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Raffaele Spinelli Natascia Magagnotti Carla Nati 《European Journal of Forest Research》2011,130(5):737-744
In Italy, poplar plantations represent an important source of wood products, and especially of high-quality veneer logs. These
plantations offer favourable conditions to the introduction of forest mechanisation, and especially easy access and industrial
management. However, owners fear that mechanised log-making may cause value losses, due to poor length measurement, log surface
damage and improper grading. This study compared the performance of manual and mechanised log-making on ten commercial operations,
in order to determine the occurrence and the severity of possible value losses due to product degrade. The study found that
length measurement errors are smaller for mechanised processing, while the frequency and severity of log surface damage are
the same for both treatments. In three cases out of five, mechanised log-making extracted the same value from the stems as
manual log-making: in the remaining two, differences were very small and went opposite directions. Significant differences
were found between operators, stressing the importance of operator skills and motivation. In fact, the log-making specifications
and the pricing structure applied to poplar processing are relatively simple and are unlikely to challenge the ability of
personnel and equipment. At present, most Italian poplar growers are unaware of the potential offered by modern technology,
whose intelligent use would boost value recovery and decrease harvesting cost. Significant benefits may derive from the introduction
of optimised bucking, which may help shifting to a more articulated and rewarding product strategy. 相似文献
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Raffaele Spinelli Rien Visser Catherine Riond Natascia Magagnotti 《Small-Scale Forestry》2017,16(2):179-193
A survey of harvesting contracts was conducted in the Alpine regions of France and Italy. The main goal was to produce a benchmark for the harvesting contract rates in the area that may guide forest owners and logging contractors when making their harvesting decisions. The sample included 443 contracts, evenly distributed between France and Italy. The mean tract size was 9.17 ha, while the mean lot size was slightly larger than 500 m3 under bark (ub). Mean removal intensity varied from 70 to 120 m3 ub ha?1, depending on country and harvesting technique (i.e. ground-based or cable-yarder based). Mean contract rate was 35€ m?3 ub, but individual contract rates varied significantly between countries and for different harvest techniques. Regression analysis showed that contract rate was strongly affected by tree size, extraction distance and harvest technique. Contrary to expectation, neither tract size nor lot size had any effect on contract rate. This may be explained by the widespread use of mobile operations that are specifically designed for handling small lots and incur minimum relocation cost. The technical factors explored in the study could only explain 40 % of the variability in the dataset, and therefore at least part of the variability must derive from non-technical factors such as local market dynamics and national economics. The study did find significant differences between countries. In particular, ground-based operations were more cost efficient in France, and cable yarder-based operations in Italy. 相似文献
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The study determined the productivity, fuel consumption and product quality obtained with a new tractor OWered drum chipper, designed to reduce the gap between industrial chippers and small-scale chippers. The machine as tested with poplar logs and beech slabs, considered as representative of the raw material commonly used for ergy wood production. After accounting for accessory work and delays, productivity of green chips ranged between and 6 tons per scheduled machine hour, which was very good for a tractor-powered unit. Specific fuel consumption f oven-dry chips varied between 2.5 and 3.0 L per ton, or 0.6 L per m_3. These figures compared favourably with those btained from previous studies of both smaller and bigger chippers. Chip quality was very good. Samples contained no versize particles, qualifying for use in small-scale plants. The average size of beech chips was significantly larger than r poplar chips, possibly due to the higher strength of beech wood. 相似文献
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Wood Extraction with Farm Tractor and Sulky: Estimating Productivity, Cost and Energy Consumption 总被引：2，自引：1，他引：1
A winch and a sulky can transform a farm tractor into an effective small-scale logging machine, closely resembling a wheeled
cable skidder. The additional cost of these implements is very small, but they offer significant benefits when extracting
timber under the conditions of small-scale forestry. The authors developed a productivity model for skidding timber with wheeled
farm tractors, equipped with winch and sulky. The origin data pool contained over 300 individual skidding cycles, extracted
from 8 separate tests. Statistical analysis of the data allowed calculating a simple mathematical relationship for estimating
skidding productivity as a function of significant work conditions, such as: piece size, winching distance, tractor power,
skidding distance and crew size. This model can provide useful directions to prospective users, contributing to operation
planning, costing and optimization. It can predict a large proportion of the variability in the data and was successfully
validated using reserved cycle records, extracted from the same data pool and not used for model development. Depending on
tractor power and piece size, the average turn volume and productivity can exceed respectively 2 m3 per cycle and 4 m3 per Scheduled Machine Hour (SMH). Top performance can reach 8 m3 SMH−1, with heavy tractors and large logs. 相似文献
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Natascia Magagnotti Carla Nati Gianni Picchi Raffaele Spinelli 《Agroforestry Systems》2011,82(1):77-86
The study compares two product strategies—chips versus firewood—and two technological levels—manual versus mechanized—as applied
to the thinning of walnut agroforestry plantations, established on ex-arable land. Such plantations are widespread all across
Europe, and their establishment was subsidized under the provisions of EU Directive 2080/90, and of regional grant schemes.
Field test data were used to build a simple deterministic model for estimating thinning productivity and cost under varying
work and economic conditions. This model can assist prospective users when checking the profitability of an operation, or
when assessing the competitiveness of alternative options. Removing nurse alder from young walnut plantations yields between
25 and 50 t of fresh biomass per hectare and is crucial to the good development of the stand. The study shows that the removal
of nurse alder from walnut plantations is economically viable, and it can also offer some profits if stand and market conditions
are favourable. As a rule, the average DBH of removal trees should not be smaller than 12 cm. Best results are obtained with
mechanized harvesting, which does not seem to cause heavier stand and soil damage than manual harvesting. Manual harvesting
is preferable only if the annual utilization of machinery is very low, and in this case it should be geared to firewood production.
The manual whole-tree harvesting (WTH) method used in this study offers the lowest performance under all conditions, and should
be replaced with some other manual alternative to WTH. Mechanized WTH offers a significant cost reduction over mechanized
short-wood (SWS) harvesting, but this difference is still rather limited: hence, other parameters come into play when deciding
what system to apply, and namely product price and mass output. In this respect, one also has to consider the cost of managing
the harvesting residue, and that of fertilizing, if soil nutrient depletion is to be feared. 相似文献
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The authors tested two mini-yarders, one for uphill and the other for downhill extraction. The two machines were modern commercial
models, offering state-of-the-art yarding technology on a miniature scale and at a much lower cost than required for purchasing
a full-size tower yarder. The two units must not be regarded as alternative, but rather as complementary, since they offer
different capabilities and advantages. Both machines were tested while harvesting firewood from the thinning of young beech
stands in Central Italy. The tests indicated that both units can reach a productivity between 1.5 and 2.4 m3 SMH−1, including all delays, as well as set-up and dismantle time. Calculated extraction cost ranged between 24 and over 30€ m−3. The authors calculated a set of regression equations for estimating machine productivity as a function of the main work
conditions. The performance of the studied mini-yarders does not seem much inferior to that achieved by professional light
tower yarder under the same work conditions, but the lighter construction of the small-scale units may result in a lower resistance
to wear and abuse. In any case, mini-yarders seem ideal for deployment under the typical conditions of small-scale forestry,
offering a good solution to wood extraction on steep terrain, competitive with animal and winch logging in terms of productivity,
cost and operator comfort. 相似文献
9.
Two tests were conducted with a new model of mini-forwarder, specifically designed for thinning operations. The tested machine
resembles a conventional industrial forwarder, with tandem bogies and central articulation, but is much smaller and lighter.
The machine was tested on forest plantations established on ex-farm land: such plantations offer favorable and homogeneous
work conditions, which allowed reasonably accurate productivity figures to be obtained with a relatively small number of observation
hours (about 10.5 h). Despite the relative inexperience of the driver, the tests indicated a productivity of between 3.1 and
3.8 m3 per scheduled machine hour (SMH) over an extraction distance of about 400 m. Extraction costs ranged from 12.4 to 15.1 € m−3 at the calculated machine rate of 47.6 € h−1. Compared to older models derived from recreation vehicles or tracked wheelbarrows, the machine tested in this study offers
a better performance and a much more comfortable workplace, with the operator sitting inside an enclosed and insulated cab.
Fitted with four bogies and provided with a much longer wheelbase, the new forwarder is likely to be safer than tracked machines
when surmounting obstacles, and it certainly offers a much smoother ride to the operator. Nevertheless, the tested machine
is still much narrower than industrial forwarders and does not enjoy the same lateral stability. Hence, the machine is ideal
for sneaking between trees and climbing over obstacles, but once on a slope it must be driven straight along the grade and
never across it, unless with much caution. Like all hydrostatically driven vehicles, the tested mini-forwarder is not suited
to long-distance extraction (>1 km): if run at high speed for too long, its hydrostatic transmission tends to overheat, forcing
the operator to make frequent stops. 相似文献
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