Small-diameter Stands Research Articles

Assessing the impact of Hurricane Ivan on aboveground forest carbon dynamics in the Florida Panhandle: A case study from Perdido Bay watershed

Hurricanes can physically transform forest ecosystems, leading to immediate and potentially long-lasting impacts on carbon dynamics. Using Forest Inventory Analysis (FIA) data from the United States Forest Service, we compared the average carbon in trees (saplings, bole, stump, tops) and foliage pre- (2001–2003) and post- (2005–2007) Hurricane Ivan for different tree categories in the Perdido Bay Watershed located in the Florida Panhandle. The log-linear regression model indicates that variables stand type (softwood/mixed/hardwood), diameter, height, physiographic class (deep sands/flatwoods/rolling uplands/small drains/swamps/bottomlands), elevation, field age and plot affected status were statistically significant (p ≤ 0.05) determinants of carbon loss from the forest stands. Results showed that plots with medium-diameter stands lost more aboveground carbon than large and small-diameter stands, similarly, softwood-dominated stands lost more aboveground carbon than hardwood and mixed wood stands. Aboveground carbon decreased in stands with large (≥ 0.15 m) and medium (≥ 0.12 m) diameter-at-breast height (DBH) by 22.74 and 30.22 metric tons/ha, respectively. We ascertained a decrease of 74.51 and 17.82 metric tons/ha of aboveground carbon in hardwood and mixed plots after Hurricane Ivan, respectively. Aboveground carbon in young (< 25 y) taller trees (> 15 m) decreased by 121.55 metric tons/ha of carbon immediately after the hurricane. These findings underscore the critical necessity of comprehending the interplay between forest structure and hurricane activity to forecast the repercussions of such disturbances on carbon stocks. Our provided framework serves as a valuable tool for researchers and policymakers to assess the vulnerability of coastal forests and facilitate strategic planning to protect forests as carbon sinks.

Private forest owner willingness to mobilise wood from dense, small-diameter tree stands

Forests are a source of renewable biomass, and their utilisation will play a vital role in the transition towards a climate-neutral economy. Small-diameter tree management could contribute to this transition via providing renewable biomass for sustainable uses and fostering tree growth towards long-lifecycle bioproducts. The utilisation of small-diameter trees in the EU is still low since new technologies and work models are required to make the operations economically profitable, environmentally sound, and socially attractive. The supply of biomass from small-diameter tree stands is dependent on forest owners with diverse perceptions on their forests and diverse ownership objectives. However, there is scarce research on forest owner perceptions on small-diameter tree management, which encompasses home consumption, self-active work, and commercial forestry services. A survey in four EU countries was designed to identify the main factors affecting the motivation of forest owners to mobilise biomass from small-diameter stands. Factor and clustering analyses were used to identify four forest owner segments: weakly-engaged traders, well-being seekers, self-active profit-seekers, and well-informed service users. The willingness to utilise biomass from small-diameter tree stands and participate in the market was shaped by forest owner knowledge of forestry, economic and socio-cultural motivations, and sensitivity to service offerings. Forest owner preferences for market participation are heterogenous, and thus different policy implementation approaches are needed and proposed.

Productivity of harvesting dense birch stands for bioenergy

Marginal lands could be utilized for increasing energy biomass production independent of industrial roundwood procurement. Dedicated energy biomass production systems on such sites would be based on low stand establishment cost, clear-cutting at an early stage, and coppice regeneration. Harvesters designed for the processing of industrial roundwood are inefficient or too costly to use in small-diameter and dense stands, while insufficient cutting capacity and uneven space distribution of trees limit the use of modified agricultural harvesters developed for short-rotation woody-crop plantations (e.g. willow). We constructed time consumption models for clear-cutting and forwarding of whole trees from un-thinned, small-diameter stands. The data originated from naturally afforested downy birch-dominated stands located in a cutaway peat production area in northern Finland. Stand age varied from 14 to 29 years and stand density was 5150–160,250 trees per hectare. In clear-cutting, a medium-sized forest harvester equipped with an accumulating felling head fitted with a circular saw disc was used, and subsequent forwarding was done using a modified medium-sized forwarder. Cutting productivity was 3–11oven-dry tons (ODt) per effective hour (E0-h), and was highly dependent on stand characteristics (e.g. mean whole-tree volume). At a distance of 300 m, for example, the productivity of forwarding in the time study plots was 6.7–10.4 ODt E0-h−1. Our study indicates that energy biomass can be harvested from young downy birch thickets efficiently by clear-cutting with appropriate machinery.

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.

Harvesting of undelimbed Scots pine (Pinus sylvestris L.) from first thinnings for integrated production of kraft pulp and energy

The present study evaluates the feasibility of undelimbed Scots pine (Pinus sylvestris L.) for integrated production of pulp and energy in a kraft pulp mill from the technical, economic and environmental points of view, focusing on the potential of bundle harvesting. The feasibility of tree sections for pulp production was tested by conducting an industrial wood-handling experiment, laboratory cooking and bleaching trials, using conventional small-diameter Scots pine pulpwood as a reference. These trials showed that undelimbed Scots pine sections can be processed in favourable conditions as a blend with conventional small-diameter pulpwood without reducing the pulp quality. However, fibre losses at various phases of the process may increase when using undelimbed material. In the economic evaluation, both pulp production and wood procurement costs were considered, using the relative wood paying capability of a kraft pulp mill as a determinant. The calculations were made for three Scots pine first-thinning stands with the breast-height diameter of the removal (6–12 cm) as the main distinctive factor. The supply chains included in the comparison were based on cut-to-length harvesting, whole-tree harvesting and bundle harvesting (whole-tree bundling). With the current ratio of pulp and energy prices, the wood paying capability declines with an increase in the proportion of the energy fraction of the raw material. The supply system based on the cut-to-length method was the most efficient option, resulting in the highest residual value at stump in most cases. A decline in the pulp price and an increase in the energy price improved the competitiveness of the whole-tree systems. With short truck transportation distances and low pulp prices, however, the harvesting of loose whole trees can result in higher residual value at stump in small-diameter stands. While savings in transportation costs did not compensate for the high cutting and compaction costs by the second prototype of the bundle harvester, an increase in transportation distances improved its competitiveness. Since harvesting undelimbed assortments increases nutrient export from the site, which can affect soil productivity, the whole-tree alternatives included in the present study cannot be recommended on infertile peatlands and mineral soils. The harvesting of loose whole trees or bundled whole trees implies a reduction in protective logging residues and an increase in site traffic or payloads. These factors increase the risk of soil damage, especially on peat soils with poor bearing capacity. Within the wood procurement parameters which were examined, the CO2 emissions of the supply systems varied from 13–27 kg m 3. Compaction of whole trees into bundles reduced emissions from transportation by 30–39%, but these reductions were insufficient to compensate for the increased emissions from cutting and compaction.

Fuel deposition rates of montane and subalpine conifers in the central Sierra Nevada, California, USA

Fire managers and researchers need information on fuel deposition rates to estimate future changes in fuel bed characteristics, determine when forests transition to another fire behavior fuel model, estimate future changes in fuel bed characteristics, and parameterize and validate ecosystem process models. This information is lacking for many ecosystems including the Sierra Nevada in California, USA. We investigated fuel deposition rates and stand characteristics of seven montane and four subalpine conifers in the Sierra Nevada. We collected foliage, miscellaneous bark and crown fragments, cones, and woody fuel classes from four replicate plots each in four stem diameter size classes for each species, for a total of 176 sampling sites. We used these data to develop predictive equations for each fuel class and diameter size class of each species based on stem and crown characteristics. There were consistent species and diameter class differences in the annual amount of foliage and fragments deposited. Foliage deposition rates ranged from just over 50 g m −2 year −1 in small diameter mountain hemlock stands to ∼300 g m −2 year −1 for the three largest diameter classes of giant sequoia. The deposition rate for most woody fuel classes increased from the smallest diameter class stands to the largest diameter class stands. Woody fuel deposition rates varied among species as well. The rates for the smallest woody fuels ranged from 0.8 g m −2 year −1 for small diameter stands of Jeffrey pine to 126.9 g m −2 year −1 for very large diameter stands of mountain hemlock. Crown height and live crown ratio were the best predictors of fuel deposition rates for most fuel classes and species. Both characteristics reflect the amount of crown biomass including foliage and woody fuels. Relationships established in this study allow predictions of fuel loads to be made on a stand basis for each of these species under current and possible future conditions. These predictions can be used to estimate fuel treatment longevity, assist in determining fuel model transitions, and predict future changes in fuel bed characteristics.

Systems analyses for harvesting small trees for forest fuel in urban forestry

Forests in urban areas are important for recreation. Social, aesthetic and recreational values are at least as important for forest management as economy and conventional forestry considerations. Systems with short, intensive harvesting phases and limited damage to ground and trees are also advantageous, in order to reduce disturbance through harvesting operations. Further, slash free stands constitute a more attractive environment for recreational activities. Forest fuel harvesting may provide these conditions. This study analyses the economic feasibility of harvesting forest fuel in dense, small diameter stands. The analyses are performed as simulated treatments in selected stand types. Both existing and non-existing forest fuel systems are tested. Conventional cleaning and conventional thinning for pulpwood are included as reference systems. The average dbh of removed trees varied between 3.0 and 10.5 cm . The potential yield of biomass in the studied stand types is high—under Swedish conditions over 35 tonnes dry substance per ha. Harvesting pulpwood exclusively means that only a small portion of the potential is utilised. Forest fuel systems based on motor–manual work are the most competitive in the smallest diameter stands. They break even from dbh ∼4.5 cm in birch stands and from ∼5.5 cm in pine. Simulated systems include a feller–chipper–forwarder and a two-machine system with a feller–bundler and a forwarder. Both are suitable for larger tree sizes than the manual methods. The conventional pulpwood method shows the poorest result, but start competing with the poorest forest-fuel systems from dbh ∼10 cm (removed trees).

Damage to Residual Trees by Four Mechanized Harvest Systems Operating in Small-Diameter, Mixed-Conifer Forests on Steep Slopes in Northeastern Washington: A Case Study

Abstract Dense stands of small-diameter timber present unique challenges for land managers. In the inland West, trees in high-density stands often grow slowly and may be at risk to insects, diseases, and catastrophic fires. In 1996, the U.S. Congress recognized a need to address forest health issues and stimulate local resource-based economies in northeastern Washington. Funds were provided for “implementation and evaluation of controlled silvicultural treatment in designated, fire-generated, overstocked, small-diameter stands” (U.S. Congress House Report 104-625). As part of this Congressionally mandated research effort, four harvest units, each thinned to a 20 ft spacing using different harvesting technologies, were surveyed for damage prior to and following commercial thinning. Comparisons were made among the systems tested to assess damage to the residual stand. Overall incidence of wounds, incidence of wounds in different size and severity classes, and wound locations were compared. Each system performed better when judged by some criteria than by others. In general, cut-to-length processing caused less damage to the residual stand than whole-tree harvest; skyline yarding was less damaging than forwarder yarding. Some of the damage may have been a function of the silvicultural prescription and season of harvest. Appropriate silvicultural prescriptions and harvesting technologies can reduce wounding to acceptable levels. West. J. Appl. For. 17(1):14–22.