dry in the stand during the following growing season so that some of the nutrient rich parts of the tree such as needles and twigs are returned to the forest floor (WTH dry), and (4) harvesting of stems and coarse branches with needles and twigs being threshed from the branches and left in the stand (SCB). The results indicated that WTH green might lead to a short-term reduction in stand volume increment of the remaining stand. Comparing the mean annual increment during the first four growing seasons after treatment, using the initial standing volume as a covariate, WTH green caused a significant growth reduction of 10–18% at Klosterheden and 5–17% at Mangehøje, compared to the SCB- and WTH dry-treatments. The effect of WTH green was attributed to an increased removal of essential nutrients such as N, P and K. The growth response following whole-tree harvesting was confined to the first four growing seasons and the effect of different treatments was not significant when data for all ten growing seasons were analysed.

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.

Effects of soil acidification and liming on ground flora establishment after clear-felling of Norway spruce in Sweden

We used 2 long-term field experiments with Norway spruce Picea abies (L.) Karst. to investigate the influence of lime, acid sulphur compounds, or nitrogen (1 site) on the rate of recruitment of new vascular species after clear-fellings. On the study sites, Farabol in southern Sweden and Fäxboda in south–central Sweden, the chemical treatments had been applied before clear-felling and whole-tree harvesting. An additional, post-harvest experiment was conducted at Farabol in which lime, hardened wood-ash, or logging residues were applied. A germination experiment including seven species was carried out in a greenhouse using sifted humus from Fäxboda that was sampled 2 years before clear-felling. The clear-fellings resulted in establishment of many ephemeral species. The number of newly established species was greater than the number of disappeared species. There was an overall positive correlation with pH in the humus layer and the number of newly established species. The treatment effects differed between the sites, probably reflecting differences in total dose and initial soil conditions. Farabol is characterised by more acid soils and greater atmospheric deposition of S and N than Fäxboda. At Farabol, liming (in total 6000 kg limestone ha −1 distributed over 12 years) resulted in about 20 new species established after clear-felling, four times more species than in untreated, sulphur-treated, or nitrogen-fertilised plots. At Fäxboda, where lime (2000 kg dolomite ha −1), sulphuric acid, and elementary S had been applied 16 years before clear-felling, the number of newly established species was about 15, and no effect of the treatments was revealed. The post-harvest treatments at Farabol showed that wood-ash and logging residues had similar effects as lime on the establishment of new species. The pot experiment showed that liming or acidification can affect the germination of seeds. Compared with untreated soil, a greater proportion of seeds of Primula veris ( P. veris) and Senecio sylvaticus ( S. sylvaticus) germinated in limed soil and the germination of P. veris was lower in acid- or sulphur-treated soils. The germination of Vaccinium myrtillus ( V. myrtillus) seeds was negatively affected by liming. No effects of the treatments were discovered on the germination of Deschampsia flexuosa, Calamagrostis arundinacea, Galeopsis bifida ( G. bifida), or Poa nemoralis. The soil water in the pot experiment had higher pH, higher concentrations of Ca and Mg, and higher NO 3 −/NH 4 + ratios in limed soil compared with other treatments. Nomenclature of plants follows Lid (1985).

Impacts of intensive forestry on early rotation trends in site carbon pools in the southeastern US

The effects of different silvicultural practices on site, especially soil, carbon (C) pools are still poorly known. We studied changes in site C pools during the first 5 years following harvesting and conversion of two extensively managed pine-hardwood stands to intensively managed loblolly pine plantations. One study site was located on the lower Atlantic Coastal Plain in North Carolina (NC) and another on the Gulf Coastal Plain in Louisiana (La). Four different harvesting-disturbance regimes were applied: stem only harvest (SO), whole tree harvest (WT), whole tree harvest with forest floor removal (WTFF), and full amelioration, i.e. whole tree harvest, disking, bedding and fertilization (FA; only in NC). Each harvesting-disturbance regime plot was split and one-half received annual herbicide treatments while the other half received no herbicide treatments. In NC, soil C decreased slightly with WT, and increased with FA, otherwise no significant changes were detected. In La, there was a consistent decrease in soil C content from the pre-harvest value in all cases where herbicides were applied. All treatments caused a reduction in the forest floor C pool in NC. In La, the most intensive treatments also resulted in a decrease in the forest floor C, but to a smaller extent. In contrast, there was no net change in forest floor C with the SO and WT treatments, even though significant amounts of logging slash were added to the forest floor at harvest in the SO plots and not in the WT. Herbicide treatment clearly decreased the C pool of hardwoods and understory, and more than doubled that of planted pines. Carbon accumulation in the planted pines was similar for trees growing in the SO, WT, and WTFF treatments on both the LA and NC sites. The full amelioration treatment (only applied at the NC site) led to a significant increase in C sequestration by the planted pine component. Due to a large amount of voluntary pines, total 5-year pine C pool was highest on the non-herbicided intensive management plots on the NC site, however. The differing response patterns of soil and forest floor C pools between the two sites may be due to their differing drainage-summer rainfall regimes. Our results suggest that while poor drainage-wet summer conditions may be impeding carbon loss from the soil component it may be accelerating the rate of decomposition of the forest floor and slash on the soil surface.

Needle chemistry in young Norway spruce stands after application of crushed wood ash

Nutrient concentrations in current and 1-year-old needles were analyzed annually for 5 years after application of hardened wood ash in 1–4-year-old Norway spruce (Picea abies (L.) Karst.) stands within a range of climate and fertility gradients. At each site, 3000 kg ha−1 hardened wood ash of two types, Nymolla and Perstorp, was applied in a randomized block design. Wood ash Nymolla contained 12 kg ha−1 P, 30 kg ha−1 K, 891 kg ha−1 Ca, 72 kg ha−1 Mg and wood ash Perstorp contained 12 kg ha−1 P, 60 kg ha−1 K, 486 kg ha−1 Ca, and 60 kg ha−1 Mg. The ash was intended to compensate for nutrients removed at the preceding harvest when logging residues were collected and removed from the site (whole-tree harvesting). The climate gradient included four climate zones throughout Sweden and each of these included a fertility gradient of three sites classified according to their ground vegetation type. There were no effects on nutrient concentrations in the needles 1 year after the application of wood ash. Five years after ash application, the concentrations of P, K and Ca in current and 1-year-old needles were higher than in the control plots. The results were consistent over all stands, irrespective of climate zone and fertility status. P and K concentrations were higher in spruce needles from plots treated with Perstorp wood ash, whereas Ca concentrations were higher in those of Nymolla treated plots. Analyses across all study sites revealed a treatment effect in terms of increased ratios of P:N, K:N and Ca:N in 1-year-old needles. The ratio P:N tended to increase with time in the Perstorp wood ash treatment compared with the control. The needle concentrations of Mg and S were not affected by the ash applications. The increase in needle nutrient concentrations after application of hardened wood ash suggests that wood ash recycling could be used in order to replace nutrients removed at whole-tree harvesting.

Damage to Residual Trees by Four Mechanized Harvest Systems Operating in Small-Diameter, Mixed-Conifer Forests on Steep Slopes in Northeastern Washington: A Case Study

Abstract Dense stands of small-diameter timber present unique challenges for land managers. In the inland West, trees in high-density stands often grow slowly and may be at risk to insects, diseases, and catastrophic fires. In 1996, the U.S. Congress recognized a need to address forest health issues and stimulate local resource-based economies in northeastern Washington. Funds were provided for “implementation and evaluation of controlled silvicultural treatment in designated, fire-generated, overstocked, small-diameter stands” (U.S. Congress House Report 104-625). As part of this Congressionally mandated research effort, four harvest units, each thinned to a 20 ft spacing using different harvesting technologies, were surveyed for damage prior to and following commercial thinning. Comparisons were made among the systems tested to assess damage to the residual stand. Overall incidence of wounds, incidence of wounds in different size and severity classes, and wound locations were compared. Each system performed better when judged by some criteria than by others. In general, cut-to-length processing caused less damage to the residual stand than whole-tree harvest; skyline yarding was less damaging than forwarder yarding. Some of the damage may have been a function of the silvicultural prescription and season of harvest. Appropriate silvicultural prescriptions and harvesting technologies can reduce wounding to acceptable levels. West. J. Appl. For. 17(1):14–22.

Soil organic matter fractions in experimental forested watersheds

Recent concerns about climate change and atmospheric greenhousegas concentrations have demonstrated the importance ofunderstanding ecosystem C source/sink relationships. Soilorganic matter fractionation was carried out in three paired,forested watershed sites where one of each watershed pairrepresented a different ecosystem perturbation. Theperturbations were 8 years of experimental N amendments at theBear Brook Watershed in Maine (BBWM), a 50 year old intensewildfire and subsequent regeneration at Acadia National Park(ANP), and a 17 year old whole-tree harvest at the Weymouth PointWatershed (WPW). At each site, mineral soils were sampled byuniform depth increments. Mineral soil (< 2 mm) was separatedinto light, occluded light, and heavy density fractions byfloatation in NaI solution (1.7 g cm-3). Mineral soil (< 2mm) was also separated into particle-size fractions of sand (2.0to 0.05 mm), silt (0.05 to 0.002 mm), and clay (< 0.002 mm) bywet sieving and centrifugation. Whole soils, and density andparticle-size fractions were analyzed for total C and N. Bothfractionation schemes showed that all soil organic matterfractions had lower C/N ratios as a result of N enrichment atBBWM. At ANP, soil organic matter fractions generally had lowerC/N associated with the wildfire and subsequent shift fromsoftwood to hardwood regeneration. Few significant whole soiland soil organic matter fraction differences were associated withthe whole-tree harvest. Within watershed pairs, both density andparticle-size fractionation techniques usually indicated similarresponses. Soil organic matter fractionation results indicatedthat there were no consistent shifts in fraction distributions inresponse to perturbation that were consistent across all pairedwatershed study sites.