Commercial Thinning Operations Research Articles

The potential of biological control against Heterobasidion root rot is not realized in practical forestry

For about 25 years, forest managers in Sweden have been treating stumps following harvesting with Phlebiopsis gigantea, retailed as Rotstop®S gel, against spore infections of Heterobasidion, which cause root rot in order to minimize losses in timber production. However, not all forest managers trust the efficacy of stump treatment and this fact has hindered widespread adoption of stump treatment using P. gigantea. In this study, we evaluated stump treatment in the field during commercial thinning operations across 15 sites, by assessing the degree of stump coverage and subsequent infection levels in stump discs. In total, 45 % of all stumps were infected with Heterobasidion spp.. Nineteen percent of all stumps were considered to have full (100 %) coverage by Rotstop®S but contractors failed to achieve the manufacturers stipulated minimum coverage (85 %) in approximately 1/3 of all stumps. Using PCR, we could only detect the presence of P. gigantea in 73 % of the tested stumps. Large variation occurred between stump coverage and the recovery of P. gigantea in wood chip samples collected from stump discs across sites. In the worst case, we detected P. gigantea in only three out of ten treated stumps at one site. Despite this discrepancy we saw a clear reduction of the size of Heterobasidion infections on stumps where stump treatment coverage was more than 85 % of the stump surface.Our results suggest that forest operators in Sweden repeatedly fail to either apply a spore solution of P. gigantea or cover enough of the stumps to provide the desired protection. The outcome of such sub-standard application, could further undermine the usage of biological control agents in forestry and limit any potential control against Heterobasidion spp..

Influencing plantation stand structure through close-to-nature silviculture

New silvicultural practices to meet the requirements of ecosystem-based forest management are being adopted operationally, even if the long-term outcomes remain unknown. In eastern Quebec, Canada, the conversion of plantations from even-aged to irregular or uneven-aged stands is being carried out in 10% of commercial thinning operations. Existing growth and yield simulators cannot be used to forecast stand development. Here we apply a novel individual tree-level simulator to plantations characterized by high levels of natural regeneration ingrowth, such as those observed in Quebec. The simulator user can either choose distance-dependent or distance-independent competition indices, depending on user preference or simulation needs. Calibration statistics and validation results indicate that both versions perform very well. When applied to operational silvicultural scenarios, the simulator shows that thinning does not influence total stand yield; however, tree spatial aggregation does change. Moreover, the variability among the different simulation runs is greater for spatial statistics than for stand yield. Overall, thinning from below has the greatest effect on stand structure, whereas the smallest is from early crop tree release, used as the initial conversion step. This pattern implies that the first and second thinnings of the conversion process towards irregular or uneven-aged stands may not have a major effect on stand structure. In the case of the conversion process, the consequences for stand structure must thus be viewed as a longer-term issue. More importantly, the conversion process does not reduce stand yield, thereby reducing one of the key concerns of forest managers.

Numerical examination of the optimal bucking method to maximize profits applied in Nasu town, Tochigi Prefecture, Japan

In this study, the optimal bucking methods were numerically applied to Nasu town, and the factors of effects on profitability of commercial thinning operations and feasibility of extracting small sized logs were discussed. As a result, commercial thinning operations could be conducted on 18% (818 ha) and 54% (2427 ha) of 35 and 45 years old forests, respectively. On the other hand, pre-commercial thinning operation would be conducted on 81% (3666 ha) and 46% (2089 ha) of 35 and 45 years old forests. This shows current situation of Japanese forestry where nearly all the thinning operations conducted were pre-commercial. Stands with extracting small sized logs accounted for approximately ten percent of the total forest area. Extracted small sized logs from 35 years old forests were more than those from 45 years old forests although saw logs from 35 years old forest were less than those from 45 years old forests. The areas of stands with extracting small sized logs were increased according to the more gentle slope and shorter forwarding distances. Thus, it was clear that the reduction of forwarding distances by establishing forest road networks were effective in order to increase stands with extracting small sized logs.

Mitigating midterm timber supply shortage using commercial thinning operations. A case study from British Columbia, Canada

Forests in the interior of British Columbia, Canada have seen a substantial change in age class structure caused by a mountain pine beetle outbreak that instigated high tree mortality, and consequently, large scale salvage operations. The current age class structure in affected regions implies a midterm timber supply shortage that has the potential to negatively impact the forest industry in affected timber supply areas in the near future. A spatially explicit landscape level forest model for Bulkley timber supply area (TSA), a typical TSA facing these challenges, was developed. Using landscape level planning software we modelled future timber supply as well as age class structure over a 250-year planning horizon for (a) current single entry forest management practices focusing mainly on clearcutting; and (b) alternative management scenarios using multi-entry (thinning) approaches. Alternative scenarios were designed to determine economically viable forest management alternatives while mitigating midterm timber supply shortage, and converting the forest structure in the region towards a more even age-class distribution. Implementing commercial thinnings in stands located within 300 m of existing roads showed the highest potential to successfully mitigate midterm timber supply shortage if entries were scheduled based on culmination of mean annual increment rather than on a fixed minimum harvestable volume. The use of thinnings shortened the overall duration of the midterm timber supply shortage, reaching sustainable harvest levels sooner than if conventional approaches were used, and higher overall timber volumes available for harvest. Alternative approaches to current forest management practices in BC prove to be promising and should be considered where possible.

How long are thinning-induced resource pulses maintained in plantation forests?

Despite the critical role of pulsed resources on the dynamics and conservation of several forest-dwelling species, the transition between the period when the effects of a thinning-induced resource pulse are maximal and the period when only residual effects remain has yet to be documented in forest habitats. In this study, we investigated the occurrence of a transition period after a woody necromass resource pulse produced by commercial thinning operations on flying coleopterans. In a large-scale manipulative study, spruce plantations were subjected to commercial thinning treatments and beetles collected using flight intercept traps during the four years that followed thinning operations. 82,062 beetles from 50 families and 242 species were recovered. For two years after thinning treatments, beetle communities differed in composition between thinned and unthinned plantations, species richness and abundance being higher in thinned areas. By the third and fourth year after thinning treatments, these differences started to fade, indicating that the transition period was occurring. This was associated with a decline in the quality of woody debris found close to or onto thinning trails. These results support our hypothesis that fine woody debris, such as those produced by commercial thinning operations, are attractive to beetles for a short period because they rapidly decay and are rarely colonized by wood-boring species, inhibiting further colonization by fungi and mycophagous beetles. Yet, despite a decline in abundance and species richness in thinned areas during the last two years of the study, thinned plantations still harboured richer and more abundant beetle communities than unthinned plantations, suggesting that thinning trails continue to improve beetle dispersal as the woody necromass resource pulse weakens.

Settling in or passing through: differentiating between wood‐boring beetle visitation and colonization after a dead wood pulse

AbstractTo determine the effect of resource pulses on animal communities, it is important to differentiate the species colonizing the resource substrate from the ones simply moving through the system. In a manipulative field study, we surveyed the response of wood‐boring beetles (Coleoptera) to the small debris produced by commercial thinning operations in white spruce plantations using two methods. First, we sampled the wood‐boring beetles visiting the plantations using flight intercept traps. Then, at the end of the resource pulse in fresh woody debris, we documented the abundance of beetle emergence holes on vertical and horizontal woody debris, which indicate wood‐boring beetle colonization. Results demonstrated that the small horizontal debris generated by commercial thinning were used by saproxylic beetles but were not a preferred resource for colonization, by contrast with vertical dead wood. Only small‐body beetles colonized the horizontal debris and most debris were not colonized. Vertical dead wood, even if present in relatively small quantity when compared to horizontal dead wood, was a major determinant of beetle colonization and community composition. Biomass removal was shown to have a strong detrimental impact on beetle colonization rates. Based on these results, we suggest that most of the saproxylic species trapped after commercial thinning operations were attracted in response to the initial pulse of resource but did not actually colonize the debris from thinning. Thus, we stress the importance of distinguishing between species visitation and colonization following a resource pulse when sampling relies on indirect trapping methods.

Comparative analyses on the cycle time, productivity, and cost between commercial thinning and clear-cutting operations in Nasu-machi Forest Owners' Co-operative, Tochigi Prefecture, Japan

This study investigates clear-cutting operations on moderately and gently sloping sites. Cycle times, productivities, and costs of those operations are analyzed and compared with those of commercial thinning operations, to enable logging contractors to easily find trends of those three variables. Felling cycle times of clear-cutting were lower than those of commercial thinning operations. Processing cycle times of clear-cutting on the gently sloping site were lower than those of clear-cutting on the moderately sloping site and commercial thinning. However, processing cycle times of clear-cutting on the moderately sloping site were similar to those of commercial thinning. Forwarding cycle times of clear-cutting on the moderately sloping site were the lowest among the estimated forwarding cycle times. Costs of operation systems were the lowest with clear-cutting on the gently sloping site, followed by clear-cutting on the moderately sloping site, and then commercial thinning with mechanized and current operation systems according to forwarding distance, with extracted volume 0.5 m3/stem. Costs of the current thinning operation system were less than those with a mechanized thinning system below extracted volume 0.3 m3/stem, because of smaller machinery expenses.

Effect of temperature on the interaction between Phlebiopsis gigantea and the root-rot forest pathogen Heterobasidion spp.

The biocontrol agent Phlebiopsis gigantea is widely applied to stump surfaces during commercial thinning operations in Northern Europe to prevent airborne infection of Norway spruce (Picea abies) stumps by the root and butt-rot pathogen Heterobasidion spp. It has been suggested that warmer climatic conditions in the future may affect the interaction between the pathogen and the biocontrol agent, and may enable Heterobasidion annosum sensu stricto, which is currently restricted to southern areas of Sweden, to move further northward. To determine whether warm temperatures do effect the interaction between P. gigantea and Heterobasidion spp., we conducted a series of experiments to investigate the effect of temperature on the growth of P. gigantea and several Heterobasidion spp. and on the ability of P. gigantea to overgrow Heterobasidion spp. in paired interaction experiments in vitro. To validate our in vitro findings, we set up field experiments to examine the interaction between P. gigantea and the Heterobasidion spp. that infect spruce in Sweden, Heterobasidionparviporum and H. annosum s.s., under different temperature regimes. Our study showed that temperature did not diminish the effectiveness of P. gigantea to protect spruce stumps against infection by H. parviporum. The growth rate of P. gigantea in stumps was higher than that of H. parviporum, particularly in sapwood. We found little support for a hypothetical increase in H. annosum s.s. damage under warmer climatic conditions. In vitro studies showed that regardless of the temperature regime, H. annosum s.s. was less resistant to overgrowth by P. gigantea than H. parviporum. Under field conditions, the relatively low infection capacity of H. annosum s.s. to P. abies stumps seems to be the crucial factor determining the outcome of the interaction. The results of paired in vitro experiments between P. gigantea and non-European Heterobasidion species, for example, Heterobasidionaraucariae, Heterobasidionirregulare and others, suggest that P. gigantea may be less effective as a biocontrol agent against species or isolates adapted to high temperatures (20–25°C), particularly those species that are able to grow rapidly at temperatures as high as 25°C.

Estimating the annual supply potential and availability of timber and logging residue using forest management records of the Tochigi prefecture, Japan

We used forest management records to estimate the annual supply potential and availability of timber and logging residue from profitable subcompartments for all the cities and towns in the Tochigi prefecture. Five log markets and three factories in the Tochigi prefecture were assumed to be the destination of timber and logging residue, and the forest operation systems were set on the basis of interviews with forestry cooperative officials. The results showed that the annual supply potential of timber and logging residue was 450,304 m3 and 549,957 tons, of which 6 % (26,304 m3) and 37 % (204,122 tons) were from precommercial thinning operations, 61 % (276,180 m3) and 50 % (276,276 tons) were from commercial thinning operations, and 33 % (147,820 m3) and 13 % (69,559 tons) were from final-felling operations, respectively. When the unit price of the logging residue was 10,000 yen/ton, the annual logging residue availability from profitable subcompartments could almost cover the annual demand of the three facilities that we considered in this study. Introduction of feed-in tariffs had a significant impact. However, the ratios of the availability to supply potential with unit prices of logging residue of 3,000, 6,000, and 10,000 yen/ton were estimated to be only 1.67, 2.06, and 4.09 %, respectively. Considering the subsidies, the ratios respectively increased to 5.79, 7.35, and 13.09 %. Furthermore, the annual logging residue availability with subsidy could meet 70 % of the annual woody biomass demand of the large-scale factory in Sano city, which is 100,000 tons.

Soil Compaction and Visual Disturbance Following an Integrated Mechanical Forest Fuel Reduction Operation in Southwest Oregon

Most mechanical forest fuel reduction treatments prescribed to extract biomass are performed with existing or modified conventional logging equipment. Treatments that commonly harvest small, non-merchantable trees are often combined with or integrated into commercial thinning operations. Only a limited amount of literature has quantified harvesting system feasibility or environmental effects from such operations. The extra stand travel required to fell and extract small trees may lead to additional soil disturbance. The objective of this study was to assess soil disturbance from an integrated forest harvesting/mechanical forest fuel reduction operation in southwest Oregon, USA. The study was conducted in a fuel reduction thinning of a densely stocked 8.1-hectare (20-acre) mixed conifer stand on gentle terrain. A tracked, swing-boom feller-buncher and two rubber-tired, grapple skidders were used for felling and extracting both non-merchantable and merchantable trees. Visually classified soil disturbance, along with penetration resistance estimates were recorded pre- and post harvesting. Results indicate that the operation did not contribute to either statistically or biologically significant soil disturbance effects, based on an a priori biological reference threshold of 3,000 kPa. A history of multiple harvest entries, low soil moisture, and high initial soil strength conditions contributed to the lack of significant effects. This investigation will aid forest managers in decision making concerning expected soil disturbance effects when prescribing integrated harvesting systems for forest fuel reduction treatments.

Impact of the white pine weevil (Pissodes strobi [Peck]) on Norway spruce (Picea abies [L.] Karst.) plantations. Part 2: Lumber properties

We studied the lumber characteristics of 148 trees acquired for that purpose during commercial thinning operations in three Norway spruce (Picea abies [L.] Karst.) plantations, aged from 32 to 34 years, which had been attacked repeatedly by the white pine weevil (Pissodes strobi [Peck]). The trees, with diameters ranging from 14 to 23 cm, were grouped into three quality classes according to the number of major deformations caused by the weevil. The effects of the deformations on bending strength and stiffness, wood density and lumber defects were examined. Results show that in general deformations caused by the weevil do not affect the lumber properties of Norway spruce on sites of medium to high quality. For the three Norway spruce plantations, the mean values of the modulus of elasticity (MOE) of the lumber varied between 8510 and 9357 MPa, and for the modulus of rupture (MOR) they ranged from 36.0 to 42.5 MPa, whereas wood density varied from 324 and 343 kg·m-3. For comparison purposes, the same measurements were taken on lumber from 38 trees in a white spruce (P. glauca [Moench] Voss) plantation that was unaffected by the weevil, but comparable to the Norway spruce plantation on one of the sites studied. The lumber properties from Norway spruce taken from deformed or undeformed stems were 34% superior to white spruce for MOE, 20% for MOR and 8% for wood density. The smaller knots in Norway spruce could explain this difference. On the other hand, a visual grading of this type of wood reveals few differences in lumber strength and stiffness. Key words: Norway spruce, Picea abies, wood characteristics, MOE, MOR, wood density, lumber, white pine weevil, Pissodes strobi, white spruce, Picea glauca

Impact du charançon du pin blanc (Pissodes strobiPeck) dans les plantations d’épinette de Norvège (Picea abies(L.) Karst.). Partie 2 : Propriétés du bois des sciages

We studied the lumber characteristics of 148 trees taken for that purpose during commercial thinning operations in three Norway spruce (Picea abies [L.] Karst.) plantations, aged from 32 to 34 years, which had been attacked by the white pine weevil (Pissodes strobi [Peck]). The trees, with diameters ranging from 14 to 23 cm, were grouped into three quality classes according to the number of major deformations caused by the weevil. The effects of the deformations on rigidity, bending strength, wood density and lumber defects were examined. Results show that in general the deformations caused by the weevil do not affect the lumber properties of Norway spruce on sites of medium- to high-quality. For the three Norway spruce plantations, the mean values of the modulus of elasticity (MOE) of the lumber vary from 8510 to 9357 MPa, and for the modulus of rupture (MOR) range from 36.0 to 42.5 MPa, whereas wood density varies from 324 to 343 kg·m-3. For comparison purposes, the same measurements were taken on lumber from 38 trees in a white spruce (P. glauca [Moench] Voss) plantation that was unaffected by the weevil, but otherwise comparable to the Norway spruce plantation on one of the sites studied. The lumber properties from the Norway spruce taken from deformed or undeformed stems are 34% superior to the white spruce for the MOE, 20% for the MOR and 8% for wood density. The smaller knots in the Norway spruce could explain this difference. On the other hand, a visual classification of this type of wood reveals few differences in the lumber's bending strength or rigidity. Key words: Norway spruce, Picea abies, wood characteristics, MOE, MOR, wood density, lumber, white pine weevil, Pissodes strobi, white spruce, Picea glauca

Analysis of Site Stand Impacts from Thinning with a Harvester- Forwarder System

The use of a harvester-forwarder system for commercial thinning operations in a Douglas-fir plantation had little detrimental impact on the residual stand. Less than five percent of the sample trees in the residual stand exhibited damage from the thinning operation. Trails occupied less than 20 percent of the harvested area with significant portions of the developed trail, over 13 percent of the harvested area, in lightly disturbed harvester trails. Trail spacing was consistent and averaged 26 metres between trails for the area studied. Changes in bulk density were greater for harvester trails, increasing an average of 25 percent in the first 10 centimetres of soil depth. Bulk densities on forwarder trails averaged 20 percent greater than measurements on adjacent control sites for the first 10 centimetres of soil depth. These bulk density values, when compared against magnitudes from the literature, suggest that little site damage was caused by thinning operations with this system.