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Pojava odumiranja stabala hrasta lužnjaka (Quercus robur L.) i poljskog jasena (Fraxinus angustifolia Vahl) gospodarski je i ekološki problem. Čimbenici koji uzrokuju odumiranje stabala mogu biti biotski, stanišni i strukturni odnosno sastojinski.Istraživanje je provedeno u gospodarskoj jedinici „Zelenika” u Posavini. Ciljevi ovog istraživanja bili su utvrditi prosječnu stopu promjene intenziteta odumiranja stabala hrasta lužnjaka i poljskog jasena, istražiti utjecaj stanišnih i strukturnih čimbenika na intenzitete odumiranja te usporediti intenzitete odumiranja hrasta lužnjaka i poljskog jasena prema dobnom razredu sastojina i mikroreljefu. Za analizu su korišteni podaci o klimi za meteorološku postaju Novska, vodostaju vodotoka Novska te podaci o razinama podzemne vode sa pjezometarske postaje „Zelenika“. Iz obrazaca O-2 Osnove gospodarenja, prikupljeni su podaci o volumenu odumrlih stabala hrasta lužnjaka i poljskog jasena te podaci o strukturnim čimbenicima. Intenziteti odumiranja izračunati su na temelju odnosa volumena odumrlih stabala po jedinici površine. S obzirom na prosječnu stopu promjene, intenziteti odumiranja hrasta lužnjaka i poljskog jasena se povećavaju. Najveći intenziteti odumiranja za obje šumske vrste su u sastojinama VI. dobnog razreda. Na osnovi provedenih istraživanja možemo zaključiti da klimatski, hidrološki i strukturni čimbenici imaju utjecaj na odumiranje hrasta lužnjaka i poljskog jasena. Hrast lužnjak osjetljiviji je na klimatske elemente u odnosu na poljski jasen. Pojava sušnih i izostanak kišnih razdoblja također značajno utječe na odumiranje. Smanjenje srednjega minimalnog vodostaja vodotoka utječe na odumiranje hrasta lužnjaka, dok smanjenje maksimalnog vodostaja vodotoka utječe na odumiranje poljskog jasena. Na intenzitete odumiranja značajno utječe pad razine podzemne vode u dubljim slojevima pedosfere. Svi strukturni čimbenici utječu na odumiranje hrasta lužnjaka, dok na odumiranje poljskog jasena značajno utječe jedino povećanje obrasti i broja stabala u sastojini., The pedunculate oak (Quercus robur L.) and narrow-leaved ash (Fraxinus angustifolia Vahl) tree dieback phenomenon presents an economic as well as ecologic problem. Factors that cause tree dieback can be biotic, biotopic (within habitat) and structural (within stand). In managed forests, the volume of dead trees or volume of trees cut in a sanitation harvests are most often used to show the intensity of tree dieback, and may also be used as an indicator of the stands condition (Capecki, 1981).Every species has its own ecological niche. Forest tree species have varying reactions to changes in environmental factors, to stress and ultimately to dying. The study was conducted in „Zelenika” management unit in Posavina. The aims of the study were to establish pedunculate oak and narrow-leaved ash tree dieback dynamics, to research the influence of biotopic and structural factors on dieback intensity and to compare dieback intensities according to the stand age class and microrelief. For analysis were climatic data for Novska meteorological station, water level data of Novska watercourse, and groundwater level data from „Zelenika” piezometric station were used. Dry years and dry periods, and wet years and wet periods, were determined using the percentile method and the Walter climate diagrams.Growing volume of withered pedunculate oak and ash trees, as well as structural factors data(stand structure elements) were collected from the O-2 form of the Forest management plan. Dieback intensities were calculated on the basis of growing volume of the withered trees per area unit ratio. The intensity of tree death was shown in absolute numbers, as m3/ha (Siwecki et al. 1998).Considering the average change rate, dieback intensities of pedunculate oak and narrow-leaved ash tree are increasing. The highest dieback intensities for both forest species were found in the VI age class (Figure 2). On the basis of the conducted research, it can be concluded that climatic, hydrological and structural factors influence pedunculate oak and narrow-leaved ash tree dieback.Pedunculate oak is more sensitive to climatic elements in comparison to narrow-leaved ash tree. Frequent dry years significantly affected the dying of these two species, which can both be considered hydrophytes in terms of their ecological demand for water. The results of this study showed that narrow-leaved ash was more vulnerable to drought than pedunculate oak.Drought and rain periods also significantly influence tree dieback (table 5). The effect of dry periods on the dieback of these two species was greater in relation to the lack of wet periods in these lowland forests. The decrease of mid and minimal water levels of watercourse influenced pedunculate oak dieback, while a decrease of maximum watercourse water levels influenced narrow-leaved ash tree dieback (table 6). Groundwater level decrease in deeper layers of pedosphere had asignificant influence on tree dieback intensities (table 7). It was revealed that all structural factors influence pedunculate oak dieback, while narrow-leaved ash tree dieback was influenced only by stocking and tree number increase in a stand (table 8).The dieback of pedunculate oak was higher in older stands. No correlation was detected between the dieback of narrow-leafed ash and stand age.

Poznavanje zakonitosti djelovanja ekoloških čimbenika i reakcija članova ekosustava na te čimbenike nužno je kako bi se podržavalo prirodno funkcioniranje šumskih ekosustava kojima se gospodari. Promjene ekoloških čimbenika utječu značajno na nadzemni i podzemni dio ekosustava. Naglašena osjetljivost jelovih i bukovo-jelovih šuma na rubu njezina areala, odumiranje stabala te propadanje čitavih sastojina pridonijeli su da istraživanja provedemo upravo u tim šumama. Cilj je ovih istraživanja definirati stanišne čimbenike koji su u vezi s odumiranjem stabla obične jele u gorskoj Hrvatskoj, te utjecaj stanišnih čimbenika na stanje hraniva u iglicama i u tlu. Prikupljeni su podaci o drvnom volumenu odumrlih stabala obične jele na razini svih odjela/odsjeka gospodarske jedinice. Iglice su uzorkovane sa stabala triju različitih stupnjeva osutosti, a uzorci tla s dubine od 30 cm. Sastojine na rubu areala obične jele u Gorskom kotaru uvelike odumiru u odnosu na sastojine u unutrašnjosti areala Gorskoga kotara. U razdoblju od 1995. do 2007. u sastojinama na rubu areala u Gorskom kotaru prosječno je godišnje odumrlo 18,3 m3/ha obične jele. U istom razdoblju u sastojinama u unutrašnjosti areala Gorskoga kotara prosječno je godišnje odumrlo 6,2 m3/ha. U sastojinama na rubu areala i u unutrašnjosti areala Gorskoga kotara prosječno godišnje odumiranje stabala obične jele veće je od godišnjega prirasta. Intenzitet odumiranja stabala (m3/ha) statistički značajno negativno i vrlo slabo korelira s vegetacijskom količinom oborine (mm) i vodnom bilancom tla (mm). U sastojinama na rubu areala i u unutrašnjisti areala Gorskoga kotara inklinacija i nadmorska visina statistički značajno i negativno utječu na intenzitet odumiranja stabala (m3/ha). Kalcij i magnezij negativno i statistički značajno koreliraju s vrijednostima temperature zraka, a pozitivno s količinom oborine u vegetacijskom razdoblju, što je značajno za razdoblje suše i povećanih vrijednosti temperature zraka na području istraživanja., Dieback of silver fir in Croatia, especially in the Dinaric part, is associated with complex changeable effects of abiotic and biotic factors. In industrial forests, the volume of dieback trees or volume of trees cut down in salvage cutting is most often used for showing tree dieback intensity, and can be used as an indicator of forest stand health status (Capecki 1981). The aim of this research was to show the correlation of silver fir dieback with habitat and structural factors, calculate the intensity of dieback according to volume, and determine tree dieback dynamics and effects of habitat factors on concentration of essential mineral nutritive elements in needles and soil. The research was carried out in the mountainous part of Croatia, in beech-fir and fir forests of Gorski Kotar. The research included the forest stands of disrupted stability and structure, at the border of the natural range of sliver fir towards a warmer area and optimum area of silver fir i.e. central part of Gorski Kotar. Data for wood mass of dieback silver fir trees were collected for the selected management units at the level of all compartments and subcompartments in the management unit. The data were being collected for twelve years (1995–2007). In the researched area, needle sampling from tree crowns was carried out on trees with three different levels of defoliation (60%). Dry needle mass was determined as well as concentration of K, Ca and Mg. Soil chemical analysis included soil reaction, and amount of phosphorus (P) and potassium (K) in the soil. The average annual silver fir dieback intensity for forest stands at the border of the natural range was 18.3 m3/ha or 9.2% of silver fir growing stock, and in forest stands in the central part of Gorski Kotar it was 6.2 m3/ha or 4.1%. The maximum annual dieback intensity in forest stands at the border of the natural range was 113.0 m3/ha, and in forest stands in the central part of Gorski Kotar it was 55.4 m3/ha. For forest stands with recorded dieback, the average annual increment was 2.7 m3/ha, and in forest stands in the central part of Gorski Kotar it was 3.3 m3/ha. In forest stands with sliver fir dieback, dieback intensity was higher than the value of the growing stock (Table 1). Intensity of the average annual silver fir dieback at the border of the natural range was from 1.6 to 18.8 m3/ha, and in forest stands in the central part of Gorski Kotar from 5.0 to 7.5 m3/ha (Fig. 1). In forest stands at the border of the natural range, the highest average annual silver fir dieback intensity was recorded in silver fir forest with hard fern (18.63 m3/ha), and the lowest in silver fir forest with small-reed (11.5 m3/ha). Dieback intensity in the central part of Gorski Kotar was lower, the highest being in silver fir forest with small-reed (14.4 m3/ha), and the lowest in the Dinaric beech-fir forest (5.8 m3/ha) (Fig. 2). In forest stands at the border of the natural range, the highest dieback intensity was recorded at west and southwest exposition, and the lowest at northwest and east exposition. In forest stands in the central part of Gorski Kotar the highest dieback intensity was at southwest, and the lowest at north exposition. In relation to altitude, the most severe dieback intensity was observed at lower, and the lowest at higher altitudes (Table 2). According to the results shown in Table 3, in forest stands at the border of the natural range, tree dieback intensity significantly and positively correlates with exposition, growing stock (0.23*) and number of silver fir trees (0.12*), and negatively with terrain slope (– 0.15*), altitude (– 0.11*), precipitation quantities in vegetation period (– 0.11*), soil water balance (– 0.11*) and increment (– 0.16*). In forest stands in the central part of Gorski Kotar silver fir dieback intensity significantly and negatively correlates with altitude (– 0.14*), precipitation quantities in vegetation period (– 0.18*) and soil water balance (– 0.12*). Calcium negatively correlates with vegetation air temperatures (– 0.23*), and positively with vegetation precipitations (0.23*), which is important for drought periods because 2007 was a »drought« year (Review No. 18). The correlation coefficients of Mg concentration show the same trend with air temperatures (– 0.48*) and precipitation quantities (0.48*). The correlation of Ca concentration and soil pH value is positive and amounts to 0.34*, while the correlation of dry needle mass and defoliation is – 0.40* (Table 4). The concentration of phosphorous and potassium in the soil correlates positively with vegetation air temperatures (0.34*, 0.29*), and negatively with vegetation precipitations (– 0.34*, – 0.29*) and altitudes (– 0.52*, – 0.50*) (Table 5). Dry needle mass (g), concentration of potassium, calcium and magnesium (mg/g) decrease with the increase of tree crown defoliation (Table 6). In the current year the mass of dry needles is 0.48 g, and in the last year it was 0.52 g. In the current year the concentration of calcium in needles is 12.34 mg/g, and in the last year it was 17.06 mg/g (Table 7). The data of Fužine and Rijeka Forest Office show that the percentage share of salvage cutting or dieback of silver fir amounts up to 100% according to prescribed yield (annual allowable cut) for the area of management units Brloško, Kobiljak-Bitoraj and Jelenje Velo (border of the natural range). On the contrary, the percentage share of salvage cuttings according to prescribed yield in the area of the management units Ravna Gora and Višnjevica (central part of Gorski Kotar) amounts up to 15%. In the area of Gorski Kotar tree dieback was recorded on all types of geological basis and forest soils, and in all silver fir forest associations. At the border of the natural range the highest dieback intensity was recorded in silver fir with hard fern, and in the central part of Gorski Kotar in silver fir with small-reed. According to our research, the highest tree dieback volumes (m3 and m3/ha) occur at the lowest altitudes and on mild slopes. Tikvić et al. (2008) reported the same results. Due to higher air temperatures and lower precipitation quantities, soil evaporation is higher at lower altitudes. During drought periods at these altitudes, soil water balance is low. Thomas et al. (2002) found positive correlation between precipitation quantities and altitude and considers that this is suitable for forest tree development at higher altitudes. In forest stands at the border of the natural range, tree dieback volume (m3/ha) is the lowest at northeast expositions, and the highest at west exposition, followed by different variants of south expositions, and compartments of different expositions. This was expected since the south and west expositions are warmer and more exposed to unfavourable currents from west Europe. The decrease of vegetation precipitation quantities significantly increases the volume of silver fir dieback. These results correspond to the results reported by other authors (Markalas 1992, Thomas et al. 2002, Tikvić et al. 2008). Even within the silver fir areal in one country, there are significant differences in factors affecting tree dieback. This can be proved by comparing the factors that affect dieback at the border of the natural range and in the central part of Gorski Kotar. Air temperature increase and precipitation quantities decrease result in the decrease of concentration of calcium and magnesium in silver fir needles, which is significant for drought periods and air temperature increase. Dry needle mass and calcium concentration are significantly higher in the last year than in the current year needles. According to the Meteorological and Hydrological Service, the year 2007 (current year needles) was a drought year. In the forest stand at the border of the natural range where dieback was recorded, the average annual dieback intensity was six times higher than the average annual increment, while in forest stands in the central part of the area, dieback intensity was two times higher than the annual increment. Tree dieback was recorded at all expositions, terrain slopes and altitudes, as well as in all forest associations. At the border of the natural range, relief, climate and structural factors have dominant effect on tree dieback, while in the central part of Gorski Kotar climatic factors have dominant effect on tree dieback. The increase of tree crown defoliation causes the decrease of dry needle mass, as well as the concentration of K, Ca and Mg. Drought resulted in lower concentration of magnesium and calcium in silver fir needles, and lower dry needle mass.

Poznavanje zakonitosti djelovanja ekoloških čimbenika i reakcija članova ekosustava na te čimbenike, nužno je kako bi se podržavalo prirodno funkcioniranje šumskih ekosustava sa kojima gospodarimo. Promjene ekoloških čimbenika utječu značajno na nadzemni i podzemni dio ekosustava. Naglašena osjetljivost jelovih i bukovo-jelovih šuma na rubu njezina areala, kao i pojava odumiranja stabala, te propadanja čitavih sastojina, pridonijeli su da istraživanja provedemo upravo u tim šumama. Cilj ovih istrživanja je definirati stanišne čimbenike koji su u vezi sa odumiranjem stabla obične jele na području gorske Hrvatske, te utjecaj stanišnih čimbenika na stanje hranjiva u iglicama i tlu. Prikupljeni su podaci o drvnom volumenu odumrlih stabala obične jele na razini svih odjela/odsjeka gospodarske jedinice. Iglice su uzorkovane sa stabala tri različita stupnja osutosti, a uzorci tla sa dubine od 30 cm. Sastojine na rubu areala obične jele u Gorskom kotaru su sastojine velikog intenziteta odumiranja stabala u odnosu na sastojine u unutrašnjost areala Gorskog kotara. U razdoblju od 1995. do 2007. u sastojinama na rubu areala u Gorskom kotaru, prosječno godišnje odumre 18, 3 m3/ha obične jele. U istom razdoblju u sastojinama u unutrašnjosti areala Gorskog kotara prosječno godišnje odumire 6, 2 m3/ha. U sastojinama na rubu areala i u unutrašnjosti areala Gorskog kotara prosječno godišnje odumiranje stabala obične jele je veće od iznosa godišnje prirasta. Intenzitet odumiranja stabala (m3/ha) statistički značajno, negativno i vrlo slabo koreliraju sa vegetacijskom količinom oborina (mm) i vodnom bilancom tla (mm). U sastojinama na rubu areala i u unutrašnjisti areala Gorskog kotara inklinacija i nadmorska visina statistički značajno i negativno utječu na intenzitet odumiranja stabala (m3/ha). Kalcij i magnezij negativno i statistički značajno koreliraju sa vrijednostima temperatura zraka, a pozitivno sa količinom oborina u vegetacijskom razdoblju, što je značajno za razdoblje suša i povećanih vrijednosti temperatura zraka na području istraživanja.

Poznavanje zakonitosti djelovanja ekoloških čimbenika i reakcija članova ekosustava na te čimbenike, nužno je kako bi se podržavalo prirodno funkcioniranje šumskih ekosustava sa kojima gospodarimo. Promjene ekoloških čimbenika utječu značajno na nadzemni i podzemni dio ekosustava. Naglašena osjetljivost jelovih i bukovo-jelovih šuma na rubu njezina areala, kao i pojava odumiranja stabala, te propadanja čitavih sastojina, pridonjeli su da istraživanja provedemo upravo u tim šumama. Cilj ovih istrživanja je definirati stanišne čimbenike koji su u vezi sa odumiranjem stabla obične jele na području gorske Hrvatske. Za područje Gorskog kotara utvrdili smo statistički značajno povećanje srednjih godišnjih i vegetacijskih temperatura zraka, povećanje broja toplih i vrućih dana, te povećanje apsolutnih maksimalnih i srednjih minimalnih temperatura zraka. Vrijednosti godišnjih i vegetacijskih količina oborina imaju negativan trend. Sastojine na rubu areala razvijaju se u klimatski nepovoljnijim uvjetima. Sastojine u unutrašnjosti Gorskog kotara, G.j. Ravna Gora i Višnjevica su sastojine preborne strukture i normalne drvne zalihe. Ove su sastojine malog intenziteta odumiranja stabala obične jele (Abies alba Mill.) i dobro pomlađene sa običnom jelom. Sastojine na rubu areala obične jele u Gorskom kotaru, tj. G.j. Kobiljak - Bitoraj, Brloško i Jelenje Velo su sastojine narušene preborne strukture. U ovim sastojinama nedostaju stabla obične jele I i II debljinskih razreda. Donji slojevi sastojine popunjeni su stablima obične bukve (Fagus sylvatica L.). Ove su sastojine velikog intenziteta odumiranja stabala obične jele i dobro su pomlađene običnom bukvom i gorskim javorom. U sastojinama na rubu areala i u unutrašnjosti Gorskog kotara prosječno godišnje odumiranje stabala obične jele je jednako ili veće od iznosa godišnjg volumnog prirasta. Količine oborina i temperature zraka u vegetacijskom razdoblju su dva najznačajnija makroklimatska elementa, o kojima ovisi odumiranje stabala i osutost krošanja, ali su svakako važni i ostali čimbenici klime. Inklinacija i nadmorska visina statistički značajno i negativno utječu na indeks odumiranja stabala (m3/ha). Osutost krošanja se statistički značajno povećava sa smanjenjem debljinskog prirasta stabla, visine krošnje i promjera krošnje, te većom asimetrijom krošnje. Za lokalitete Brloško i Bitoraj ne postoje statistički značajne razlike u vremenu trajanja stupnjeva osutosti krošanja. Postoje statistički značajne razlike u trajanju između pojedinih stupnjeva osutosti. Također postoji statistički značajna interakcija između lokaliteta i stupnja osutosti što ukazuje da se stupnjevi osutosti ponašaju različito na analiziranim lokalitetima. Kalcij negativno i statistički značajno korelira sa vrijednostima temperatura zraka, a pozitivno sa količinom oborina u vegetacijskom razdoblju, što je značajno za razdoblje suša i povećanih vrijednosti temperatura zraka na području istraživanja. U šumskim otvorima izmjerena su veće vrijednosti srednjih temperatura zraka i tla u odnosu na šumu. Mjerene fizikalne i kemijske karakteristike tala su veće u šumi u odnosu na velike šumske otvore. Izuzetak čini mali šumski otvor (progala). Mikrobiološkim istraživanjima šumskih tala utvrđena je slaba do osrednja biogenost tala. S obzirom na zastupljenost pojedinih fizioloških skupina mikroorganizama i enzimatsku aktivnost tala nismo uočili veću degradaciju i osiromašenje tala u šumskim otvorima koji su starosti do tri godine. Sezonska dinamika mikroorganizama varirala je u širokim granicama i usko je povezana s razvojem tipa vegetacije odnosno dotokom svježe organske tvari i ovisi o sezonskom razdoblju uzimanja uzoraka tla. S obzirom na brojnost starijih biljaka (kom/ha) utvrđena je dobra pomlađenost listopadnim vrstama drveća unutar samih otvora (progala, plješina) i to gorskim javorom i običnom bukvom. Najveća brojnost biljka obične jele do tri godine starosti je u prostoru proširenog otvora.

Radijacijsko cijepljenje monomera na polimere je polimerizacija radikalima koja se normalno zbiva u viskoznome mediju, a vrlo često i u mikroheterogenome kristalastome materijalu. Istraživana je uloga kinetičkih i strukturnih čimbenika u reakciji cijepljenja. Cijepljenje stirena na polietilen i polipropilen inicirano je radijacijskim postupcima (izravno ozračivanje polimera i monomera, prethodno ozračivanje polimera u podtlaku, prethodno ozračivanje polimera u zraku) i kemijskim inicijatorima (azoizobutiro-nitrilom i benzoilperoksidom). Istraživan je utjecaj temperature, brzine doze, gustoće polimera, debljine ispitka, dodatka metanola monomeru i prethodnog umreživanja polimera na reakciju cijepljenja. Pokazano je da se na reakciju cijepljenja iniciranu izravnim ozraživanjem stirena i polietilena ili polipropilena može primijeniti pretpostavka stacionarnog stanja koja se primjenjuje na homopolimerizaciju. Mjerenja bubrenja pokazala su da je dotok monomera u polimer brži nego njegova potrošnja u reakciji, pa difuzija ne određuje brzinu reakcije. Brzina reakcije cijepljenja bila je konstantna i za brzine doze manje od 102 Gy/h dobivena je ovisnost brzine cijepljenja o kvadratnom korijenu iz brzine doze kakvu zahtijeva klasična jednadžba za homopolimerizaciju. Neovisnost brzine cijepljenja o brzini doze iznad 102 Gy/h uzrokovana je sudjelovanjem primarnih radikala u reakciji terminacije. S porastom gustoće polimera (0,92 – 0,96 g/cm3) i debljine filma ili folije (0,05 – 1 mm) zbog povišenja viskoznosti reakcijskog medija i posljedičnog sniženja brzine terminacije, brzina i prinos cijepljenja rastu, ali za vrlo krute deblje folije visoke gustoće opažena je vrlo mala brzina i nizak prinos cijepljenja, osobito pri niskim temperaturama. Razmatran je utjecaj strukturnih čimbenika i umreživanja na reakciju cijepljenja., Radiation grafting of monomers on polymers is radical polymerization which usually takes place in viscous medium and quite often in a micro-heterogeneous semicrystalline matrix. The role of kinetic and structural factors in the graft polymerization was investigated. Grafting of styrene on polyethylene and polypropylene was initiated by radiation methods (direct irradiation of polymer and monomer, pre-irradiation of polymer in vacuum, pre-irradiation of polymer in air) and by chemical initiators (azoisobutyronitrile and benzoil peroxide). The effect of temperature, dose rate, polymer density and specimen thickness, addition of methanol to monomer and pre-crosslinking of polymer on the grafting was investigated. It was shown that a steady-state assumption, which is conventional in homopolymerization, can be applied for radiation grafting initiated by direct irradiation of styrene and polyethylene or polypropylene. Swelling measurements have shown that monomer supply in polymer is higher than monomer consumption and the diffusion is not rate-determined step. The rate of grafting was constant and at the dose rates lower than 102 Gy/h the square root dependence of grafting rate on dose rate was valid as classical equation for homopolymerization request. The independence of the grafting rate on the dose rate above 102 Gy/h was due to participation of primary radicals in the termination reaction. The grafting rate and yield increased with the increase of the polymer density (0.92-0.96 g/cm3) and the film and foil thickness (0.05-1 mm) due to the increased viscosity of the reaction medium and consequently decreased rate of termination but lower yield of grafting and very slow reaction was observed for very rigid high density thick foils, especially at lower temperature. The effect of structural factors and crosslinking on grafting reaction has been discussed.