DIGITALNA ARHIVA ŠUMARSKOG LISTA
prilagođeno pretraživanje po punom tekstu
|ŠUMARSKI LIST 7-8/2015 str. 51 <-- 51 --> PDF|
quality of bucking in both CTL as well as cutting and processing with chainsaw (Han, Renzia 2005).
Similar to our research was conducted by Serbian researchers dealing with efficiency of mechanized cutting in Poplar plantations (Danilović et all, 2011). The main aim was to study productivity when different methods of work are used and tree forking effect on the time needed for steam processing. They found considerably longer (52%) average time needed to process forked steams in Poplar plantations.
In coniferous stands (black pine) the impact of tree´s forkness on work productivity using mechanized cutting was analyzed in Croatia (Vusić and Rukavina, 2010). They elaborated productivity models for time consumption for straight and forked tress, which show considerable decrees in productivity (between 50% and 70%) for forked trees.
The assessment of the effectiveness has also been included in the study of suitability of their use (Krč, Košir 2003). In particular, the study discussed the economics of CTL introduction (Krč 2004) and the effectiveness of machine operators’ training for work with harvester and forwarder (Malovrh etal. 2004).
In the year 2010, the research focusing on standard times for large harvesters (John Deere 1270D, John Deere 1470D, Ecolog 580C) has been concluded by Slovenian Forest Institute for the purposes of national standard times tables. Standard times are valid for most frequent use of harvesters (together with forwarding) in thinnings of conifers and broadleaves (cutting intensity between 50 and 100 m3/ha). Following the Slovenian tradition, the trees were marked as were also the trails for cutting and forwarding. The average tree in a cutting unit did not exceed 1.8 m3 for conifers and 1.5 m3 for broadleaves (maximum cutting diameters 60 cm, tip-to-tip diameters up to 40 cm). Combinations between chain saw and harvesters have been recorded, but not included in the final report. One of the main problems has been recording and evaluation of delay times. The technology has not been stabilised yet and several different work day organisations have been met.
Purpose of the research – Cilj istraživanja
Current professional work study and research efforts are mainly concerned with the mechanized cutting in association with wood forwarding.
This study focuses on young hardwood stands and has the following objectives:
1. Identification of differences in the productivity in cut-to-length technology (mechanized cutting) for typical values of the influential variables,
2. Comparison of productivity between fully mechanized cutting and motor-manual cutting, skidding with tractors of different kind.
3. Analyzing the structure of unproductive time. It is assumed that the reduced productivity in hardwood stands compared with the conifers stands largely reflects in higher share of unproductive time. Consequently, there is a smaller proportion of the main productive time due to difficult working conditions, and in particular the hardness of wood and unfavorable morphology in comparison with conifers stands.
MATERIALS AND METHODS
Materijali i metode
Experimental sites – Područje istraživanja
The research area is located in the southeast region of Slovenia, in the vicinity of the town Novo Mesto, regional forest management unit Mirna Gora. The prevailing plant association (Omphalodo – Fagetum galietosum odorata) is one of the best in the Dinaric fir-beech forest sites, now secondary forest of silver fir, spruce and beech with a capacity up to 8.9 m3/ha of annual increment. The section is located on moderate slopes with its altitude ranging between 810 and 930 m. Relief is undulated and sink-holed, mostly of north-east orientation with a maximum slope of 45 %. Rockiness is due to dolomite bedrock very small, but the ground bearing capacity is not problematic and considered above average in the wider region.
The experimental plots (Figure 1, strata I to IV), belong to the developmental stage of older pole-wood stand (DBH between 20 and 30 cm). The current stand tree structure on experimental plot consists of beech dominated stands (13.86 ha) with Norway spruce and maple (Acer sp.). On a small part of the section (4,6 ha) there are Norway spruce pole stands with mixture of deciduous trees while the rest includes pole-wood stand of beech (Fagus sylvatica) with a mixture of mountain maple (Acer pseudoplatanus).There are also portions of low quality mature spruce stand with a mixture of deciduous trees in the sink-holes, with deep soil and rich in nutrients. In some parts of the studied area there are separated trees of mountain elm (Ulmus glabra). Table 1 shows the volume structure of stand by extended DBH size classes.
The average growing stock is 338 m3/ha. The total ten-year allowable cut defined by forest management plan for forest compartment (basic forest inventory unit) amounts to 861 m3 for conifers and 1,841 m3 for deciduous trees, and together represents 22.1% of the total growing stock. Most of the stand originates from the time after 1918 when there was a forest rail-way causing clear cuttings along its track. The new stand developed from a mixture of artificially introduced spruce and natural regeneration of fir and various deciduous species from the wider surroundings. The stands were never thinned with the exception of some remnants