Full-tree Harvesting Research Articles

Cradle-to-gate life cycle analysis of slow pyrolysis biochar from forest harvest residues in Ontario, Canada

Climate change mitigation technologies have been a focus in reducing atmospheric carbon levels for the past few years. One such mitigation technology is pyrolysis, where biomass feedstocks are combusted at elevated temperatures for varying durations to produce three main products: biochar, bio-oil, and biogas. While bio-oil and biogas are typically used to produce energy via further combustion, biochar can be used in several different applications. Furthermore, using forest harvest residues as a feedstock for biochar production helps use excess biomass from the forestry industry that was previously assumed unmarketable. In our study, we combined forest carbon analysis modelling with cradle-to-gate life cycle emissions to determine the greenhouse gas emissions of biochar produced from forest harvest residues. We examined three collection scenarios, spanning two harvesting methods in one forest management unit in northern Ontario, Canada. From our analysis, we observed immediate reductions (− 0.85 tCO2eq·tbiochar−1 in year 1) in CO2-equivalent emissions (CO2eq) when producing biochar from forest harvest residues that would have undergone controlled burning, without considering the end use of the biochar. For the forest harvest residues that would remain in-forest to decay over time, producing biochar would increase overall emissions by about 6 tCO2eq·tbiochar−1. Throughout the 100-year timeframe examined–in ascending order of cumulative emissions–scenario ranking was: full tree harvesting with slash pile burn < full tree harvesting with slash pile decay < cut-to-length/tree-length harvesting.Graphical

Boreal forest soil biotic communities are affected by harvesting, site preparation with no additional effects of higher biomass removal 5 years post-harvest

The market for forest products has diversified to include biomass energy products sourced from materials that were typically left on-site after harvest. In this study we examined whether intensified biomass removal following harvest will effect site soil biological diversity and metabolic functioning, and how decisions surrounding sampling, in sites prepared with disc-trenching soil scarification, influence the effect assessment of harvesting activities. We compared the influence of harvesting, below-ground biomass removal, stem only versus full tree harvesting, micro-topographic features and seasonal effects on soil biota. We assessed soil biotic changes using potential enzyme activity assays and metabarcoding using targeted primers for four groups (arthropods, bacteria, fungi and broad eukaryotes). We found that harvesting and forest floor removal had strong influences on soil biotic communities, with changes that generally favoured more general soil saprotrophy and reductions in plant-associated organisms. Disc-trenching created differences between micro-topographic features where organic soil was redistributed and trenches, where it was removed. We found no significant difference to how seasonal variation effected communities in harvested sites, compared to unharvested sites. These results show that there is significant site heterogeneity due to disc scarification, and that the sampling micro-topographic features should be considered during study design. Additional studies are needed to assess the effects of higher biomass removal on these features as these sites age.

Forest road density in flat and sloping site conditions in Brazil

ABSTRACT Forest road densities which are too high increase production costs, planting area loss, and environmental impacts. To solve this problem and plan an adequate forest road density, it is necessary to analyze and consider the topography, road network-related costs, and the type and number of machines to meet the required wood production. The aim of this study was to determine the current road density (RD), the optimal economic road density (ORD) and operational road density (OD) in flat and sloping site conditions for the full tree harvesting system in Southern Brazil. The RD was determined by the ratio of total road lengthand the total productive area. ORD was determined based on the transport geometry model, considering the minimization of the sum of unit costs of road construction and maintenance, loss of productive area, mitigation of road impacts, and wood extraction. The OD was determined considering the minimum number of extraction machines necessary to meet the annual demand for wood. All forest road densities were lower in flat site conditions than in sloping areas. In both conditions (flat and sloping), RDs (126 and 180 m ha−1, respectively) were higher than ORDs (53 and 65 m ha−1, respectively), which were lower than ODs (92 and 123 m ha−1, respectively). Therefore, OD can be an alternative parameter for managers to use in forest road network planning, mainly in conditions where ORD is not feasible to adopt.

Effects of harvesting intensity, vegetation control and fertilization on 5–20 year post-harvest N availability in boreal jack pine and black spruce forest soils in northern Ontario, Canada

The impact of harvesting intensity, vegetation control and fertilization on soil N availability 5–20 years post-harvest was determined at 18 jack pine and black spruce forests in northern Ontario, Canada. The study sites are affiliated with the North American long-term soil productivity (LTSP) study. Boreal forest growth is commonly N limited and young stands approaching crown closure acquire most of their N from the soil. The study sites represented a range of soil types and were harvested with three levels of organic matter removal (stem-only harvest, full-tree harvest and full-tree harvest with organic horizon removal by blading). Three study sites had multiple applications of glyphosate to control competing vegetation and one site included a trial with two applications of N, P, K fertilizer to the full-tree harvest treatment. We used short-term anaerobic laboratory incubations and in-situ closed top tube growing season incubations to determine mineralizable N and net N mineralization, respectively. Profile (organic plus mineral horizons) mineralizable N pools were higher in operational clearcut (stem-only and full-tree harvesting) treatments compared to the uncut reference forest 10–14 years post harvest. Full-tree harvesting with blading significantly reduced profile mineralizable N pools at this time compared to operational harvesting, while the same treatment at one upland site also reduced net N mineralization pools. Profile mineralizable N pools and microbial biomass C and N were lower in full-tree compared to stem-only harvesting treatments, suggesting that increased slash retention with stem-only harvesting was playing a role in enhanced soil N availability at a time when plantations were approaching a period of greater N demand. Fertilization and vegetation control treatments had few effects on N indices, although net N mineralization pools for the stem-only and full-tree harvest that also had the repeated herbicide treatment were consistently, but not significantly, lower than non-herbicided treatments. Soil N indices were useful predictors of dominant height growth for jack pine to a greater degree than for black spruce, and soil N concentrations were as effective at predicting height growth as more resource intensive measurements. Our results point to the importance of continued monitoring of soil and stand conditions at these LTSP sites as treatment effects on soil N cycling and site productivity will likely continue to evolve. At this stage of stand development, full-tree harvesting plus organic horizon removal, followed by operational harvesting has led to lower soil N availability than operational tree-length harvesting, and stands with understory vegetation control are now showing indications of reduced N availability.

PRODUCTIVITY AND ENERGY EFFICIENCY OF WINCHING OPERATIONS IN PINE STANDS IN MOUNTAINOUS REGIONS

The objective of this study was to evaluate the productivity and energy efficiency of tree extraction in mountainous regions by means of a tractor with winch in two work team compositions: I: one tractor operator and a cable operator; and II: one tractor operator and two cable operators. The study was carried out in Vale do Ribeira region using a full tree harvesting system through a time and motion study in different conditions of extraction distance (6 to 135 meters) and log yard (5 to 241 meters), and land slope (from 7 to 37º). To evaluate the cycles, a regression analysis was carried out for each treatment and subsequently compared using the Graybill F test. Then a regression with a dummy variable was performed. The productivity was 9.26 m3 PMH0-1 with a cable operator and 12.12 m³ PMH0-1 at an extraction distance of 100 m; the specific fuel consumption was 44.26 g kW-1 PMH0-1 in both treatments, and the energy efficiency was 4.92 g kW-1 m³ with a forest worker and 3.13 g kW-1 m³ with two forest workers. Consequently, although the specific fuel consumption was equal in both treatments, the increase in productivity resulting from the addition of a cable operator,improved the energy efficiency in the extraction using a tractor with winch.

Quality assessment of pine wood harvesting by residue inventory using line intercept cluster sampling

ABSTRACT Inadequate wood harvesting can lead to a loss of marketable biomass for energy purposes and affect subsequent forestry operations. Therefore, woody residue inventory tools are essential for guiding forest managers and ensuring operational wood harvest quality. In this study, we aimed to propose and evaluate the line intercept sampling in systematic clusters to inventory wood cutting and chipping residues. The study was carried out in a 15-year-old Pinus taeda L. stand under clearcutting by a full-tree harvesting system. This wood harvesting system was composed by a directional feller, a skidder and harvester machines, followed of a forest chipper which produced the residual biomass for energy purposes, in which residue pieces with small-end diameter equal to or greater than 4 cm were considered for commercial energy purposes. Residue inventory was carried out after wood harvesting and chipping operations through 10 clusters composed of four lines with 15.71 m each. These clusters were randomly distributed in which the residue diameters and lengths were measured. The number of woody pieces per hectare and their volume estimations were performed aiming at 20% sampling error. Confidence intervals with a 95% significance level were from 21,054 to 37,978 woody pieces per hectare, and from 16.03 to 26.12 m3 per hectare, in which only 13% of the woody pieces were above the commercial limit diameter. Line intercept sampling in clusters has proven to be efficient for quality control of wood harvesting and chipping operations.

Conceptual decision-making framework for the sustainable harvesting of forest and woodland species for medicinal tree bark in southern Africa

Tree bark is widely used in traditional medicine in southern Africa. The growing demand for medicinal bark requires scientifically sound harvest systems for sustainable use. A conceptual framework and decision matrix are presented to aid forest managers in selecting the most appropriate system for the sustainable harvesting of particular species. The conceptual framework is based on the results of experimental bark harvesting of selected forest and woodland tree species in southern Africa, where tree response to bark stripping was assessed. The extent and rate of bark regrowth and the susceptibility of the exposed wood to fungal and insect damage, are of particular importance to assess harvest options. The decision matrix groups species based on tree response to bark stripping, and identifies the most appropriate harvest option for a particular species. Species-specific harvest prescriptions are formulated and alternatives to strip harvesting are identified where avoidance is advised. The conceptual framework and decision matrix were applied to forest woodland species on which experimental bark harvesting was conducted in Malawi, South Africa and Zambia. Of the 22 species studied, 10 have the potential for strip harvesting, based on extent of bark regrowth and susceptibility to fungal and insect damage. These were assessed further in terms of prescriptions for strip harvesting. For the remainder, full-tree harvesting in a single-tree selection system would be the most viable harvest option. Alternatives to strip and full-tree harvesting are also discussed.

Limited initial impacts of biomass harvesting on composition of wood-inhabiting fungi within residual stumps.

Growing pressures linked to global warming are prompting governments to put policies in place to find alternatives to fossil fuels. In this study, we compared the impact of tree-length harvesting to more intensive full-tree harvesting on the composition of fungi residing in residual stumps 5 years after harvest. In the tree-length treatment, a larger amount of residual material was left around the residual stumps in contrast to the full-tree treatment where a large amount of woody debris was removed. We collected sawdust from five randomly selected residual stumps in five blocks in each of the tree-length and full-tree treatments, yielding a total of 50 samples (25 in each treatment). We characterized the fungal operational taxonomic units (OTUs) present in each stump using high-throughput DNA sequencing of the fungal ITS region. We observed no differences in Shannon diversity between tree-length and full-tree harvesting. Likewise, we observed few differences in the composition of fungal OTUs among tree-length and full-tree samples using non-metric multidimensional scaling. Using the differential abundance analysis implemented with DESeq2, we did, however, detect several associations between specific fungal taxa and the intensity of residual biomass harvest. For example, Peniophorella pallida (Bres.) KH Larss. and Tephromela sp. were found mainly in the full-tree treatment, while Phlebia livida (Pers.) Bres. and Cladophialophora chaetospira (Grove) Crous & Arzanlou were found mainly in the tree-length treatment. While none of the 20 most abundant species in our study were identified as pathogens we did identify one conifer pathogen species Serpula himantioides (Fr.) P. Karst found mainly in the full-tree treatment.

Effect of Topping Trees on Biomass and Nitrogen Removal in the Thinning of Norway Spruce Stands

In Central Europe, full-tree (FT) harvesting is an increasingly common harvesting method in steep terrain harvesting due to the increased use of highly economical processor tower yarders. In conventional FT harvesting, nutrient removal from harvest sites is substantially higher than in cut-to-length (CTL) harvesting due to the extraction of nutrient-rich branches and foliage. One strategy to reduce the adverse impact of FT harvesting is to cut off the tops of felled trees prior to extraction (topping). The purpose of this study was to assess the effect of implementing topping treatments in FT harvesting on biomass and nutrient removal. The effect of conventional FT harvesting on the amount of logging residues left on the site was assessed in three different Norway spruce (Picea abies)-dominated stands following cable yarding operations by collecting logging residues from the forest floor. The additional effect of topping trees on the amount of logging residues was assessed by using biomass models. These models were created based on the data of 25 sample trees, which were felled and sampled destructively within the stands. The results show that conventional FT harvesting considerably increases nutrient removal in comparison to CTL, but still do not remove all nutrients from the sites. After conventional FT harvesting, 5–18% of the nutrients remained on the sites. Topping trees at a diameter of 8 cm substantially increased the amount of remaining nutrients to 30–34%.

Mechanisation of different logging operations : environmental impact assessment using life cycle assessment (LCA) approach

Different logging systems (or harvesting systems) can be used for wood extraction. Cable logging system is typically carried out on steep slopes and other rough terrain. In these contexts, also cable yarding can be an efficient and effective harvesting system. Ninety-five per cent of timber production in southern Italy comes from terrain classified as very steep slope, limiting the use of machines for ground-based extraction. Cable extraction is a desirable alternative to either a skidder or forwarder on a sensitive site. To each harvesting system a different environmental load is associated depending on machine productivity and site characteristics. In this study, three different logging systems were analysed and compared using the Life Cycle Assessment approach. The compared logging systems are characterised by felling with chainsaw and three different extraction methods: by farm tractors equipped with a winch; by a skidder; and by a cable crane. The Full Tree harvesting method was adopted for both felling sites; trees were felled and transported to roadside with branches and top intact. The functional unit is 1 m3 of wood; the system boundary involves all the operations carried out in the forestry (felling, bunching and extraction) and all the related inputs (diesel fuel, lubricating oil, capital goods such as chainsaw, tractors, skidder, cable yarder) and related emissions. Inventory data were collected in three different test sites located in southern Italy and concern working times, productivity, wood yield, fuel consumption. The cable yarder shows the worst performances for 7 of the 8 evaluated impact categories. The use of skidder shows a lower impact for 5 of the 8 evaluated impact categories while, for the remaining 3, the best performances are achieved by the logging system in which tractor is used. For climate change, the impact is equal to 8.57, 8.04 and 10.46 kg CO2eq/m3 for the harvesting system with extraction carried out using tractor, skidder and cable yarder, respectively.

Performance of a Mobile Star Screen to Improve Woodchip Quality of Forest Residues

Low harvesting costs and increasing demand for forest-derived biomass led to an increased use of full-tree (FT) harvesting in steep terrain areas in Austria. Logging residues, as a by-product of FT harvesting, present an easily accessible bioenergy resource, but high portions of fine particles and contaminants like earth particles and stones make them a complex and difficult fuel, as they affect storage capability, conversion efficiency, or emission rates adversely. The present research focuses on the productivity and performance of a star screen, which was used to remove fine and oversize particles from previously chipped, fresh Norway spruce (Picea abies (L.) Karst.) logging residue woodchips. Three screen settings, which differed in terms of different rotation speeds of the fine star elements (1861 rpm, 2239 rpm, 2624 rpm) were analyzed. Time studies of the star screen were carried out to estimate screening productivity and costs. Furthermore, 115 samples were collected from all material streams, which were assessed for particle size distribution, calorific value, ash content, and component and elemental composition. Average productivity was 20.6 tonnes (t) per productive system hour (PSH15), corresponding to screening costs of 9.02 €/t. The results indicated that the screening of chipped logging residues with a star screen influenced material characteristics of the medium fraction, as it decreased the ash content, the incidence of fine particles, and the nutrient content. The different screen settings had a noticeable influence on the quality characteristics of the screening products. An increase of the rotation speed of the fine stars reduced screening costs per unit of screened material in the medium fraction, but also lowered screening quality.

Are shallow-soiled sites sensitive to increased biomass removals? An operational, paired-wise comparison approach

Although commonly cited as being particularly sensitive to biomass/nutrient removals via full-tree harvesting (i.e., entire aboveground portion of the tree is removed and processed at roadside), there have been no long-term experimental trials installed or reported on to date that specifically target shallow-soiled (<20cm) sites common in strongly glaciated boreal landscapes. This study reports on ten year results examining the effects (i.e., regeneration potential, tree growth, soil N availability, and foliar nutrition) of operational full-tree harvesting compared to operational stem only harvesting (i.e., individual stems delimbed and topped at the stump) on replicated, shallow-soiled sites with contrasting soil textures (i.e., sand versus loam) and dominant commercial tree species (i.e., jack pine – Pinus banksiana Lamb. versus black spruce – Picea mariana (Mill.) B.S.P.). The operational harvests at the seven study sites were all conducted during the fall prior to freeze up.In terms of tree regeneration metrics, the harvest treatments only had a significant effect on free-to-grow (>1m) crop tree (jack pine or black spruce) density. Despite the removal of cone-bearing branch material to roadside, the FT harvest treatment blocks had significantly higher densities compared to the SO blocks likely the result of increased mineral soil exposure, improved seedbed receptivity, and warmer soil surface temperatures during the growing season. Initially (5th year), jack pine height growth was better on the FT treatment blocks, but by year 10 this significant effect on total height was gone and the 5-year growth increment was better on the SO treatments. In contrast, black spruce height growth was better on the SO blocks in both year 5 and 10, although the 5-year increment was not significantly different between harvest treatments. Although soil N pools were higher in the SO treatments in year 10, the difference was only reflected in jack pine foliar N, suggesting black spruce may be less sensitive/responsive to declines in soil N pools.The 10-year results would suggest that no additional biomass retention restrictions are necessary for full-tree harvesting operations that are targeting traditional wood products (sawlogs and/or pulp & paper) on these shallow-soiled sites. However, some of the noted shifts in some of the measured parameters between year 5 and 10 would suggest longer-term monitoring of these sites will be necessary to provide more conclusive empirical evidence as to the long-term effects of full-tree harvesting on shallow soils within the boreal forest region.

Reconciling Harvest Intensity and Plant Diversity in Boreal Ecosystems: Does Intensification Influence Understory Plant Diversity?

Overall demand for forest products in the boreal forest is increasing to supply growing bio-energy demands in addition to traditional forest products. As a result, there is a need to refine current forest policies to reconcile production and ecosystem function within the context of ecologically sustainable management. This study assessed understory plants' richness, evenness, and diversity in six harvested boreal black spruce-dominated stands situated on loam, sand, and peat site types 15years after the application of four harvest treatments of increasing biomass removals. Treatments included uncut, stem-only harvest, full-tree harvest, and full-tree harvest+blading of O horizon. Following canopy removal, species richness and diversity (Shannon's and Simpson's indices) increased on all soil types. The more than doubling of slash loading on the stem-only treatment plots compared to the full-tree plots led to significantly lower species diversity on loam sites; however, the reverse was observed on peat sites where the slash provided warmer, drier microsites facilitating the establishment of a broader array of species. Preexisting ericaceous shrub and sphagnum components continued to dominate on the peat sites. Compositional shifts were most evident for the full-tree+bladed treatment on all soil types, with increases in herbaceous cover including ruderal species. The results suggest that the intensification of harvesting on plant diversity varies with soil type, and these differential results should be considered in the refinement of forest biomass-harvesting guidelines to ensure ecological sustainability and biodiversity conservation over a broad suite of soil types.

Black spruce growth response to varying levels of biomass harvest intensity across a range of soil types: 15-year results

With a growing interest in the diversification (e.g., bioenergy, biochemicals) of the forest industry beyond the traditional product streams, concerns that higher harvest utilization levels may compromise site productivity have been heightened. This study reports on 15-year tree growth responses to varying levels of biomass removals conducted on four soil types: loamy tills, outwash sands, wet mineral, and peatlands. Experimental harvest treatments included stem-only, full-tree, full-tree chipping (a full-tree harvest with the roadside material chipped and returned to the site), and full-tree + bladed (a full-tree harvest followed by forest floor removal). Results indicated no significant effect on height growth on the loamy tills, a significant decline for the blading treatment on the sandy soils, and an increase when the blading treatment was applied to the peatland sites. At the stand level, better planted seedling survival and higher recruitment of naturals on the more extreme removal treatment (forest floor removal on sandy sites) tended to nullify any negative impacts identified in the individual-tree growth measurements. The more than doubling of the slash loading on the stem-only treatment plots compared with the full-tree plots did not result in differences in tree productivity levels between these two operational treatments. The stands, however, were just approaching crown closure by year 15, suggesting that ongoing monitoring will be required to confirm that the growth trajectories for the various harvest treatment – soil type combinations can be maintained.

Ergonomic evaluation and comparison of wood harvesting systems in Northwest Russia

A comparison of 14 currently applicable wood harvesting systems was assessed with respect to ergonomic point of view. For this purpose, the research method, based on the Hodges–Lehmann rule and the integrated work-severity rate of single machinery, was developed for ergonomic evaluation of cut-to-length, tree-length and full-tree harvesting systems. Altogether, about 130 different parameters of 36 units of equipment that impact on the ergonomics and work conditions were measured and estimated in interviews undertaken directly at forestry harvesting workplaces in 15 logging companies in the Republic of Karelia, Northwest Russia. Then the results were compared to the effective norms, and the degree of compliance with the stipulated values was determined. The estimates obtained for the degree of compliance were combined. This permits a direct comparison of the workload on forestry harvesting workers such as operators, lumberjacks and choker setters. In many respects, the current ergonomic standard is standard, except for the operators of cable skidders, chainsaws and choker settings. Visibility and work postures were considered to be the most critical features influencing the operator's performance. Problems still exist, despite the extensive development of cabs. The best working conditions in terms of harvesting systems were provided by “harvester + forwarder” in cut-to-length harvesting, and “feller–buncher + grapple skidder” in full-tree harvesting. The motor-manual tree-length harvesting performed with cable skidders showed the worst results in terms of ergonomics.

Comparative effects of full-tree and tree-length shelterwood harvesting on residual tree damage and coarse woody debris volume in the Great Lakes – St. Lawrence forest

Residual stand damage and coarse woody debris loads were evaluated in 15 hardwood and white pine uniform shelterwood harvest blocks, in the Great Lakes – St. Lawrence Forest Region, using tree-length (TL) and full-tree (FT) harvesting techniques. Stand-level damage rates to residual stems in both the TL and FT harvest operations were below Ontario’s allowable “major” damage limits of 15% to all residual trees and 10% to acceptable growing stock (AGS) trees. No significant differences in damage rates were observed between the TL and FT harvest systems and were comparable to past assessments in TL and FT harvested blocks. Despite efforts to increase utilization of material from these study sites, no significant differences were observed in coarse woody debris (CWD) volume or the distribution of that volume across decay classes.

Soil acidification and nutrient sustainability of forest ecosystems in the northeastern German lowlands - Results of the national forest soil inventory

Between the first and second national forest soil inventory in the northeastern German lowlands a significant soil acidification took place with regionally varying intensity. It manifests itself in a reduced base saturation in the whole rooting zone. This applies to the base cations magnesium and calcium. For potassium, however, no significant changes were detected. The acidification dynamic is the strongest in the southern part of Brandenburg. The specific immission situation in this region during the past four decades explains this. Particularly in southern Brandenburg high dust depositions (fly ashes from brown coal-fired power stations) buffered the acid components and enriched the soil with base cati ons in the 1970s and 1980s. Since the reduction of these atmospheric depositions, the bases were obviously totally incorporated in the biomass or leached out with seepage water. Currently, the majority of the forest sites in Mecklenburg-Vorpommern and Brandenburg are poor in basic nutrient elements (Ca, Mg, K). Especially the element magnesium is assumed to be lacking. This paper presents an assessment of the long-term availability of the nutrients Ca, Mg und K on the basis of calculated nutrient balances for various forest management scenarios (e.g. full-tree harvest). The results show that the sustainable supply is critical especially for intensive forest use on numerous sites.

Effects of organic matter removal, soil compaction and vegetation control on 10th year biomass and foliar nutrition: LTSP continent-wide comparisons

We examined 10th year above-ground planted tree and total stand biomass, and planted tree foliar N and P concentrations across gradients in soil disturbance at 45 North American Long-Term Soil Productivity (LTSP) installations. While ranging across several climate regions, these installations all share a common experimental design with similar measurement protocols. Across all installations planted tree biomass with stem-only harvest (OM0), no compaction (C0) and chemical vegetation control (VC), ranged from 2 to 90Mgha−1. When compared with the OM0, full-tree harvest (OM1) had little consistent effect on any response variable. Full-tree harvest plus forest floor removal (OM2) also demonstrated few consistent effects on planted tree biomass, although Boreal – Great Lakes conifers showed some positive effects, reflecting high survival, but also negative effects on foliar nutrition. Compaction (C2), regardless of OM treatment, increased planted tree stand biomass consistently in Warm Humid climates, and compaction with intact forest floors (OM0C2) did so across all regions. However, most installations had medium – or coarse-textured soils and compaction did not achieve theoretical growth-limiting bulk densities. Combining OM2 with C2 resulted in lesser gains in planted tree biomass. Planted tree biomass gains with the OM0C2 were attributed largely to changes in physical soil characteristics, not to vegetation control or nutrient availability. Total stand biomass (Mgha−1) was either unaffected or, with aspen, reduced by compaction. Vegetation control (VC) consistently enhanced planted tree biomass, regardless of climate, and also enhanced foliar nutrient concentrations on Warm Humid and Mediterranean sites. VC also increased total stand biomass on sites without abundant woody competitors, but decreased it on shrub-dominated Mediterranean sites. For many of the site types and species investigated, harvest-related organic matter removal and soil compaction (excepting aspen vegetative reproduction) have not resulted in large losses in stand biomass 10year after harvest. Most stands, however, have not yet reached canopy closure, and treatment effects may continue to evolve.

Evaluation of full tree skidding by HSM-904 skidder in patch cutting of aspen plantation in Northern Iran

This paper presents research results of the performance of HSM-904 grapple skidder using a full tree harvesting method in a non-native aspen Populus deltoides plantation in even terrain conditions in Shafaroud, Northern Iran. Patch cutting as a silvicultural method was used in the plantation (2,000 ha). To evaluate the newly introduced machine to a ground skidding system in the aspen plantation and the possibility to increase the production rate, an empirical time study was conducted. The elements of the skidding work phase were identified and 58 cycles were recorded for the study. The models for effective time consumption, total productivity and work phase models are calculated. The average load per cycle was 2.2 m&lt;sup&gt;3&lt;/sup&gt;, the average one-way skidding distance was 253 m. The average travel speed of unloaded skidder was 5.53 km·h&lt;sup&gt;-1&lt;/sup&gt; and the average speed of loaded skidder was lower than the speed of the unloaded one by 2.94 km·h&lt;sup&gt;-1&lt;/sup&gt;. The average output in the study was 7.1 m&lt;sup&gt;3&lt;/sup&gt; per effective hour and the unit cost was 13.9 USD·m&lt;sup&gt;-3&lt;/sup&gt;.

Machine systems for the production of fuel chips from woody biomass using the full-tree harvesting method

The processing chain and corresponding machine systems for woody biomass harvesting and fuel chips production from logging residues, low-quality and small-sized wood are examined. The features of these systems are the possibility of full-tree harvesting during principal felling and cleaning cutting.