Structure, Texture and Regeneration of Dinaric Beech-fir Virgin forest of Čorkova Uvala

Istraživanje je obavljeno u dinarskoj bukovo-jelovoj prašumi Čorkova uvala u Nacionalnom parku Plitvička jezera, u razdoblju 2004–2005. godine, na sistematskom uzorku od 68 ploha postavljenih u obliku mreže, s razmacima 100 m, svaka površine 805 m2. Istraživanjem je ustanovljeno stanje strukture, teksture i pomlađivanja u prašumskoj sastojini, koja se prostire na 80,50 ha. Prašumsku sastojinu u prosjeku tvori 440 stabala po hektaru. Ukupni broj stabala opada s porastom prsnog promjera, a koeficijent (q) distribucije stabala po prsnim promjerima iznosi 1,20. Volumen sastojine iznosi 671,23 m3/ha, od čega je 52 % jele, 42 % otpada na bjelogoricu, a ostatak u iznosu od 6 % pripada volumenu smreke. Među tanjim stablima, čiji su prsni promjeri do 30 cm, kumulirano je 7,55 % ukupnoga volumena. Na stablima sred­njih prsnih promjera između 31 i 50 cm kumulirano je 19,92 % ukupnoga volumena sastojine. Ostatak volumena u iznosu od 72,53 % kumuliran je na stablima velikih prsnih promjera iznad 50 cm. Ustanovljeno je postojanje razvojnih faza, ali na malim površinama, pa se može zaključiti o prebornom obliku sastojinskog sklopa. Po hektaru površine prašumske sastojine nalazi se u prosjeku deset odumrlih (suhih i trulih) stabala, od čega je sedam stabala obične jele. Ukupna brojnost mladoga naraštaja najveća je na lokalitetima na kojima je ustanovljena prijelazna inicijalna/preborna faza razvoja. Ti su lokaliteti najrjeđe zastupljeni po njezinoj površini. Po hektaru površine prašumske sastojine u prosjeku nalazimo 6190 biljaka pomlatka. Na jelu otpada 60 %, bukvu 28 %, smreku 2 %, a na gorski javor 10 % ukupnoga broja mladoga naraštaja.Not so very long ago (the end of the 19th century) a large part of the Dinaric Mountain range in Croatia was covered by beech-fir and beech virgin forests. These forests have since been gradually converted into natural managed forests (Prpić et al. 2001). Nevertheless, several Dinaric beech-fir virgin forests have remained until the present day, including Čorkova Uvala, Devčića Tavani, Nadžak-Bilo, Plješivička Uvala, Javorov Kal and Štirovača (Prpić et al. 2001, Vukelić and Tomljanović 2001). Their total area amounts to 360 ha. The best investigated of these is Čorkova Uvala. The first scientific forest research in this forest dates back to 1957. Its structure has since been analyzed on several occasions: in a permanent sample plot of one hectare (Tikvić et al. 2006, 2004, Prpić and Seletković 1996, Prpić 1979, 1972), in 12 sample plots of 2,500 m2 each, systematically placed in the form of a network at a distance of 250 m from each other (Kramarić and Iuculano 1989) and in 153 sample plots, each sized 200 m2 and systematically set up in the central part of the old growth stand in the form of a network 50 m from one another (Mayer et al. 1980). In addition, several inventories have also been conducted as part of the management program for the management unit of Čorkova Uvala (1987), and the structure of a wider area of Čorkova Uvala – Čudinka reserve has been analyzed (Cestar et al. 1983). Most of these investigations and inventories provide an average picture of the old growth stand structure. Apart from the results of Mayer et al. (1980), there have been no in-depth analyses of its structure and regeneration. More recently, research into natural regeneration in the old growth stand of Čorkova Uvala has been intensified and initial results have been published (Roženberger et al. 2007). This work presents the results of initial comparative research into the structure, texture and regeneration in the old growth stand of Čorkova Uvala. This research was undertaken in the Dinaric beech-fir virgin forest of Čorkova Uvala in Plitvice Lakes National Park in the period 2004–2005. The research involved a systematic sample of 68 plots of 805 m2 each. The plots, set up in the form of a network, were placed 100 m from one another. The activities in each plot included measuring the terrain slope, describing the relief, assessing the canopy, identifying life stages of the virgin forest, measuring breast diameters on all trees (d1.30 > 3 cm) and classifying them by tree species. Dead trees were recorded separately. A height sample was measured in the plots and in their immediate proximity. The young growth was measured in each plot over an area of 80 m2 and classified by tree species and height. Research provided the condition of the structure, texture and regeneration in the old growth stand extending over 80.50 ha. The old growth stand is made up of 440 trees per hectare on average. Common beech and other hardwoods (OHW) account for almost half of the trees (49 %). There are 45 % of fir trees (Abies alba Mill.) and 6 % of common spruces (Picea abies Karst.). The total tree number declines with an increase in breast diameters. The coefficient (q) of tree distribution by breast diameter is 1.20. Stand volume is 671.23 m2/ha, of which fir accounts for 52 %, broadleaves account for 42 %, and the remaining 6 % relates to spruce. 7.55 % of the total volume is accumulated among thinner trees with breast diameters up to 30 cm. Trees with mean breast diameters between 31 and 50 cm contain 19.92 % of the total stand volume. The remaining volume of 72.53 % is accumulated on trees with breast diameters above 50 cm. Different developmental stages have been identified, albeit over small areas, allowing us to conclude that the stand profile has the selection form. The initial developmental stage was determined in 9 % of the cases, the optimal stage in 18 % of the cases, the terminal stage in 65 % of the cases (ageing and decomposition), and the typical selection developmental stage in 8 % of the cases. The late optimal stage and the ageing stage are the most common due to the depression-like relief of Čorkova Uvala, which protects it from severe winds and allows mature and dead trees to remain standing for long periods. The decomposition stage occurs over small areas as a consequence of fall of singe trees or small groups of trees. In the area of the old growth stand the typical initial stage is relatively modest. It occurs in gaps but also under the canopy. The typical selection stage was found in the smallest number of cases. It is the densest (548 trees/ha), with a volume of 434.70 m3/ha and the highest participation of the silver fir. There are on average ten dead (dry and rotten) trees per one hectare of the old growth stand, of which seven are trees of silver fir. The highest number of dead fir trees was recorded in the 11–20 cm diameter class. The total abundance of the young growth was found in the localities in which a transitional initial/selection developmental stage was recorded. These localities are the least represented. There are 6,190 seedlings on average per one hectare of the old growth stand. Fir accounts for 60 %, beech for 28 %, spruce for 2 % and sycamore for 10 % of the total number of the young growth. Two thirds of the seedlings are up to 50 cm tall. On average, a fir taller than 50 cm is found on every 12 m2 of the area and one taller than 100 cm on every 30 m2 of the area. Unlike beech and sycamore, no fir taller than 300 cm was found up to the taxation limit. Of the total number of the young growth up to 100 cm in height, beech accounts for 15 %, spruce for 2 % and sycamore for 9 %. Beech and sycamore prevail in height classes above 100 cm. The young growth of spruce has a secondary role and occurs sporadically, reaching a height of up to 175 cm

Variability of morphological and biological characteristics of Wild Service Tree (Sorbus torminalis (L.) Crantz) fruits and seeds from different altitudes

Aims and objectives of research: The study aimed to research the influence of altitude on dimensions, i.e. the shape of Wild Service tree fruits (Sorbus torminalis (L.) Crantz). We also wanted to test the variability of major biological characteristics of fruits and seed, the elements of seed quality and their relations. Materials and Methods: In September 2003 we gathered fruits from 24 Wild Service Trees of different ages and positions in the stand structure on three sites (Medvednica, Psunj and Južni Dilj) situated at different altitudes. The altitude of each tree was determined with the GPSmap 60CSxdevice, after which dendrometric measurements were carried out and fruits were collected.We measured fruit length (FL) and width (FW) and calculated their index (FL/FW). The mass of each fruit was weighed on the laboratory scales Sartorius and the number of fruits per kilo was calculated. The seeds were manually extracted from the fruits and the number of filled (sound) seeds per fruit was counted in line with the ISTA rules. In order to break the double seed dormancy we applied the stratification in accordance with the ISTA rules. For the statistical analysis of the data we used ANOVA, LSD test, correlation analysis and canonical discriminant multivariate analysis with the locality as a grouping variable. All statistical analyses were performed using STATISTICA 8.0 program package. Results: We obtained a positive and strong correlation between fruit length and altitude (R=0.67), i.e. between fruit shape index and altitude (R=0.71), which means that the higher the altitude of the population of the Wild Service Tree in the Republic of Croatia, the longer the fruits. At higher altitudes the Wild Service Tree seed shows a larger degree of dormancy and requires somewhat longer period of stratification. Conclusion: The observed differences between the three studied locations might be attributed to changed climatic and soil conditions

Floristic composition as an indicator of destabilisation of lowland forest ecosystems in Posavina

Background and Purpose: The succession of forests in the Posavina region follows a pattern from forests of black alder and ash through stands of pedunculate oak to pedunculate oak-hornbeam forests. In the past hundred years, this lowland area has been affected by a number of factors, among which anthropogenic influences hold a primary position. This has resulted in a considerable deviation from normal, natural succession. The purpose of this paper is to analyse the present condition, the degree of destabilisation and the future developmental trends of pedunculate oak stands by drawing on previous pedological, hydrological and vegetational research. One of the best indicators of the above is the ecoindicator values of the floristic composition. Materials and Methods: Phytocoenological relevés were taken in 25 localities of both stable and destabilised forest ecosystems of pedunculate oak in Žutica Forest. The principles of the Zurich-Montpellier School were applied for this process. The numerical analysis was carried out by means of SYN-TAX 2000 software. JUICE 6.3 and CANOCO 4.5 were also used to process the relevés, construct the phytocoenological tables and correlate species compositions and vegetation typeswith ecological factors. The obtained results were compared with the results of earlier ecological research. Results: Phytocoenological research revealed significant changes in the floristic composition. Ecoindicator values of plant species indicate a substantial change in ecological parameters and increased destabilisation, which leads to larger quantities of light, thermophilicity and humidity in sites. In addition, the sites are richer in nitrogen and the soil reaction becomes more basophilic, while central European species replace intermediary ones. Conclusions: The investigated plots show a regression process contrary to the normal direction of vegetation development in lowland areas. A return has been observed from the final community to transitional communities, and in some localities even to initial and pioneer communities

Selection of tree species for the substitution of poplar plantations along the river Drava near Osijek

U radu su prikazani rezultati istraživanja preživljenja i rasta nekih vrsta drveća kojima bi se u slučaju potrebe mogla obaviti zamjena topola u nasadima. Pokus je postavljen na području Šumarije Valpovo, u Gospodarskoj jedinici Valpovačke podravske šume, šumski predjel Topolje, odsjek 23a. Taj lokalitet predstavlja tipičan primjer slabog uspijevanja i odumiranja nasada topola, čak i nakon višekratnih popunjavanja sadnicama topole i njege. Pokus je postavljen po shemi slučajno-bloknog rasporeda, sa šest tretiranja u četiri bloka. Tretirani su sljedeći sastojinski oblici: A – hrast lužnjak, B – poljski jasen, C – bagrem, D – hrast lužnjak s običnim grabom, E – divlja trešnja s poljskim jasenom i F – divlja trešnja s običnim grabom. Pokus je postavljen 18. studenog 2009. godine.  Preživljenje biljaka je utvrđeno svake godine tijekom petogodišnjeg praćenja pokusa. Tijekom zime 2015. godine izmjerene su visine svih stabala te je određen prostorni položaj živih i odumrlih jedinki po plohicama. S obzirom na preživljenje i visine kao indikatore rasta i razvoja biljaka, najbolje su rezultate pokazali redom obični bagrem, poljski jasen i hrast lužnjak. Najlošije rezultate postigli su divlja trešnja i obični grab. S obzirom na mikroreljef, najbolje preživljenje je pokazao obični bagrem koji podjednako dobro raste u nizi i na gredi. Poljski jasen i hrast lužnjak bolje preživljenje imaju u nizi. Divlja trešnja i obični grab imaju općenito loše preživljenje, neovisno o mikroreljefu. Rezultati istraživanja pokazali su kako je nasade topola u promijenjenim stanišnim prilikama nakon višekratnih ophodnji moguće zamijeniti sa sastojinom koja svojim sastojinskim oblikom odgovara terminalnoj šumskoj zajednici istraživanoga podučja – veza i poljskog jasena s hrastom lužnjakom (Fraxino-Ulmetum laevis Slavnić 1952). Postupku treba prethoditi izrada detaljnog šumskouzgojnog plana, koji bi između ostalog definirao područja niza i greda u određenom odjelu. Nize i vlažne grede treba prepustiti poljskom jasenu koji je pokazao vrlo dobre rezultate u pokusu. Hrast lužnjak je pokazao zavidnu stabilnost i vitalitet, pa ga treba upotrebljavati u smjesi s poljskim jasenom. Obični bagrem preporuča se za najsuše lokalitete s pjeskovitim tlima koja su naglo ostala bez podzemne i poplavne vode, na kojima nema uvjeta za nastavak uzgajanja topola.The paper presents the results of research on the survival and growth of several tree species which could be used to replace poplars in plantations if necessary. The experiment was established in the area of Valpovo Forest Office, in the Management Unit of Valpovačke Podravske Šume, forest area of Topolje, sub-compartment 23a. This locality is a typical example of poor growth and dieback of poplar plantations even after multiple restocking with poplar seedlings and tending. The experiment was set up according to the randomized block design, with six treatments in four blocks. The following stand forms were treated: A - pedunculate oak, B - narrow-leaved ash, C - black locust, D - pedunculate oak with common hornbeam, E - wild cherry with narrow-leaved ash, and F - wild cherry with common hornbeam. The experiment was established on November 18, 2000. Plant survival was recorded every year over a five-year trial monitoring period. During the winter of 2015, the height of all the trees was measured and the spatial position of live and dead individuals per subplot was determined. In terms of survival and height as indicators of plant growth and development, the best results were manifested by black locust, followed by narrow-leaved ash and pedunculate oak. The poorest results were achieved by wild cherry and common hornbeam. With regard to the micro-relief, the best survival was displayed by black locust, which grows equally well both in unsoaked micro depressions (niza) and on micro elevations (greda). Narrow-leaved ash and pedunculate oak survived better in micro-depressions. In general, wild cherry and common hornbeam showed poor survival irrespectively of the micro-relief. Research results confirm the hypothesis regarding the need to replace or substitute poplar plantations under changed site conditions towards a stand whose stand form is adequately suited to the terminal forest community of the study area - spreading elm and narrow-leaved ash with pedunculate oak (Fraxino-Ulmetum laevis Slavnić 1952). The procedure should be preceded by a detailed forest management plan which would, among other things, define the areas of micro-depressions and micro-elevations in a particular compartment. Micro-depressions and wet micro-elevations should be reserved for narrow-leaved ash, which showed very good results in the trial. Pedunculate oak displayed very good stability and vitality and should therefore be used in a mixture with narrow-leaved ash. Black locust proved to be suitable in all conditions, but it is recommended to use it over the driest and sandy soils which have abruptly remained without ground and floodwater

Generating Virtual Even-Aged Silver Fir Stand Structure Based on the Measured Sample Plots

Background and Purpose: The aim of this article is to create a virtual forest stand based on the field measurement of spatially separated sample plots and to examine its credibility based on the deviation of the basic characteristics of the virtual stand as compared to the field measurements. Material and Methods: Field measurements were made on 20 circular sample plots with a 20 m radius, set on a 100x100 m grid. By using the univariate Ripley’s K function the regularity of the spatial pattern of trees was analysed. The diameter distribution and the frequencies of height within individual diameter class were mathematically fitted and used for generating the virtual stand. The whole process of generating the virtual stand was done in the R software. Area of study are even-aged silver fir stands in the Croatian Dinarides. Results: The main unit of the virtual stand is a tree, with the purpose that the virtual stand can then be used as a basis for forest stand growth simulators. The result of the research was a virtual stand of 3 ha whose characteristics only slightly differed from the field measured plots. Within the virtual stand, special emphasis has been put on tree heights, which were generated according to the variability of tree height for trees of the same diameter at breast height. Conclusions: Considering the distribution of diameters at breast height, tree heights, the number of trees, basal area and volume, the virtual stand has minimal deviations from the situation in the field and it adequately shows variability measured in the field

Natural regeneration of Norway Spruce (Picea abies (L.) Karst.) stands on northern Velebit

Background and Purpose: Natural regeneration is a natural phenomenon that depends on numerous factors. Regeneration of virgin forests is successful even without any human interference. For the regeneration of economic forests we do not have that much time and thus try to speed up the process. The study of factors involved in natural regeneration as the most perfect system of forest ecosystem regeneration requires long lasting research. Material and Methods: Numbers and heights of seedlings and new growths, as well as the species participating in natural regeneration were measured on four test plots over the period of four years (1995, 1998, 1999, 2000). The plots were located at different elevations and contained different plant communities. The Norway spruce seed yield and its quality (germination) were also researched. Results: Very poor appearance of seedlings and new growth and even the decline in the numbers were observed on all test plots. This can be directly correlated to management in which single-tree selection management and piling of timber supply result in poor light conditions and gradual disappearance of Norway spruce. Seed germination ranging from 13% on plot I to 48% on plot II shows that the seed has very low natural germination and only abundant crops can lead to greater natural regeneration. Conclusion: Norway spruce is a species whose natural regeneration in the above mentioned structural and site conditions is a difficult process. Natural regeneration of Norway spruce is affected by management, timber supply, condition of vegetation on the soil, as well as the intensity of light. The seed quality and its quantity did not affect regeneration on test plot