The Influence of Snow Cover Changes on Red Deer (Cervus elaphus L.) Migrations in the Western Part of Gorski Kotar Region in Croatia

Background and Purpose: Animal migrations are a direct result of reproduction, behaviour characteristics, predators, population density, disturbance, loss of habitat, climatic, vegetational and nutritional factors. The availability and accessibility of natural food in winter months is dependent on snow cover. The main objective of this study was to determine the migrational activities of red deer and to examine the dependency between migrations and climatic factors. Materials and Methods: The study was carried out in the northwest Dinarid mountains, i.e. in the western part of Gorski Kotar region, which represents a large integral forest complex, distinctive due to its significant vertical drops, diverse relief characteristics and habitat conditions. Data on red deer migrations was collected over a 12 year period from hunting records, gamekeeper logs and records from game counting and monitoring. Results and Conclusions: The results of the macroclimatic analysis show a statistically significant difference (p<0.05) between the monitored weather stations in the study area. The Klana site stood out as the most appropriate red deer winter habitat, based on climatic conditions. Climatic conditions play a key role in seasonal red deer migrations or non-migrations. The Crni Lug site was assessed to be the least favourable due to macroclimatic conditions (snow depth)

Comparison between tree dieback of pedunculate oak and narrow-leaved ash in relation to ecological constitution of species

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

Contribution to the knowledge of the moisture content parameters of live (LFMC) and dead (DFMC) forest fuel of strawberry tree (Viburnum tinus L.)

Klimatski parametri imaju velik utjecaj na požare. Najznačajniji klimatski čimbenici koji se uzimaju u obzir kad su u pitanju šumski požari su temperatura i vlaga, odnosno voda (oborine). Sadržaj vlage živog goriva (LFMC) i mrtvog goriva (DFMC) su složeni fenomeni koji se međusobno razlikuju kod pojedine vrste drveća. Promjene u sadržaju vlage su povezane s atmosferskim prilikama i dostupnoj vlagi u tlu s jedne strane te ekofizikalnim karakteristikama vrste s druge strane. Rezultatima ovih istraživanja utvrđene su točne vrijednosti sadržaja vlage živog i mrtvog goriva lemprike (Viburnum tinus L.). Oni bi trebali pomoći kao smjernice u što boljoj protupožarnoj politici, a na korist potrajnog gospodarenja i očuvanja općekorisnih funkcija šuma.In recent years, there has been an increase in the number of forest fires and burned areas in the wider Mediterranean area, including our country. The increased danger is present in all areas affected by the Mediterranean climate. Climatic parameters have a great impact on fires. The most important climatic factors that are taken into account when it comes to forest fires are temperature and humidity or water (precipitation). The moisture content of live (LFMC) and dead fuel (DFMC) are complex phenomena that differ among tree species. Changes in moisture content are related to atmospheric conditions and available soil moisture on the one hand, and the eco-physical characteristics of the species on the other. The results of these researches determined the exact values of live and dead fuel moisture content in the strawberry tree (Viburnum tinus L.). They should help as guidelines in the best possible fire policy, and in favour of sustainable management and preservation of public forest functions. Taking into account the influence of the researched meteorological factors on the live fuel moisture content and the dead fuel moisture content, it can be concluded from the obtained results that the researched meteorological factors have an impact on the dead fuel moisture content, while there was no such impact on the live fuel moisture content

Comparison of vitality and laboratory germination of holm oak acorns (Quercus ilex L.)

Šume hrasta crnike u Hrvatskoj nalaze u raznim degradacijskim stadijima, a jedan od njih je i makija koja je nepovoljniji stadij za klijanje sjemenki hrasta crnike u usporedbi sa crnikovim panjačama ili sastojinama visokog uzgojnog oblika. Crnika je kserofitna vrsta šumskog drveća. Geološku podlogu na kojoj dolazi crnika čine vapnenci i dolomiti koji su i najzastupljeniji na našem sredozemnom području. Crnika počinje cvjetati u osmoj godini života, rodi sjemenom u dobi 12. do 15. godine, a puni urod je svake 4. do 6. godine. Urod žira hrasta crnike je varijabilan, gdje su u osmogodišnjem periodu zabilježena tri obilna uroda žira. Puni urod hrasta crnike ovisi o klimatskim prilikama, ali se značajno razlikuje i između različitih staništa, posebice s obzirom na geološku podlogu i tip tla. Za laboratorijske analize, žir hrasta crnike sakupljen je na području G.J. „Kamenjak“ na otoku Rabu. Navedenom G.J. upravljaju „Hrvatske šume d.o.o.“. Sjeme je sakupljeno u odijelima 15a, 16a, 26a i 27a u periodu od 01. 12. 2020. do 10. 01. 2021. Sakupljanje je obavljeno metodom stresanja žira sa stabala na postavljene prostirke ispod krošanja i metodom sakupljanja otpalog žira s tla. Procjena vitaliteta sjemena metodom tetrazola i laboratorijske klijavosti napravljena je prema ISTA pravilima za hrast crniku. Postotak laboratorijske klijavosti utvrđen je prema postotku pravilnih klijanaca koji su normalno proklijali nakon 35. dana ispitivanja. Ukupni vitalitet žira hrasta crnike bio je visok i iznosio je 90,25 %, dok su ostatak od 9,75 % činile nevitalne sjemenke. Od vitalnog sjemena najveći postotak (79,50 %) čini sjeme kojemu je potpuno obojen embrij i kotiledoni. Žira s kotiledonima koji ima nekroze do 1/3 na distalnom dijelu, a nisu povezane sa embrionalnom šupljinom bilo je 10,75 %. U prvih sedam dana nije proklijao niti jedan žir pa je energija klijavosti iznosila 0,00 %. U prvih 14 dana laboratorijska klijavost je iznosila je 30,50 %, nakon 21. dana 76,50 %, nakon 28. dana 83,75 % te nakon 35. dana 88,50 %. Razlika između procjene vitaliteta žira i ukupne laboratorijske klijavosti iznosila je svega 1,75 %. Metoda procjene vitaliteta je brža i jeftinija od ispitivanja klijavosti. Rezultate procjene vitaliteta dobivamo za 18 sati, dok klijavost ispitujemo 28 ili 35 dana. Za praksu se može na osnovu rezultata ovih istraživanja predložiti ispitivanje vitaliteta žira hrasta crnike, a ne laboratorijske klijavosti kako preporučuju ISTA pravila (1993). Prosječno vrijeme klijanja (MGT) iznosilo je 19,91 dana. Pravilnih klijanaca bilo je 74,25 %, a nepravilnih 14,25 %. Na kraju ispitivanja utvrđeno je 8,50 % okularno zdravog žira koji nije proklijao dok je gnjilog žira bilo 3,00 %. Najčešća nepravilnost u iznosu od 56,14 % utvrđena je za kategoriju dva spojena klijanca, slijedi nekroza primarnih listova (12,28 %) i zakržljao primarni korijen (10,53 %). Ostale nepravilnosti pojavljuju se u manje od 10 % slučajeva.Holm oak forests in Croatia are in various stages of degradation, and one of them is maquis, which is a less favorable stage for the germination of holm oak seeds compared to holm oak stumps or stands of high growth form. Holm oak is a xerophytic species of forest trees. From the geological base, it comes from limestone, which is the most common in our Mediterranean area, and dolomite. Begins to flower in the eighth year of life, and the seed harvest begins at the age of 12 to 15 years, and the full harvest is every 4 to 6 years. The holm oak acorn crop is variable, where three abundant acorn crops were recorded in the eight-year period. The full harvest of holm oak depends on climatic conditions, but it also differs significantly between different habitats, especially the geological base and soil type. For laboratory analyses, holm oak acorns were collected in the area of G.J. "Kamenjak" on the island of Rab. The aforementioned G.J. managed by "Hrvatske šume d.o.o." The seeds were collected in department unit 15a, 16a, 26a and 27a in the period from 01/12/2020 to 10/01/2021. The collection was carried out using the method of shaking acorns from the trees onto mats placed under the canopy and the method of collecting fallen acorns from the ground. Assessment of seed vitality using the tetrazole method and laboratory germination was made according to the ISTA rules for holm oak. The percentage of laboratory germination was determined according to the percentage of normal seedlings that germinated normally after the 35th day of testing. The total vitality of holm oak acorns was high and amounted to 90.25 %, while the rest of 9.75 % consisted of non-vital seeds. Of the vital seeds, the largest percentage (79.50 %) consists of seeds with fully colored embryo and cotyledons. Acorns with cotyledons that has necrosis up to 1/3 on the distal part and are not connected to the embryonic cavity was 10.75 %. In the first seven days, not a single acorn germinated, so the germination energy was 0.00 %. In the first 14 days, laboratory germination was 30.50 %, after the 21st day 76.50 %, after the 28th day 83.75 % and after the 35th day 88.50 %. The difference between the assessment of acorn vitality and total laboratory germination was only 1.75 %. The vitality assessment method is faster and cheaper than the germination test. We get the results of the vitality assessment in 18 hours, while we test the germination after 28 or 35 days. Practical procedures can be based on the results of these studies suggest testing the vitality of the holm oak and not the laboratory germination as recommended by the ISTA rules. The average germination time (MGT) was 19.91 days. There were 74.25 % of regular seedlings and 14.25 % of irregular ones. At the end of the test, 8.50 % of the visually healthy acorns did not germinate, while 3.00 % of the rotten acorns were found. The most common irregularity in the amount of 56.14 % was determined for the category of two joined seedlings, followed by necrosis of primary leaves (12.28 %) and stunted primary root (10.53 %). Other irregularities appear in less than 10,00 % of cases

Contribution to the knowledge of the moisture content parameters of live (LFMC) and dead (DFMC) forest fuel of strawberry tree (Viburnum tinus L.)

Klimatski parametri imaju velik utjecaj na požare. Najznačajniji klimatski čimbenici koji se uzimaju u obzir kad su u pitanju šumski požari su temperatura i vlaga, odnosno voda (oborine). Sadržaj vlage živog goriva (LFMC) i mrtvog goriva (DFMC) su složeni fenomeni koji se međusobno razlikuju kod pojedine vrste drveća. Promjene u sadržaju vlage su povezane s atmosferskim prilikama i dostupnoj vlagi u tlu s jedne strane te ekofizikalnim karakteristikama vrste s druge strane. Rezultatima ovih istraživanja utvrđene su točne vrijednosti sadržaja vlage živog i mrtvog goriva lemprike (Viburnum tinus L.). Oni bi trebali pomoći kao smjernice u što boljoj protupožarnoj politici, a na korist potrajnog gospodarenja i očuvanja općekorisnih funkcija šuma.In recent years, there has been an increase in the number of forest fires and burned areas in the wider Mediterranean area, including our country. The increased danger is present in all areas affected by the Mediterranean climate. Climatic parameters have a great impact on fires. The most important climatic factors that are taken into account when it comes to forest fires are temperature and humidity or water (precipitation). The moisture content of live (LFMC) and dead fuel (DFMC) are complex phenomena that differ among tree species. Changes in moisture content are related to atmospheric conditions and available soil moisture on the one hand, and the eco-physical characteristics of the species on the other. The results of these researches determined the exact values of live and dead fuel moisture content in the strawberry tree (Viburnum tinus L.). They should help as guidelines in the best possible fire policy, and in favour of sustainable management and preservation of public forest functions. Taking into account the influence of the researched meteorological factors on the live fuel moisture content and the dead fuel moisture content, it can be concluded from the obtained results that the researched meteorological factors have an impact on the dead fuel moisture content, while there was no such impact on the live fuel moisture content

Mikroklima i prirodno pomlađivanje šumskih progala nastalih odumiranjem stabala obične jele (Abies alba Mill.)

Salvage cutting is a frequent operation to remedy the dieback of silver fir trees (Abies alba Mill.), which results in reduced stand canopy density and formation of forest gaps. This study was conducted in the beech-fir forest range of mountainous Croatia. The aim of the study was to determine microclimate conditions and natural regeneration in large and small forest gaps. Microclimate elements were measured and the density of plants from natural regeneration determined within forest gaps, in forest gap edge areas, and in control plots. Soil temperatures were significantly affected by changes in forest gap sizes with respect to the values of air temperatures, and were highest within the gaps as compared to gap edge areas and control forest stands. Microclimate had a significant affect on the number of small seedlings of silver fir and common beech in the large forest gaps, while this was not the case for the small forest gaps.Zbog intenzivnog odumiranja stabala obične jele (Abies alba Mill.) učestale su sanitarne sječe te dolazi do prekidanja sastojinskog sklopa i stvaranja šumskih progala. Istraživanje je obavljeno u bukovo – jelovim šumama na području Gorskog Kotara. Cilj istraživanja bio je utvrditi promjene mikroklimatskih uvjeta i prirodno pomlađivanje u velikim i malim šumskim progalama. U središtu i na rubovima šumskih progala, te u pripadajućim kontrolnim plohama mjereni su mikroklimatski elementi, kao i brojnost biljaka iz prirodnog pomlađenja. Temperature tla su značajnije reagirale na promjene veličine šumskih progala u odnosu na vrijednosti temperature zraka i bile su najveće u progalama u usporedbi s rubom progala i kontrolnim šumskim sastojinama. Broj biljaka obične jele u velikim i malim šumskim progalama je nedovoljan za uraštanje ove vrste u više slojeve sastojine. Brojnost biljaka starijeg pomlatka na rubovima velikih i malih progala te u sredini progala je bila značajno veća za listopadne vrste u odnosu na običnu jelu. Kod biljaka starijeg pomlatka nismo utvrdili značajne razlike u brojnosti biljaka između malih i velikih šumskih progala. Mikroklima je imala značajan utjecaj na broj biljaka mlađeg pomlatka obične jele i bukve u velikoj šumskoj progali, dok za malu šumsku progalu to nije bio slučaj

Temporal Patterns of Vehicle Collisions with Roe Deer and Wild Boar in the Dinaric Area

The purpose of this study was to determine the frequency of wildlife-vehicle collisions (WVC) based on the animal species, and to deepen the knowledge of temporal patterns of vehicle collisions with roe deer and wild boar. The study analyses the data from police reports on vehicle collisions with animals on state roads, by date and time, section of road, and animal species over a 5-year period (2012–2016). These data were analysed to determine the temporal dynamics of vehicle collisions with roe deer and wild boar by month, time of day, and moon phase. On the state roads in the Dinaric area, roe deer are most commonly involved in vehicle collisions (70.1% of all collisions), followed by wild boar (11.0%). Other large species involved in collisions were fallow deer (4.8%), brown bear (1.8%), red deer (0.9%), grey wolf (0.7%), and European mouflon (0.5%), respectively. Most collisions with roe deer occurred in the period April–August, with reduced frequency during autumn and winter. For wild boar, there was no association between month and frequency of collisions. At the annual level, collisions with roe deer were significantly higher during night (37%) and twilight (41%) than during the day (22%). For wild boar, most collisions occurred during twilight (26%) and night (72%), although the difference between these two periods was not statistically significant. For roe deer, collisions had no association with lunar phase, though wild boar collisions during twilight (dawn or dusk) were more common during twilight periods on days with less moonlight. Since vehicle collisions with wildlife showed certain temporal patterns, these should be taken into consideration in developing statistical models of spatial WVC patterns, and also in planning strategies and countermeasures to mitigate WVC issues

Promjena snježnih uvjeta gorskoga i pretplaninskoga vegetacijskoga pojasa Velebita

Količina snježne oborine mijenja se po pojedinim razdobljima. Povećanje temperature zraka, kao jedno od obilježja klimatskih promjena, osobito utječe i na snježne uvjete. Cilj je ovoga istraživanja bio analiza trenda broja dana sa snijegom i kretanje maksimalne visine snijega te usporedba srednjega broja dana i maksimalne visine snijega s višegodišnjim prosjekom 1981–2010. i s prijašnjim podacima opisa klime. Istraživanje je provedeno na dvjema meteorološkim postajama (Baške Oštarije i Oltari) u gorskom vegetacijskom pojasu te na meteorološkoj postaji Zavižan u pretplaninskom vegetacijskom pojasu. Analiza je trenda napravljena Mann-Kendallovim testom. T-testom je uspoređen broj dana sa snijegom i maksimalna visina snijega s višegodišnjim prosjekom (referentnim nizom) i podacima iz opisa klime vegetacijskih pojasa 1948–1960. godine. Prosječan broj dana sa snijegom (≥ 1 cm) u gorskom vegetacijskom pojasu na meteorološkoj postaji Baške Oštarije iznosio je 66, na meteorološkoj postaji Oltari iznosio je 91 dan, a u pretplaninskom vegetacijskom pojasu na meteorološkoj postaji Zavižan iznosio je 158 dana. Maksimalna visina snijega u gorskom pojasu prosječno je iznosila 60,09 cm, odnosno 78,25 cm, dok je u pretplaninskom pojasu bila 165,04 cm. Za meteorološku postaju Oltari, u gorskom vegetacijskom pojasu, statistički je značajan trend smanjivanja broja dana sa snijegom ≥ 1 cm. Na Zavižanu, u pretplaninskom vegetacijskom pojasu, ustanovljen je statistički značajan trend smanjivanja broja dana sa snijegom ≥ 1 cm, ≥ 10 cm i ≥ 30 cm visine. Na Zavižanu je recentni prosječan broj dana sa snijegom od ≥ 1 cm do ≥ 30 cm bio značajno niži u odnosu na višegodišnji prosjek 1981–2010. Prema rezultatima pojedinačnoga t-testa broj dana sa snijegom (> 1 cm) i maksimalna visina snijega (cm) značajno su manje na području obaju vegetacijskih pojasa u odnosu na razdoblje 1948–1960. godine

Mikroklimatski uvjeti u vrtači na području krša

Mikroklima je specifična klima nekoga manjega, a često ograničenoga prostora, šume, livade, nekih reljefnih oblika itd. Ona ovisi o makroklimi širega prostora, ali i o drugim stanišnim i sastojinskim čimbenicima. Cilj je istraživanja bio analizirati mikroklimu vrtače ili ponikve, krškoga fenomena. Istraživanje je obavljeno na području Cipala u Nacionalnom parku Sjeverni Velebit. Mikroklima je izmjerena na tri različite pozicije vrtače, a to su obod (rub), sredina i dno vrtače. Izmjereni su klimatski elementi temperatura zraka (°C), relativna vlažnost zraka (%), temperatura tla (°C) i volumetrijska vlaga tla (%). Najveća je amplituda temperature zraka bila na obodu vrtače. Temperatura se zraka smanjivala s dubinom vrtače, a relativna se vlaga zraka povećavala s dubinom vrtače. Za oba je klimatska elementa postojala statistički značajna razlika samo na dnu vrtače. Temperaturni gradijent u vrtači je iznosio 0,7 °C. Temperatura se tla značajno smanjivala od oboda vrtače do dna vrtače. Apsolutna minimalna vrijednost vlage tla bila je na obodu vrtače, a apsolutna maksimalna vlaga tla bila je na sredini vrtače, gdje je utvrđena i najveće kolebanje vlage tla. Volumetrijska se vlaga tla statistički značajno razlikovala na sva tri mjesta u vrtači. Mikroklima vrtače utjecala je na obrnuti raspored šumskih ekosustava s obzirom na nadmorsku visinu

Dynamics, Hydrological Relations and Pollution of Precipitation and Flood Waters in a Forest Ecosystem

Background and Purpose: Water in forest ecosystems can be present in various forms. The hydrological water cycle unfolds via fundamental hydrological processes such as evapotranspiration, precipitation, infiltration and outflow. Certain infrastructure works and recent climate changes within lowland forest areas have resulted in changes in flood water and ground water trends, and in quantities of precipitation and evapotranspiration. One of the chemical water quality indicators is the presence of metals in water. Higher metal concentrations in natural waters are undesirable since they are polluters of aquatic systems and detrimental to living organisms. Particularly dangerous are cadmium and lead. The objective of this paper was to analyse watercourse levels, ground water depths, and relations between precipitation waters, flood waters, ground waters, relative air humidity and evapotranspiration. An additional objective was to analyse the pollution of precipitation and flood waters in lowland forest ecosystems. Materials and Methods: The study was conducted in the Posavina region in Croatia. Precipitation data from Nova Gradiška meteorological station, watercourse levels of the Sava River and ground water depth data from piezometer stations were used in the analysis of the hydrological relations. For water quality analysis, precipitation was collected at six sample sites during the spring of 2015 and 2016. Flood water and precipitation were collected in three repetitions during the spring of 2015 and 2016. Results: Trends of the Sava River water levels and ground water levels dropped significantly. The precipitation volume trend in the study area was positive, but not statistically significant, while evapotranspiration amounts increased significantly. Conclusions: A significant correlation has been found between particular water forms in the hydrological cycle, i.e. between precipitation waters, flood waters and ground waters, and between relative air humidity and evapotranspiration. No pollution of precipitation waters and flood waters with metals was found