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1.
Forest harvesting is one of the most significant disturbances affecting forest plant composition and structure in eastern North American forests, yet few studies have quantified the landscape-scale effects of widespread, low-intensity harvests by non-industrial private forest owners. Using spatially explicit data on all harvests over the last 20 years, we sampled the vegetation at 126 sites throughout central and western Massachusetts, one-third of which had not been harvested, and two-thirds of which had been harvested once since 1984. Seedling and sapling densities increased with increasing harvest intensity, but decreased to levels similar to unharvested sites by year 20 for all but the most intensive harvests. The composition of understory trees appears to be only slightly changed by harvesting, and was strongly correlated with adult tree composition. Regeneration was dominated by Betula lenta followed by Pinus strobus; Quercus spp. exhibited little sapling recruitment, even in Quercus-dominated stands. Total vascular plant species richness increased substantially with harvesting on low C:N sites (i.e., rich soils), but was only slightly increased on high C:N sites. While harvesting was associated with a statistically significant change in vascular plant composition, non-metric multidimensional scaling revealed that climate (temperature, precipitation) and C:N ratios were the major correlates of composition. Overall, the compositional impacts of harvesting were minor, perhaps because of the low-intensity of harvesting. However, our results support observations from elsewhere in the northeastern U.S. of limited oak regeneration on both harvested and unharvested sites. In addition, our results suggest that increased harvest intensity may be expected to alter forest composition, particularly on rich sites where invasive species may increase as a result of harvesting.  相似文献   

2.
The concepts of sustainable original harvest (SOH) and sustainable disturbance harvest (SDH), and simple indices such as the ratio of successive harvests do not provide a reliable indication of the sustainability of a harvest. Some limitations of these concepts are illustrated in the context of selection harvesting of timber from natural forests. Four models are used to demonstrate that maintaining an SOH or SDH indicates little about the long-term sustainability of a timber harvest. The concepts may offer greater utility in evenaged systems harvested by clear-felling, but still suffer the limitation that many factors may mask any change in site productivity. Any measure of sustainability should include an appraisal of the condition and vitality of the residual resource. Simple indices based on successive harvests do not consider the residual stand, and can be misleading.  相似文献   

3.
Boreal forest birds have adapted to changes caused by natural disturbances such as fire and this adaptation forms the basis for the Natural Disturbance Paradigm (NDP) underlying recent proposed changes in forest harvesting practices in western Canada. To date, this paradigm has been evaluated primarily at the stand level and within conventional harvesting systems. The potential for improvements in avian conservation at the landscape scale by adopting the NDP approach is largely unknown. We examined the effects of landscape-scale disturbances on forest bird communities by contrasting richness and abundance of birds in (1) 16 single-pass harvest sites with residual forest patches, (2) 29 multi-pass harvest sites with residuals; and (3) 15 salvage-logged post-fire sites with variable harvest intensity. We contrasted bird communities in these treatments with those in unsalvaged post-fire sites of similar age. Post-fire sites were used to provide a metric of the Natural Range of Variation (NRV) to be expected in bird communities. Sites were surveyed for avian community composition and abundance 1–5 years post-disturbance. Redundancy analysis indicated that bird communities differed from the NRV in all of the harvest treatments. However, single-pass harvests provided a somewhat better fit to NRV than did multi-pass harvesting. Avian community similarity was influenced by non-linear responses to area harvested, amount of residual retention, residual composition and pre-disturbance forest composition. An optimization routine created from a General Linear Model, suggests that community similarity to NRV can be maximized by using single-pass harvests over multi-pass harvests, harvesting 66–88% of the timber in the planning unit, and retaining 5–19% of the disturbance area as live residual patches, with 50% of harvests having at least 9% of the area in residuals.  相似文献   

4.
Widespread commercial harvesting of wild edible mushrooms from the forests of the Pacific Northwest United States (PNW-US) began 10–15 years ago. A large proportion of suitable forest habitat in this region is managed by the Forest Service (US Department of Agriculture) and Bureau of Land Management (US Department of the Interior). These lands are managed under an ecosystem management philosophy that entails multiple-use, sustainable forest product harvesting, resource monitoring, public participation in forest management issues, and holistic planning. Managing the harvest of edible mushrooms engages every aspect of this management philosophy. We examine a variety of issues raised by mushroom harvesting and how these issues interact with forest ecosystem management choices. We discuss regulations currently being used by managers to conserve the mushroom resource while further information is gathered, unique challenges and considerations inherent to sampling fungi, and current research and monitoring activities in the Pacific Northwest. Although current scientific evidence suggests that harvesting likely will not harm the resource in the short term, no statistically-based monitoring information exists about the cumulative impacts of intensive and widespread commercial harvesting over long-time periods. We outline a three pronged approach to long-term monitoring of the resource: (1) tracking harvest quantities in areas with intense commercial harvests; (2) sampling productivity in areas with no mushroom or timber harvests; and (3) conducting research to model the relations between forest management and mushroom productivity. Public participation and a broad collaboration among public land management agencies, private forest landowners, forest managers, researchers, and research organizations will make this approach cost effective and the results widely applicable.  相似文献   

5.
Forest managers often seek to balance economic benefits from timber harvesting with maintenance of habitat for wildlife, ecosystem function, and human uses. Most research on the relationship between avian abundance and active timber management has been short-term, lasting one to two years, creating the need to investigate long-term avian responses and to identify harvest thresholds when a small change in habitat results in a disproportionate response in relative abundance and nest success. Our objectives were to identify trends in relative abundance and nest success and to identify landscape-scale disturbance thresholds for avian species and habitat guilds in response to a variety of harvest treatments (clear-cuts, heavy and light partial harvests) over 14 years. We conducted point counts and monitored nests at an industrial forest in the central Appalachians of West Virginia during 1996-1998, 2001-2003, and 2007-2009. Early successional species increased in relative abundance across all three time periods, whereas interior-edge and forest-interior guilds peaked in relative abundance mid-study after which the forest-interior guild declined. Of 41 species with >10 detections, four (10%) declined significantly, 13 (32%) increased significantly (only three species among all periods), and 9 (22%) peaked in abundance mid-study (over the entire study period, four species had no significant change in abundance, four declined, and one increased). Based on piecewise linear models, forest-interior and interior-edge guilds’ relative abundance harvest thresholds were 28% total harvests (all harvests combined), 10% clear-cut harvests, and 18% light partial harvests, after which abundances declined. Harvest thresholds for the early successional guild were 42% total harvests, 11% clear-cut harvest, and 10% light partial harvests, and relative abundances increased after surpassing thresholds albeit at a reduced rate of increase after the clear-cut threshold. Threshold confidence intervals for individual species overlapped their guild threshold intervals 91% of the time. Even though relative abundance of most species (80%) did not decline as the area affected by timber management increased, implementing management at or below our approximate forest-interior and interior-edge harvest thresholds would reduce the number of declining species by half, maintain higher relative abundances of four species with a net decline in abundance but that peaked in abundance mid-study, and maintain higher relative abundances of ten additional species. In contrast, this management strategy also would prevent the increase in relative abundance of seven species and limit the increase in abundance of three species that increased throughout the study.  相似文献   

6.
Non-industrial private forest is the dominant ownership type in the eastern USA. Most of the private owners have non-consumptive, appreciative values and through surveys report little interest in the generation of timber revenue. Timber harvesting in Massachusetts was investigated for a 25-year period to compare the frequency and volume of harvests for five commercial species on private land, to species-specific stumpage prices reported on a quarterly basis. For four of the five species, there was no relationship; however, for one species a consistent effect was identified, whereby the volume harvested and number of harvest events were found to be significantly related to stumpage price, west of the Connecticut River. This effect is absent for eastern Massachusetts, and also not apparent consistently for other species. It is concluded that under some circumstances, private landowner harvest decisions are influenced by stumpage price.  相似文献   

7.
Early successional birds have declined in the northeastern United States due to the regeneration of forest on abandoned farm fields and the suppression of natural disturbances that once provided appropriate habitat. These species have become increasingly dependent on early successional habitats generated by such activities as timber harvesting. Recent approaches of timber harvesting, which range from single-tree harvesting to clearcutting, create forest openings of different sizes and configurations embedded in landscapes with different land use patterns. To assess the importance of forest openings created by timber harvesting for shrubland birds, we surveyed birds on 50 m radius plots in 34 harvest sites (0.5–21 ha). We collected data on multi-scaled habitat variables ranging from plot-level vegetation characteristics to land use patterns within 1 km of each study site. We also monitored mating and nesting success of Blue-winged Warblers (Vermivora pinus) in 10 forest openings.

The abundance of most shrubland species was influenced by plot-level habitat variables, such as tree density and vegetation height, rather than shrubland area or the composition of land uses in the surrounding landscape. Only Eastern Towhees (Pipilo erythrophthalmus) were more frequent in survey plots in larger forest openings. In contrast, neither abundance nor reproductive activity of Blue-winged Warblers was correlated with the size of the forest opening. Their abundance was negatively related to vegetation height, however. Only 54% of the territorial male Blue-winged Warblers in forest openings were mated. We documented relatively low nest success rates of 21.1% during the egg laying and incubation nest stages, but increased success rates during the later stages of nesting.

Our results indicate that even small forest openings with low vegetation provide habitat for Blue-winged Warblers and other shrubland birds. The overall reproductive rate of territorial male Blue-winged Warblers in forests openings was low during the 2 years of the study, however. Further studies are needed to assess the long-term value of this type of habitat for sustaining shrubland bird populations.  相似文献   


8.
Forest management that incorporates the emulation of natural disturbances is promoted as a coarse filter approach to maintaining natural ecosystem functions, yet the initial outcomes of different natural and anthropogenic disturbances of similar severity may be quite different. We question whether a variant of diameter-limit partial harvesting effectively generates structural and compositional patterns similar to those found after spruce budworm outbreaks or windthrow, and whether stands issued from these two partial natural disturbances are more similar to each other or to those resulting from the studied partial harvests. We conducted our study 20-25 years after these partial disturbances occurred to determine whether the patterns converged or diverged over time. Results showed that post-disturbance vegetation distribution and abundance were similar after all partial disturbance types. Tree diameter distribution followed a reverse-J pattern and mean densities of mature trees were similar, although a higher proportion of deciduous species was observed in the partial harvest sites. Snag densities converged among the three partial disturbance types, despite initial differences that likely occurred in snag abundance and differences in the type of mortality (selective tree removal in partial cuts, uprooting/snapping in windthrow and standing mortality after insect outbreaks). The density of moderately decomposed coarse woody debris was significantly lower after partial harvesting relative to after windthrow and spruce budworm disturbances. Although a higher total number of canopy gaps was observed in the sites disturbed by spruce budworm, the percentage of canopy openness was similar among the three partial disturbances. Our results suggest that convergence of structural and compositional components occurred over the 25 year period since the disturbance. Thus after one entry, the studied partial harvests may be reasonable analogs to both of the studied natural disturbances in terms of medium-term post-disturbance species composition and structural complexity.  相似文献   

9.
Forest amphibians, especially salamanders, prefer forests with shaded, cool, and moist forest floors. Timber harvesting opens the forest canopy and exposes the forest floor to direct sunlight, which can increase forest floor temperatures and reduce soil moisture. These microclimatic changes can potentially degrade the harvested stand for amphibian habitat or affect other biotic resources or ecological processes at the forest floor and in the understory. The degree of forest floor disturbance is directly related to the intensity of harvesting, however, the duration of this effect is unknown. We conducted a study of forest floor temperature and relative humidity over a 12-year chronosequence (1993–2004) of timber harvests. We compared simultaneous, paired measurements of temperature and relative humidity at three positions (soil, forest floor, air) in harvested and control sites over three seasonal survey sessions. Vegetation composition and structure were measured at each survey location. Ambient weather conditions were recorded at three open-field locations across the study area.  相似文献   

10.
Sustained yield policies designed to ensure an even annual flow of timber harvests remain the most common approach to forest management on public lands in Canada. Such policies have been criticized on the environmental grounds that timber production is emphasized at the expense of other values, and on the economic grounds that policy-makers try to maximize the harvests level without regard for economic optimality (measured by whether or not revenues cover variable costs of production). In a case study from Northern Ontario, we used a spatially explicit harvest scheduling model to evaluate financial outputs for various scenarios, introducing different timber flow constraints, as well as varying utilization policies. We show that current policies do contribute to firms harvesting at uneconomic levels. More specifically, our results show that reducing harvest levels could increase firm profitability (measured in an increase in net revenues associated with harvesting operations). We estimate that to meet the annual allowable cut (AAC) of approximately 375,000 cubic metres (m3), the firm loses $500,000 annually (measured by the amount by which total harvesting costs exceed log values delivered at the mill). Reducing the target AAC to just under 300,000 m3 leads to a reversed situation, harvesting revenues now exceeding costs by $1.2 million annually. Dropping the even flow constraint leads to even higher annual profitability of $3.5 million, with the drawback that harvesting levels show significant variation over the 100-year planning period. Our results also show that the largest factor influencing the level of profitability is attributed to access costs (principally roading costs). In this case, other harvesting policies, such as utilization standards, may not be significant factors affecting costs in this region of Northern Ontario.  相似文献   

11.
Single-tree and small-group selection silviculture are widely used uneven-age management regimes in the northeastern United States to create structural diversity and provide high quality timber. However, analysis of long-term performance of these systems is uncommon, largely due to limited access to long-term data sets in the region. The Bartlett Experimental Forest, one of the few permanent experimental research sites in the region, offers a rare opportunity to investigate effects of management practices over 60 yr. Modern forestry seeks both economic and ecological goals, and typically entails harvesting to promote growth and regeneration of commercially valuable trees while creating structural and biological diversity. Comparatively little attention has been given to whether silvicultural treatments can sustainably achieve these goals over many harvests and rotations. We examined two selection silviculture techniques and an unmanaged site in New Hampshire to assess tree quality changes by comparing tree grades over 60 yr. We also measured a one-time inventory of downed-woody debris abundances, an important contributor to ecological diversity. We found that tree grades improved over 60 yr of management and differences among abundances of downed wood between sites. We conclude that selection silviculture has the potential to influence tree quality and ecological diversity.  相似文献   

12.
Avian use of even-aged timber harvests is likely affected by stand attributes such as size, amount of edge, and retained basal area, all characteristics that can easily be manipulated in timber harvesting plans. However, few studies have examined their effects during the post-breeding period. We studied the impacts of clearcut, low-leave two-age, and high-leave two-age harvesting on post-breeding birds using transect sampling and mist-netting in north-central West Virginia. In our approach, we studied the effects of these harvest types as well as stand size and edge on species characteristic of both early-successional and mature forest habitats. In 2005-2006, 13 stands ranging from 4 to 10 years post-harvest and 4-21 ha in size were sampled from late June through mid-August. Capture rates and relative abundance were similar among treatments for generalist birds. Early-successional birds had the lowest capture rates and fewer species (∼30% lower), and late-successional birds reached their highest abundance and species totals (double the other treatments) in high-leave two-age stands. Area sensitivity was evident for all breeding habitat groups. Both generalist and late-successional bird captures were negatively related to stand size, but these groups showed no clear edge effects. Mean relative abundance decreased to nearly zero for the latter group in the largest stands. In contrast, early-successional species tended to use stand interiors more often and responded positively to stand size. Capture rates for this group tripled as stand size increased from 4 to 21 ha. Few birds in the forest periphery responded to harvest edge types despite within-stand edge effects evident for several species. To create suitable habitat for early-successional birds, large, non-linear openings with a low retained basal area are ideal, while smaller harvests and increased residual tree retention would provide habitat for more late-successional birds post-breeding. Although our study has identified habitat use patterns for different species in timber harvests, understanding habitat-specific bird survival is needed to help determine the quality of silvicultural harvests for post-breeding birds.  相似文献   

13.
This paper addresses the effects of economic transition policies on forestry in China. The effects of de-collectivization and market liberalization on the forest land area and timber harvest are studied using panel data from four provinces covering the period 1978–1995. Fixed effects ordinary least squares models for forest land cover and annual harvests per hectare are estimated, allowing for differences across provinces and prefectures in northern and southern China. The results show that land tenure reform in general has had a positive effect on forest land expansion, but the absolute size of the effects varies from province to province. The positive impact of the reform on timber harvesting has not taken place at the cost of forest land cover. The claim that market liberalization leads to over-harvesting of forest resources in developing countries is not supported by our results.  相似文献   

14.
Tropical forests are characterized by diverse assemblages of plant and animal species compared to temperate forests. Corollary to this general rule is that most tree species, whether valued for timber or not, occur at low densities (<1 adult tree ha−1) or may be locally rare. In the Brazilian Amazon, many of the most highly valued timber species occur at extremely low densities yet are intensively harvested with little regard for impacts on population structures and dynamics. These include big-leaf mahogany (Swietenia macrophylla), ipê (Tabebuia serratifolia and Tabebuia impetiginosa), jatobá (Hymenaea courbaril), and freijó cinza (Cordia goeldiana). Brazilian forest regulations prohibit harvests of species that meet the legal definition of rare – fewer than three trees per 100 ha – but treat all species populations exceeding this density threshold equally. In this paper we simulate logging impacts on a group of timber species occurring at low densities that are widely distributed across eastern and southern Amazonia, based on field data collected at four research sites since 1997, asking: under current Brazilian forest legislation, what are the prospects for second harvests on 30-year cutting cycles given observed population structures, growth, and mortality rates? Ecologically ‘rare’ species constitute majorities in commercial species assemblages in all but one of the seven large-scale inventories we analyzed from sites spanning the Amazon (range 49–100% of total commercial species). Although densities of only six of 37 study species populations met the Brazilian legal definition of a rare species, timber stocks of five of the six timber species declined substantially at all sites between first and second harvests in simulations based on legally allowable harvest intensities. Reducing species-level harvest intensity by increasing minimum felling diameters or increasing seed tree retention levels improved prospects for second harvests of those populations with a relatively high proportion of submerchantable stems, but did not dramatically improve projections for populations with relatively flat diameter distributions. We argue that restrictions on logging very low-density timber tree populations, such as the current Brazilian standard, provide inadequate minimum protection for vulnerable species. Population declines, even if reduced-impact logging (RIL) is eventually adopted uniformly, can be anticipated for a large pool of high-value timber species unless harvest intensities are adapted to timber species population ecology, and silvicultural treatments are adopted to remedy poor natural stocking in logged stands.  相似文献   

15.
As forests of the eastern United States become fragmented into smaller ownership parcels, there is a growing need for timber harvesting contactors who can economically harvest timber and perform silvicultural operations on small tracts. Traditional large-scale harvesting operators are ill-suited for work on small parcels, due to their high fixed costs. By contrast, small-scale operators, characterized by few workers and low capital investment, offer an opportunity to serve this landowner segment. This paper presents financial and productivity results from a small-scale timber harvesting pilot study conducted on small forested parcels in western Maryland, USA. Acceptable financial performance is possible for these operations, provided that the operator pays close attention to the important factors determining productivity and profitability, including: (1) average tree volume, (2) net delivered price, (3) time utilization, and (4) distance to the site. Although profitable harvesting of saw log quality trees on parcels less than 10 ha is possible, harvesting of small or poor-quality trees remains economically unattractive.  相似文献   

16.
We studied the effects of partial cutting on understory vegetation communities within 19 mixed maple forests in an agriculture-dominated landscape in southwestern Ontario. Woodlots that had been recently harvested were grouped according to provincial silviculture guidelines (standard and heavy cuts) and compared to woodlots that had been uncut for at least 24 years (reference stands). We found significant differences in richness, diversity, and quality of understory vegetation in response to harvest indices. More intensive harvesting resulted in increased richness and diversity, but mostly through the addition of habitat generalists and weedy species. However, partial harvest does not appear to drive vegetation community composition, as ordination methods found no clear community differences between the treatments. Use of the single-tree selection system based on basal area and harvest intensity targets will have an effect on the understory plants, but other factors including past management, disturbance history, and site level microclimate features will also play an important role in shaping vegetation communities. We caution against the removal of large volumes of trees ≥38 cm in diameter, and large reductions in canopy cover, as this can reduce the presence of “conservative” (forest dependent specialist) species, despite a general increase in species richness and diversity. Furthermore, we recommend additional research to investigate the potential for incremental degradation to occur on sites with a long-term history of harvesting, as we found that richness of exotics increased on sites with a history of forest management.  相似文献   

17.
The threat of climate change is now recognized as an imminent issue at the forefront of the forest sector. Incorporating adaptation to climate change into forest management will be vital in the continual and sustainable provision of forest ecosystem services. The objective of this study is to investigate climate change adaptation in forest management using the landscape disturbance model LANDIS-II. The study area was comprised of 14,000 ha of forested watersheds in central Nova Scotia, Canada, managed by Halifax Water, the municipal water utility. Simulated climate change adaptation was directed towards three components of timber harvesting: the canopy-opening size of harvests, the age of harvested trees within a stand, and the species composition of harvested trees within a stand. These three adaptation treatments were simulated singly and in combination with each other in the modeling experiment. The timber supply was found to benefit from climate change in the absence of any adaptation treatment, though there was a loss of target tree species and old growth forest. In the age treatment, all trees in a harvested stand at or below the age of sexual maturity were exempt from harvesting. This was done to promote more-rapid succession to climax forest communities typical of the study area. It was the most effective in maintaining the timber supply, but least effective in promoting resistance to climate change at the prescribed harvest intensity. In the composition treatment, individual tree species were selected for harvest based on their response to climate change in previous research and on management values at Halifax Water to progressively facilitate forest transition under the altered climate. This proved the most effective treatment for maximizing forest age and old-growth area and for promoting stands composed of climatically suited target species. The size treatment was aimed towards building stand complexity and resilience to climate change, and was the most influential treatment on the response of timber supply, forest age, and forest composition to timber harvest when it was combined with other treatments. The combination of all three adaptation treatments yielded an adequate representation of target species and old forest without overly diminishing the timber supply, and was therefore the most effective in minimizing the trade-offs between management values and objectives. These findings support a diverse and multi-faceted approach to climate change adaptation.  相似文献   

18.
In response to concerns about the effects of traditional timber harvesting practices on biodiversity, we examined the effects of alternative silvicultural systems, including partial cutting and modified herbicide use on understory plant communities in an aspen-dominated mixedwood stand. These alternative silvicultural systems match disturbance rates that, based on the intermediate disturbance hypothesis, would support more diverse understory vegetation communities than uncut or clear-cut forests treated with a broadcast spray. Our results indicated that both understory vegetation cover and number of plant species increased at 5 and 10 years after timber harvesting in aspen-dominated boreal mixedwood stands. The highest amount of understory vegetation cover were found in the pre-harvesting herbicide spray treatment areas, likely because understory plants were not directly exposed to the herbicide, whereas the most species occurred in the partial cutting treatment, which represented the most diverse stand structure with both harvested and leave corridors. Understory composition by percent cover of individual species at 10 years post-harvesting was affected by all treatment attributes (i.e., level of harvesting removal, type and time of herbicide application, and mechanical site preparation); however, understory vegetation responded the most to harvesting level. Among treatments, the difference in understory composition was largely attributed to changes in understory species of different shade tolerance.  相似文献   

19.
Sustainable management of bottomland hardwood forest ecosystems requires a knowledge of responses to management impacts, including timber harvesting. The effects of clearcutting and partial cutting on woody vegetation regeneration dynamics, surface and groundwater quality, soil physical properties, and soil respiration were tested in a bottomland hardwood ecosystem in southeastern Texas, USA, through comparison with non-cut control areas. Overstory removal only slightly affected composition of woody vegetation regeneration 1 year after harvesting compared with pre-harvest composition. Initial composition in both cutting treatments appeared to be the strongest determinant of post-harvest composition, at least for the first year after harvesting. There were few significant differences in groundwater properties when harvesting treatments were compared with control areas during a 17-month period following harvest. Turbidity, temperature, electrical conductivity, dissolved O2, NH4-N, NO3-N, and PO4-P of streamwater did not vary significantly among treatments. Slight decreases in total and macroporosity were observed in association with higher bulk densities at 0–5 cm depth in the clearcut and partial cut treatments. Saturated hydraulic conductivity values did not decline significantly with treatment intensity. No significant differences among treatments in measured soil physical properties were observed at 5–10 cm depth. Although in situ soil respiration increased with harvest intensity, treatment had no significant effect on mineral soil respiration. In summary, most variables showed only slight response to harvesting, thereby indicating that harvesting practices can be conducted with minimal initial impacts on measured response variables.  相似文献   

20.
Modern forwarders are an effective extraction option for timber harvesting operations that provide the opportunity for higher levels of mechanization. With their ability to carry logs from the forest to the roadside or processing areas, they have an established lower environmental impact in comparison to tree-length skidding options. However, little is published regarding their productivity potential or the factors that influence productivity. Three case studies were carried out; (1) a selective harvest in Calabria, Italy, with a smaller 12 t capacity John Deere 1110E, (2) a clear-cut on the West Coast of New Zealand, with a larger 19 t capacity John Deere 1910E and (3) a larger clear-cut operation in Canterbury, New Zealand, with two John Deere 1910E forwarders. An elemental time and motion study was used resulting in 73.4 h of detailed data, with 159 cycles extracting 2241 m3 of timber. Productivity models were created for all three sites as well as one combined model. Average cycle time was 33.2, 24.2 and 22.8 min, and average productivity 24.6, 37.1 and 42.7 t per productive machine hour, respectively. Cycle time was the fastest, and consequently productivity the highest, at the Canterbury site where the terrain roughness was low, overcoming any effect of the average small piece size (0.59 m3). Travel speed was slowest at the West Coast site showing the effect of wet and difficult terrain, with travel empty speed being just 3.8 km/h, compared to 6.7 and 6.9 km/h at the other two sites. Productivity at the two clear-cut operations was significantly higher than the selective cut, compounded by the use of the larger capacity forwarders. Distance and payload were significant factors for each cycle time model; in the combined model the sites were also significant. The calculated unit cost of forwarder extraction in the sites ranged from €2.55 to €4.70/m3. For regions such as southern Italy that have relatively low levels of forest mechanization, this information can be used to help design and improve more traditional labor-intensive harvesting systems.  相似文献   

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