Značajke kore podravske crne johe Stankić, Igor; Kovač, Saša; Poršinsky, Tomislav
Nova mehanizacija šumarstva,
12/2010, Letnik:
31, Številka:
1
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Kora je vanjski omotač drveta koju čine vanjski i unutrašnji dio. Od svih značajki kore najveću pozornost zauzima njezina debljina i udio u obujmu stabala i izrađenoga obloga drva. U procesu ...pridobivanja drva, prilikom preuzimanja izrađene tehničke oblovine, u hrvatskom se šumarstvu koriste dvoulazne tablice (vrsta drva i promjer obloga drva s korom) odbitaka dvostruke debljine kore koje nisu rezultat znanstvenih istraživanja. Cilj je ovoga rada istražiti značajke kore crne johe s obzirom na: 1) udjel kore u obujmu stabla, 2) udjel kore ovisno o relativnoj visini stabla te 3) ovisnost dvostruke debljine kore o promjeru obloga drva. Istraživanje je provedeno u gospodarskoj jedinici »Đurđevačka Bilogora«, u sastojini privatnoga šumovlasnika nastaloj pošumljavanjem. Uzorkom je obuhvaćeno 35 primjernih stabala crne johe, po 5 u svakom debljinskom stupnju, od 7,5 cm do 37,5 cm. Utvrđivanje je obujma primjernih stabala provedeno metodom sekcioniranja. Istraživanja su značajki kore crne johe pokazala: • porastom prsnoga promjera udio se kore u obujmu krupnoga drva stabla eksponencijalno smanjuje od 23,6 % (debljinski razred 7,5 cm) do 16,4 % (debljinski razred 37,5 cm), • porastom relativne visine stabla (h/H) udio se kore linearno povećava od 17,8 % (pridanak) do 21,8 % (vrh stabla), • porastom promjera obloga drva s korom dvostruka debljina kore eksponencijalno se povećava od 0,9 cm (7 cm) do 2,7 cm (37 cm). Rezultati provedenoga istraživanja otkrili su potrebu za: • daljnjim istraživanjem ovisnosti dvostruke debljine kore o promjeru obloga drva s korom komercijalnih vrsta drva – čime bi se osigurala nepristranost između kupaca i prodavatelja, • korištenjem mogućnosti (ugradnjom u propisnost) odbijanja kore na tehničkoj oblovini s obzirom na udjel kore u obujmu ovisno o debljini oblovine s korom (što je u suglasju s normom HRN EN 1309–2:2006) – čime bi se osigurala racionalizacija proizvodnje, odnosno krajnjega proizvoda.
Kretnost je vozila određena: 1) dimenzijskim značajkama, 2) sposobnošću svladavanja terenskih čimbenika pri kretanju, 3) vučnim značajkama, 4) okolišnom pogodnošću. Vučna se značajka vozila najčešće ...prikazuje krivuljom klizanja ( – ) te ona ovisi o stanju podloge (nosivosti tla) i ukupnom djelovanju svih sila na vozilo. S obzirom na način prihvata tereta vučna je značajka skidera vrlo kompleksna. Cilj je ovoga rada istražiti: 1) vučnu značajku skidera – faktore bruto i neto vuče, 2) klizanje kotača te 3) korisnost kotača pri kretanju niz nagibe od 15 % i 30 %. Poznavanjem vučnih značajki skidera omogućilo bi se modeliranje njegove kretnosti pri privlačenju drva.
Pri kretanju skidera niz nagib uočene su negativne vrijednosti vučnih sila zato što skider vuče teret svojom masom te se i prijenos snage s motora na kotače vozila ne koristi za vuču tereta (drva) već radi stalnoga kočenja vozila motorom. Faktori bruto i neto vuče iz istoga su razloga negativnoga predznaka kao i klizanje kotača. Pri privlačenju drva niz nagib najvažnije je izbjegavanje blokiranja kotača, što dovodi do potpunoga proklizavanje vozila uz narušavanje upravljivosti, o čemu vozač mora stalno voditi računa.
In the area of Croatian lowland forests, forwarders are usually used for extraction of timber assortments. Within the project »Systematization of norms for the production of timber assortments«, ...which was financed by the state company »Hrvatske šume« d.o.o. (»Croatian Forests« LLC), the process of development and implementation of new productivity norms for forwarders was carried out. Initially, for the execution of the research, it was necessary to gather data about technical characteristics of forwarders most frequently used in Croatia, but also around the world. The morphological analysis was performed and it was the basis for the classification of forwarders into classes. Three classes of forwarders were obtained after cluster analysis and load capacity appeared to be the most important factor. Machine performance was evaluated on 30 research sites. The standard method of time study (snap-back chronometric technique) was used. During the recording process, data of factors influencing forwarding (stand and terrain conditions) were collected. After analyzing the collected data, it was determined that the forwarding productivity depends on the forwarder class, average extraction distance, load characteristics, terrain and stand conditions. Regression analysis was used for identifying the time consumption of individual work components, and the productivity model for forwarding was developed. The obtained model was implemented into the application HsPPI. This is a part of the information system developed by IT Department of the state enterprise »Hrvatske šume« d.o.o. and is used for production planning in timber harvesting. The system is based on dBase IV databases and two main program modules. The main parts of the system are: tree marking data, assortment structure plan, production plan (felling, processing and extraction) and sales plan. Within a part of the production plan there is a module for calculating productivity norms for timber forwarding.
Forest traffic infrastructure is one of the basic preconditions for good quality forest ecosystem management. Since 1991, when the Republic of Croatia gained independence and the company Hrvatske ...šume d.o.o. Zagreb (then Public Enterprise Hrvatske Šume Zagreb) was founded, a large amount of financial resources has been invested in the construction of new and the maintenance and repair of the existing forest roads. Despite considerable past investments in this forestry segment, many more kilometres of forest roads will have to be built until optimal forest openness is achieved. This article analyzes the situation with regard to forest roads in Croatia and focuses on the current state of openness, planned openness, annual construction plans, average construction costs, design costs and others. Problems occurring in the procedure of opening up forests (planning, design, construction with supervision and maintenance) are defined and some basic guidelines for their solution proposed.
Virtualni organizacijski oblici poduzeća (strateški savezi, partnerstva, mrežne i outsourcing veze, virtualni timovi i poduzeća) u suvremenom globalnom poslovanju postaju dominantni. Virtualne ...organizacije jedinstvenoga hijerarhijskog ustroja omogućuju racionalizaciju troškova poslovanja, efikasnije iskorištenje postojećih kapaciteta i fleksibilnost u odgovorima na izazove tržišta.
Ako žele opstati u globalnom okruženju, hrvatska se poduzeća za preradu drva i proizvodnju namještaja moraju specijalizirati za područja u kojima mogu postići vrhunske svjetske rezultate i na njima temeljiti daljnje zajedničko poslovanje, razvijajući i njegujući partnerske odnose s komplementarnim poslovnim partnerima. Proces transformacije (virtualizacije) hrvatskih poduzeća za preradu drva i proizvodnju namještaja teče sporo i uz dosta strateških
pogrešaka koje dovode do kriznih situacija i propasti poduzeća. Znatnija primjena koncepta virtualne organizacije na mikrorazini omogućila bi bržu i bezbolniju transformaciju klasičnih poduzeća, dok bi na makrorazini povećala konkurentnost cijeloga drvnog kompleksa.
The paper presents a comparison of two approaches to describing vehicle trafficability of cohesive soils. The first approach is based on soil consistency and Atterberg index indicators. The second ...approach is based on the cone penetrometer measurement and on the vane shear test, as well as on the EcoWood classification of soil strength.
The research was carried out in the lowland region of pedunculate oak forests in the Sava River basin. Three cut-blocks of different moisture and forest soil strength were selected, in which timber was extracted by a forwarder. Measurements and sampling were carried out
on undisturbed soil. Research results have shown that both approaches to describing vehicle trafficability of cohesive soils describe the soil strength of forest wilderness in a similar way and provide a good basis for developing a trafficability evaluation system, as a future task of forest engineering. The soil cone index and shear strength values calculated in this research do not concur with
the classes of EcoWood soil strength classification and indicate that the limits and ranges of these parameters are questionable. The problem of defining the threshold values of soil strength parameters covered by this research will be the subject of future investigations.
Za kvalitetno i racionalno gospodarenje šumskim ekosustavom neophodno je postojanje prostorno optimalno položene mreže primarne i se kundarne šumske prometne infrastrukture. Postoje različiti ...parametri za kvanti tativnu i kvalitativnu procjenu postojeće mreže šumske prometne infrastrukture, kao i za definiranje nedovoljno otvorenih ili neotvorenih šumskih područja. Re lativna otvorenost (primarna ili sekundarna) u kombinaciji s metodom omeđe nih površina i GIS alatima, predstavlja vrlo učinkovito sredstvo pri raščlambi kolikoće i kakvoće primarnih i sekundarnih šumskih prometnica: Pri tome se dobija vrlo jasan i pregledan vizualan prikaz rezultata svih analiza. Istraživa nja su provedena u g.j. “Bovan-Jelar” Šumarije Perušić smještenoj u gorskom području Like. Formiran je GIS istraživanog područja te uspostavljen katastar primarnih i sekundarnih šumskih prometnica. Obavljena je analiza sekundarne otvorenosti za skider tipa Timberjack 240 C oprem ljen dvobubanjskim vitlom Adler duljine uža 30, 45 i 60 m. Definirane su neotvorene površine i, u odabra nim odsjecima, za inačicu duljine uža vitla od 60 m, predložene idejne trase bu dućih traktorskih putova kojima će se unaprijediti postojeća mreža sekundarnih šumskih prometnica. Analiza je sekundarne otvorenosti napravljena i za novo projektiranu sekundarnu prometnu infrastrukturu, a polučeni su rezultati uspoređeni sa sadašnjim stanjem sekundarne otvorenosti.
Nowadays, under conditions in which forest areas are being opened with increasing number of forest roads due to great need for forest resources, the need for a well-kept system of forest roads ...becomes a necessary prerequisite in the process of intensification of forest ecosystems management. Cadastre of primary forest traffic infrastructure on the territory of the Republic of Croatia has already been established, and now the need for secondary forest road cadastre arises. Development of secondary forest road cadastre methodology will make a great and important step in inventarisation of the entire secondary forest traffic infrastructure. Although this is a comprehensive and very demanding job, it will result in numerous benefits to forest profession. Once established, a comprehensive forest traffic infrastructure cadastre will be able to easily and relatively quickly supplement newly built forest communications. Based on numerous analyses of primary and secondary forest traffic infrastructure, forest experts can enhance the quality of forest communications spatial configuration and direct the process of further primary and secondary forest opening up with the final goal of establishing the optimal primary and secondary forest network from technical-technological, economic, environmental-ecological and sociological-aesthetic point of view.
Background and Purpose: The role of environmental effects in timber harvesting has great importance in decision making and planning logging operations. Consequently, more emphasis should be put on a ...planning system so that environmentally sensitive sites for a certain harvesting system can be recognized and the most suitable machinery selected for given terrain conditions. Material and
Methods: Four main data sources have been used for the model of ecoefficient harvesting system prediction: 1) a digital elevation model (DEM), 2) a digital network of forest roads, 3) forest inventory data and 4) ecoefficient limitations for harvesting systems. Software ArcGIS 9 was used for GIS processing and data analysis.
Results: A model for selecting an ecoefficient harvesting system for commercial forests of Northern Velebit is based on three influencing factors: terrain slope, extraction distance and breast height diameter of trees. Based on the model, a harvesting system is determined for each forest subcompartment. The results show that breast height tree diameter restricts mechanized felling and processing. Fully mechanized harvesting systems could be used only over 7.27% of the researched area. Ground based extraction represents the main technology.
Conclusions: In order to establish functional terrain classification, a model for determining an ecoefficient harvesting system should comprise a geographic information system, and terrain and forest stand data. Specific terrain (limestone combined with relief characteristics) and forest stand conditions (mixed selective forests with natural regeneration) limit the application of some harvesting systems which would otherwise be environmentally acceptable in many other cases.
