Butt Logs Research Articles

Tree pruning improves tree form but not understory plant production in mixed stands of Sitka spruce and western hemlock, USA

Abstract Precommercial thinning and tree pruning are frequently used together to improve timber quality and wildlife habitat in even-aged Sitka spruce (Picea sitchensis) and western hemlock (Tsuga heterophylla) stands. Thinning enhances crop tree growth and understory plant production; however, the benefits and drawbacks of tree pruning have received less attention. Tree pruning was investigated in two long-term experiments on the Tongass National Forest, Alaska, USA. Experiment 1 tracked four uniformly thinned sites for ~30 years that received 2.4, 3.6, and 5.2 m lift, and no pruning treatments. Experiment 2 tracked 11 sites for 16 years that received thinning/no pruning, thinning plus pruning (25% of trees), thinning plus pruning (50% of trees), and no thinning/no pruning treatments. We investigated (i) how pruning lift height affects tree form and understory production and (ii) how pruning density affects canopy closure and understory production. In Experiment 1, pruning reduced butt log taper and did not adversely affect diameter or height in either species. Pruning lift was visible in height-to-live crown measurements. Crown recession occurred first in low lift treatments and later in all treatments until crown form was similar after 28–31 years. Epicormic branching rates in Sitka spruce peaked 6–9 years after treatment before falling sharply. Deer forage declined through time and did not differ between lift treatments. In Experiment 2, canopy closure was lower shortly after thinning and pruning, but did not differ from the control after 16 years. Epicormic branching rates were greater shortly after thinning and pruning but did not differ from the control after 16 years. Deer forage declined with canopy closure and thinned and pruned treatments exhibited greater forage than the control. We conclude that pruning can improve log quality for timber applications but does not enhance understory plant biomass and deer forage over thinning treatment alone.

Measuring Butt Log and Middle Log Volume of Eucalyptus Camaldulensis Using Different Methods in Erbil Province

The volume of each butt log and middle log of an individual tree at a 5-meter log length was calculated by using five different formulas (Newton`s, Smalian`s, Huber`s, Hossfeld`s, and Centroid method). The volume of the butt logs and middle logs was compared to the real volume (control), which was calculated by aggregating the volume measurements at (0.5) meters using Newton's method. Measurements were taken from 50 trees of (Eucalyptus camaldulensis) planted in Al-Khabat area in Erbil governorate. The sampled trees presented diameter at breast height (DBH) ranged from 30.2 to 75.6 cm and total tree height range from 13 to 27 m. The result showed that Newton`s formula was superior to all other formulas for estimating butt log volume of eucalyptus tree species plantation and Smalian`s formula was less accurate than other formulas. On the other hand, the centroid method was superior to all other formulas for estimating the middle log volume of eucalyptus tree species in the district of khabat in Erbil province. Moreover, the Hossfeld formula was less accurate than other formulas.

Non-destructive evaluation of strength and stiffness of Eucalyptus pellita. A comparison of near infrared spectroscopy and acoustic wave velocity assessment

Tree improvement programmes benefit from measured data for multiple phenotypes in order to potentially gain maximum genetic leverage for selection. Diameter at breast height, tree height and tree form have traditionally dominated the measured phenotype due to their ease of measurement, and the fact that logs are traded by volume. More complex traits, including those that potentially offer economic benefit in terms of quality and end-product performance such as strength and stiffness, are more difficult to measure in standing trees and are frequently overlooked. These traits are therefore in need of rapid methods of assessment. Tree improvement of Eucalyptus pellita in Malaysian Borneo for solid wood and veneer product utilisation is one such example of where selection for improved stiffness is desirable. Genetic trials of E. pellita were assessed using acoustic velocity measurements at several intervention points, including the standing tree, fallen stem, logs and boards, along with near infrared spectroscopic measurement of the final test samples. Calibrations were developed for modulus of elasticity (MOE), modulus of rupture (MOR) and compression parallel to the grain, using reference values obtained from 3-point bending of small clearwood test samples obtained from the trees following felling and sawing to ensure back-to-log recovery of the test sample location. Dynamic MOE calculated from the standing tree acoustic velocity showed good correlation with the mean MOE from static bending for the wood in the butt log, representing the location where standing tree acoustic velocity measurements were obtained. The Savitzky-Golay second derivative pre-treatment yields the best performing calibration for the microNIR and MPA on ground wood for MOE (R2Cal = 0.76, r2CV = 0.80, r2Pred = 0.46, RMSEC and RMSECV = 1.4 GPa, RMSEP = 2.3 GPa, LV = 3) for the microNIR and R2Cal = 0.98, r2CV and r2Pred = 0.70, RMSEC = 0.5 GPa, RMSECV and RMSEP =1.5 GPa, LV = 4 for the MPA.

Predicting resin pockets and blemishes in radiata pine lumber from log properties

Background: Resin pockets and blemishes in pruned logs of radiata pine (Pinus radiata D.Don) can reduce the value of clear and moulding grades of lumber. External resin features (ERF) on the bark of the logs have proved an effective method of predicting the incidence of resin pockets in the lumber. Resin canals have been associated with resin blemishes in radiata pine, and could prove useful in improving the prediction of the grade recovery of lumber. Methods: Pruned butt logs of radiata pine trees from two forests in the North Island, New Zealand, were selected for low, moderate, and severe levels of external resin features (ERF) on the bark, and for low, average, and high resin canal diameter, frequency and brightness from breast height increment cores. The relationships were evaluated between these properties, and the lumber resin features and grade recovery of the logs. Results: The number of resin pockets, the blemish rating, and the percentage of boards with resin streaks and resinous heartwood increased, and the recovery of clears and moulding grade boards and the lumber value declined, with the severity of the ERF class of the logs. Multiple regression models gave good predictions of the grade recovery and loss of lumber value, using the log ERF class, volume, heartwood content, and number of Type 1 resin pockets on the ends of the logs, as independent variables. The resin canal properties did not improve the regression models. Resin blemishes were associated with Type 2 resin pockets, and were more frequent in the forest where false growth rings were present. This suggests the constitutive resin flow from resin canals, rather than the resin canal size and frequency, is more important in determining the incidence of resin blemishes. Conclusions: The prediction of the grade recovery of lumber using the ERFs of radiata pine logs, was supplemented by the log volume, heartwood content and number of Type 1 resin pockets on the ends of the logs. The environmental factors that drive the constitutive resin enrichment of resin canals, such as drought conditions that give rise to false growth rings, could be useful in improving the prediction of grade recovery for forest stands.

Influence of log and stack parameters on the conversion factors for Norway Spruce wood stacks using a 3D simulation model

ABSTRACT One method for estimating the solid wood content in a stack involves using conversion factors and multiplying these by the measured gross volume. The conversion factors can vary depending on several log and stack parameters. The aim of this study was to analyze eleven parameters using a 3D simulation model based on 541 measured logs of Norway spruce. To this end, 50 data sets were created from measured logs, where the parameters of interest in this study (e.g., length, crookedness, taper …) were classified according to different ranges. After that, 64 runs of simulations were carried out. In each simulation run, 150 stacks were modeled. The simulation results were compared with previous studies and with the measurement guidelines of several countries. This analysis revealed that the parameters midpoint diameter, length, crookedness, delimbing quality and the proportion of moderately and highly crooked logs in a stack have a considerable influence on the conversion factors. Taper, proportion of butt logs in a stack and stack height have a modest effect as do the proportion of tapered and crooked logs for low and high taper and low crookedness. In contrast, ovality and the proportion of logs stacked in opposite directions have a marginal influence on the conversion factors. Based on findings from these analyses, the current measurement guidelines of different countries can now be adapted to achieve a higher degree of accuracy.

Efficiency of Visual and Machine Strength Grading of Sawn Timber with Respect to Log Type

A batch of pine timber sawn from butt, middle and top logs was strength graded with the visual method (classification into grading classes KW—best quality, KS—medium quality, KG—inferior quality and Reject) and with the machine strength grading method—performed with the use of a mobile timber grader (classification into C strength classes). We compared the efficiency of grading classes and strength classes, depending on the type of log from which the material was obtained (butt, middle, top). Next, a strength grading machine was used to measure the modulus of elasticity in bending (MOE) and static bending strength (MOR). The ANOVA confirmed the influence of both the log type (butt, middle, top), the C strength class, and the visual strength grading class on the values of density (DEN) and MOR. Timber density and MOR decreased from the butt log section to the top log section. The ANOVA confirmed the influence of log type on MOE values, but only to a limited extent.

Semi-empirical estimation of log taper using stem profile equations

In January 2019 the forest industry in Ukraine adopted European standards for measuring and grading of round wood based on mid-point diameters, which caused major discrepancies from traditionally used estimates of timber volume using top diameters. To compare methods of merchantable wood volume estimation, we investigated the stem form inside bark for two dominant tree species in Ukraine, i.e. Scots pine (Pinus sylvestris L.) and common oak (Quercus robur L.). We used tree stem measurements to fit stem profile equations, whereas simulation was applied to derive log taper. We found that Newnham's (1992) variable-exponent taper equation performed well for predicting stem taper for both tree species. Then, we simulated the structure of harvested wood, so that it replicated annual distribution of logs by their length and diameters. As a result, the average log taper was estimated at 0.836 ÷ 0.855 cm·m<sup>–1</sup> and 1.180 ÷ 0.121 cm·m<sup>–1</sup> for pine and oak, respectively. The study also indicated that log taper varied along stems. The higher rates of diameter decrease were found for butt logs, for which the taper was 2.5–3.5 times higher than its average for the whole stem. The results of our study ensure the stacked round wood volume conversion between estimates obtained using top and mid-point diameters.

Compression and flexural properties of plantation-grown Eucalyptus pellita in Borneo, Malaysia. Potential for structural timber end use

ABSTRACT Plantation-grown Eucalyptus pellita in Sabah, Malaysia, was analysed for compression and flexural properties to assess the potential for solid-timber and engineered wood product end uses. It is necessary to consider not only the volume of wood produced in a plantation but also the wood quality, particularly those aspects important for end-product performance. Tree volume is readily measured from height and diameter at breast height using appropriate form factors. This paper discusses the compression, strength and stiffness of E. pellita compared with tropical hardwood species, and variation within trees and at different ages (7–23 years). Small clearwood test samples obtained from radial positions within log heights were subjected to analysis of compression parallel to grain and three-point bending according to ISO 13061-4, 2014. Results indicate that plantation-grown E. pellita in the tropics has potential for structural-use applications. The average basic density across the trials was 658 kg m−3, while the bending strength for all trials was in the range of 11.7–15.5 GPa for modulus of elasticity and 96.3−120.1 MPa for modulus of rupture, and the compression strength parallel to grain ranged from 52.3 to 67.8 MPa. Mean mechanical strength increased from pith to bark and from the butt log to the top log. Because the wood-processing sector in Malaysia is transitioning from reliance on a harvest of mixed tropical hardwood towards plantation-grown species, these results indicate that plantation-grown E. pellita meets the structural requirements of strength and stiffness.

Accuracy of common stem volume formulae using terrestrial photogrammetric point clouds: a case study with savanna trees in Benin

Recent applications of digital photogrammetry in forestry have highlighted its utility as a viable mensuration technique. However, in tropical regions little research has been done on the accuracy of this approach for stem volume calculation. In this study, the performance of Structure from Motion photogrammetry for estimating individual tree stem volume in relation to traditional approaches was evaluated. We selected 30 trees from five savanna species growing at the periphery of the W National Park in northern Benin and measured their circumferences at different heights using traditional tape and clinometer. Stem volumes of sample trees were estimated from the measured circumferences using nine volumetric formulae for solids of revolution, including cylinder, cone, paraboloid, neiloid and their respective fustrums. Each tree was photographed and stem volume determined using a taper function derived from tri-dimensional stem models. This reference volume was compared with the results of formulaic estimations. Tree stem profiles were further decomposed into different portions, approximately corresponding to the stump, butt logs and logs, and the suitability of each solid of revolution was assessed for simulating the resulting shapes. Stem volumes calculated using the fustrums of paraboloid and neiloid formulae were the closest to reference volumes with a bias and root mean square error of 8.0% and 24.4%, respectively. Stems closely resembled fustrums of a paraboloid and a neiloid. Individual stem portions assumed different solids as follows: fustrums of paraboloid and neiloid were more prevalent from the stump to breast height, while a paraboloid closely matched stem shapes beyond this point. Therefore, a more accurate stem volumetric estimate was attained when stems were considered as a composite of at least three geometric solids.

Hardwood Log Grading in the United States—Part III: An Assessment of the Current Status of Log Grading in the Hardwood Industry

Abstract This article documents how the hardwood industry, in the absence of a standardized, industry-wide log grading system, has gone about grading and scaling hardwood logs by surveying mills, primarily in the Appalachian region. In total, 135 surveys were completed by respondents and returned via mail, with only 110 of those surveys considered usable for further analysis, after a thorough review of the individual surveys. Survey responses were grouped around annual production level, with three defined levels; ≤2.5 million board feet (MMBF), >2.5 and ≤8.0 MMBF, and >8.0 MMBF. Responding mills used some variation of a log grading system based on the number of clear faces on the log and the small end diameter of the log. The most common log rule used by mills in this study was the Doyle log rule, with over 75 percent using Doyle for scaling logs. Nearly 90 percent of all mills sampled graded logs without rolling the log to examine all four sides/faces. Half of all the sawmills surveyed pay the same price per thousand board feet (MBF) for butt logs and uppers. When asked if they would support the development of a standard log grading system, about two-thirds of the respondents (66%) indicated they would indeed support a standardized system for Appalachian hardwoods. These findings can help guide the development of a set of log grading standards for buyers and sellers in the Appalachian region and other parts of the world where hardwood lumber is produced.

The Influence of Scots Pine Log Type (Pinus sylvestris L.) on the Mechanical Properties of Lumber

The paper presents an analysis of the influence of geographical origin and Scots pine log type on the mechanical properties of the timber sawn from them. The tested timber was sawn from logs obtained from three different forestry regions in Poland, located in the western part of the country. A batch of 150 timber pieces was obtained from each region. The cross-section had the dimensions of 40 mm × 138 mm. The timber was sawn from logs of three different types: butt, middle and top, from a fresh, mixed forest around 120 years old. The timber was dried in industrial conditions and planed four times. The values determined for the timber under research were the static modulus of elasticity in bending (MOE), and the bending strength (MOR). Moreover, timber density (DEN) was determined with the stereometric method. For all three sites, the highest average values of the tested timber properties were obtained for timber made of butt logs, and the lowest for timber made of top logs. It was concluded that the tested Scots pine properties depended on the type of log, and to limited extent, on its geographic origin. The statistical analysis revealed that the geographic origin of the logs that the tested timber was made of had a statistically significant impact on the variance of all the tested timber properties. The type of log also had a statistically significant influence on the variance of all the tested properties.

Unrecorded volume of Norway spruce timber in cut-to-length harvesting

ABSTRACT Knowing credible records of harvested timber is in the interest of the forest owner, forest entrepreneur and timber-sector stakeholder. Therefore, the objective of the research was to determine the share of unrecorded Norway spruce timber volume in length allowance on the total timber volume produced by harvester technology in Czechia. We analyzed 176,980 merchantable logs (total volume of 10,333 m3) produced by 15 harvesters. Primary data were obtained from .stm files. Logs were categorized into five grades according to metric and qualitative requirements of the customers, also butt logs were distinguished. Statistical analysis were processed in the Statistica 13 package. Results showed that 1.99% of the volume of produced timber were excluded from the primary forestry records. Mean unrecorded volume of length allowance to assortments that contained both the cross-cut and cutting window allowances, varied from 2.99% up to 3.16%, while 0.27% to 0.46% of volume were unrecorded for those assortments that contained only the cutting window. In higher quality grades, we found shorter logs had a higher mean relative volume of length allowance than longer logs. The mean relative volumes of length allowances also varied between butt and other logs.

Estimation of Over- and Under-Bark Volume of Scots Pine Timber Produced by Harvesters

Harvesters produce one third of timber in Czechia. The aim of this study was to analyze the over- and under-bark volume estimates of Scots pine (Pinus sylvestris L.) timber produced by a mid-performance harvester. The data were collected between March 2017 and June 2018. In total, 4661 stems cut into 29,834 logs were analyzed. For volume estimation, StanForD offers several price categories using various algorithms. Three of these price categories are relevant for Czech forestry—M3s, M3toDE, and M3miDE. The M3s price category is based on the estimation of partial volumes of 10 cm long sections, which are summed. Therefore, this price category represents the volume estimation closest to the true volume. By comparison, the M3toDE and M3miDE price categories use the same algorithm for volume estimation, which is based on the Huber formula using a midspan diameter rounded down to the nearest whole centimeter. The M3toDE price category underestimated the over-bark volume by 6.48% compared to the reference price category M3s. The mean log volume estimated through the M3s price category was significantly higher than the M3toDE volume both in individual grades and without grading. We found significant differences between under-bark volume estimates by the diameter band bark deduction method (DBM) and the parametric linear bark deduction method (PLM) used in harvester’s systems according to the Guidelines for Electronic Scaling of Timber for Harvesters in Czechia (GEH) for Scots pine butt logs with rough bark, and also for other logs with normal bark thickness. To obtain under-bark volume estimates of Scots pine timber that are comparable with the Guidelines for Timber Scaling in Czechia (GTS) using the parametric nonlinear bark deduction method (PNM), we recommend using the algorithm of the M3toDE price category, with double bark thickness determined by the diameter band bark deduction method.

Influence of pine (Pinus sylvestris L.) growth rings width on the strength properties of structural sawn timber

Annual growth ring width was considered relative to the mechanical properties of timber from the Silesian Forestry Region in Poland. The timber was acquired from raw wood aged approximately 120 years old, with log quality A, B, and C. The study was conducted on 210 pieces of timber; 70 of them were from each part of the log: butt, middle, and top. The tested parameters, modulus of elasticity (MOE) and modulus of rupture (MOR), were measured on fully dimensional timber (40 × 138 × 3500 mm3) that had been dried and planed in industrial conditions. The density of wood (stereometric method) and annual rings width were calculated after MOR and MOE determination on samples including the entire cross-section cut near the failure zone. The tests revealed that the correlation between the width of growth rings and MOE or MOR depended on the log area: it was the highest for timber from butt logs and the lowest for timber from top logs. Moreover, the correlation between growth ring width and MOE or MOR depended also on the quality class of the logs from which the samples were obtained: it was the highest for timber from class A, and the lowest for class C.

Deformations of boards from uneven-aged Norway spruce stands

This study focused on wood distortion of boards sawn from Norway spruce (Picea abies (L.) Karst.) trees grown in uneven-aged stands. The stands were multi-aged with tree ages up to 170 years. In total, 60 trees were harvested from six stands that had been managed by single-tree selection for decades. A butt log and a top log were sawn from each tree, both 2.5 m long. Wood deformations were measured from boards dried to an average moisture content of 7–10% from the 2.5 m long boards. A linear mixed model was constructed to describe the variation in twist deformations in the boards after drying. According to the model analysis, twist increased with greater grain angle, greater average annual ring width and relative ring width difference, greater knot size and count, and the interaction of grain angle with the vertical log position along the stem. Greater distance of the board from the pith was associated with lesser twist. Contrary to expectations, proportion of compression wood and tree position in the stand diameter distribution were not correlated with twist. Pin knots, although their occurrence and size was minimal, had a high degree of correlation with twist. The occurrence and severity of twist remained approximately at the same level as in even-aged Norway spruce as observed in other studies.

Sawlog quality and tree dimensions of Scots pine 34 years after artificial moose browsing damage

Moose ( L.) browsing causes severe damage in Scots pine ( L.) seedling stands. The effects of this damage on the quality of sawlogs were studied in a long-term controlled experiment. This article reports the stem size and external quality characteristics of Scots pine stems 34 years after artificial moose browsing damage. Damaging the trees by clipping the main stem at the seedling stage reduced the diameter, height, and tree volume of the trees at the end of the experiment. The tree growth reduction was dependent on the severity of clipping. The differences between the damaged and the control trees were more obvious in diameter than in height at the time of final felling. Stem form defects and vertical branches were the most typical externally detectable defects caused by clipping. Defects in the butt logs were detected in 71–89% of the damaged trees, depending on the clipping treatment severity. The stronger the clipping treatment, the more likely the stem form was defected and the more commonly were vertical branches and crooks detected in the stems. The results indicate that both tree dimensions and stem quality suffer from moose browsing. The findings of this controlled experiment more likely underestimate than overestimate the damage in comparison to real moose browsing. Further analyses are required to assess the effects of browsing damage on the internal quality of sawlogs and subsequent economic outcomes.Alces alcesPinus sylvestris

Effects of Density Control and Fertilization on Log Wood Quality from a Douglas-fir Stand in Western Oregon, USA

Abstract This study aimed to investigate the effects of juvenile spacing (precommercial thinning), thinning, and fertilization on Douglas-fir butt log (first 4.9 m) and second log (4.9–10 m) quality attributes: juvenile wood percentage, heartwood percentage, rings per inch, specific gravity, and modulus of elasticity. A 41-year-old, 36.6 m site index Douglas-fir stand in western Oregon, USA was selected as the first stand to explore. Nine common silviculture pathway treatments of juvenile spacing, thinning, and fertilization were applied to independent 0.404-hectare plots. Ninety-nine trees were felled and disks cut at five heights along the stem. Wood properties were measured and calculated from the disks for log quality attributes. There was no effect of silvicultural treatments on log heartwood percentage, but significant effects on other log quality attributes were observed. Juvenile wood percentage and rings per inch declined with stand density control and fertilization treatment. Responses to thinning and fertilization in log specific gravity depend on juvenile spacing. Also, thinning and juvenile spacing were shown to have impacts on log modulus of elasticity.

Predicting knottiness of Scots pine stems for quality bucking

Stem shapes and wood properties are typically unknown at the time of harvesting. To date, approaches that integrate information about past tree growth into the harvesting and bucking process are rarely used. New models were developed and their potential demonstrated for stem bucking procedures for cut-to-length harvesters that integrate information about external and internal stem characteristics detected during harvesting. In total 221 stems were sampled from nine Scots pine (Pinus sylvestris L.) stands in Finland. The widths of rings 11−20 from the pith were measured using images taken from the end face of each butt log. The total volume of knots in each whorl was measured by using a 4D X-ray log scanner. In addition, 13 stems were test sawn, and the diameters of individual knots were measured from the sawn boards. A model system was developed for predicting the horizontal diameter of the thickest knot for each whorl along a stem. The first submodel predicts the knot volume profile from the stem base upwards, and the second submodel converts the predicted knot volume to maximum knot diameter. The results showed that the knottiness of stems of a given size may vary greatly depending on their early growth rate. The developed system will be used to guide logging operations to achieve more profitable bucking procedures.

TESTING ACCURACY OF BUTT LOG VOLUME ESTIMATED BY USING SEVEN FORMULAS FOR CALIBRAIN PINE ( Pinus brutia Ten )

The observed volumes obtained by several volume calculation methods for the butt log volume of Calibrain pine (Pinus brutia Ten.). These butt logs were compared with true volume of each butt log which was determined by aggregating the volumes of measured short (1m) using Smalian’s formula. 150 of sample trees were measured into Zaweta and Atrush districts of Dohuk province. The sample trees presented diameter at breast height from 13.9 to 37.6 cm. and total height from 8 - 19.2 meter.The volume of each butt log was estimated by using (Smalian’s, Huber’s, Newton’s, Hossfeld’s, Bruce’s, Sorenson’s and Centroid method). The accuracy of these seven procedures was analyzed considering volume of butt log lengths 6-m. The results showed that Centroid method was superior for all volumes. As expected, Sorenson formula was the procedure with the worst performance. TESTING ACCURACY OF BUTT LOG VOLUME ESTIMATED BY USING SEVEN FORMULAS FOR CALIBRAIN PINE ( Pinus brutia Ten )

In-stand debarking with the use of modified harvesting heads: a potential solution for key challenges in European forestry

Modern forestry is increasingly confronted with challenges that appear with intensive forest management and the progression of the effects of climate change. The forestry sector is able to react to the changing conditions by adapting management plans, forest structure or planting tree species with a higher stress resistance. However, during stand management activities, silvicultural treatments and harvesting operations can have an impact on the further development of the remaining forest ecosystem. In Germany, the most widely used harvesting system for thinning operations is a single-grip harvester used for felling and processing trees followed by a forwarder for timber extraction from the machine operating trails to roadside. In this research project, debarking rollers and other modifications designed for Eucalyptus harvesting heads were tested on conventional harvesting heads for the first time to assess the possibility of adding debarking to mechanized forest operations under Central European conditions. Seven field tests with varying tree species, diameters and age classes, were established within German state forests in Lower Saxony and in Bavaria. These tests were repeated in both summer and winter seasons to evaluate the influence of associated tree sap flows on debarking quality. Three different harvesting heads were modified to assess the altered mechanical characteristics and setups. To assess debarking ability originating from head modifications, a photo-optical measurement system developed within the scope of the project was used. The results demonstrate that especially for summertime operations, simple modifications to currently used harvesting heads are able to provide an average debarking efficiency up to 90% depending on the modifications. Another key finding is that a negatively affected sap flow, experienced during wintertime operations, resulted in 46% lower debarking efficiency, while spruce bark beetle infestations only resulted in a wider spread of the variation. Additionally, the vertical position of the log within the tree proved to have an influence on debarking efficiency, resulting in 15% lower average debarking for butt logs and 9% for top logs as compared to middle logs. Since a debarking process requires the stem to be fed through the harvesting head on multiple occasions to remove bark, average harvesting productivity might be reduced by approx. 10% compared to productivity measured with conventional harvesting heads. Considering the results and the extent of the modifications, the system proved to be a potential addition to existing harvesting methods facing changing challenges in future forestry.