Timber Losses during Harvesting in Managed Shorea robusta Forests of Nepal

Logging and sawing of timber using conventional tools by unskilled workers causes enormous damage to the valuable timber, residual stand, regeneration, and forest soil in Nepal. The purpose of this study was to find out the volume reduction factor and identify major strategies to reduce timber losses in the tree harvesting process in the Terai Shorea robusta forest of Nepal. Field measurements and product flow analysis of 51 felled trees from felling coupes and randomly selected 167 sawed logs were examined to study harvesting losses. Responses from 116 forest experts were analyzed to explore strategies for reducing harvesting and processing losses. The results showed that timber losses in the felling and bucking stage with and without stem rot were 23% and 22%, respectively. Similarly, timber losses in the sawing stage with and without stem rot were 31% and 30%, respectively. Paired t-test at 5% level of significance revealed that there was significant loss in both tree felling and log sawing stages with present harvesting practice. The most leading factor contributing to timber loss in all of the three stages was the use of inappropriate equipment during tree harvesting. Use of synthetic ropes for directional felling and skidding as well as flexible and portable sawing machine with size adjustment options during sawing were mainly recommended as strategies to reduce timber losses. This study serves as a baseline study to identify and quantify timber losses in different stages of tree conversion and also formulate their reduction strategies in Nepal.

Analysing the Impact of Harvesting Methods on the Quantity of Harvesting Residues: An Australian Case Study

Many parameters can influence the weight of harvesting residues per hectare that remain on plantation sites after extracting sawlogs and pulpwoods. This study aimed at quantifying the impact of the cut-to-length and whole-tree harvesting methods on the weight of harvesting residues using 26 case studies in Australian plantations. A database was created using case studies conducted in different plantations, to measure the weight of harvesting residues per hectare and the components of harvesting residues. An analysis of variance was applied to test the impact made by the harvesting methods. The results confirmed that the cut-to-length harvesting method produced a larger weight of residues (104.0 tonnes of wet matter per hectare (tWM/ha) without additional biomass recovery and 64.7 tWM/ha with additional biomass recovery after sawlog/pulpwood extraction) than the whole-tree harvesting method (12.5 tWM/ha). The fraction test showed that stem wood formed the largest proportion of the harvesting residues in cut-to-length sites and needles were the largest component of the pine harvesting residues in sites cleared by the whole-tree harvesting method. The outcomes of this study could assist plantation managers to set proper strategies for harvesting residues management. Future research could study the impact of product type, silvicultural regime, stand quality, age, equipment, etc., on the weight of harvesting residues.

Modelling the effects of forest management intensification on base cation concentrations in soil water and on tree growth in spruce forests in Sweden

The study investigated the effects of forest residue extraction on tree growth and base cations concentrations in soil water under different climatic conditions in Sweden. For this purpose, the dynamic model ForSAFE was used to compare the effects of whole-tree harvesting and stem harvesting on tree biomass and the soil solution over time at 6 different forest sites. The study confirmed the results from experimental sites showing a temporary reduction of base cation concentration in the soil solution for a period of 20–30 years after whole-tree harvesting. The model showed that this was mainly caused by the reduced inputs of organic material after residue extraction and thereby reduced nutrient mineralisation in the soil. The model results also showed that whole-tree harvesting can affect tree growth at nitrogen-poor forest sites, such as the ones in northern Sweden, due to the decrease of nitrogen availability after residue removal. Possible ways of reducing this impact could be to compensate the losses with fertilisation or extract residue without foliage in areas of Sweden with low nitrogen deposition. The study highlighted the need to better understand the medium- and long-term effects of whole-tree harvesting on tree growth, since the results suggested that reduced tree growth after whole-tree harvesting could be only temporary. However, these results do not account for prolonged extraction of forest residues that could progressively deplete nutrient pools and lead to permanent effects on tree growth.

Analysis of a feller-buncher productivity: a case study of whole-tree harvesting from Marmara region, Turkey

In fully mechanized forest harvesting systems, tree felling activities are mostly performed by using harvesters or feller-bunchers. In some regions of Turkey, where terrain conditions and stand characteristics are suitable, fully mechanized harvesting systems have been recently practiced by some of the logging contractors as private forest industry demands for large amounts of forest products throughout the year. Thus, performances of these newly practiced harvesting systems should be carefully analyzed in order to implement productive and cost-effective mechanized harvesting systems. In this study, productivity of whole-tree harvesting using a feller-buncher was investigated based on stand parameters including tree height, DBH, and volume. The DBH of the felled trees were divided into four classes (i.e. very small: 16-19 cm, small: 20-23 cm, medium: 24-27 cm and large: 28-31 cm) to investigate the effects of various DBH class on the time consumption of cutting stage and productivity of the feller-buncher. To estimate productivity of feller-buncher in harvesting operation, multiple linear and polynomial regressions were also developed and discussed after the interpretation of diagnostic plots. The results indicated that the average productivity of the feller-buncher was 74.96 m3 /h which was closely related with tree height (r = 0.63), DBH (r = 0.67), and volume (r = 0.67). The average moving time was the most time-consuming stage (60%), followed by cutting (29%) and bunching stages (11%). It was found that DBH classes caused statistically significant (p < 0.05) effects on the time spent on cutting stage and productivity of the feller-buncher. The cutting time and productivity increased from very small to large diameter classes, while bunching time increased from very small to small diameter and then medium diameter to large diameter classes. Polynomial regression had a positive impact on the performance of the estimation model of manually field-measured data based on the error parameters.

Imitated Whole Tree Harvesting Show Negligible Effect on Economic Value of Spruce Stands

The increased removal of forest-derived biomass with whole-tree harvesting (WTH) has raised concerns about the long-term productivity and sustainability of forest ecosystems. If true, this effect needs to be factored in the assessment of long-term feasibility to implement such a drastic forest management measure. Therefore, the economic performance of five experimental plantations in three different forest types, where in 1971 simulated WTH event occurred, was compared with pure, planted and conventionally managed (CH) Norway spruce stands of similar age and growing conditions. Potential incomes of CH and WTH stands were based on timber prices for period 2014–2020. However, regarding the economics of root and stump biomass utilization, they were not included in the estimates. In any given price level, the difference of internal rate of return between the forest types and selected managements were from 2.5% to 6.2%. Therefore, Norway spruce stands demonstrate good potential of independence regardless of stump removal at the previous rotation.

Assessing Biomass Removal and Woody Debris in Whole-Tree Harvesting System: Are the Recommended Levels of Residues Ensured?

Forest biomass is a sustainable source of renewable energy and a valuable alternative to finite fossil fuels. However, its overharvesting may lead to soil nutrient depletion and threaten future stand productivity, as well as affect the habitat for biodiversity. This paper provides quantitative data on biomass removal, fine woody debris [d ≤ 7 cm], and coarse woody debris [d > 7 cm] left on the forest floor in whole tree harvesting systems. Using tree allometric equations and inventory field methods for woody debris estimation, we assessed biomass removal on nine fuelwood harvesting sites in Central France, as well as fine and coarse woody debris left on the sites. The aboveground biomass estimates showed a high variability between the studied sites, it varied between 118 and 519 Mg ha−1. However, less variability was found among sites managed as coppice-with-standards 174 ± 56 Mg ha−1. Exported biomass was 107 ± 42 Mg ha−1 on average, including 35 ± 9% of fine wood. The amounts of both fine and coarse woody debris left on sites were generally less than 10% of the total harvested biomass in 2/3 of the studied sites. These amounts are lower than the minimum retention levels recommended by the sustainable forest biomass harvesting guidelines. Therefore, more technical effort and additional management measures should be taken to ensure more woody debris, especially in poor forest soils and thus, to guarantee a sustainable biomass harvesting.

A Combined Measurement and Modelling Approach to Assess the Sustainability of Whole-Tree Harvesting—A Swedish Case Study

The demand of renewable energy has increased the interest in whole-tree harvesting. The sustainability of whole-tree harvesting after clear-cutting, from an acidification point of view, depends on two factors: the present acidification status and the further loss of buffering capacity at harvesting. The aims of this study were to investigate the relationship between these two factors at 26 sites along an acidification gradient in Sweden, to divide the sites into risk classes, and to examine the geographical distribution of them in order to provide policy-relevant insights. The present status was represented by the acid neutralizing capacity (ANC) in soil solution, and the loss of buffering capacity was represented by the estimated exceedance of critical biomass harvesting (CBH). The sites were divided into three risk classes combining ANC and exceedance of CBH. ANC and exceedance of CBH were negatively correlated, and most sites had either ANC < 0 and exceedance (high risk) or ANC > 0 and no exceedance (low risk). There was a geographical pattern, with the high risk class concentrated to southern Sweden, which was mainly explained by higher historical sulfur deposition and site productivity in the south. The risk classes can be used in the formulation of policies on whole-tree harvesting and wood ash recycling.