Sawlog Harvest Research Articles

Effects of altered fire intervals on critical timber production and conservation values

Forests exhibit thresholds in disturbance intervals that influence sustainability of production and natural values including sawlog production, species existence and habitat attributes. Fire is a key disturbance agent in temperate forests and frequency of fire is increasing, threatening sustainability of these forest values. We used mechanistically diverse, theoretical fire interval distributions for mountain ash forest in Victoria, Australia, in the recent past and future to estimate the probability of realising: (i) minimum sawlog harvesting rotation time; (ii) canopy species maturation; and (iii) adequate habitat hollows for fauna. The likelihood of realising fire intervals exceeding these key stand age thresholds diminishes markedly for the future fire regime compared with the recent past. For example, we estimate that only one in five future fire intervals will be sufficiently long (~80 years) to grow sawlogs in this forest type, and that the probability of forests developing adequate habitat hollows (~180 years) could be as low as 0.03 (3% of fire intervals). Therefore, there is a need to rethink where sawlogs can be sourced sustainably, such as from fast-growing plantations that can be harvested and then regrown rapidly, and to reserve large areas of existing 80-year-old forest from timber harvesting.

Evaluating the Economic Incentives of Biomass Removal on Site Preparation for Different Harvesting Systems in Australia

Research Highlights: This study evaluated the impacts of biomass recovery on site preparation costs while proposing a mathematical model and framework to catalogue the benefits depending on harvesting system. Background and Objectives: Biomass as a viable product depends on the requisite costs of production compared to the price paid by relative markets. The removal of biomass directly impacts site preparation costs, and the operational and economic ramifications of this should inform the feasibility of biomass harvesting and market viability. The relative incentives for biomass removal depend on the quantity, presentation, and location of the residues and are thus a result of the commercial sawlog harvesting system. This incentive also largely depends on the required work to prepare a site for replanting. Materials and Methods: This study developed a mathematical model to connect the concepts of site preparation, harvesting, and biomass costs and revenues to determine the maximum net revenue. This work also developed a framework for understanding and calculating the key model inputs related to site preparation and the relative economic site preparation incentive for biomass harvesting. The framework was then illustrated by using industry data from plantations in Queensland, Australia. Results and Conclusions: The analysis identified a potential reduction in site preparation costs due to biomass harvesting of USD 75–450 ha−1, with a greater incentive when using cut-to-length harvesting systems compared with whole-tree harvesting due to the greater volume of residues after cut-to-length harvesting. For example, a removal of 20 t ha−1 of recoverable biomass after cut-to-length harvesting may equate to an economic incentive of USD 22 t−1. Depending on the biomass market, this incentive may represent a significant percentage (or even exceed) the biomass market price. The combination of biomass market price plus site preparation economic incentive may make biomass an attractive market opportunity, even in challenging biomarkets.

Estimating potential harvestable biomass for bioenergy from sustainably managed private native forests in Southeast Queensland, Australia

BackgroundAustralia’s energy future is at the crossroads and the role of renewable sources is in focus. Biomass from sustainably managed forests provide a significant opportunity for electricity and heat generation and production of liquid fuels. Australia has extensive native forests of which a significant proportion are on private land. However, there is limited knowledge on the potential capacity of this resource to contribute to the expansion of a biomass for bioenergy industry. In addition, there are concerns on how to reconcile biomass harvesting with environmental protection.MethodsWe used regional ecosystem vegetation mapping for Queensland to stratify harvestable forests within the 1.8 m hectares of private native forests present in the Southeast Queensland bioregion in 2014. We used a dataset of 52,620 individual tree measurements from 541 forest inventory plots collected over the last 10 years. Tree biomass was estimated using current biomass allometric equations for Australia. Biomass potentially available from selective sawlog harvesting and silvicultural treatment across the bioregion was calculated and mapped.ResultsCurrent sawlog harvesting extracts 41.4% of the standing tree biomass and a biomass for bioenergy harvest would retain on average 36% of felled tree biomass on site for the protection of environmental and fauna habitat values. The estimated area extent of harvestable private native forests in the bioregion in 2013 was 888,000 ha and estimated available biomass for bioenergy in living trees was 13.6 million tonnes (t). The spotted gum (Corymbia citriodora subsp. variegata) forests were the most extensive, covering an area of 379,823 ha and with a biomass for bioenergy yield of 14.2 t∙ha−1 (with approximately 11.2 t∙ha−1 of the biomass harvested from silvicultural thinning and 3 t∙ha−1 recovered from sawlog harvest residual).ConclusionsSilvicultural treatment of private native forests in the Southeast Queensland bioregion, has the capacity to supply a large quantity of biomass for bioenergy. The availability of a biomass for bioenergy market, and integration of sawlog harvesting and silvicultural treatment operations, could provide land owners with additional commercial incentive to improve the management of private native forests. This could potentially promote restoration of degraded forests, ecological sustainability and continued provision of wood products.

Using Different Approaches to Approximate a Pareto Front for a Multiobjective Evolutionary Algorithm: Optimal Thinning Regimes forEucalyptus fastigata

A stand-level, multiobjective evolutionary algorithm (MOEA) for determining a set of efficient thinning regimes satisfying two objectives, that is, value production for sawlog harvesting and volume production for a pulpwood market, was successfully demonstrated for aEucalyptus fastigatatrial in Kaingaroa Forest, New Zealand. The MOEA approximated the set of efficient thinning regimes (with a discontinuous Pareto front) by employing a ranking scheme developed by Fonseca and Fleming (1993), which was a Pareto-based ranking (a.k.a Multiobjective Genetic Algorithm—MOGA). In this paper we solve the same problem using an improved version of a fitness sharing Pareto ranking algorithm (a.k.a Nondominated Sorting Genetic Algorithm—NSGA II) originally developed by Srinivas and Deb (1994) and examine the results. Our findings indicate that NSGA II approximates the entire Pareto front whereas MOGA only determines a subdomain of the Pareto points.

Efficient thinning regimes for Eucalyptus fastigata: Multi-objective stand-level optimisation using the island model genetic algorithm

A stand-level optimisation problem formulated to determine a set of efficient thinning regimes satisfying two objectives, i.e. value production for sawlog harvesting and volume production for a pulpwood market, was demonstrated for a Eucalyptus fastigata trial in Kaingaroa Forest, New Zealand. Genetic algorithms were used to estimate the set of efficient thinning regimes (i.e. regimes that occur when it is not possible to increase the achievement of one objective without reducing another) known as a Pareto frontier. Each thinning regime specified a unique combination of initial planting density; frequency, timing and intensity of thinning; final crop number; and rotation length. Specifications for the “best” regime in the Pareto set (i.e. the one that satisfied a balanced trade-off between value and volume production) were similar to those recommended through professional judgment based on pooled long-term field observations from different eucalypt species grown throughout New Zealand. The advantage of Pareto optimality was the ability of not only identifying a unique thinning regime, but equally efficient regimes each providing a different combination of value and volume production. Research on this approach has the potential of being applied to other forest sites, providing there is sufficient re-measurement data to reflect stand growth dynamics.

Effects of harvest management practices on forest biomass and soil carbon in eucalypt forests in New South Wales, Australia: Simulations with the forest succession model LINKAGES

Understanding long-term changes in forest ecosystem carbon stocks under forest management practices such as timber harvesting is important for assessing the contribution of forests to the global carbon cycle. Harvesting effects are complicated by the amount, type, and condition of residue left on-site, the decomposition rate of this residue, the incorporation of residue into soil organic matter and the rate of new detritus input to the forest floor from regrowing vegetation. In an attempt to address these complexities, the forest succession model LINKAGES was used to assess the production of aboveground biomass, detritus, and soil carbon stocks in native Eucalyptus forests as influenced by five harvest management practices in New South Wales, Australia. The original decomposition sub-routines of LINKAGES were modified by adding components of the Rothamsted (RothC) soil organic matter turnover model. Simulation results using the new model were compared to data from long-term forest inventory plots. Good agreement was observed between simulated and measured above-ground biomass, but mixed results were obtained for basal area. Harvesting operations examined included removing trees for quota sawlogs (QSL, DBH >80 cm), integrated sawlogs (ISL, DBH >20 cm) and whole-tree harvesting in integrated sawlogs (WTH). We also examined the impact of different cutting cycles (20, 50 or 80 years) and intensities (removing 20, 50 or 80 m 3). Generally medium and high intensities of shorter cutting cycles in sawlog harvesting systems produced considerably higher soil carbon values compared to no harvesting. On average, soil carbon was 2–9% lower in whole-tree harvest simulations whereas in sawlog harvest simulations soil carbon was 5–17% higher than in no harvesting.

Effects of forest management on soil C and N storage: meta analysis

The effects of forest management on soil carbon (C) and nitrogen (N) are important to understand not only because these are often master variables determining soil fertility but also because of the role of soils as a source or sink for C on a global scale. This paper reviews the literature on forest management effects on soil C and N and reports the results of a meta analysis of these data. The meta analysis showed that forest harvesting, on average, had little or no effect on soil C and N. Significant effects of harvest type and species were noted, with sawlog harvesting causing increases (+18%) in soil C and N and whole-tree harvesting causing decreases (−6%). The positive effect of sawlog harvesting appeared to be restricted to coniferous species. Fire resulted in no significant overall effects of fire on either C or N (when categories were combined); but there was a significant effect of time since fire, with an increase in both soil C and N after 10 years (compared to controls). Significant differences among fire treatments were found, with the counterintuitive result of lower soil C following prescribed fire and higher soil C following wildfire. The latter is attributed to the sequestration of charcoal and recalcitrant, hydrophobic organic matter and to the effects of naturally invading, post-fire, N-fixing vegetation. Both fertilization and N-fixing vegetation caused marked overall increases in soil C and N.

Harvesting Effects on Long‐Term Changes in Nutrient Pools of Mixed Oak Forest

AbstractThe effects of sawlog harvesting (SAW) vs. whole‐tree harvesting (WTH) on C and nutrient budgets of a mixed oak forest near Oak Ridge, TN, were assessed by sampling soils and vegetation just prior to and 15 yr after harvesting. Fifteen years after harvest, large woody residues in the SAW treatment lost >80% of their mass and nutrient content. Greater concentrations of Ca, K, and Mg were found in both foliage and soils in the SAW treatment than in the WTH treatment, but there were no signs of deficiency in these nutrients and no differences in growth due to treatment. There were nod eclines in exchangeable Ca2+ in the WTH treatment, and the increases in soil exchangeable Ca2+ pools in the SAW watersheds were approximately equal to the amount of Ca2+ released by decomposing residues. On the other hand, no treatment effects on soil C, vegetation biomass, species composition, vegetation N or P concentration, soil bulk density, or soil N were found 15 yr after treatment. Contrary to what has been speculated on regarding the basis of nutrient budgets, this study showed no detrimental effects of WTH on productivity or soil nutrient status (i.e., reductions from preharvest conditions). The results did show, however, that nutrients (especially Ca) from logging residues are largely retained in soils and reflected in elevated foliar nutrient concentrations.

The Effects of Harvesting Practices on West Virginia's Wood Supply

Abstract The status of West Virginia's timber resource was assessed by comparing preharvest and postharvest stand structures of 99 recent harvests. Stands were classified according to silvicultural practice and their potential for production of high-quality sawlogs. Results indicate that West Virginia's forest owners focus on extracting sawtimber. Only 27 stands could sustain another commercial sawlog harvest in the current rotation. Because local demand for low-grade logs and pulpwood is increasing, in the next forest rotation there exist opportunities for landowners to abandon diameter-limit sales in favor of more productive, managed forests.

Long-term effects of commercial sawlog harvest on soil cation concentrations

There is increasing concern about the effects of nutrient removal associated with various forest harvesting practices on long-term site productivity. We measured exchangeable soil cation concentration responses to a commercial clearcut sawlog harvest in mixed hardwoods on a 59-ha watershed in the southern Appalachians. Soils were sampled 17 months prior to, and periodically for 17 years after, harvest. Concentrations of Ca, Mg, and K, increased significantly in the 0–10-cm soil layer for 3 years following harvest compared to pre-treatment levels. Concentrations of Mg and K were still significantly above pre-treatment levels 17–20 years following harvest. Calcium concentrations did not change significantly at the 10–30 cm depth, but both Mg and K showed significantly higher concentrations in some post-treatment years. Soils in the adjacent reference watershed showed no significant changes in soil cation concentrations over the same 17-year period. Results indicate that sawlog harvest using cable-yarding techniques on these sites does not adversely impact soil cation concentrations.

Forest Management Effects on Surface Soil Carbon and Nitrogen

AbstractChanges in surface soil C and N can result from forest management practices and may provide an index of impacts on long‐term site productivity. Soil C and N were measured over time for five watersheds in the southern Appalachians: two aggrading hardwood forests, one south‐ and one north‐facing, undisturbed since the 1920s; a white pine (Pinus strobus L.) plantation planted in 1956; and two regenerating hardwood forests, a whole‐tree harvest in 1980, and a commercial sawlog harvest in 1977. Soils on harvested watersheds were sampled before and for ≈15 yr after harvest. Surface soil C concentration on the undisturbed watersheds varied significantly among sample years. Concentrations fluctuated on the south‐facing and decreased on the north‐facing watershed. The pattern for total N was similar. Total N decreased significantly on the north‐facing but was stable on the south‐facing watershed. In the white pine plantation, C increased while N concentrations decreased during the 20‐yr period. Soil C and N concentrations generally declined the first year following whole‐tree harvest. Fourteen years after cutting, C remained stable, while N was greater compared with reference watershed soils. The commercial sawlog harvest resulted in large increases in surface soil C and N concentrations immediately after cutting. Carbon levels remained elevated 17 yr following cutting. Our data suggest that the forest management practices examined do not result in long‐term decreases in soil C and N. However, the high interannual variation on all watersheds suggests that care must be taken in selecting control sites to determine long‐term treatment impacts.

First-year regeneration in upland hardwoods after two levels of residue removal

The effects of whole-tree removal versus conventional sawlog harvest on 1 st-year regeneration in an upland mixed hardwood site were compared, and sprouting dynamics of species and stump size classes were described. Average sprout production for stumps sampled was greater after conventional harvest: stumps produced taller, denser, and more abundant sprouts. Although sample sizes were small, maximum heights of stump sprouts of Quercusprinus L., Quercusvelutina Lam., and Acerrubrum L. were greater on the conventionally harvested area, and sprouts of Liriodendrontulipifera L. and Oxydendrumarboreum (L.) DC. averaged taller after residue removal. However, most species produced more seedlings after residue removal. Differences were related to greater site disturbance with whole-tree harvest. Number of sprouts and biomass per stump showed a binomial-shaped distribution in relation to stump diameter across both treatments, with a maximum at about 30 cm. Biomass of grape (Vitis spp.) was least following whole-tree removal, but this may be related to site quality or the small size of the study area. Regression estimates of sprout dry weight as a function of height were used to estimate sprout production. Conservative estimates of total stump sprout biomass, excluding foliage, 1year after whole-tree removal averaged 433 kg/ha and after conventional harvest averaged 679 kg/ha.

Size-Volume Classification of Appalachian Hardwood Sawlog Harvesting Residue

Abstract Length and diameter, not quality, limit the use of low-grade roundwood in a number of wood manufacturing processes; therefore the length, diameter, and volume relationship was examined for bolewood hardwood logging residue from sawlog-only harvesting operations. Estimations were made of available residue by length and minimum diameter as well as the volume of bolts or logs of a given diameter and length that can be cut from bolewood residue. At an 8-inch minimum diameter, 81 percent of the residue is available; this decreases to 40 percent if a 12-inch minimum diameter is desired. This is with no cutting except to minimum diameter. Sixty-one percent of the residue can be cut into 8-foot logs with an 8-inch minimum diameter. If the desired long length is increased to 12 feet, 51 percent of the residue can be cut into pieces of this length having a minimum small end diameter of 8 inches.

Effects of Sawlog vs. Whole‐Tree Harvesting on the Nitrogen, Phosphorus, Potassium, and Calcium Budgets of an Upland Mixed Oak Forest

AbstractWhole‐tree harvesting increased the export of biomass N, P, K, and Ca by 2.6, 2.9, 3.1, 3.3, and 2.6 times, respectively, compared to sawlog harvesting in an upland mixed oak forest in eastern Tennessee. Whole‐tree harvesting after leaf fall reduced the potential drains of N, P, K, and Ca by 7, 7, 23, and 5%, respectively, compared with potential removal by harvesting during the growing season. Due to low soil Ca content and high Ca content in woody tissues, whole‐tree harvesting depleted total ecosystem Ca to a much greater extent than N, P, or K. Soil reserves and atmospheric inputs may be adequate to sustain total N, P, and K supplies with whole‐tree harvesting, but soil amendments may be necessary to sustain Ca supplies.