Whole-tree Research Articles

Carbon footprint of the predominant mechanized timber harvesting methods in the Northeastern US

Estimating carbon footprint of forest operations is essential to budget the environmental impacts of the industry. The study objectives were to a) assess the carbon footprint of whole-tree (WT), cut-to-length (CTL), and hybrid cut-to-length (Hyb CTL) harvesting methods in the Northeastern US; b) assess global warming potential of various processes involved in timber harvesting for different harvest methods; and c) evaluate variation in the carbon footprint for the summer and winter harvest. SimaPro 9.3.0.3 software and allied databases (USLCI and US-EI 2.2) adhering to ISO 14,040 and 14,044 standards were used for cradle-to-gate life cycle assessment (LCA) with a functional unit of 1 tonne of green roundwood. Tool for reduction and assessment of chemicals and other environmental impacts (TRACI v 2.1) was used for impact assessment. The input variables were quantity of fuel (liter tonne-1) and lubricants (kg tonne-1) for respective harvesting operations. The results of LCA showed that carbon footprint was highest for WT (11.57 kg CO2 eq), followed by Hyb CTL (11.09 kg CO2 eq) and CTL (9.91 kg CO2 eq) methods. Secondary transportation (trucking) had highest global warming potential among the processes. Winter harvest had a higher carbon footprint than summer by 2 and 3 percent, respectively, for CTL and Hyb CTL methods. The extra time needed to warm up engine resulted in a higher carbon footprint for winter harvest. Higher carbon footprint for WT method can be attributed to greater number of equipment involved for WT resulting in more fuel consumption, compared to other methods. Among the stump-to-landing processes, skidding contributed foremost in WT, whereas felling and processing in CTL, and processing in Hyb CTL, respectively. These results could be used in the upstream process for future LCA of different wood products manufactured in the region.

A Multi-Criterion Evaluation Process for Determining Cost-Effective Harvesting Systems in Fragmented Boreal Forests

Nordic forests, like those found in Canada, used to consist of large and relatively homogeneous mature stands. Such a spatial pattern allows for harvest operations to be highly concentrated, minimizing procurement costs. However, the growing fragmentation of these forests makes planning difficult and increases the costs of road building and machinery relocation. While operational solutions have been developed in regions with small harvest areas, their transferability to different settings is unknown. Finding the most suitable combination of equipment for a given context is challenging considering the multitude of possibilities. The objective of this study is to identify, from all possible options, a subset of harvest systems expected to perform well in fragmented boreal forests. The results from this research are two-fold. First, a comprehensive review of forest machines and harvest systems is provided. Second, a multi-criteria decision analysis (MCDA) methodology is proposed to evaluate the alternatives. In a boreal forest context, the conventional harvester-forwarder system (CTL) was ranked among the best solutions, along with mild adaptations of the usual configurations. Several whole-tree (WT) system configurations were also highly ranked. While the results are specific to the case studied, the review and selection methodology can serve in different operational contexts.

Short‐term effects of organic matter and compaction manipulations on soil temperature, moisture, and soil respiration for 2 years in the Oregon Cascades

AbstractUnderstanding the factors controlling nutrient dynamics can help guide forest management plans to promote their long‐term productivity. We used experimental treatments with three levels of biomass removals and two levels of compaction to monitor the impacts to soil biophysical characteristics in an intensively managed forest. Soil temperature, moisture, and respiration observations began 6 mo after treatment installation completion and continued for 2 yr. Compaction had few consistent significant effects on measured variables, and there were negligible differences in volumetric soil water content between whole tree (WT) and bole only (BO) harvesting. Compared with BO, the 10‐cm average and maximum growing season temperatures in WT significantly increased by 1.2 and 2.5 °C, respectively. The effects of WT removals resulted in whole profile (10–100 cm) increases in the average and maximum growing season soil temperatures. The WT removals resulted in an increase of 1.4 times more soil growing degree days (SGDD) at 10 cm and 1.6 times more at 100 cm compared with BO. Despite favorable temperature and moisture conditions, differences in soil respiration could not be explained by biomass or compaction treatments. The uncut reference forest was consistently cooler and drier, but respired more CO2 throughout both years of observation compared with treated areas. The large physical disturbance of forest harvesting on the site likely masked any incremental treatment differences by homogenizing the microbial response in the ensuing 2‐yr study period. Future research should continue to investigate whether these soil biophysical changes influence site productivity or more sensitive indices of soil C dynamics.

Residual Stand Damage under Different Harvesting Methods and Mitigation Strategies

A major component of sustainable forest management are the stands left behind after the logging operation. Large mechanized harvesting equipment involved in current forest management can inflict damage on residual trees; and can pose a risk of mortality from diseases, natural calamities, and/or degrade future economic value. The primary objective of this study was to evaluate the residual stand damage under different harvesting methods and silvicultural prescriptions i.e., crop tree release (CTR), diameter limit cut (DLC), and overstory removal (OSR). The second objective was to evaluate the intensity and frequency of damage occurring on the bole, canopy, and root at tree and stand level. The third objective was to document strategies adopted globally to minimize stand damage due to timber harvesting. Five harvest blocks implementing three silvicultural prescriptions, were selected as the treatments across two different industrial timberlands in central and northern Maine (Study Site (SS) I and II, respectively). A hybrid cut-to-length (Hyb CTL) and whole-tree (WT) harvesting method were employed for conducting the harvest in SS I and II, respectively. Systematic transect sampling was employed to collect information on type, frequency, and intensity of damages. The inventory captured 41 and 8 damaged trees per hectare with 62 and 22 damages per hectare from SS I and SS II respectively. Bole damage was the most frequent damage across all treatments. The Hyb CTL had lower damage density (damage per ha) and severity compared to WT. The average number of trees damaged per ha was higher for CTR prescriptions compared to DLC. There were no significant differences in the height of the damages from the ground level between treatments within each study site; however, there was a significant difference between the study sites. Species damaged was directly related to the residual trees left behind and was dominated by American beech, yellow birch, sugar maple, and eastern hemlock. Finally, the study provides strategies that can be adopted at different forest managerial phases to mitigate residual stand damage.

Impacts of forest harvest removal and fertiliser additions on end of rotation biomass, carbon and nutrient stocks of Pinus radiata

Forest harvesting practices remove tree biomass and the nutrients that they contain. There is uncertainty around the impact of this nutrient removal on the long-term sustainable production of forests over multiple rotations. To explore the impact of harvest management practices on planted forest sustainability, three long-term trials in Pinus radiata D. Don forests were assessed at the end of their second rotation of 26 to 27 years to determine the impact of harvest residue removal and fertiliser additions on sustainable forest productivity. The harvest residue removal treatments were stem only (SO), whole-tree (WT), and whole-tree plus forest floor (FF) removal with and without urea-nitrogen fertiliser additions (cumulative range across three sites 950 – 3200 kg N ha−1) from early rotation out to mid-rotation (last fertiliser application age range across sites 8 – 22 years). The FF removal treatment reduced soil carbon and nitrogen stocks throughout the subsequent rotation, whereas forest floor carbon and nutrient stocks had recovered from the FF removal treatment by the end of the rotation. Forest productivity was reduced at one site with the FF removal treatment, taking 3 years longer for stems to reach 35 cm diameter at breast height than other residue removal treatments. Between WT and SO harvest residue treatments there were very limited impacts on soil carbon and nutrient stocks, no impact on forest floor mass, carbon and nutrient stocks and the sum of the above ground live biomass, carbon and nutrient stocks or tree productivity. Across all harvest removal treatments fertiliser addition increased soil carbon and nitrogen stocks for sites with low initial soil stocks. The increased soil carbon and nitrogen stocks from fertiliser addition were associated with forest productivity gains with the time to reach 35 cm (diameter at breast height) for one site reduced by 3 – 5 years. Fertiliser addition to sites with FF removal was able to mitigate soil carbon and nitrogen stocks only when very large amounts of fertiliser were added (cumulative amounts of 1150 and 3200 kg N ha−1). The end of rotation results from this long-term study demonstrate the importance of harvest residues and forest floor material at low fertility sites for long-term nutrient sustainability in planted forests.

Wood biomass recovery cost under different harvesting methods and market conditions

ABSTRACT Harvesting woody biomass, often considered a by-product, poses a major challenge in terms of low operational productivity and revenue. However, woody biomass (branches, treetops, and small-diameter trees or SDT) is gaining global attention for its multifaceted uses in soil reclamation, renewable energy production, and carbon offsetting. The operational cost of harvesting woody biomass is a crucial factor influencing the economic feasibility of harvesting and can fluctuate substantially depending on the cost apportioning method used. The objectives of this study were 1) to estimate the cost of producing pulpwood chips from SDT; 2) to examine the factors influencing cost and productivity of whole-tree (WT) and hybrid cut-to-length (Hyb-CTL) treatments; and 3) to compare and estimate the cost of producing sawlog and chips from hardwood pulp with two cost apportioning methods. The total harvesting cost was 53% higher in Hyb-CTL (US$ 17.30 m−3) than that of WT (US$ 11.30 m−3). The cost of producing wood chips from hardwood pulp as a by-product (US$ 3.07 m−3) was half of the cost calculated using the joint-products allocation method (US$ 7.65 m−3). The cost of producing wood chips utilizing exclusive product allocation (US$ 47.53 m−3) was four times the cost of producing sawlogs (US$ 11.23 m−3). This study provides working values that can enable timberland managers and operational foresters to evaluate the cost of harvesting woody biomass under different market conditions (i.e., demand for woody biomass). This study can also aid managerial decisions regarding silvicultural prescriptions and to help efficiently manage stands that have large proportions of SDT.

Production economics: comparing hybrid tree-length with whole-tree harvesting methods

Abstract Felled trees with tops and branches are transported to the landing with a grapple skidder in conventional ground-based whole-tree (WT) harvesting. This method has greater potential to damage advance regeneration than those in which trees are processed at-stump. Hybrid tree-length (Hyb TL) harvesting using an stroke-boom delimber for in-woods processing might be a feasible alternative, but little is known about the production economics of this method. An experimental strip-cutting study was conducted in central Maine, US in the winter of 2018 to: (1) evaluate and compare operational productivity and costs of ground-based Hyb TL and WT methods; (2) identify factors influencing productivity of at-stump and at-landing log processing; and (3) calculate best management practice (BMP) implementation costs in WT harvesting. Time-motion data were recorded for operational phases such as felling, extraction, processing, sorting and loading; machine rates were calculated to determine productivity and costs of operations. Total cost of Hyb TL (US $17.01 m−3) was lower than that of WT ($18.38 m−3). Processing cost was lower at-stump than at-landing ($2.66 and $2.73 m−3 for Hyb TL and WT, respectively). This is likely due to fewer logs handled per cycle at-landing (1.2 logs per turn) compared to the number handled per cycle at-stump (1.4 logs per turn). Sensitivity analysis showed that a 30-m increase in average in-woods distance travelled by the delimber would result in a 41 per cent increase in the processing cost. Cost of BMP implementation in WT was $2.25 m−3 or $59.2 per productive machine hour. Results suggest that it is feasible to apply Hyb TL method in an industrial harvesting operation, though distance of in-woods delimber movement influences processing costs. Insights from this study will help forest managers and loggers efficiently plan and execute harvesting operations.

Productivity and cost of whole-tree and tree-length harvesting in fuel reduction thinning treatments using cable yarding systems

Cable yarding systems are often used to reduce hazardous fuels in dense overstocked forest stands on steep terrain (>35%) in the western United States. However, treatment costs tend to be high. The aim of this study was to broaden our knowledge by evaluating two different harvesting methods (whole-tree (WT) and tree-length (TL)) used for fuel reduction thinning treatment on mixed-conifer forest stand. Different harvesting methods greatly affected the productivity and cost of fuel reduction thinning, especially in felling and yarding operations. Total sawlog removal costs (stump-to-truck) were US$26.13/m3 in the WT-harvested unit and US$24.01/m3 in TL harvested unit. TL thinning resulted in higher felling time and lower production rate due to increased amounts of time for processing trees at the stump. In yarding operation, however, TL method had a higher production rate than WT method because TL method had higher number of pieces per yarding cycle. Processing production rates at a landing were relatively similar throughout treatments although trees in a TL thinning unit were already limbed and bucked at the stump. Loading productivity was consistent throughout treatments because loading occurred independently from other activities. For fuel reduction thinning treatments using a cable yarding system, TL thinning was more cost-effective than WT thinning if leaving tree tops and branches on site is acceptable from a fuels management perspective.

Estimation of Nutrient Exports Resulting from Thinning and Intensive Biomass Extraction in Medium-Aged Spruce and Pine Stands in Saxony, Northeast Germany

A growing interest in using forest biomass for bioenergy generation may stimulate intensive harvesting scenarios in Germany. We calculated and compared nutrient exports of conventional stem only (SO), whole tree without needles (WT excl. needles), and whole tree (WT) harvesting in two medium aged Norway spruce (Picea abies L. Karst.) and Scots pine (Pinus sylvestris L.) stands differing in productivity, and related them to soil nutrient pools and fluxes at the study sites. We established allometric biomass functions for each aboveground tree compartment and analyzed their nutrient contents. We analyzed soil nutrient stocks, estimated weathering rates, and obtained deposition and seepage data from nearby Level II stations. WT (excl. needles) and WT treatments cause nutrient losses 1.5 to 3.6 times higher than SO, while the biomass gain is only 1.18 to 1.25 in case of WT (excl. needles) and 1.28 to 1.30 in case of WT in the pine and spruce stand, respectively. Within the investigated 25-year period, WT harvesting would cause exports of N, K+, Ca2+, and Mg2+ of 6.6, 8.8, 5.4, and 0.8 kg·ha−1 in the pine stand and 13.9, 7.0, 10.6, and 1.8 kg·ha−1 in the spruce stand annually. The relative impact of WT and WT (excl. needles) on the nutrient balance is similar in the pine and spruce stands, despite differences in stand productivities, and thus the absolute amount of nutrients removed. In addition to the impact of intensive harvesting, both sites are characterized by high seepage losses of base cations, further impairing the nutrient budget. While intensive biomass extraction causes detrimental effects on many key soil ecological properties, our calculations may serve to implement measures to improve the nutrient balance in forested ecosystems.

The effect of harvesting method on biomass retention and operational efficiency in low-value mountain forests

This study determined the biomass retention effects and the technical–financial performance of alternative harvesting practices, applied to mountain sites. The two alternatives were: whole-tree (WT) and tree-length (TL) harvesting. Five cable yarding sites were selected from a larger pool of available sales, and on each site two adjacent and parallel cable corridors were set up, using the same base equipment and crew. For each of the 10 corridors (i.e. 5 sites × 2 corridors), the following data were recorded: biomass retention, product output, time and fuel inputs. Opting for TL harvesting resulted in a large (66 %) and significant increase in biomass retention, which may prove attractive where intensified biomass removal may jeopardize soil fertility and biodiversity. TL harvesting also resulted in a moderate increase (13 %) of total harvesting cost. Furthermore, TL harvesting required 30 % more labour input than WT, which may represent a disadvantage when forest labour is scarce. The increased labour use in TL harvesting occurs mainly at the stump site, where accident risk is highest. For all these reasons, managers should take their decision very carefully and opt out of more efficient WT harvesting only when the risk derived from increased biomass removal is quite severe.

Evaluating harvest costs and profit of commercial thinnings in softwood stands in west-central Maine: A case study

Precommercial thinning (PCT) is a common silvicultural treatment in the management of young conifer forests. The positive effects of PCT on tree growth are well documented, however, there have been few operational studies of thinning productivity associated with later harvests in such stands and associated cost comparison with high-density, small-diameter stands. In the winters of 2012/2013 and 2013/2014 a long-term herbicide and PCT study in west-central Maine was commercially thinned using cut-to-length (CTL) and whole-tree (WT) harvesting systems in PCT and non-PCT stands, respectively. Thinning prescriptions consisted of three nominal removal intensities (33%, 50%, and 66% of the standing softwood volume) in a randomized block design with three to four replications. Stand density, basal area, hardwood content, and removal intensity were not significant in explaining variation in harvester and feller-buncher productivity. An analysis of unit cost of production indicated that wood chip production using a WT system in non-PCT stands is less costly than the production of roundwood using a CTL system in PCT stands. Profit, however, is similar for products harvested by either system. Our conclusion is that the WT system used in the study is economically feasible to treat highdensity, small-diameter stands in a commercial thinning.

Comparison of the cost and energy efficiencies of present and future biomass supply systems for young dense forests

The objective was to study the effect of future harvesting and handling technologies on the cost and energy efficiency of supply chains for young dense thinnings. The system costs and energy requirements were modeled using type of stands, products delivered, and transport distances as variables. In total, 14 systems were analyzed, of which five represented future systems. The effects of increasing the payloads of off-road and road transportation of whole tree (WT) parts by 10%, 20%, and 30% were also analyzed. If boom-corridor thinning technologies, optimized bundle-harvesters, and load-compression devices are developed, on average, costs are reduced by 12–27% and 11–30% less energy is required when compared with present systems. For example, at an average harvested tree size of 22 dm3, the supply of WT using future technologies would reduce the cost by up to 15% and the energy requirements by 21%. These effects increase with reduced tree sizes and increased transportation distances. The effects of future technologies are especially significant for tree sizes below 30 dm3, representing a significant part of the potential that could be harvested annually in Sweden. Thus, there should be increased research and development of boom-corridor felling technology, bundle-harvesters, and load-compression devices.

The effect of mechanization level and harvesting system on the thinning cost of Mediterranean softwood plantations

The study compared motor-manual cut-to-length (CTL) harvesting, motor-manual whole-tree (WT) harvesting, mechanized CTL harvesting and mechanized WT harvesting as applied to the production of energy chips from the second thinning of Mediterranean pine plantations in flat terrain. Mechanization increased productivity between 6 and 20 times, depending on process step. It also allowed reducing thinning cost by a factor 4. Shifting from CTL to WT harvesting resulted in a reduction of harvesting cost between 40 and 50%. Fuel consumption was between 40 and 100% higher for CTL harvesting than for WT harvesting. Mechanization entailed a reduction of fuel consumption between 10 and 40%. Stand damage was generally low, between 1.5 and 6%. Mechanized CTL harvesting resulted in the lowest incidence of wounding, and the difference between mechanized CTL and manual WT harvesting was statistically significant. Soil compaction was absent or very small, depending on treatment. Mechanized thinning may produce larger increases of soil bulk density, compared to motor-manual thinning, but the difference is small, although significant. CTL harvesting leaves a larger amount of biomass on the soil, which relieves possible concerns about soil nutrient depletion. On the other hand, heavy residue loads may increase fire risk especially in sensitive Mediterranean environments.

Impact of Whole-Tree and Cut-to-Length Harvesting on Postharvest Condition and Logging Costs for Early Commercial Thinning in Maine

Regenerating clearcuts dating from the spruce budworm outbreak of the 1980s are beginning to reach merchantable size throughout northern Maine and would benefit from commercial thinning, but there is no consensus among foresters and the logging industry about how such stands can be efficiently thinned. This study investigated silviculturally effective, operational solutions to implement early commercial thinning treatments. Comparisons between two wholetree (WT) and two cut-to-length (CTL) systems were made in terms of residual stem damage, retention of downed woody material, product utilization, and unit cost of production. Results show significantly more crop trees removed (P 0.030) and more high severity wound area per plot (P 0.011) for the WT systems. There was no difference in the number of stems wounded per plot at the high severity level between harvest methods (P 0.312). Harvest-generated and retained downed wood material volume averaged 511.9 and 205.6 ft/ac for CTL and WT plots, respectively. Round wood production was the same for CTL and WT plots (average 30 tons/ac), but more than four times more biomass was produced from the WT operations. Production costs were not significantly different between harvest methods due in part to high machine productivity and increased biomass production for the WT systems.

Landscape Establishment of Woody Ornamentals Grown in Alternative Wood-Based Container Substrates

Due to concerns over future pine bark (PB) availability for container plant production, recent research has focused on evaluating suitable alternatives. For alternatives to be considered suitable substrate replacements, they must not only have desirable characteristics as a container substrate (e.g., adequate drainage, inert, pathogen free, etc.), but must also cause no negative fertility effects (e.g., nitrogen immobilization) following planting in the landscape. The study objective was to evaluate the landscape performance of three woody ornamentals grown in PB and in two alternative wood-based substrates, namely WholeTree (WT) and Clean Chip Residual (CCR). Crapemyrtle (Lagerstroemia indica × faurei ‘Acoma’), magnolia (Magnolia grandiflora ‘D.D. Blanchard’), and shumard oak (Quercus shumardii) were container grown in PB, WT, or CCR for an entire growing season prior to being planted into the landscape. Plants were grown in the landscape for two growing seasons. Data suggest that all species exhibited similar landscape performance when grown in WT or CCR compared to the PB standard. Therefore, the use of WT and CCR as alternative wood-based substrates for crapemyrtle, magnolia, and oak production may be acceptable from a landscape establishment standpoint.

Nitrogen leaching following whole-tree and bole-only harvests on two contrasting Pacific Northwest sites

Short-term pulses of increased N leaching typically follow the harvest of forest stands, but the magnitude of these pulses after conventional bole-only (BO) and whole-tree (WT) harvests often is difficult to predict. In this study, we measured N leaching until 6 and 8years post-harvest on two western Washington Douglas-fir (Pseudotsuga menziesii var. menziesii) sites: a relatively low-productivity site with a gravelly loamy sand soil formed in glacial outwash and a high-productivity site with a silt loam soil derived primarily from basalt. We tested BO and WT harvest treatments and presence/absence of 5years of competing vegetation control (VC). Trends in the magnitude and duration of post-harvest N-leaching pulses differed between sites. At the higher-productivity site, estimated N leaching between years 3 and 8 following harvest totaled 250 and 94kgNha−1 in BO and WT harvest treatments with VC, respectively. At the lower-productivity site, estimated N leaching totaled 32 and 17kgNha−1 between years 3 and 6 following harvest in BO and WT harvest treatments with VC, respectively. In both BO and WT treatments, annual N leaching did not fall below 2kgNha−1 (the rate measured in mature forest stands at both sites) until year 8 at the higher-productivity site and until year 6 at the lower-productivity site. Cumulative amounts of N leached among site/treatment combinations were small compared to the soil total-N pool and ranged from 0.5% to 2.5%. The N leaching patterns among treatments at these two sites suggest that differences in soil N content and C:N ratio, post-harvest vegetation regrowth, and harvest residues influenced the amount of N leached. The major source of leached N was most likely the soil (including forest floor) rather than harvest debris, based on site and treatment comparisons. Although the maximum post-harvest pulse of 250kgNha−1 was much higher than values reported in most comparable studies, this level of N leaching is unlikely to be reached under operational conditions, where VC is less intensive than in this study.

Low-Value Trees as Alternative Substrates in Greenhouse Production of Three Annual Species

Abstract Peat and perlite have served as industry standards in greenhouse substrates for over 50 years. The continued availability of peat, paralleled with its inert characteristics, as well as its ability to stay generally pathogen-free have all contributed to its success in the horticulture industry. Expanded perlite has long been used as an amendment in container mediums to provide air space to container substrates without adding to bulk density or affecting substrate pH and EC. However, due to increased restrictions on the harvesting of peat, as well as fluctuations in fuel prices necessary for shipping, the future availability of peat is a largely unknown factor in greenhouse production. Additionally, growers consider perlite to be a general nuisance due to the lung and eye irritation problems. Because of these problems, researchers have focused on identifying and evaluating possible alternatives to standard substrates. These studies evaluated three possible substrate alternatives for use in greenhouse production, including fresh sweetgum (SG), hickory (H), and eastern redcedar (RC), in addition to WholeTree (WT) substrate. Three greenhouse annual crops (petunia, impatiens, and vinca) were planted in varying ratios of these species mixed with peat. Plants grown with SG and H as amendments did not perform as well as a traditional peat:perlite mix with respect to flower number, growth indices, and plant dry weight. However, plants grown in RC tended to be equivalent to those grown in a traditional mix. Data showed that greenhouse producers could amend their standard greenhouse substrate with up to 50% eastern redcedar with little to no differences in plant growth.

Soil carbon and nutrient pools in Douglas-fir plantations 5 years after manipulating biomass and competing vegetation in the Pacific Northwest

We assessed changes in mineral soil total carbon (C) and nutrient (exchangeable Ca, K, Mg, and total N) pools to 60 cm depth 5 years after manipulating biomass and competing vegetation at two contrasting Douglas-fir plantations (Matlock, WA, and Molalla, OR). Biomass treatments included whole-tree (WT) and bole-only (BO) harvest, and competing vegetation control (VC) treatments were applied as either initial or annual herbicide applications. There were main effects of biomass removal and VC on the absolute change in soil pools of some elements at both sites, but significant effects were more prevalent at the lower soil quality Matlock site than the Molalla site, and were generally confined to the top 15 cm of soil. In all cases, treatment effects were associated with increases in C and nutrients following BO and initial VC treatments combined with little change in soil pools following WT and annual VC treatments. At the Matlock site, total soil pools (0–60 cm) of C, N, and Ca significantly increased in the BO and initial VC treatments, and Mg increased and K decreased regardless of treatment. At the Molalla site, soil C and nutrient pools did not change in response to treatments, but total soil Mg increased in all treatments during the study period. Correlation analyses indicated little influence of soil nutrient pools on early growth at Matlock likely because soil water is more limiting than nutrient availability at that site, but vegetation growth was correlated to nutrient pools at Molalla indicating changes in pools associated with harvesting and treatment could influence crop development in the future. These early results indicate low potential for intensive management practices to reduce mineral soil pools of C and nutrients, but there is uncertainty on the long-term growth response because treatments may have influenced nutrient storage in pools other than mineral soil.

A harvest and transport cost model for Eucalyptus spp. fast-growing short rotation plantations

This project developed a cost model for the mechanical harvesting of fast-growing Eucalyptus plantations. With such a model, forest managers can check the profitability of a prospective operation under different work conditions and assess the competitiveness of alternative options, which in turn will lead to supply chain optimization. The model is based on mathematical relationships that return machine productivity as a function of operational conditions. These relationships were calculated on data obtained from detailed time studies, conducted on all the main equipment types used in Eucalyptus plantations. Tests were conducted on 11 different machines that harvested a total 2465 oven-dry tonnes over 23 ha on 12 sites in 3 countries. The time study sessions lasted 250 h. Both the Cut-to-Length (CTL) system and the Whole-Tree (WT) system were studied. The model was validated with success and was used to make a number of different simulations. Simulation results show that the WT system allows cheaper harvesting and transport than the CTL system for a range of conditions. Under the conditions of our simulations and in favourable terrain, WT harvesting results in a delivered cost of about 20 euro/green tonne of bark-free pulp chips, whereas CTL harvesting results in a cost between 25 and over 30 euro/green tonne of debarked pulp roundwood.

Soil compaction associated with cut-to-length and whole-tree harvesting of a coniferous forest

The degree and extent of soil compaction, which may reduce productivity of forest soils, is believed to vary by the type of harvesting system, and a field-based study was conducted to compare soil compaction from cut-to-length (CTL) and whole-tree (WT) harvesting operations. The CTL harvesting system used less area to transport logs to the landings than did the WT harvesting system (19%–20% vs. 24%–25%). At high soil moisture levels (25%–30%), both CTL and WT harvestings caused a significant increase of soil resistance to penetration (SRP) and bulk density (BD) in the track compared with the undisturbed area (p < 0.05). In the center of trails, however, only WT harvesting resulted in a significant increase of SRP and BD compared with the undisturbed area (p < 0.05). Slash covered 69% of the forwarding trail area in the CTL harvesting units; 37% was covered by heavy slash (40 kg·m–2) while 32% was covered by light slash (7.3 kg·m–2). Heavy slash was more effective in reducing soil compaction in the CTL units (p < 0.05). Prediction models were developed that can be used to estimate percent increases in SRP and BD over undisturbed areas for both CTL and WT harvesting systems.