Kristijan Tomljanović

Forests are among the most biodiverse terrestrial ecosystems, in which small mammals play an important ecological role. Their presence is influenced by various habitat parameters, including vegetation structure, microclimate, food resources, and human-driven forest management practices. The aim of our study was to assess rodent diversity across different forests, with a particular focus on forest stand age and forest plant communities. For this purpose, we analyzed 17 years of forest rodent monitoring data across five forest plant communities. This study represents the first long-term monitoring results of small mammals in managed forests of continental Croatia. Trapping was conducted as part of routine rodent monitoring in state-owned forests, incorporating data collected from various research projects. The results showed that lowland forests, particularly floodplain oak forests, exhibited higher biodiversity compared to other forest plant communities. In addition, younger stands exhibited higher species richness than older stands. Canonical correspondence analysis (CCA) indicated that Microtus species were associated with lowland forests and younger stands. Overall, the findings demonstrate that both forest plant communities and stand age play important roles in shaping rodent diversity in continental Croatian forests. The obtained data provide a basis for optimizing forest management practices in continental forests.

Forests in Croatia are characterized by higher levels of biodiversity in species composition. Three significant events occurred in Croatian forests over the past ten years, all of which have a common denominator—sanitary felling. The challenge in the sustainable development of forests started with the ice storm of 2014 that amounted to damage and raised costs in forest stands to EUR 231,180,921. The second challenge was in 2017 when the bark beetle outbreak occurred in the Gorski Kotar region. In December 2017, a windstorm in the same area caused damage to approximately 500,000 m³ of wood stock. The third climate extreme was in the summer of 2023 when three storms with strong winds and heavy rain damaged even-aged forests of common beech and pedunculated oak. The damage was substantial: 3,954,181 m³ of timber was mostly broken and destroyed across 21,888.61 ha of area, and the most damage was in the pedunculate oak forests of Slavonia, i.e., Quercus robur subsp. Slavonica, at 1,939,175 m³. For the main meteorological stations in lowland Croatia, data on precipitation amounts (mm) and wind speeds (m/s) were collected for the period 1981–2023, and the results of our analysis for the last decade are presented. Meteorological drought was analyzed using the rain anomaly index RAI. Data regarding open space fires in the Mediterranean karst area of Croatia were collected from the Croatian Firefighting Association, and the calculation of the burned area index (BAI) was determined. Throughout the entire area of Gorski Kotar County, a sample of permanent plots was set and used to assess the extent of forest damage from the ice storm in 2014 and for the establishment of permanent monitoring of the recovery of trees and forests damaged by the ice storm. The monitoring of bark beetles in the Gorski Kotar region started in 1995 and is still in progress. The aftermath of bark beetle outbreaks in two uneven-aged silver fir stands was studied after a bark beetle outbreak and a sanitary felling of 4655.34 m³. In the area of lowland Croatia, a statistically significant and positive correlation was found between sanitary fellings, maximum wind speeds, and rain anomaly indices in even-aged forests. In conclusion, sustainable development will be at risk due to difficult recovery, rising costs, and overall climate change in the years to come.

Tick-borne encephalitis (TBE) is a common arbovirus infection in Croatia. The aim of the study was to analyse 17 years of data on TBE seroprevalence and acute TBE cases in correlation with winter temperature, precipitation and wildlife abundance to identify possible patterns that may be predictive indicators of TBE incidence. Clinical diagnosis of TBE was confirmed by determining IgM and IgG anti-TBE antibodies. Of the 19,094 analysed patients, 4.2% had acute TBE, significantly more often in older age (p < 0.001) and male gender (p < 0.001). Overall seroprevalence of TBE among the tested population was 5.8% and varied annually from 2.8% to 10.7%. The mean acute TBE incidence rate was 1.1/100,000 population with significant regional differences: 1.7/100,000 in the continental vs. 0.2/100,000 and 0.5/100,000 in the Mediterranean and Alpine regions, respectively. A particularly high incidence of 3.1/100,000 was recorded in northern Croatia. TBE displayed a seasonal pattern, peaking in June and July. Moderate negative correlations were observed between TBE acute cases and winter temperatures from December to February (r = −0.461; p = 0.062), relative rodent abundance (r = −0.414; p = 0.098) and yearly precipitation from one year before (r = −0.401; p = 0.123). The analysis showed that more acute TBE cases are recorded after a warmer winter and a negative correlation between the abundance of forest Apodemus sp. and the number of TBE cases in the same year.

Sitni glodavci (Rodentia, Murinae: pravi miševi, Arvicolinae: voluharice) uvelike pridonose održavanju ravnoteže i raznolikosti šumskih zajednica. Jednako tako oni mogu biti uzročnici otežane prirodne obnove šuma, ali i rezervoari te prijenosnici brojnih uzročnika zoonoza, bolesti prijetećih za zdravlje ljudi te domaćih i divljih životinja. Iako od početka 1980-ih godina dominantna metoda kontrole brojnosti glodavaca u državnim šumama uključuje primjenu rodenticida, sve se veća pažnja pridaje sustavnomu monitoringu glodavaca, prevenciji šteta i primjeni bioloških metoda zaštite. U ovom je istraživanju testiran učinak primjene tzv. T-stajališta (N = 4 kom.) na primamu pernatih predatora sitnih glodavaca te na smanjenje šteta od glodavaca na pomladnoj površini sastojine poljskoga jasena (Fraxinus angustifolia Vahl.) u Šumariji Kutina, u razdoblju od listopada 2023. do rujna 2024. godine. Pregledom 213 videosnimki te 17 881 fotografije zabilježeno je ukupno 126 slijetanja šest vrsta ptica, od kojih je 114 (91,47 %) doleta bilo vezano uz tri ptičje vrste (šumska sova /Strix aluco/, škanjac mišar /Buteo buteo/ i rusi svračak /Lanius collurio/), koje se više-manje prehranjuju sitnim glodavcima. Da je primjena T-stajališta pomogla smanjenju šteta od glodavaca, razvidno je iz usporedbe broja sadnica poljskoga jasena čiju su koru nagrizli glodavci, što je u najvećem omjeru (30,23 %) zabilježeno na kontrolnoj plohi, bez sletnoga mjesta, dok je manji udio (13,95 % i 6,98 %) zabilježen na dvjema plohama na koje su te ptičje vrste dolijetale. Iako ne statistički značajna, umjereno jaka negativna korelacija (r(3) = –0,57, p < 0,05) utvrđena je između broja doleta šumske sove te broja nagrizenih jasenovih sadnica. Dobiveni rezultati govore u prilog pozitivnomu učinku ove biološke kontrole glodavaca, koja, osim što je ekonomična, može pridonijeti uspjehu pomlađivanja šuma uz minimalan utjecaj na okoliš. Preporučuje se daljnje testiranje primjenjivosti T-stajališta i u drugim tipovima šumskih zajednica.

Tick-borne encephalitis (TBE) is the most significant arboviral infection in Croatia. The aim of the study was to analyse and correlate 17-year TBE seroprevalence data with winter temperature, precipitation and wildlife abundance to identify possible patterns that can be predictive of TBE incidence. TBE diagnosis was based on IgM/IgG anti-TBE antibodies and individual clinical interpretation of the results. Of the 19,094 analysed patients, 4.2% had acute TBE, significantly more often in older age (p<0.001) and in men (p<0.001). Overall seroprevalence of TBE among the tested population was 5.8%, and varied annually from 2.8% to 10.7%. The mean acute TBE incidence rate was 1.1 per 100.000 population with significant regional differences: 1.7 in the continental vs. 0.2 and 0.5 in the Mediterranean and Alpine regions, respectively. Particularly high incidence of 3.1 was recorded in northern Croatia. TBE displayed a seasonal pattern, peaking in June and July. Moderate negative correlations were observed between TBE acute cases and winter temperatures from December to February (r=-0.461; p=0.062), relative rodent abundance (r=-0.414; p=0.098) and yearly precipitation from one year before (r=-0.401; p=0.123). Considerable efforts are needed to understand the impact on TBE incidence to improve disease prevention.

The objective of this study was to assess the chemical characteristics of cold-pressed beech nut oil. The nuts, gathered from the forest, comprised 25.35% water, 13.19% oil, and 19.40% protein. The predominant fatty acid was linoleic acid (40.5%), followed by oleic acid (35.0%) and gondoic acid (7.7%). All four tocopherols were present in the oil, with γ-tocopherol being the dominant form at 99.38 mg per 100 g of oil. The total sterol content was 2708.73 mg per kg of oil, with β-sitosterol constituting 80.5% of all sterols. The main characteristics of the oil included its relatively high tocopherol and gondoic acid content, a dominant oleic–linoleic fatty acid profile, and elevated levels of carotenoids.

Narrow-leaved ash (Fraxinus angustifolia Vahl), a highly valued European forest tree species, has been severely affected by a large-scale decline, which is most probably driven by a complex of multiple interacting factors including fungi, which contribute to and accelerate this process. Red deer (Cervus elaphus L.) can be considered as one of the contributing factors, as they inflict damage on the stems of young trees by stripping the bark. These wounds not only represent suitable entry points for fungi which can cause tissue necroses and decomposition, they can lead to changes in the wood structure as well. The aims of this research were to analyze chosen parameters of bark stripping wounds in narrow-leaved ash stands, identify fungi present in the tissue exposed by wounding, and inspect the effect of wounding on the wood structure. Bark stripping was observed on ash trees from 2 cm up to 18 cm of DBH and between 0.1 m and 1.9 m of stem height. The most susceptible trees were those with an average DBH of 5 ± 2.5 cm. On most of the ash trees (51%), one-third to two-thirds of the circumference was damaged. In wounded tissue, 174 fungal isolates were found, most of which belonged to known endophytic fungi from the genera Trichoderma, Fusarium, and Clonostachys. It was observed that earlywood cells in the wounding zone had narrower lumens compared to ones in adjacent healthy zone with regard to different trees and stem heights.

This study compared oak butt-log volume estimations gained through terrestrial measurements in the forest stand with a remote approach using an unmanned aerial system (UAS) and photogrammetric post-processing. Terrestrial measurements were conducted in the lowland part of Croatia after a completed motor–manual final felling of a 140-year-old even-aged oak stand. Butt-logs’ volumes were estimated with four methods: the sectioning method and Huber’s, Smailan’s and Riecke–Newton’s methods. Measuring diameters and lengths and estimating volumes remotely were based on orthophotos using four different software: ArcGIS, QGIS, AutoCAD and Pix4D. Riecke–Newton’s method for volume estimation had the smallest relative bias of +1.74%, while for Huber’s method it was −8.07% and with Smailan’s method it was +21.23%. Log volume estimations gained remotely via ArcGIS and QGIS were, in the case of Huber’s method, at +3.63% relative bias, and in the case of Riecke–Newton’s method at +1.39% relative bias. Volume estimation using the sectioning method resulted in a total of 51.334 m³ for the whole sample, while the sectioning method performed with the help of AutoCAD resulted in 55.151 m³, i.e., +7.43% relative bias. Volume estimation of thirty oak butt-logs given by Pix4D software (version 4.8.4) resulted in +9.34% relative bias (56.134 m³). Comparing terrestrial measurements and the volume estimations based on them to those gained remotely showed a very high correlation in all cases. This study showed that using a UAS for log volume estimation surveys has the potential for broader use, especially after final felling in even-aged forests where the remaining trees in the stand would not block photogrammetric analysis.

Upotreba fotozamki posljednjih petnaestak godina uobičajena je praksa brojnih studija vezanih uz istraživanje divljih životinja. Kamere se razlikuju veličinom, načinom napajanja i pohrane/slanja podataka, konstrukcijom, performansama i na koncu namjenom. U ovom su istraživanju uspoređena dva načina rada fotozamki u monitoringu divljih životinja (krupnih sisavaca) u Nacionalnom parku Plitvička jezera. Prvi je način rada ciklično snimanje svakih 30 min. Drugi je način rada snimanje po aktivaciji senzora pokreta. U šest mjeseci ukupno je snimljena 36 621 fotografija, od čega je 28 618 fotografija snimljeno cikličnim snimanjem, a 8003 snimljene su na temelju aktivacije senzora pokreta. Od cikličnih snimaka samo je 1 % fotografija iskoristivo (životinja koja je predmet istraživanja), dok je kod drugoga oblika snimanja 30 % fotografija bilo iskoristivo. Rezultati pokazuju značajne razlike između dvaju načina programiranja rada kamera u korist programiranja kamere da radi samo po aktivaciji senzora pokreta.