|A WORD FROM THE EDITOR-IN-CHIEF|
|MORE ABOUT FORESTS AND NATURE PROTECTIONIN RELATION TO NATURA 2000 IN CROATIA|
|Classification of forest ecosystems and their habitats into the national ecological network in the continental part of Croatia was performed very successfully; however, in the Mediterranean part the task was made more difficult by the degraded condition of the forest vegetation. Since the continental part abounds in forests managed on a close-to-nature principle, it would be opportune to raise as many high forests as possible of holm and pubescent oak in the Croatian part of the Mediterranean within the NATURA 2000 ecological network. These forests could be raised from both degraded forests with preserved parts of the ecosystem (maquis, pubescent oak scrub), and from pine cultures with naturally occurring autochthonous species. This would considerably increase the non-market value of these forests.
Croatian forests managed on a close-to-nature principle represent an exceptional asset for Europe, owing in the first place to their numerous non-market functions, in particular those associated withnature protection. In addition to the FSC forest certification, the technologies used by the Zagreb School of Silviculture ensure biological diversity in naturally managed forests equal to biodiversity in virgin forests, which further enhances their naturalness.
The 250-year history and hard work of the forestry profession in Croatia has resulted in a number ofpositive benefits currently attributed to Croatian state forests. Would it not be logical, therefore, that the task of caring for the national ecological forest network in Croatia is given to this profession? I should stress that as a profession we are very well organized and adequately trained, as testified by the composition and structure of Croatian forests, of which every single one could be proclaimed a national park under the European criteria. We, instead, are competing in giving areas with forests as basic phenomena the status of protected areas. We are establishing new administrations but hesitating to employ professional foresters, because “all they do is cut down forests”. We, in fact, arethrowing away money which is short anyway, instead of gathering specialists from different fields (foresters, biologists, veterinarians, sociologists) in the joint task of nature protection. Every forest keeper is well trained in all those forest matters which aranger (a professional term taken over from the USA) is supposed to know. We are spending considerable means on educatingrangers despite the fact that our forest keepers, who care for tree phenophases and forest wildlife, are already well trained and equipped for the job.
I speak on behalf of the forest profession and suggest that representatives of the State Institute of Nature Protection and forestry professionals sit down at the round table and use NATURA 2000 as an opportunity to reach a satisfying agreement on nature protection in the Republic of Croatia.
I would like to remind the readership that the issue of Forestry Journal 1–2/2008 already tackled the possibility oftranslocatingthe State Administration for Nature Protection from the Ministry of Culture to the Ministry of Forestry, Regional Development and Water Management. This would undoubtedly eliminate various misunderstandings related to nature protection in forested areas and the role of biologists in the protection of forest ecosystems. Or is it more convenient to live in the shade of a minister who, overwhelmed by the enormity of workin his field, finds little time for nature protection?
Emeritus Professor Branimir Prpić, Ph.D.
PRPIĆ, Branimir ŠL
|ORIGINAL SCIENTIFIC PAPERS|
|Vedriš,M., A.Jazbec, M.Frntić, M.Božić, E.Goršić||UDK 630* 529 (001)||369|
|Precision of Structure Elements’ Estimation in a Beech – Fir Stand Depending on Circular Sample Plot Size|
|Summary: Stand structure estimate is based on data from sample plots. The aim of this research was to compare the stand structure estimates based on sample of circular plots with different radii. Through this influence of plot size on structure estimate and efficiency of stand measurement was also indirectly assessed. Measurements were made in beech-fir selection stand in the Educational and experimental forest site “Zalesina” in Gorski kotar region, Croatia. Stand size is 20,63 ha, it is situated from 790 to 850 m above sea level, and belongs to site class II. Stand exposition is south to east, terrain slope is 5–10°. Tree breast height diameters (DBH) were measured on systematic sample of 17 concentric circular sample plots. Tree location from plot centre was recorded by azimuth and distance. All trees of DBH 10 cm or more were measured on 13 meter radius plot, trees of DBH 30 cm and more were measured on 19 m radius plot and trees of DBH 50 cm and more on 26 m radius plot. Computer programme CirCon for calculation of stand parameters based on measured plots and simulated plots, with radii different from measured ones, has been developed. Plots based on real measurements were simulated according to ones used in forest management practice (singular and concentric circle plots). We simulated 8 methods: K7,98 (7.98 m radius plots), K9,77 (9.77 m radius plots), K11,28 (11.28 m radius plots), K12,62 (12.62 m radius plots); K5-12 (concentric circle plots with radii 5 and 12 m), K7-13 (concentric plots with radii 7 and 13 m), K7-13-20 (concentric plots with radii 7, 13 and 20 m) and K13-19-26 (three concentric circles of 13, 19 and 26 m radius). Calculated estimates for number of trees, basal area and volume on the same standing points differed between methods depending on spatial tree distribution and size of plots. Descriptive statistics (arithmetic mean, standard deviation, standard error) was made for each variable (number of trees, basal area and volume) on stand level. Sample error with 95 % confidence (SE/mean*t0.05,) was also calculated to express the precision of estimates. Different estimates by methods depending on plot size were compared by repeated measures ANOVA, due to lack of independence between methods (plot sizes) on the same standpoints.
Estimates of number of trees by methods (Figure 2) ranged between 275.4 and 303.5 per hectare, although differences were not statistically significant at 0.05 confidence level (Repeated measures ANOVA: F = 0.6027, df = 7, p = 0.7526). Precision expressed by relative sample error varied from 13.58 % (K13-19-26) to 28.34 % (K5-12). Better results (lesser sample error) were obtained on bigger plots, though concentric circles (K5-12, K7-13 and K7-13-20) have considerably greater sample error due to fewer trees per plot.
Basal area estimates by methods ranged from 34.80 to 37.76 m2per hectare (Figure 3), making no statistically significant differences (Repeated measures ANOVA: F = 0.2948, df = 7, p = 0.9547). Relative precision ranged from 10.13 % (K13-19-26) to 26.96 % on smallest plots (K7,98). Sample error of basal area estimate on concentric circles was just slightly bigger in spite of fewer trees per plot. Reason for that is stability of basal area on plots regardless to fewer trees: concentric circles include fewer trees but have great share of bigger ones that contribute to basal area more than smaller ones.
Estimate of stand volume by methods ranged from 457.93 to 496.47 m3per hectare (Figure 4). There was no statistical difference in volume estimates between analysed methods (Repeated measures ANOVA: F = 0.2650, df = 7, p = 0.9661). Relative precision ranged between 10.14 % (K7-13-20) and 30.36%(K7,98). Better precision was obtained with bigger plots, due to more trees per plot. Concentric circles produce just slight increase in sample error while lowering the cost of measurement by reducing the number of trees per plot.
Number of measured trees per plot was computed as an indicator of plot efficiency. Differences in number of trees per plot between plot sizes were statistically significant at 0.05 level (Repeated measures ANOVA: F = 187.621, df = 7, p = 0.0000), except for: K7,98 and K5-12; K7-13 and K9,77; K7-13-20 and K12,62 (Fisher LSD Post-hoc test).
Evident increasing trend of number of trees per plot by increasing of plot size is the main cause of better precision. Although concentric circles reduce number of trees per plot, loss of precision for basal area and volume are minimal (Figure 5). Therefore plots K5-12 are acceptable for use in this kind of stands, with remark that they require well trained staff and modern instruments. Plots K7-13 do not improve precision while increasing number of trees per plot (9), therefore are not recommended. Triple concentric circles K7-13-20 reduce sample error almost by 10 %, although by significant increase of measured trees per plot.
Plots K11,28 reduce number of trees per plot with minimal increase in sample error compared to K12,62 plots. That fact makes them acceptable choice for gain in efficiency. However, K11,28 sample should be adjusted with more plots to satisfy required sampling intensity (5 % of stand), which would increase costs. In order to simplify the sampling plan, legislation does not require precision rather sampling intensity (5 % of stand area), which restricts opportunity to optimize sample size.
The choice of plot size is based on inventory goals and should depend on cost of measurements and expected precision. This kind of research can provide useful base for determining plot size by costs and precision of data. Exact ratio of cost and precision could be computed by including time measurement per plots of different sizes.
Key words: basal area; CirConcomputer model; circular sample plots; estimation; forest inventory; number of trees; precision; volume
VEDRIŠ, Mislav ŠL
FRNTIĆ, Marko ŠL
BOŽIĆ, Mario ŠL
GORŠIĆ, Ernest ŠL
|Matošević,D., M.Pernek, T.Dubravac, B.Barić||UDK 630* 453 (001)||381|
|Research of Leafminers onWoody Plants in Croatia|
|Summary: The paper presents results of faunistic study of leafminers on woody plants in Croatia. The starting point of this research was lack of knowledge about leafminer fauna on woody plants in Croatia and longterm researches and rich lefminer fauna of neighbournig countries (Slovenia, Bosnia and Herzegovina, Hungary). The leafminers were collected on woody plants in the continental and submediterranean region of Croatia during the period of 4 years (2004 – 2007). They were collected with mines in different larval developmental stages, reared to pupae and adults when needed for identification. The species were identified by the main diagnostic characteristics: adults, pupae, shape and colour of leafmines, its position on leaves, frasslines and host plant species. In the results section for each found species of leafminers a host plant, colleciton site and date, number of generations, months when mines can be found on leaves and note on new record (Table 1) is given. In total, 98 species from the orders Hymenoptera (9 species), Coleoptera (2), Lepidoptera (78) and Diptera (9) were found. Out of them, 38 species can be considered as new records for Croatia. Five species of leafminers have been recently introduced into the Croatian fauna as new invasive species. Leafminers found during this research have varied in their choice of host plant, 23 species are defined as first degree monophags, 23 species are second degree monophags, 27 species are third degree monophags, 24 species are systematic oligophags, and only 1 species was polifagous. This is not final number of leafminer species on woody plants in Croatia and continuation of this kind of research is strongly suggested.
Key words: epidoptera; Hymenoptera; iptera; leafminers; new record; oleoptera
MATOŠEVIĆ, Dinka ŠL
PERNEK, Milan ŠL
DUBRAVAC, Tomislav ŠL
|Dubravac,T., S.Dekanić||UDK 630* 423 (001)||391|
|Structure and Dynamics of the Harvest of Dead and Declining Trees of Pedunculate Oak in the Stands of Spačva Forest from 1996 to 2006|
|Summary: From the literature sources and observations from the field forestry experts, two major assumptions regarding the relationship between the pedunculate oak dieback and the stand´s age and phytocoenological community emerge: (1) middle-aged, older and old stands are most susceptible to oak dieback and decline, and (2)highest intensity of oak dieback and decline occurs in the stands of pedunculate oak in microtopographically lowest positions – microdepressions. In the current contribution, we investigate two afforementioned statements in the pedunculate oak stands from first to sixth age class in the Spačva forest complex. As an indicator of the susceptibility of the stands to oak dieback and decline we used dynamics and structure of the harvest of the dead and declining oaks in the period of 11 years (1996– 2006). Analysis is based on the available data regularily gathered during the forest management in the “Hrvatske šume” Ltd., and archived in the database HS Fond. From the acquired data, total of 962 subcompartments with total area of 20 671 ha were selected according to the set of criteria for the further analysis, and divided into three groups according to phytocoenolgical association (Table 2 and Table 3).
In the selected subcompartments during the monitoring period in total 850 835 m3of pedunculate oak was harvested, out of which 58 % (492 583 m3) were dead and declining trees (Figure 9 and Figure 10). In more than 69 % of the subcompartments, harvest events were recorded three and more times, and in the 20 % almost every second year (five harvesting events) (Figure 8).
With regard to stand age, intensity of the harvest of the dead and declining oaks increases steeply after the stand age of 80 years (Figure 11). However, further analysis showed great variability of the intensity within the same age class (Figure 12). Thus, it is impossible to arrive at the general conlcusion about the role of the stand age in the proces of oak decline, because stand age most likely only amplifies negative factors already present in the stand.
There were no statisticaly significant differences in the total intensity of the harvest of dead and declining oaks (m3/ha) during the monitoring period between the stands of the different phytocoenological communities (Figure 14; Kruskal-Wallis test, n=891; H=3,825; p>0,05). Difference is more prouounced with regard to dynamics of harvesting intensity. In that sense it is confirmed that stands in the microdepresions are more unstable compared to the stands of the other two forest communities with highest (7,1 % in 1998) but also the lowest (1.8 % in 2000) recorded average yearly intensity of oak growing stock harvested trough dead and declining trees (Figure 13). Moreover, the consequences of the harvest of the dead and declining trees are more severe given the lack of the understory in the stands in the lowest microtopographical positions. Further research is needed to properly quantify those differences.
Spatial database of the pedunculate oak stands in the Spačva forest that emerged as one of the results in this research will be continuously updated in the following years. Interconnection of this database with other spatialy explicit databases, e.g. measurements of groundwater levels, will enable more complex and in-depth spatiotemporal analysis of oak decline and dieback. Conclusions based on the results of this research relate to the pedunculate oak stands in the Spačva forest, and require verification for other larger oak complexes in Croatia with further application of the methodology outlined in this contribution.
Key words: dieback; pedunculate oak; phytocoenological community; Spačva forest; stand age
DUBRAVAC, Tomislav ŠL
DEKANIĆ, Stjepan ŠL
|Godina, K.||UDK 630* 569 (001)||407|
|Development Structure Elements in Mixed Oak Stands in Aria of ForestAdministration Bjelovar with Retrospect on Modelling Growth andYield of Mixed Stands|
|Summary: Most yield tables are constructed for pure stands. From them can be exported yield tables for mixed stands. In them, due to a simple calculated construction, refers among tree species according to the number of trees, height and diameter of the mean tree, often do not represent realistic relationships in mixed stands. For modelling growth and yield, it is important to understand biodiversity, dynamics mixed stands and growth models. The growth model of a stand is an abstraction of a natural dynamics in forest stands, and it can be simple or complex, according to its construction. Among complex models for modelling dynamics of mixed stands the most appropriate are gap models.
In unmanaged mixed stands of three subassociations within three age groups (12–15; 19–22; 27–30 yrs.), the sample plots (table 1) were used for measurement and evaluating the vitality of each tree as a consequence of competition for light among tree crowns. Based on consideration of the vertical structure, diameter and crown luminance, the subassociation of pendunculate oak and common hornbeam has the greatest share of vital trees of the main species (picture 2). With age increasing in all subassociations, growing the share of too suppressed (-+) and dry trees (-) of pendunculate oak, but expressed in basal area, their share is less (picture 3). In the subassociation of pendunculate oak and narrow ash within the third age group, a great number of dominant and some predominant trees, influences the reduce in number of trees in lower layer, which is recognised by the omission of semidry and dry trees of secondary species (picture 4). The subassociation of pendunculate oak, narrow ash and black alder distinguishes itself by even more intense extraction of the main tree species, so there are a great number of suppressed yet perspective (+-) and dry (-) penduculate oak trees (picture 5). After simulated harvest, the growth of mean tree was projected according to the tree species. Simultaneously with the vitality evaluation, the competition among neighbouring dominant trees was being determined, and the influence on lower perspective trees, primarily of the main species, was evaluated. The simulated harvest gave the advantage to pendunculate oak and the predominant and dominant trees of the secondary species were mainly removed. The structure of the stand did not involve dry (-) and too suppressed trees (-+), which, with the previously mentioned, gives the total simulated harvest (picture 6 and 7). This was the way the main stand was gained. A growth projections of the mean tree was performed for the main stand according to the tree species, and the structural elements were determined in this way after five years. The growth projection for a single subassociation was gained from samples of circumference and tree heights after total simulated harvest that could more represented the regularly managed stands.
The height growth models during a period of time, for each of the three researched subassociations, are gained by equalizing of tree heights samples according to the modified Mihajlov function (formula 1) in aplication programme Statistica 6.0. The same way were obtained circumference growth models. A portion of the explained variability (R2) is the largest in height growth models after total simulated harvest, and it is considerably lower in circumference growth models before the simulated harvest. Variability (S.D.) increases with the age increase, and there is a greater circumference variability in relation to the heights.
The current diameter and height increment of the pendunculate oak is the biggest in subassociation with common hornbeam, while it is considerably lower and roughly equal in correlation within the remaining subassociations. The competition of the main stand trees is mostly manifested through the height increment in purpose of conquering the local area for undisturbed crown development. For all tree species in research stands, the height increment is mainly bigger, while the diameter increment is lower in relation to the yield table (picture 13–15).
The basal areas and volume projections of researched mixed stands for the three age groups after the simulated harvest are considerably different in relation to the mensuration stand (picture 10–12). The differences in relation to the mensuration stand appear due to equalization of data by Mihajlov’s growth function, because the biggest amount of the diameter and height growth are realised within the first age group. Then, the volume of died and unqualitative trees, since they were not adequately and in time cut, increases mainly successively in relation to the first age group (table 2).
Different volume projections reflect on the current volume increment, which is considered as accumulated iVt(a) and productive iVt(p). The accumulated current volume increment is the volume difference of the main stand at the end and at the beginning of the period (picture 16). The accumulated increment is under a strong influence of harvest, and it can be positive, negative or equal to zero. For pendunculate oak as the main species, a positive amount accumulates, while secondary species can also have negative amounts of the accumulated increment. The production current volume increment is an volume increase of the main stand until the next harvest. The productive increment depends mainly on structural elements of the mean tree and regards to prominent vertical structure of the mixed stand, on the number of trees and on giving the advantage to the main tree species for the undisturbed development. The productive current volume increment for all mixedstands is considerably bigger in relation to the yield tables (Špiranec, 1975), and in the second age group, the subassociations of the pendunculate oak and narrow ash are even bigger by 182 % (picture 17). This points to a very high development potential of young unmanaged mixed stands, which decreases with an increase in age as a consequence of mortality, falling off increments and harvest. There is a question of how to preserve the developmental potential in mixed stands. Silviculture interventions should be done in time in order to enable trees supstitutions from lower to higher layers and, on the basis of a spatial structure, an optimal diameter and height increment for the trees of the main stand.
|Cerovečki, Z.||UDK 630* 188 (001)||417|
|Beech Forests and Milava –As.Calamagrosti arundinaceae-Fagetum(Ht. 1950) Cerovečki ass. nov. of the Mountain of West Croatia|
|Summary: In the border area between the continental and littoral beech forests, according to I. Horvat (1962) the beech forests with the reed grass described as.Calamagrosti arundinaceae-Fagetum(Ht. 1950)Cerovečki ass.novaare developed. The association is divided into two subassociations, the more thermophilous one (caricetosum albae) and the more mesophilous one (abietetosum albae). The subassociation with the white reed comprises the pure beech forests, which on Obruč from the physiognomic point of view are found as two different types. One type includes the normally developed high-value economic forests coverig considerable areas of that region, and the forests of the stunted looking beech, limited to the extended plateau under the cliff to the northeast from the highest peak of Obruč. The latter type has developed under the influence of the specific climatic conditins and the characteristic massif orography. Generally, the area of Obruč, Pakleno, Crni vrh and Sljeme is specific with respect to the climatic phenomena and phytogeographical belonging. The beech and reed grass forests grow in the said area on the moderately inclined slopes and plateaus above rendzinas or moderately deep and soils between the blocks of rock.
The forests of the as. Calamagrosti arundinaceae-Fagetumhave been classified into the allianceAremonio-Fagion, the order Fagetalia sylvaticae and the classQuerco-Fagetea.
CEROVEČKI, Zdravko ŠL
|Pašičko,R., D.Kajba, J.Domac||UDK 630* 425 (biomasa–Biomass)||425|
|Impacts of EmissionTrading Markets on Competitiveness of Forestry Biomass in Croatia|
|Summary: A rising share of renewable energy sources in the overall energy balance is one of the strategic goals of a growing number of countries. By signing international agreements (e.g. the Kyoto Protocol), and in accordance with the legislature and accession to the EU, Croatia undertook the obligation to make concrete steps and increase the use of renewable energy sources, as stated by the paradigm “sustainable development”. In Croatia, biomass is a renewable energy source with the greatest potential.
The goal of this work is to explore the impact of the European Emission Trading Scheme (EU ETS Scheme) and flexible mechanisms of the Kyoto Protocol – the Joint Implementation Mechanism, JI, and the Clean Development Mechanism, CDM, – on the competitiveness of biomass energy production. Compared to fossil fuels, the advantage of biomass is that energy from biomass combustion is considered CO2free technology, since biomass sequesters CO2as part of photosynthesis.
The EU ETS restricts emission amounts at the national level and at the level of single installation. Every industrial operator is allocated a certain amount of emission allowances. In order to satisfy their needs, the operators may trade with their allowances and purchase emission allowances on the market. The JI and CDM projects represent flexible Kyoto mechanisms which allow investment in emissions reduction outside the investing country. The amount of emissions reduced in such projects is used to satisfy the allowances of the investing countries, while the price of CO2emissions per ton is determined by the market. An allocated amount of emissions which an installation or a country may emit increases the competitiveness of low-carbon technologies.
Forest management and exploatation produces large quantities of forest biomass, which can be used for energy production. Biomass can additionally be generated by the establishment of bioenergy plantations and biomass production in short rotation crops (SRC) of forest tree species.
The article presents a mathematical economic model which explores the impact of CO2prices on investment decisions related to the construction of new electrical power plants or a change of fuels in the existing plants. The model determines emissions allowance prices at which biomass becomes more competitive than other technologies. Changes in CO2prices affect short run marginal costs (SRMC) and long run marginal costs (LRMC) of electrical energy production, where a decision on the replacement of fuel in the existing plant depends on trends in short run marginal costs, whereas an investment decision to construct new electrical plants depends on long run marginal costs.
According to the results of the applied model, biomass fuel in the existing plants (comparison of SRMC) is more competitive than gas even with minimal biomass prices and no additional CO2allowance price or feed-in tariffs. With CO2prices larger than 26 €/t CO2, biomass becomes more competitive than gas and coal for its minimal price, while for its maximal price it is more competitive at CO2prices larger than 21 €/t CO2.
Key words: Croatia; EU ETS scheme; forest biomass; short run (SRMC) and long run marginal costs (LRMC)
KAJBA, Davorin ŠL
|Grgurević, D.||UDK 630* 272 (Cactaceae)||439|
|Succulents (fat plants) on theAdriatic Coast and their Use in Parks|
|Summary: Succulent plants are gradually colonizing the Croatian coast. These plants initially the collector’s items, but when their ability to tolerate low temperatures was discovered, they began to be grown in the open. Since this species was often mentioned by Croatian Renaissance writers, it can be said with certainty that Opuntia sp. occurred in the Mediterranean and the Adriatic region as early as the 16thcentury, shortly after the discovery of America.
Many of the Opuntia sp. and Agave americana plants developed spontaneously by adapting to the new ecological conditions. In fact, the American agave virtually became a symbol of some parts of the Croatian coast. Certain cacti species, such as C. Peruvians „Monstruosus“, which may reach over 4 metres in height, manifest high resistance to cold and are frequently found along the Croatian coast.
Due to global warming, some plants, such as Aptenia cordifolia, a species unheard of in these parts only some ten years ago, have acclimatized to the conditions and spread across the coastal area. Apart from these exotic succulents, the Croatian coast is also home to some European fat plants, such as Sedum sp – stonecrop, and Sempervivum sp. –houseleek. Succulents are plants that thrive in stony areas. Still, we should be cautious not to over-plant them, since they impart an exotic appearance.