SELECTED ECOLOGICAL ASPECTS OF FULLY MECHANIZED LOGGING TECHNOLOGIES AND WOOD SKIDDING UTILIZATION IN THE THINNINGS

Tibor Lukáč, Ján Koreň

ABSTRACT

The presented paper analyzes the results of experimental determination related to selected quality indicators of logging in intermediate coniferous stands up to 30 – 45 years, using fully mechanized technology on the basis of medium or large category of harvester Valmet 911.1/6 and forwarder Valmet 9840.1/6 working in three-shift operation.

Key words: harvester technologies, tree mechanical damage, soil demage..

ESSENTIAL ISSUES AND PAPER AIM

Scientific knowledge as well as practical experience of european countries with strong economy and forestry prove that one way which enable to change the exploitation activity into the high efficient, ergonomically advantageous, economic and ecologically substantial production system is judgematical implementation of fully mechanized integrated exploitation technologies and wood logging on the basis of the multioperational machines (harvesters, forwarders, harwarders and mountain harvesters, or cable processors). In reasonable cases (especially from the point of view of ecology) there is necessity to combine fully mechanized,i.e.harvester technologies with motomanual trees cutting and if appropriate also with their extraction to the skidding line by some another mean way.

The issues related to the economical, ecological and technically suitable utilization of particular harvester technologies in different soil-sites, terrain and stand conditions continue to be the subject of the interdisciplinary research and professional experts discussions. Constantly discussed issue is e.g. potential damaging of productive and ecological function of stand soil by multioperational machines thoroughfare moving across dense network of the skidding lines of 3.5 – 4.0 (m) width (as for standard it is considered spacing distance of skidding lines equal to the double of harvesters hydromanipulator optimal reach of intermediate power category, which is 20 (m)).

Following this context it is necessary to resolve e.g. complicated issue of allowed intensity and area extent of of upper soil horizons mechanical damaging, issue of determination of simple, applicable indicators in the practice (external attributes) for relations quantification between mechanical soil damage and potential negative impacts to the soil, resp. forest ecosystem and at the same time the issue of suitable method for practical preventive feasible soil load of certain kind and consistency of forest machines thoroughfares (maximum contact pressure of the mobile mechanism), depending on momentary moisture in such way that machines thoroughfares without any consequence to non-permissible soil damage (e.g. expert information system ProFor“ according to [7].

Results of present research, given e.g. by [1, 2, 6, 8, 9, 10, 11, 12] declare that phytotechnics aims, especially aims of tending logging, can be considerably depreciated by stem damage and trees roots of main stand. Present knowledge enable to identify and quantify frame factors, which are crucial for the intensity of tree hurt and hurt impacts to the value wood production or stability of forest stands. It is necessary to supplement them in particular directions or to indicate the recommendations for the practice.

The paper gives selected results of our department research, acquired during the scientific project GL-1020 solution “Research of technological, performance and environmental parameters of multioperational machines.....“. The paper is focused on the contribution to the creation of data basis for identification as well as for the quantification of ecological criterions and cofficients utilized in the practice for the selection decision process and different utilization of the technical means and logging technologies, wood skidding on the basis of harvesters and forwarders, according to the strategy of sustainable development integrated forest management.

METHODOLOGY

Experimental measurements consisted of detection of mechanical hurt intensity as for above ground part of the remaining stand trees and intensity of the soil concretion in the skidding lines during the thinning process within the coniferous stands aging to 50 years by fully mechanized integrated technology on the harvester Valmet 911.1/6 and forwarder Valmet 840.1/8 basis. Selected technical parameters of verified machines are given in the table 1.

The measurements have been carried out in the stand 242b of Beňuš forest enterprise and in the stands 322, 326a, 327 and 328a of Kriváň forest enterprise during the months october – november 2003. There was division indicated within approximately 20 m spacing distance, what represents double reach of harvester hydromanipulator, while the attempt was maximum utilization of existing skidding lines network. Due to the fact of triple working hours (24 hours daily), for indication the reflex colour tint was applied. During the logging marking there was attempt to focus on good visibility of the marks from the rotary harvester cabin, moving through skidding lines of 3.5 – 4.0 width.

4 – 15 research areas have been established in each stand, having the dimensions 20 m times the distance of the lines spacing (approximately 20 (m)), with the centre in the skidding line.

Intensity of the above-ground trees mechanical hurt has been detected within both sides of the skidding lines, in the remaining stands according to [8] methodology.

The hurt has been observed in three transects given by the distance from the skidding line edge: b < 1 (m), b = 1 – 5 (m), b > 5 (m) – till the centre of the working field.

Continuing the knowledge from the previous research [4, 5] there were mechanical soil deformation intensity parameters for the machines thoroughfares applied: change of the soil surface level – by the special micronivelation equipment and the change of the penetration resistance R_c (MPa) in the 0.05 (m) intervals into the depth of 0.3 (m) using the easy statical penetrometer STP-A with conic head of the apical angle α = 30(°).

RESULTS

Trees hurt during the fully mechanized logging technology in the preparatory felling stands

Basic information dealing with the above ground trees mechanical hurt intensity of the remaining stand is given in the table 2.

Table 2 declares that the average number of the hurt trees in the researched 6 stands is in the range 6.6 – 10.8 % (average 9.0%). Following the working area width, the values of the average hurt are changing from 0 % close to the transport boundary, to 55% at the skidding line edge, i.e. at b < 1.0 (m). Similar flow appears within the working area width also in the case of the average hurt tree size. The average hurt tree area S in the observed 6 stands: in the line distance b > 5.0 (m) S = 0.0058 (m²), at b = 1 – 5 (m) S = 0.0078 (m²) and at b < 1.0 (m) S = 0.0188 (m²).

The average numer of hurt trees 9.0% is comparable with the results of large scale research given in e.g.[2, 9].

It is necessary to remark that above mentioned results have been achieved at continuous non stop machines performance (the difference between daily and night work duality was approximately 3%).

Certain influence on the trees hurt extent can be assigned to the minor experience of the performance personnel with the logging indication taking into the consideration the technical and technological harvester possibilities, in the connection with the pressure on the operator to exploitate each tree which is assigned for the logging (to eliminate the conflicts during the work distribution). According to the data [3], as for the harvester technology the best suitable solution from the point of view of the silvicultural aim, ergonomic operator loading and work productivity and efficiency is the logging indication on the basis of the target trees thinning method principle, i.e. separate marking of the trees which are not allowed neither to be logged nor damaged and separate trees marking which should be logged (eventually such trees which could be, however need not be logged).

As for the integrity it is necessary to mention that the stands in Kriváň forest enterprise have been established by row planting and at the previous tending treatments there was schematical or combined choice applied. In such case the most suitable for the harvester performance would be the scarf conduction of the skidding lines, with the direction to the trees rows. In the researched stands, the skidding lines had to be conducted through the slope parallelly to the trees rows. Strong branchiness cause difficult look-out for the operator, and the risk of the trees hurt was increased, especially in the transect 1 – 5 (m) from the skidding line. As consequence appeared the high hurt intensity, which was e.g. in the 327 compartment 11.3%, what represents double comparing with the stand 242b in Beňuš forest enterprise, where only 6.0% remaining stand trees have been hurt.

From the table 2 it is possible to see more than double diference between the share of hurt edge trees beside the skidding lines, i.e. at b < 1.0 (m), in the stands 242b and 327. Larger hurt in the stand 242b is the result of common influence of these factors: greater number of produced assortments (in the stand 242b 5 assortments, in the stand 327 only 2 assortments) and following this there was a necessity of larger number of the forwarder passage, which transported at the same time mostly only two assortments, in the stand 242b there was more segmented micro- as well as mezzorelief and adhesion conditions requested antisliding chains for the forwarder, lower branchiness of the stand decreased the possibility of the plank buttress protection by the branches layer.

In the table 3 there are given results of the variance analysis characteristics influence: slope inclination J %, density of stand H (pcs.ha^-1) and intervention intensity Z (% of selected trees number) in the researched transects P_0-1, P_1-5, P_0-10 in the stands 322, 326a, 327 and 328a to the relative damage multitude IP proved:
- significant slope inclination influence on edge trees hurt beside skidding lines (b<1 (m)). In this transect the average of the hurt was 31.3% of remaining trees, at the slope inclination J = 15% IP = 21.2%, at the slope inclination J = 45% IP = 51.0%.
- in the transect b = 1-5 (m) the average hurt represented 8.1% of the trees, while more than important appeared stand density influence (at H = 850 (ks.ha^-1) IP = 5.9%, at H = 1750 (pcs.ha^-1) IP = 18.2%) and as very significant choice intensity influence (at Z = 18% IP = 4.1%, at Z = 39% IP = 13.7).

Legend: – dispersion among classes; - residual dispersion; FA – statistical characteristics of Fischer-Snedecer division α – significance level ++/ – difference very significant +/ – significant difference

Soil transformation by the logging and transportation means passage

Soil in the research areas of the stands 326a and 327 has been classified as middle deep, cambizem modal. From the point of view of the graininess composition it is sandy-clay soil, based on granodiorits, in the depth over 20 (cm) surbased. During the logging works time the soil was dry, moderate humid, with good bearing capacity.

Harvester and then forwarder, too, moved through the skidding lines, which were protected by the branches and tops from the logged trees to 70% length. Branches layer was after compression of 0.05 – 0.2 (m) width. Usually one harvester passage and two forwarder passages created in the skidding lines shallow tracks of 6 (cm) depth.

Basic information dealing with the intensity of mechanical transformation of surface soil horizons in the harvester and forwarder tracks, equipped with 600 (mm) wide tires filled by liquid, comparing with the passage impact LKT 81 and LKT 81 TE in the comparable soil conditions is provided by the table 4.

Following the data of the table 4 there is conclusion that average values of the penetration resistance R_c in the machines Valmet tracks not covered, not protected by the branch mat, were higher 34.1–215.8% comparing with the untouched soil, in the places with the protection branches layer 5–20 (cm) it is 19.3–163.1%. For the tractive unit LKT 81 the increase is in the range 0.178-0.500 (Mpa), i.e. 24.0-146.5%.

Possible impacts of these changes R_c on water-air soil mode and assumptions of their duration could be derived from the results of previous own research. For example changes of the penetration resistance as a consequence of 20 passages of LKT 81 and LKT 81 TE, given in the table 4 appeared as a decrease of the soil permeability for the water in all three measured profiles from  2 to 5 grades of 7 elements of the classifying scale Dolgov-Žitkov [5], what in the practice represent 32-810 multiple decrease of the vertical soil permeability. As a consequence of the natural regeneration within 5 years the permeability has been increased in the profile 0.11 – 0.2 (m) of one grade. As for the profile 0.21 – 0.30 (m) there was only nonsignificant change.

DISCUSSION AND CONCLUSION

Results of the experimental measurements confirmed that harvester technologies utilization during the stands tending to the age of 50 years can significantly improve the quality of logging works comparing with the classical technologies of raw stems production.

Using the machines with the wheeled undercarriage for the slope inclination 35% (40%), the number of mechanically hurt trees could be kept under the 10 % limit, the target trees under the 5 % limit. Early wounds treatment should be the component part of the technological procedure.

Nowadays spacing distance of the skidding lines 20 (m) is considered in the given natural and stand conditions as suitable one. Such spacing distance is indicated as standard, because from the technical technological and economical point of view fully correspond to the mechanized Technologies on the harvesters basis. As for harvester hydromanipulator reach over double spacing distance (approximately 20 (m)) it is necessary to consider with the combined, partly mechanized technological procedures – with motomanual felling of the trees, which are out of the hydromanipulator reach, resp. with the trees extraction to the line by the another type of mean. Disadvantage can be lower efficiency and wariness to the remaining stand, as asset it is lower share of the stand soil damaged by the vehicles passage.

Observed multioperational machines caused larger soil transformation than LKT 81 units. From among the technical parameters of utilized machines (tires pressure, wheels loading, type of drive, tires width, wheels diameter, regulation of the inside pressure in the low-pressure tires according to the carrying capacity of the subsoil) in this result the negative share belong to the high wheels loading, high inside tires pressure and the fact, that they were filled by liquid. Taking into consideration the fact that the tires liquid would be changed by air in the case of the harvester and forwarder, although the high inside pressure 280 (kPa) caused the evaluation responsing to the standard, following the methodology [13].

It is well known that the trees dispose by the quantity of mechanisms, by the help of which they compensate the restrictions within the root system caused by the soil transformation and in normal conditions the residual roots are able to ensure acquisition of the water and nutrients, tree anchoring and to achieve the appropriate increment to the stand conditions. As for the extreme situations (dryness, strong wind, soils more poor from the point of view of the nutrients and carbons, soils sorptionally nonsaturated), the restriction influence can be shown by considerable measure. Soil transformation appear as assumption for the tree or the stand damage by abiotic and biotic factors.

Due to the real assumption, that technical parameters of the present and in the close future produced multioperational machines with wheeled undercarriages don´t enable to decrease the contact wheels pressure under 100 – 120 (kPa), using them the production and ecology soil functions within the total stand area cannot be considered. There is recommendation that´s why to regulate the machines movement especially to the skidding lines, where is the tolerance of certain surface soil horizons grade damage.

For the preventive soil protection against its permanent or longterm damage it will be necessary to apply the system of measures also here (e.g. on the methodology basis [7], which enable in operative and objective way to make decisions related to the utilization of different Technologies according to the integrated forests functions, i.e. taking into consideration the natural and the stand conditions.

REFERENCES

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