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HR  EN   

3-4/2009

WEB EDITION


Scientific-technical and professional journal
of Croatia Forestry Society
                         Issued continously since 1877.
       First issue of this web edition start with number 1-2/2008.
   ISSN No.: 1846-9140              UDC 630*https://doi.org/10.31298/sl
PAPER EDITION
DIGITAL ARCHIVE

HRČAK
Portal of scientific
journals of Croatia
   Issued by: Croatian Forestry Society

   Address: Trg Mažuranića 11, HR-10000 Zagreb, Croatia
   Phone/fax: ++385 1 4828477
   e-mail: urednistvo@sumari.hr
   Editor in Chief: Branimir Prpić


     
 
A WORD FROM THE EDITOR-IN-CHIEF
 
Branimir Prpić   120
ON THE RELATIONSHIP BETWEEN FORESTRY AND OFFICIAL NATURE PROTECTION      
Together with Mr. P. Jurjević, MSc, President of the Croatian Forestry Association, I attended a sector meeting of theforestry workshop held on April 1, 2009. The meeting was organized by the State Institute for Nature Protectionwith thepurpose of discussing a consulting process for the Natura 2000 Ecological Network in Croatia.
To start with, I was astonished not to see any forestry experts among the Institute’s representatives, despite the factthat, until recently, the Institute had always been headed by forestry professionals (Kevo, Šobat, Meštrović, Mihanić). Thebasic phenomenon in the majority of the Croatian national parks and nature parks is a forest: therefore, it is surprisingthat the workshop was not run by a forester working in the State Institute for Nature Protection, if indeed there are anyforesters employed by the Institute.
The forestry science marches on, and the entire discussion on Natura 2000 would certainly have had a different coursehad it been chaired by an experienced forest silviculturalist, ecologist or protector. This was particularly evident whenProfessor Vukelić took the stand:his team had completed their part of work around the National Ecological Networkexceptionally professionally.
Through the Croatian Forestry Association, the forestry science and profession have laid invaluable scientific andexpert foundations for an efficient management with Croatian forests according to the principles of the Zagreb School ofSilviculture. Their work has resulted in the establishment of a naturally managed forest, which has a protective role in 95% of state-owned forests. This does not exist in Europe any more; thus, Croatian forests in fact represent sites of generalnature protection, something to take into account in protecting 20 % of large forest communities.
We were apprehensive about the debates in the sector workshop concerning the prolongation of the rotation period. We ourselves had advocated this approach prior to the occurrence of the atmospheric glasshouse effect, but have sinceabandoned this idea since old forests are inefficient as carbon sinks.We were also puzzled by the report of the StateInstitute for Nature Protection on the “Current State of Nature and Nature Protection in Croatia”, issued for forestry (seein more detail: minutes of the 3rdmeeting of the Managing and Supervisory Board of the Croatian Forestry Association,“Forestry Journal” 11–12/2008, p. 589, paragraph. 2, written by the secretary Damir Delač, BSc.).
Although forestry at the Faculty of Forestry in Zagreb is firmly based on a biologicalprogram of forest as an ecosystem and although foresters are undoubtedly the best educated persons to deal with forest nature protection, we still needbiologiststocomplement the structure of forest ecosystems in the sense of studying a part of animal and plant world, mycorrhiza and allelopathy. However,they can in no way give instructions on how to manage forests. This part of work shouldbe allocated to experienced silviculturalists, ecologists, foresters, phytocoenologists and forest protectors.
An example of good cooperation is that with Dr. Jasminka Radović, a biologist who perceives forests as an exceptional natural wealth in Croatia.

Professor Branimir Prpić, PhD

    authors:
    PRPIĆ, Branimir    ŠL
 
 
ORIGINAL SCIENTIFIC PAPERS
 
Topić,V., L. Butorac, Z. Đurđević, B. Kekelić, G. Jelić  UDK 630* 232.3 (001) Cupressus sempervirens var. pyramidalis Nyman 121
Effect of Container Type on Growth and Developtment of Seedlings of Common Cypress (Cupressus sempervirens var. pyramidalis Nyman) in Nurseriers and Forest Cultures      
Summary: Cypress is a forest tree species that is widely distributed across the entire Mediterranean region. Grown in the Adriatic area, in many coastal and island localities of Central and South Dalmatia it regenerates naturally but does not form large forest stands. Instead, it occurs in smaller orbigger groups. It is mostly found near Orebić, Župa Dubrovačka and further south, while some individual trees can also occur in the warmer sub-Mediterranean parts of Obrovac, Knin, Vrlika and Sinj. Compared to many other Mediterranean species, cypress has a very large distribution range and should, therefore, have an important role in afforesting karst areas, particularly in view of its great economic, ecologic and landscape value.
This paper investigates the impact of container type on the development of common cypress grown in nurseries and forest cultures at various methods of preparing the soil for afforestation. The research was undertaken in the nurseries of Split Forest Administration and in the experimental plot Podi in thearea of Šibenik Forest Office. The goal was to determine which of the studied containers, already in use in regular forest production for several years, have the greatest impact on the development of cypress seedlings in the nurseries and in the experimental plot. The seedlings were planted in the soil undermined with a ripper and in dug holes. Three types of containers were used: Bosnaplast 12, Bosnaplast 18 and PVC bag 7/24. The containers were filled with standard 2:1 peat and soil mixture commonly used in regular nursery production. The seeds were hand-sown in containers on 23 April 2003. After reaching one year, the plants were measured and analyzed in the nurseries and laboratories.
The variables studied in the nurseries and laboratories included plant height, root collar diameter, plant weight, root weight, total plant weight and plant weight - root weight ratio. Root system deformations were observed in each container during plant measurements. Measurements were carried out successively every month on three occasions. Each time three plants were chosen (maximal, medium and minimal height) from each container for morphologic determination. Plant heights were measured with a ruler in cm and root collars with a shubler. The weight of the aboveground and underground plant part was measured with precise scales to two decimals. Scener STD 1600 and Vin RHizo Pro software were used to determine overall length of all the root parts by diameter degrees, as well as total volume, volume by diameter degrees, the average root diameter and root area.
In the experimental plot of Podi, the block method was used to prepare the soil and plant the seedlings in the soil undermined with a ripper, and so was classical afforestation in the holes of 40 x 40 x 40 cm. A total of 826 plants were planted in three separate blocks of 40 x 50 m and monitored. After planting one-year-old seedlings of common cypress, the heights of all the planted stock were measured annually over the period 2003 to 2008 and the survival percentage was determined. A correlation-regression analysis was applied to determine the quantitative grades of particular variables (container type, planting method) on the growth and development of common cypress seedlings in the nurseries and in the experimental plot. Container volume had a strong and positive effect on the growth and development of one-year-old seedlings of common cypress in the nursery (Table 1). Plants grown in larger-volume containers (PVC 7/24) attained bigger heights (r2 = 0.981), bigger plant weight (r2 = 0.985) and bigger root weight (r2 = 0.792), compared to plants grown in smaller containers (B18), particularly in Bosnaplast 12 containers (Figure 1).
Research showed that cypress seedlings developed differently not only in different but also in the same container type. The first analysis of the root system done four months after sowing showed very poor root growth of cypress seedlings, especially of less developed ones, in all container types (Figure 2). Only by the end of October and the beginning of November was root development satisfactory in better developed plants grown in Bosnaplast 12 containers, but not so in Bosnaplast 18 and PVC 7/24 containers. The root system developed better and was richer in a PVC bag than in a B18 container, and especially in a B12 container (Figure 4). During one vegetation, no spiraling of the root system was observed in plants grown in these containers, or it was very slight (Figures 3 and 5), whereas root development, particularly in poorly developed plants, was not adequate. For this reason, seedlings of common cypress should be kept in PVC 7/24 containers and in B18 containers for more than one vegetation, but not longer than for two vegetations. Table 2 shows data on average heights of common cypress plants and their survival percentages by container type and planting method in the first five years of research in the experimental plot. According to the Table, at the end of the first vegetation period, taking into account all container types and afforestation methods, the survival of common cypress plants ranged from 28.0 % to 78.8 %. The best results were obtained in the soil undermined with a ripper and planted with seedlings from PVC 7/24 containers (78.8 %), followed by plants from B18 containers (62.5 %), and plants from B12 containers (61.3 %). In the experimental plot the survival percentage of common cypress planted with a classical method in dug holes was by 50 % lower than that of plants planted in the ripped soil in all container types.
Regression analysis showed the dependence of plant survival percentage and plant height in the plot on container type and planting method (Figures 7 and 8). Plants of common cypress growing in larger containers and undermined soil attained bigger heights (r2 = 0.981) and bigger survival percentage (r2 = 0,792) than those planted in holes.
Five-year monitoring of plant development in the experimental plot showed that the afforestation method with common cypresses planted in the soil undermined with a ripper to 50 to 70 cm in depth gave better results than the classical method of afforestation in dug holes of 40 x 40 x 40 cm. Common cypress plants from polyethylene bags of 923 cm3 planted in the soil undermined with a ripper had an average height of 74.5 cm and maximal height of 181.0 cm. Those planted in dug holes reached a height of 54.5 cm and maximum height of 128.0 cm (Figures 9 and 10). Plants from B12 containers showed the smallest height increment. The average plant height in the soil undermined with a ripper was 48.4 cm and the maximal height was 101.0 cm, while that in dug holes was 38.4 cm to 76.0 cm. The above data show that common cypress is a very useful species for afforesting karst areas and establishing mixed cultures in particular, on condition that the soil is properly prepared for afforestation and only good quality planting stock used. This material includes two-year-old seedlings grown in larger volume containers (900 to 1000 cm3). Planting should be timely and expertly performed and obligatory tending treatments should be applied in the first several years after planting.

    authors:
    TOPIĆ, Vlado      ŠL
    Butorac, Lukrecija
    ĐURĐEVIĆ, Zoran    ŠL
    KEKELIĆ, Branko      ŠL
    JELIĆ, Goran    ŠL
 
Anić,I., J. Vukelić, S. Mikac, D. Bakšić, D. Ugarković  UDK 630* 181.2 (001) Abies alba Mill. 135
Effects of Global Climate Change on the Ecological Niche of Silver Fir(Abies albaMill.) in Croatia      
Summary: The aim of this research is to determine the following: the fundamental ecological niche or potential distribution range of silver fir in Croatia on the basis of selected climatic factors, differences between parts of fir distribution range with reference to the selected climatic factors and changes in the ecological niche in terms of the climate change model for the period 2000 – 2100.
Climatic data for the period 1950 – 2000 used in this work were taken from the Worldclime database (Hijmans et al. 2005). Eight climatic variables and relief factors were employed to construct the prognostic model, such as altitute (m), slope (°) and others. Highly correlated variables were rejected. To predict climate changes for the period 2000 – 2100, a CCM3 model (Climate Change Model) was used, which is based on double the current level of greenhouse gases (CO, CH 4, N2O, CFC-11 and CFC-12) (Govindasamy et al. 2003). All climatic data in grid form were 2entered in 30-second resolution (~ 1 km2). Data on fir occurrence in Croatia were taken from the latest research on the distribution of forest sites (Vukelić et al. 2008), ICP plots, phytocoenological relevé database of the Republic of Croatia and management plans. In each plot fir occurrence was graded with binary variables – 1 (present) and 0 (absent).
Independent variables used to construct the logistic model and prediction included elevation – Elev (m), slope – Slope (°), mean annual temperature – MeanAnnT (°C), mean annual temperature range – MeanAnnTR (°C), obtained as the difference between the mean temperature of the warmest and the coldest month, then the ratio between the mean monthly temperature range and the mean annual temperature range – IsoTherm (°C), mean temperature of the driest quarter - MeanTDQ (°C), mean temperature of the coldest quarter – Mean TCM (°C), mean annual precipitation quantity – MeanAnnP (mm), mean annual precipitation in the warmest quarter – MeanPWQ (mm) and coefficient of seasonal precipitation variation – PreS (mm).
The distribution range of fir was divided into three parts: DIN – the Dinaric part of fir range within the community Omphalodo-Fagetum /Tregubov 1957/ Marinček et al. 1993, ACD – the Dinaric part of acidophilic fir communities (Blechno-Abietetum Horvat /1938/ 1950) and PAN – the Pannonian part encompassing fir range within the community Festuco drymeiae-Abietetum (Vukelić et Baričević 2007). Discriminant analysis (DA) was used to analyze and visualize ecological niches within the range. The prognostic model of ecological niches for the current distribution range of fir and that for the period until 2100 with regard to climate change model was made by means of logistic regression (LOGREG), expressions: p(y)= exp(LP)/(1+exp(LP)), where LP represents linear combination of independent variables (Flantua et al. 2007).
According to the research, the current range of silver fir in Croatia does not differ dramatically (p . 0.9) from the potential one. This suggests that longlasting forest management did not contribute to its reduction. However, the selected climatic factors could have a signficant effect on the occurrence of silver fir in Croatia. The prognostic model shows that in conditions of global climate changes its potential range (p = . 0.9) in Croatia could decrease by ~ 85% in the period 2000 – 2100.
Key words: Abies albaMill.; climatic factors; distribution range; ecological niche; global climate changes

    authors:
    ANIĆ, Igor      ŠL
    VUKELIĆ, Joso      ŠL
    MIKAC, Stjepan    ŠL
    BAKŠIĆ, Darko      ŠL
    UGARKOVIĆ, Damir    ŠL
 
Klobučar,D., R. Pernar  UDK 630* 585 (001) 145
Artificial Neural Networks in the Estimation of Stand Density from Cyclic Recordings      
Summary: In the field of remote sensing the results of research undertaken with the purpose of determining quantitative and qualitative stand parameters showed the usefulness of artificial neural networks (Ardö et al. 1997, Skidmore et al. 1997, Wang & Dong 1997, Moisen & Frescino 2002, Ingram et al. 2005, Joshi et al. 2006, Kuplich 2006, Verbeke et al. 2006, Klobučar et al. 2008) as an alternative approach to classical statistical methods.
This paper explores the possibility of estimating and distributing stand density using methods of artificial neural networks. These methods involve particular textural features of first and second order histograms on a digital ortophoto compiled from black and white aerial photographs at an approximate scale of 1:20,000. The paper is also aimed at collecting data with an acceptable accuracy, which will reduce material investments. Research encompassed the area of the MU “Jamaričko Brdo”, Lipovljani forest administration. Cyclic surveying was conducted in 2000.
In order to determine textural features of first and second order histograms, a sample was cut out from a digital ortophoto for 80 stand scenes (compartments/subcompartments) in management classes of pedunculate oak, sessile oak and common beech of the fourth (the most common), fifth and sixth age class.
A multi-layer perceptron was used to solve the problem of stand density estimation. A multi-layer perceptron is a neural network without feedback connections, where supervised learning is carried out with the error back propagation algorithm.
An early stopping method was applied to improve generalization. The early stopping method is a statistical cross-validation method in which the available data are divided into three sets: training, validation and testing set. Of the overall dataset, 50 % (or 40 compartments/subcompartments) relates to the training set, whereas the two remaining datasets were divided equally: 25 % (20 compartments/subcompartments) relate to the validation set and 25 % (20 compartments/ subcompartments) to the testing set.
There are numerous variations of error back propagation algorithms. As for the early stopping method, it is not advisable to use an algorithm which converges too rapidly (Xiangcheng et al. 2005, Demuth et al. 2006). Consequently, two algorithms were used: resilient back-propagation and scaled conjugate gradient algorithm.
Prior to training the neural network itself, the data were preprocessed. In this sense, two operations were performed using MATLAB functions: normalization of input-output values and analysis of the main components of input values.
Training encompassed a total of seven algorithm models with error back propagation with one or two hidden layers containing a different number of hidden neurons. Different activation functions were also applied in hidden and output layers.
Self-organizing neural network was used to control densities according to their distribution into three categories (normal, less than normal, poor). To study the applicability of this neural network, 80 compartments/subcompartments were divided into two sets: training set and testing set, each consisting of 40 compartments/subcompartments. The data were preprocessed before the neural network was trained, just as was the case with the multilayer perceptron.
Textural features of first order histograms (arithmetic means, standard deviation, smoothness, third moment, evenness and entropy) and second order histograms (absolute value of difference, inertia, covariance, entropy and energy) were used as input data for the neural network, whereas output density values were taken from the Management plan.
Output values may also be represented as the number of trees, basal area or volume per hectare or as some other quantitative and qualitative stand values. Stand density was used as an output value for two reasons: a) poorer spectral features of the applied photographs, and b) the fact that, from the aspect of the forestry profession, the photographs were obtained in the unfavorable period (time of the year in which the ground is the least covered with vegetation).
To test the difference in stand density values between the data from the Management plan and the optimal model of artificial neural network, the analysis of variance for repeated measurements was used.
Research confirmed good generalization characteristics of a multilayer perceptron in density estimation, as well as the fact that a self-organizing neural network can be used to control and distribute stand densities. The applied procedure of density estimation achieves an acceptable accuracy and a high degree of automatism, which removes the subjective nature of classical remote sensing methods.
This research confirmed the advantages and disadvantages of artificial neural networks. The advantages are as follows: it is not necessary to know data models, the networks can be used to analyze new conditions, and they tolerate imperfect data. The disadvantages are: the need to determine optimal architecture and the impossibility of estimation outside the scope of learning data values. However, despite their numerous advantages, artificial neural networks will not completely replace classical statistical methods. Instead, a dual approach and integration of these two techniques in decision making processes will be a very useful tool in forest resource management of the 21st century. They are currently broadly applied, so we could say that this is a time of transition to the technology of artificial neural networks. Consequently, forestry of the Republic of Croatia should make broader use of this new technology.
Key words: artificial neural networks; cyclic aerial photographs; density; remote sensing; texture

    authors:
    Klobučar, Damir
    PERNAR, FINTIĆ, Renata      ŠL
 
Pernek,M., D. Matošević  UDK 630* 453 (001) Obolodiplosis robiniae 157
Black Locust Gall Midge(Obolodiplosis robiniae), New Pest on Black Locust Trees and first Record of ParasitoidPlatygaster robinaein Croatia      
Summary: Black locust gall midge (Obolodiplosis robiniae) (Diptera: Cecidomyiidae) is the most recent invasive species in Europe originating, like its host plant, from North America. It started its quick spread in Europe in 2003 from the Veneto region in Italy where it was first found. Platygaster robiniae( Hymenoptera: Platygastridae), parasitoid of the midge was first described as species in 2008. In the researches of the black locust gall midge only one record was given for Croatia (in 2006) but without details. The aim of this research was to record the distribution, biology, parasitoids and damages of this newly introduced insect species in Croatia.
The presence of black locust gall midge was recorded by inspection of black locust leaves on the following localities: the greater surrounding of Zagreb, Jastrebarsko, northwestern (Đurmanec, Lepoglava, Ivanec), submediterranean (island Krk) and mediterranean (surrounding of Zadar) part of Croatia (Table 1). The presence of larvae and parasiotids in galls was researched on the sites in Zagreb. On 9 July 2008 a sample of 20 black locust leaves was taken from 3 trees and analised. Galls (Figure 1) with white (Figure 2) and yellow larvae (Figure 3) were found on the leaves. White larvae are young and yellow older instars.
In the sample of 20 leaves i.e. 251 leaflets of black locust 599 galls were found which is 2,3 galls on average per leaflet. Total number of larvae was 1183 or 2 larvae on average per gall, out of which yellow larve (916) were numerous than white (82) (Table 2). Parasitised larve (Figure 4) and cocoons of parasitoidPlatygaster robiniae(Figure 5) were found in galls. The percentage of parasitism of black locust gall midge in the sample was 15,6 % (Table 2).
The black locust gall midge can be cosidered as a new invasive species in Europe as well as in Croatia. The midge was very probably introduced to Europe with planting material and its main vectors of dispersal in Europe were black locust ornamental plants trade and intensive international vehicle transport. The dispersal in Croatia had two main entries: from Slovenia and Hungary for the continental part and from Italy for the Mediterranean part.
The observations of the black locus midge biology in the northwestern Croatia in 2008 have not shown the development of new generation after July. The last larvae in galls were found on 9 July. Our own observations and different data on overwintering of other researchers have shown a need for more researches of the various aspects of black locust midge biology (number of generations, overwintering).
In the galls of the black locust gall midge the parasitised larvae (Figure 4) and cocoons of parasitoidPlatygaster robiniae(Figure 5) were found on all localities of research in Croatia. This is the first record of this species in Croatia. From the percentage of parasitism of 15,6 % it can be presumed that the midge is present in Croatia for several years (which confirms the record from 2006) and that the parasitoid has successfully adapted itself to the new pest. In the next year a more intensive spread of black locust gall midge in Croatia can be expected, but also a multiple rise in parasitism levels.
Black locust gall midge makes distinctive damages on leaflets of black locust - galls (Figure 1). Numerous galls on leaflets influence the assimilation process and can cause premature leaf drop. The galls influence the aestethic value of black locust ornamental plants. The estimation of damages caused by the midge vary considerably in Europaean countries. Black locust is not an important forest species in Croatia so the black locust gall midge is not considered as important forest pests. Aesthetic damages can be expected on ornamental plants.
Key words: black locust; damage; Diptera: Cecidomyiidae; Hymenoptera: Platygastridae; new introduction

    authors:
    PERNEK, Milan      ŠL
    MATOŠEVIĆ, Dinka      ŠL
 
Butorac,L., V. Topić, G. Jelić  UDK 630* 116 + 434 (001) Pinus halepensis Mill. 165
Sufrace Runoff and Soil Loss in Burnt Stands of Aleppo Pine(Pinus halepensisMill.) Growing on Colluvial Soils      
Summary: Severe degradation of forest ecosystems in the Mediterranean karst area is largely responsible for their lessened anti-erosion function. Almost 60% of the area is covered with coppices, scrub, maquis and bare land, while high forests of mostly Aleppo and black pine account for only 9.9 % of the forested area (Topić, 1994). In addition, fires in this area are generally of alarming proportions, making it possible to attribute soil erosion, to a certain extent, to the impact of forest fires.
This paper presents the results of research into erosion and surface runoff in the Aleppo pine area burnt in a fire on 11August 2001. Post-fire vegetation progression was monitored and so was its impact on soil protection from erosion and surface runoff.
Research was conducted in the Žrnovnica river in a wider area of the town of Split. This is the eu-Mediterranean phytogeographic region characterized by the Mediterranean climate with distinct oscillations of monthly temperatures and precipitation. Mean annual air temperature is 15.9 °C and mean monthly precipitation is 826 mm. Annual precipitation is not uniformly distributed across all the months and seasons. The cold part of the year is responsible for 63 % of the mean annual precipitation quantity.
A stationary forest experiment, set up in August 2002, involved a burnt area of Aleppo pine growing on colluvial soil with predominant stone detritus at an altitude of 83 m and slope of 30° (GPS coordinates: N 43° 31’, E 16° 22’). Research encompassed a period spanning from August 2002 to the end of December 2005.
Research was centered round a 20 m x 5 m experimental plot set up parallel with the slope. The plot was furnished with an erosion collection tank and fenced off with a tin fence. The positioning of the fence prevented the reception of lateral water and/or soil suspension, as well as uncontrolled water or soil suspension loss. Precipitation quantity, precipitation intensity and surface runoff were measured in the plot, and so was the quantity of erosion sediment as the basic indicator of the effect of forest vegetation and vegetation in general. A pedological profile opened in the plot provided soil samples that were analyzed in the laboratory.
The measure of the association between surface runoff, soil loss and precipitation characteristics was estimated with Pearson’s correlation coefficient (Sokal, 1995). A significance level of 5 % was considered statistically significant for all statistical analyses. All statistical analyses were made using the STATISTICA 7.1 software (StatSoft, Inc. (2006).
During the study period (2002 – 2005) there were 265 rainy days with total precipitation of 3,244.1 mm. Mean annual precipitation reached 973.2 mm. Surface runoff and soil losses were recorded in 63 rainy days. They were caused by 24 low-intensity precipitation events, 20 moderate intensity events, 9 high intensity events and 2 very high intensity precipitation events. No data on precipitation intensity for 8 days with runoff are available because there was no ombrograph in the plot at the very beginning of monitoring.
Surf ace runoff was caused by precipitation between 8.2 mm (high intensity) and 133.7 mm (very high intensity). Precipitation less than 10 mm caused surface runoff in only two cases. In almost 50 % of the cases the quantity of surface runoff was equal to or less than 0.1 mm/m2. Total surface runoff in this plot for the study period (2002–2005) was 14.6 mm/m2; 4.71mm/m2in 2002, 2.08 mm/m2in 2003, 4.40 mm/m2in 2004 and 3.41 mm/m2in 2005). Monthly values of surface runoff ranged from zero to maximal 3.03 mm/m2in September 2002. The mean surface runoff coefficient was 0.0042. It is evident that the surface runoff percentage in the burnt area on skeletal colluvial soil was low and that interception, evaporation and infiltration of water in the soil reached as much as 99.6 %. The total erosion sediment quantity in the study area in the period 2002 to 2005 was 11.22 g/m2; (10.83 g/m2in 2002, 0.016 g/m2in 2003, 0.123 g/m2in 2004, and 0.246g/m2in 2005). Monthly soil loss values ranged from zero in summer months to maximal 9.50 g/m2in September 2002. The surface runoff coefficient ranged from 0.0020 to maximal 0.1165 in erodible days. The highest surface runoff and soil loss was concentrated in autumn and winter months, which coincides with the seasonal distribution of precipitation in the study area. The burnt area is covered with natural grass vegetation. In contrast, Aleppo pine regenerates poorly and occurs only in traces. It is the grass cover, occurring as early as the first year after the fire, and the features of the soil in which the plot was set up that are responsible for such low surface runoff and soil loss values. The grass cover protects the soil from raindrops hitting the ground, while its dense roots guard it against erosion. Such low soil losses can also be attributed to the geological and pedological characteristics of the plot, which was set up in distinctly skeletal colluvial soil that is exceptionally water permeable and acts as a “sieve”, thus making the losses negligible or almost non-existent. Surface runoff and soil erosion in such soil and vegetation are not distinct.
Key words: Aleppo pine; burnt area; colluvial soil; karst; precipitation; soil erosion; surface runoff

    authors:
    Butorac, Lukrecija
    TOPIĆ, Vlado      ŠL
    JELIĆ, Goran    ŠL
 
Vuletić,D., S. Krajter, M. Mrazek,A. Ćorić  UDK 630* 652 + 289 (001) 173
Non Wood Forest Products and Services – Are we Using them Enough?      
Summary: Nowadays under the influence of climate changes it becomes clearer that forestry profession needs to take advantage from multifunctional character of resource that manages using all its products and services on sustainable way (National forest policy and strategy, NN 120/03). This process needs to be welcomed in private forest sector as well. Beside timber there are number of non-wood forest products and services provided by forests.
Non-wood forest products and services comprises different forest fruits, mushrooms, handicrafts from wooden and non wooden material, and especially social services like recreation, tourism, hunting, etc. (Sabadi et al. 2005). More intensive use of non-wood forest products and services opens number of possibilities for development of micro, small and medium entrepreneurships which can foster economical development in rural areas.
For the purpose of better understanding of existing level of usage and development possibilities based on this products, under the Project: “Identifying of values of non- wood forest products and services and possibilities of its use” financed by Croatian forests ltd.co on field of its Forest District Karlovac covering area of Peters’ mountain, this investigation has been conducted on citizens of tree municipalities: Topusko, Vojnić and Gvozd. The aim was to find out how local citizens recognized forest functions and its products and services, and are they use them and how. Special aim was to find out presence of interest for starting the entrepreneurship among local citizens. For method the interview face-to-face using semi-structured questionnaire was chosen. Peters’ mountain is area traditionally forestry oriented but recently also known as recreational area with more expressed social services.
Project is realized in cooperation of Forest research institute, Jastrebarsko, Department for forest management and forestry economics, Croatian forests ltd.co Forest District Karlovac and postgraduate student from Paris 12 University. Additionally this project will result with two master theses.
Presented results showing that this type of research, beside all its difficulties and imperfections provide valuable information and good basis for objective assessment of non-wood forest products and services use, as well existing interest for starting private entrepreneurship. Level of non-wood forest products usage can be assessed as high with prevailing use of mushrooms (76,0 %), followed by forests’ fruits (51,4 %), honey (25,5 %) and medicinal plants (20,2 %) (table 1). In case of recognition of forest functions’ importance, the most important is timber production function (79,3 %), second is health (67,3 %), and non-wood forest products (50,5 %). Beside the strong recognition of productive forest function important is to stress very strong recognition of social forest functions.
Majority of respondents (60 %) visiting forest often, 42 % of them even during Winter, and most frequently chosen reasons for visit are leisure and entertainment (41,3 %), health (36,5 %) and sport and recreation (21,2 %) (table 3). The frequency of visits, and interest for sport and recreation growing with achieved level of education and household income. Visitors while they are in forests most often picking forests’ fruits (75 %), walk (64,9 %) or observe wildlife (31,7 %).
Concerning their satisfaction with situation in forest and offer 45,3 % are completely satisfied, 42,2 % are partially satisfied and only 12,5 % are not satisfied at all. Level of satisfaction has reverse proportionality with level of education and household incomes.
Interest for starting private entrepreneurship is studied using model of logistic regression which put some light of direction and strength of influence of investigated variables on one Yes/No question. Results revealed that private forest owners has 2,6 times bigger willingness for starting the entrepreneurship than other population (table 2). On appearance of positive answer on that question use of non-wood forest products has positive influence. Based on results gained the average possible private entrepreneur can be described as private forest owner which use forest fruits for private purpose but also for sale, he has low level of education and low household income. In addition he is not enough informed on possibilities and existing development programs, he expecting primarily financial help from local authorities but also additional training; and he is not very keen to affiliate with other entrepreneurs.
On those findings clear need for more intensive influence of local authorities and Forest Extension Service is stressed out. Main areas of work could be raising awareness on possibilities for improving private forest estate, starting private entrepreneurship based on intensified use of forest products and services. Those activities has to be facilitated by Forest Extension Service but also by Croatian forests ltd.co which can act as motivator or work in cooperation with new private entrepreneurs.
Key words: Non wood forest products and services; Peter‘s mountain; private entrepreneurship; questionnaire; rural development

    authors:
    VULETIĆ, Dijana      ŠL
    KRAJTER, Silvija    ŠL
    MRAZEK, Marko    ŠL
    Ćorić, Anna
 
Govorčin,S., T.Sinković, R. Hrčka  UDK 630* 812 + 813 (001) Fraxinus excelsior L. 185
Some Physical and Mechanical Properties of Recent and Heat Treated Ash– Fraxinus Excelsior L.      
Summary: The aim of this paper is to study differences in some physical and mechanical properties of heat treated and recent wood. Wood used in this research was ash (Fraxinus excelsiorL.) from the area of Otok, region of Slavonia in Croatia. The felled tree was 85 years old with the diameter at breast height of 53 centimetres. A heart board was made from the tree trunk in the north-south direction, 4 metre long and 6 centimetres thick. The heart board was dried naturally with an average water content of 12 %. The heart board was sawn in four equal parts so that four heart boards were obtained – each 1 metre long. Looking from stump to top of the tree, the first and third heart boards were not heat treated and they were used for establishing the properties of recent ash. From the above four heart boards, samples were made for determining macroscopic, physical and mechanical properties of recent and heat treated ash. Treatment of ash (Fraxinus excelsiorL.) at the temperature of 200 oC caused significant changes of technical properties relatively physical and mechanical properties of the treated wood. Maximum possible number of samples was made for each physical and mechanical property in radial direction, i.e. from heart to bark. Maximum shrinkage was determined in radial and tangential direction, as well as maximum volume shrinkage, density in absolutely dry condition, nominal density and water content after a fortnight of soaking in water of physical properties. Determination was also made of compression strength parallel to the grain, static bending strength, hardness in longitudinal, radial and tangential direction. The investigation of some physical and mechanical properties of recent ash (Fraxinus excelsiorL.) and heat treated ash at 200 oC show diametrically different values of investigated properties.
The investigation of mechanical properties of recent ash was carried out on samples with water content of 12 %, while the water content of the heat treated ash samples was 4 %. In order to be able to compare the results of mechanical properties, their values were converted to the water content of 4 % for recent ash and 12 % for heat treated ash. For increasing or decreasing mechanical properties of wood, correction factor was used in accordance with Forest Product Laboratory, Madison. The comparison of mean values of physical and mechanical properties of recent and heat treated ash was carried out in accordance with Mann-Whitney test with the help of statistical software Statistica. Density distribution in absolutely dry condition in radial direction of heat treated ash deviates from the distribution common for recent ash. The loss of mass with a relatively constant sample volume is evident in radial direction, and especially in the heart section. Mean value of density in absolutely dry condition of recent ash is higher by 8.4 % than density of heat treated ash. Shrinkage in radial and tangential direction and volume shrinkage of recent ash are higher that shrinkage in heat treated ash. Shrinkage in radial direction is higher by 70 %, in tangential direction by 62.2 % and volume shrinkage by 63.7 %. All above said physical properties of recent ash are significantly different from physical properties of heat treated ash. The investigated mechanical properties of recent ash are also significantly higher than mechanical properties of heat treated ash. Compression strength in longitudinal direction of recent ash is higher by 36.8 %, static bending strength is higher by 48 %, hardness in longitudinal direction (cross-cut) is higher by 31.3 %, hardness in radial direction (tangential cut) is higher by 22.8 % and hardness in tangential direction (radial cut) is higher by 25.9 % than the stated mechanical properties of heat treated ash at 200 oC. All investigated mechanical properties of recent ash differ significantly from these properties of heat treated ash. Dimensional stability of ash under such regime of heat treatment resulted in increased dimensional stability, and however the investigated mechanical properties are significantly lower. The above said percentages of higher values of mechanical properties of recent ash than of heat treated ash with water content of 12 % and 4 % indicate that they are similar at 12 % and 4 %. The similarity of these percentages indicates that the correction coefficients for calculating mechanical properties at different water contents is also satisfactory for heat treated ash.

    authors:
    GOVORČIN, Slavko    ŠL
    SINKOVIĆ, Tomislav    ŠL
    Hrčka, Richard