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HR  EN   



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

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: Boris Hrašovec

Uredništvo   1
For the first time, after the 41 years of editorship and care for the “Jornal of the Forestry Society of Croatia”, deeply honored and widely respected name of professor emeritus dr. sc. Branimir Prpić, is leaving its long lasting place within the journal’s editorial board and moving everlastingly into the written pages of Croatian forestry and science. His name and personality are cherished in the memories of generations of foresters and scientists, not only in Croatia. During the 135 year long period of the existence of our journal, professor Prpić steered the journal in the role of the editor-in-chief for the longest time since it’s founding back in 1877. He was appointed as an editor-in-chief of the “Journal of the Forestry Society of Croatia” in 1970 and in the uninterrupted row of years he had this position until 2010. One year after his last active year as an editor-in-chief professor Branimir Prpić died in Zagreb on January 1, 2012.
On the pages of our journal, professor Prpić writes the column “A word from the Editor” which he introduced in 1975. In the beginning intermittently, but starting with the first issue in 1994, he writes and signs this column regularly, until his latest active years. The themes he treated were varied, ranging from strictly specialist to those which reflected the current moment in forestry and the forestry profession. In a way, his column mirrored the history of forestry during the past 40 years. In order to write with authority about such different topics and complement them with conclusions and messages which the profession wholeheartedly adopted as its mission, Professor Prpić had to possess vast knowledge and experience, which he certainly did. He had acquired and stored the knowledge and experience over many years of work, first as a practicing forester after graduation, and thenat the Faculty of Forestry of the University of Zagreb as junior researcher, assistant professor, associate professor, full professor and finally emeritus professor. He also held the posts of Head of the Department of Silviculture, Head of the Department of Research in Forestry, Vice Dean and Dean. Inheriting the course of Forest Ecology from Academician Anić, he taught it as an independentsubject from the academic year 1968/69, when the majority of present-day “experts”in this field did not have the least idea what the word ecology meant. This segment of his teaching and scientific work and activity was treated in more detail in the text published on the occasion of his receiving the Lifetime Achievement Award within the National Award for Science in 2010 (Forestry Journal No. 9–10/2011).
In the said publication we made particular reference to the articles treating the topics from the column A Word from the Editor. These articles can be divided into several units, depending on the field of forestry which they deal with. These are, first of all, ecological topics, such as forest decline and ecosystem stability on which fresh-water ecosystems depend,e.g. sources of potable water, since they are all connected with forests by a number of factors.His main focus of interest wason non-market forest functions, which he classified into three basic groups: ecological, social and socio-ecological, and for which he proposed a method of determining their monetary value. We are currently witnessing the way in which the society treats these forest functions: the financial means intended for the preservation of these values are again being reduced by 50% and are being classed into parafiscal taxes. Those not familiar with this topic consider the money invested into these functions an unnecessary tax, while quasi entrepreneurs are rubbing their hands with satisfaction for not having to pay for them. Yet, neither doubt their right to clean air, sufficient potable water, places for recreation, shade in hot days, beautiful scenery (or perhaps they find bare stone land a prettier landscape?), protection from erosions and the other 15 non-market forest functions listed in the Forest Law.
His editorship of the Forest Journal set high standards, owing to which the articles published in this magazine are being cited in all the relevant biotechnical journals in the world.
Professor Prpić was an ideal, a teacher and a friend to all generations of Croatian foresters. He selflessly offered both specialist and moral support to all the colleagues who turned to him for help. We are absolutely certain that the forestry profession will show fullappreciation of his contribution to its development and that it will continue to expand on the fundamental postulates of the profession which Professor Prpić advocated using his scientific and specialist knowledge.

Editorial Board

Škvorc,Ž., K.Sever, J.Franjić, D.Krstonošić, M.Poljak  UDK 630* 114.2 + 561 - 562
(Quercus roburL.) (001)
Photosyntesis Intensity andVegetative Growth of Pedunculate Oak (Quercus roburL.) in Common-Garden Experiment        
Summary: The effect of various types of environmental stress factors on forest trees is most often manifested through the reduced absorption of mineral nutriments. This results in lowered efficiency of photosynthetic pigments on the leaf’s cellular level and production of insufficient amounts of carbohydrates necessary for normal vegetative growth. Due to sudden increase in concentration of carotenoids in relation to chlorophyll, which is susceptible to a sudden destruction under the effect of stress factors, a change takes place in the relative amounts of chlorophyll and carotenoids. Because of this, the leaves in the crown of a tree temporarily lose their green color and turn yellow, which is indicative of plant’s lack of nitrogen nutrition, i.e. the nitrogen deficiency in the soil. The role of nitrogen as a plant nutriment is connected with numerous physiological processes responsible for successful growth and development of plants. For example, nitrogen is an essential element responsible for an uninterrupted continuation of photosynthetic process and vegetative plant growth, primarily because of its role in the synthesis of chlorophyll and certain proteins, such as ribulose-1,5-bisphosphate carboxylase oxygenase (Rubisco), which is responsible for CO2assimilation. In the previous studies of forest trees, significant differences were determined in the intensity of photosynthesis and vegetative development regarding the diverse conditions in the habitats. These variations are usually due to the lengths of summer droughts and high temperatures, the intensity of illumination, and the differences between dry and wet years.
The aim of this study was to, (1) determine the effect of various chemical characteristics of the soil on the intensity of photosynthesis and the vegetative growth of pedunculate oak, (2) establish a connection between content index of the total amount of chlorophyll in the leaf, and the intensity of photosynthesis and the vegetative growth of pedunculate oak.
The study was conducted during the vegetative period in 2010, on 4-yearold plants, planted with 2 – 2,5 meters of space between plants. Based on visual differences in the leaf color, two plots have been set aside – the chlorotic and the control plots (without chlorosis). Each field contained 8 plants, i.e. 16 in total. The average height of the plants under study before the start amounted to 1.96 ± 0.44 meters, and the diameter of the trunk 2.5 centimeters, measured 30 centimeters above ground.
In order to determine the differences in the soil’s chemical characteristics between the two studied plots, the samples were taken on the depth of 0–30 centimeters. The soil reaction was determined with a potentiometer in the suspension of soil and water, i.e. soil and nKCl. Humus was determined by the Thorin method, and the total nitrogen level by the Kendahl method. The content of physiologically active phosphorus and potassium was determined by the Al-method.
The study determined height and diameter increment for the plants studied, and also height and diameter increment for primary branches of each plant. The number of spring and summer shoots with its attending leaves was also determined. Based on the number and surface area of leaves, as well as the projection of crown surface on the ground, index of leaf surface was calculated for each tree.
The measurements of photosynthesis intensity and the index of total chlorophyll content were performed early in September. The photosynthesis intensity was measured with the help of the infrared gas analizer portable device LCpro + (ADC BioScientific). While taking photosynthesis intensity measurements, each leaf was subjected to illumination intensity of 1500 µmol m-2 s-1, CO2concentration of 380 ± 10 µmol mol-1and the air temperature of 25 ± 2 °C. The chlorophyll content index was determined by using chlorophyll content meter CCM-200. By using a portable chamber for measuring water potential, the measurement of water potential was taken in the leaves (.) of plants under study.
The chemical characteristics of the soil in the test plots were shown in Table 1. There was an extremely acidic reaction in the chlorotic plot, and acidic in the control plot. The chlorotic plot was marked by an extremely low nitrogen supply, while the control plot had a medium to good nitrogen supply. The content of physiologically active phosphorus in the chlorotic plot was extremely low, while the control plot was averagely supplied with physiologically active phosphorus. Both plots under study featured accessible potassium levels on the lower margins of an average supply. The humus content in the studied plots was very low, especially in the chlorotic plot.
Statistically significant difference in the measured values of water potential of the plants grown in the plots was determined only during noon measuring throughout July. In August and September, statistically significant differences in the measured values of water potential were not determined (Table 3).
All the parameters of the vegetative growth of the plants under study which were grown on the control plot had statistically significant higher values compared to the plants grown on the chlorotic plot, except for the number of primary branches, which showed no statistically significant differences between the two studied plot trials (Table 4). Leaf surface index, value of which was taken in the middle and near the end of the vegetative cycle, was statistically significantly higher in the control plot than in the chlorotic plot (Figure 2).
There was statistically significant difference in the intensity of photosynthesis measured on spring leaves of studied plants between the control and the chlorotic plot. The intensity of photosynthesis on the control plot was 28.4 µmol CO2m-2 s-1, while its value on the chlorotic plot was 19.3 µmol CO2m-2 s-1. Content index values of total chlorophyll in the leaves of the studied plants were statistically significantly different regarding the plots under study, no matter whether the measuring of chlorophyll content was conducted on spring or summer leaves (Figure 4).
Regression analysis determined a high positive correlation between the content index of total chlorophyll measured on spring leaves of studied plants with the intensity of photosynthesis, leaf surface index, tree’s girth increment, and also length and girth increment in the primary branches (Table 5). The correlation between content index of total chlorophyll and tree’s height increment was very weak.
The results of the study indicate that the soil’s chemical characteristics have an effect on the photosynthetic activity and the concentration of chlorophyll in the leaves of pedunculate oak. The higher values of the total chlorophyll’s content index and the intensity of photosynthesis were recorded for plants grown on the soil with a higher concentration of humus, nitrogen, phosphorus and potassium. Positive correlations between the content indexes of total chlorophyll in leaves and the intensity of photosynthesis, as well as most of the parameters of vegetative growth, indicate the possibility of successful application of chlorophyll measuring methods when determining vitality of particular trees and forest stands of pedunculate oak.

Key words: Chemical composition of soil; chlorophyll content; diameter increment; height increment; leaf area index

    ŠKVORC, Željko    ŠL
    SEVER, Krunoslav    ŠL
    FRANJIĆ, Jozo      ŠL
    KRSTONOŠIĆ, Daniel    ŠL
    Poljak, Milan
Diminić,D., N.Potočić, I.Seletković  UDK 630* 232 + 443
(Pinus nigra Arnold) (001)
The Role of Site in Predisposition ofAustrian Pine (Pinus nigraArnold) to Pathogenic FungusSphaeropsis sapinea(Fr.) Dyko et Sutton in Istria (Croatia)        
Summary: Austrian pine (Pinus nigra Arnold) was commonly planted during the last century in Croatia. Afforestation took place on various sites to prevent land from erosion and, or to restore forest vegetation, mainly in karst areas. Since 1992 the study on health status of Austrian pine plantations in Croatia revealed significant dieback symptoms in some areas as the consequence ofSphaeropsis sapineaoccurrence.
Research carried out in November 2001 found the fungus presence with different impact to P. nigrain Istria, healthy sites and also ones with various disease symptoms were observed (Figure 1, Table 1). In plantations which revealed good health statusS. sapineawas found only on cones, but in plantations with dieback symptoms its presence was found in needles, shoots and branches, causing in some cases dieback of trees. According to dieback symptoms observed, research localities were categorised in four health categories as shown in Figure 1.
It was revealed that along the drought (Figures 19 and 20, an example for period 1961–1990 vs. 1999), the site conditions also played an important role in pines’ predisposition to fungus attack during last years. This conclusion was supported by analyses of nutrition status in pines and site conditions (soil sub-types, soil types and depth, site rockiness, exposition and inclination, Table 1). Analyses of nutrition status obtained clear difference among sites comparing the nitrogen (N) and potassium (K) concentrations in pine needles (Figures 6–11). In sites with lower N/K ratio the disease symptoms were not observed, but in sites with increased N/K ratio the dieback symptoms were revealed, following nitrogen and potassium relation in general (Figures 12 and 13). According to Brown (1999) fertilization only by nitrogen can increase the susceptibility of broadleaved trees to pathogenic organisms due to the influence of nitrogen on growth of aboveground plant biomass, and imbalance of above- and belowground plant parts biomass can lead to the increased susceptibility of trees to water stress. Higher nitrogen concentartions as pines’ predisposition to S. sapinea were confirmed by De Kam et al. (1991), Van Dijk et al. (1992) and Stanosz et al. (2004). Opposite to nitrogen, potassium play important role in plant resistance to drought and pathogenic organisms (Bergmann 1992, Marschner 1995).
Inoculation experiment in Austrian pine seedlings confirmed the S. sapinea pathogenicity and also the same capability of isolates obtained from healthy needles (VIPAVA, IMI 368260) and ones with symptoms (DP 04-1 and DP 06-3, described in Diminić et al. 2004) to cause bark necrosis. Previous fertilization with ammonium sulphate caused increased seedlings growth according to treatments: 0, 20, 40 and 80 g/m2, and also increased length of bark necrosis in inoculated pines (Tables 2 and 3, Figures 14–18), which supported the nitrogen role in disease development.
According to up-to-day worldwide knowledge and results of our research, it can be concluded thatS. sapineacan live (latent phase) in healthy looking pines in Istria. And, in drought periods it can turn to serious pathogen, causing dieback in predisposed trees. It this circumstances, site play an important role in pines’ resistance to disease, indirectly influencing appearance (or not) of various dieback symptoms.

Key words: dieback; drought; health status; Pinus nigra; plantations; site conditions; Sphaeropsis sapinea

    DIMINIĆ, Danko    ŠL
    POTOČIĆ, Nenad      ŠL
    SELETKOVIĆ, Ivan      ŠL
Andrašev,S., M.Bobinac, S.Rončević, M.Vučković, B.Stajić, G.Janjatović, Z.Obućina  UDK 630* 232.5 + 242 (001) 37
Effects of Thinning in a Plantation of Poplar Clone I-214 withWide Spacing        
Summary:Research was conducted in the experiment plot of euramerican poplar, clone I-214, which was founded with one year seedling type 1/1 with spacing 6 × 6 m in the square system on the alluvial soils of river Sava basin in which browning processes is expressed.
Eleven years after the plantation establishment 3 blocks with two experimental plot of 0.2016 ha, which are separated by a so-called. protective order, were singled out. In the experimental plot all the trees were numbered and measured by two cross-dbh, with an accuracy of 1 mm, and height, with an accuracy of 1 dm. The crown projection radius of 8 positions, each rotated to 45o, were measured.
On the three experimental plots (one in each block) selective thinning was carried out (PP-E), at which in each plots 50 % of trees were cut down, or the distance between the trees raised on average 8.5 × 8.5 m. Firstly, a collective called. promising trees set aside, in the number that corresponds to an average distance of 8.5 × 8.5 m, and their main competitors were removed. The trees behind in development, which is mainly due to additional filling in plantations two years after planting, are also removed because they were judged as silvicutural non-perspective. The remaining three experimental plots were control (PP-K).
In each repetition trees for dendrometric analysis were sampled, the dominant one (dg20%) and a mean tree which has mean quadratic diameter (dg). In the 16thyears of plantation development diameters at breast height (dbh) and height of each tree were re-measured, sa well as crown projection radius.
The development of mean and dominant trees showed that the investigated habitat is the medium favorable for the cultivation of the poplar clone I-214. Current increment of diameter, height and volume in the 11thyear was in the intensive phase, where volume increment has not yet culminated (Figure 1–3).
As a suitable element of growth to determine the start of thinning operation on a biological point of view, can be ring width along the spindle tree. In the first five years the tree has had a full solitary growth, and from the seventh year there is a competitive relationship between trees in plantation, which is manifested by changing the ring width along the spindle tree (Figure 4 and 5). This means that before the seventh year thinning does not have any biological justification.
Models 1 and 2 of volume tables, constructed measuring felled trees from thinning (Table 2), and which are the dependence of the volume of tree from diameter at breast height (model 1) and from the diameter at breast and height (model 2), proved to be equally good at calculating the volume per hectare in the 11thyear and more convenient compared to other tables and models (Table 3). To calculate the volume in the 16thyear two input volume tables can be successfully used (model 2), while the application of model 1 is limited at the 11thyear.
In the 11th year at the experimental plot an average of 263–266 trees per hectare are found, which represents a survival rate of about 95 %. Total basal area averaged from 14.70 to 14.97 m2/ha, while volume was an average from 156.67 to 157.62 m3·ha-1. By applying the statistical t-test significant difference in the number of trees, basal area and volume per hectare was not determined within the experimental plots before applying the silvicultural treatments (Table 4).
By applying thinning operation,122 trees per hectare (46%), 6.45 m2/ha (43 %) of the total basal area, 66.08 m3/ha (42%) of the total volume and 2645 m2/ha (40 %) of the the crown projection area were removed, which represent a strong procedure and is located above the so-called. critical basal area (Table 4, 13).Size of allowable cut in the thinning of 66.08 m3/ha was in the limits expected on the basis of previous research for the density of 278 trees per hectare and the habitat medium favorable for the development of poplar clone I-214. However, the assortment structureof allowable cut is more favorable compared to thinning in younger plantations in the more favorable habitats and produces 50 % of technical wood, 30% of pulpwood and 20 % of wastewood (Table 4, 9, 15).
Between 11 and 16 years on both series of experimental plot the mortality of trees was not determined. Five years after application of thinning treatment a significant difference in the number of trees, basal area, volume and crown projection areas of trees per hectarewere determined between the experimental and control plots (Table 4). The significant difference in the mean diameters, heights and crown projection areas of the mean and the dominant trees (Table 5, 6), as well as between the diameter strucures (Figure 7) were also determined between investigated plots.
For a period of 5 years after application of thinning operation at the experimental field current basal area and volume increment per hectare accounted 85 % of basal area increment and 75 % of volume increment of the control plots wich had the number of trees twice higher than experimental plots (Table 14). For five years of positive reactions to increase growing space of remaining trees on the experimental plots the size of the total basal area and volume of trees removed by thinning operation is not compensated: the total basal area and the volume per hectare amounted to 2/3, and the crown projection area amounted 87 % of the size of the control plot.
The reaction of trees on experimental plot with thinning treatment for 5 years is great and is reflected in greater mean diameter by 10.6 %, greater mean tree volume by 21.9 % and increased the crown projection area by 59.0 % compared to control plot. In contrast, the mean Lorey’s height at the experimental plot with thinning treatment decreased by 4.2 % compared to control plot. This has contributed to the intensification of the current (average periodic) volume increment compared to the period before applying thinning operation. Greater assimilation apparatus of trees in the experimental plots with thinning tretament and higher current diameter and volume increment indicate the need to extend the production cycle at the best assortment structure compared to the control plot.
The research results indicate the validity of efforts that the thinning operation in poplar plantations should be treated as a biological and an economic category. As a biological category the thinning operation contributes to accelerating the growth of the remaining phenotypically better established trees and achieve optimum production. As economic categories with thinning operation realized the previous crop, and it being understood that the assortment of allowable cut in the thinning cover cost cutting and the establishment of plantations with more trees. In this framework it is necessary to direct further research, because the poplar plantations,which are aimed to applying thinning operation, are flexible enough to allow adaptation to changing market conditions.

Key words: effects of thinning; growth; poplar clone I-214; selective thinning; wide planting

    Andrašev, Siniša
    Bobinac, Martin
    Rončević, Savo
    Vučković, Milivoj
    Stajić, Branko
    Janjatović, Gojko
    Obućina, Zoran
Matošević, Dinka  UDK 630* 453 (Aproceros leucopoda) 57
First record of Elm Sawfly (Aproceros leucopoda), new Invasive Species in Croatia        
Summary: An invasive sawfly (Aproceros leucopoda; Hymenoptera, Argidae) has been attacking elms (Ulmus sp.) in Europe. It orginates from Japan and has been first recorded in Europe in 2003. In the paper the occurrence of A. leucopoda in Croatia is reported for the first time and prognosis of future dispersal and damages is given. Potential host plants of A. leucopoda are all native and introduced elm species in Europe. The sawfly has up to 4 generations per year and parthenogenetic reproduction, After six larval instars, eonymphs make loosely spun cocoons on the leaves (Figure 3 ). Adults (Figure 4) lay eggs along leaf margins. Young larvae (Figure 5) make distinctive zigzag feeding tracks on leaves (Figure 1 ), older larval instars devour the whole leaf and only midveins are left (Figure 2 ). The larve can completely defoliate elm trees which was the case in Japan, Hungary, Italy, Poland and Romania.
A. leucopoda was first recorded in Croatia in 2011 on several locations (Table 1, Figure 6). On the leaves a tipical zigzag feeding tracks were recorded, larvae and cocoons were found and adults were raised from the colected cocoons. The species was identified with the help od the key in Blank et al. (2010). The number of generations per year was not determined. The damage on the elm trees in Croatia was not severe, no defoliation was observed and only single leaves were completely consumed.
A. leucopoda can be considered as invasive species in Europe and Croatia, it can be expected that the sawfly will disperse to other parts of Croatia (to forests and urban trees) in the coming years. The sawfly will disperse actively (females are strong flyers) and passively (with traded material and vehicles). Complete defoliation of elm trees in Croatia can not be excluded in the coming years.

Key words: damage; elm; invasive species; prognosis of dispersal; sawfly

    MATOŠEVIĆ, Dinka      ŠL
Matović,B., M.Koprivica, Z.Maunaga  UDK 630* 527 + 521 63
Application of Generalized Taper Model of Norway Spruce Tree in Forestry Practice        
Summary: By applying modified Brink’s function, this paper presents the unique generalized taper model of Norway spruce tree, developed for the area of Bosnia and west Serbia. The objective of this research is adapt generalized taper models (Models 1 and 2) for trees presented in the paper Matović, et al. (2007), for practical use in forestry.
The significant quality of the modified Brink’s function is the correlation of the characteristics of individual trees and stands and the function parameters, so in this way generalized taper models can be calculated for the use in a definite geographic region.
The study of Norway spruce taper is based on the data collected from 86 even-aged stands in the region of Bosnia and west Serbia, which is adjacent to Bosnia. The total number of model trees is 156, and the number of data pairs (diameter-height) is 2028.
The original parameters i, p and q of the modified Brink’s function were first calculated for all model trees by the optimisation method - equations (1). By applying the multiple regression method, a link has been established between original values of parameters i, p and q, and characteristics of individual trees (diameter at breast height and tree height), i.e. Model 3 has been obtained.
Model 3 is consisted of three functions used for determining the parameters of generalized taper model i, p and q. Unknown parameters of the three functions a1, a2, a3,...,.a15 are determined on the basis of available data, by applying multiple regression – equations (2), (3) and (4).
In order to test the estimation of taper volume, on the material used for the development of generalized taper models of spruce trees by applying multiple regression, dual input volume tables were created. For that purpose Näslund and Schumacher-Hall functions were used – equations (6) and (7).
This research confirms that Model 3 shows less accuracy in estimating the diameter along the taper and volume than Models 1 and 2, which besides using the diameter at breast height and tree height, also require using the stand quadratic mean diameter. However, such difference, from the aspect of practical use, is not important, so Model 3 that applies only the diameter at breast height and tree height (in fact, reduced to the level of dual input volume tables) can be successfully used in forestry practice.
Obtained Model 3 is the superior substitute for conventional dual input volume tables, because besides the total volume it enables the volume estimation for particular parts of the standing tree, and also estimation of the diameter along the taper. Model 3 indirectly enables the calculation of tree heights with some diameters characteristic for forestry practice.
Model 3, with all above mentioned practical possibilities, can be very simply used by applying one EXCEL application. Because of the dimensions of trees used for Model 3 design, it can be reliably used in practice for Norway spruce trees with diameters at breast height of 10 to 60 cm and height of 6 to 37 m.

Key words: generalized model; modified Brink’s function; taper

    Matović, Bratislav
    Koprivica, Miloš
    Maunaga, Zoran