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Mrtvo drvo sudjeluje s oko 8% u ukupnim šumskim zalihama ugljika na globalnoj razini te čini jedno od pet pohraništa ugljika u šumskom ekosustavu za koje se u Nacionalnom izvješću o inventaru stakleničkih plinova obračunavaju zalihe i promjene zaliha ugljika. Za izračun zalihe ugljika u mrtvom drvetu potrebni su faktori konverzije volumena mrtvog drveta po stupnjevima raspadanja: gustoća mrtvog drveta i sadržaj ugljika. Cilj ovog istraživanja je pružiti lokalne vrijednosti za navedene faktore, a u svrhu unaprjeđenja procjene zaliha i promjena zaliha ugljika u mrtvom drvetu na nacionalnoj razini. Postavljena je hipoteza da se faktori konverzije volumena mrtvog drveta razlikuju za iste grupe vrsta drveća između različitih biogeografskih regija. Istraživanje je provedeno na deset vrsta šumskog drveća u tri biogeografske regije Republike Hrvatske: kontinentalnoj, alpinskoj i mediteranskoj. Uzorkovani su koluti ležećeg mrtvog drva po stupnjevima raspadanja od 0 do 4, gdje 0 predstavlja uzorak svježe posječenog stabla, a 4 jako raspadnuto drvo. Svim uzorcima analizirana je gustoća mrtvog drveta i sadržaj ugljika. Gustoća mrtvog drveta imala je očekivano opadajući trend s povećanjem stupnja raspadanja drveta dok za koncentraciju ugljika nije zabilježen trend u odnosu na stupanj raspadanja drveta. Kod prstenasto poroznih vrsta drveća uočena je statistički značajna razlika u gustoći između uzoraka iz mediteranske i kontinentalne regije u stupnjevima raspadanja drveta od 0 do 2, dok je kod četinjača uočen suprotan trend, odnosno, statistički značajna razlika između alpinske i mediteranske regije u stupnjevima raspadanja drveta od 2 do 4. Time je potvrđena hipoteza da se između istih grupa vrsta drveća faktori konverzije volumena mrtvog drveta razlikuju između različitih biogeografskih regija. Korištenjem utvrđenih faktora konverzije volumena mrtvog drveta procjene nacionalnih zaliha ugljika u mrtvom drvetu smanjene su za 29.0 do 43.7% što potvrđuje važnost lokalnih faktora konverzije

Dead wood (DW) is an important component of forest ecosystem and in the context of climate change and carbon (C) accounting policy under UNFCCC and EU regulations it is recognized as a long-term C pool. The aim of our study was to provide national DW volume conversion factors, i.e. dead wood densities (DWD) and C concentrations (CC) by decay classes, which could be used for accounting of C stocks and C stock changes in DW pool in the National GHG Inventory Report (NIR). We hypothesized that investigated traits for specific tree species group (ring-porous, diffuse-porous, non-porous) will differ with respect to different biogeographical region (BGR). Research was conducted on ten tree species from three BGRs, Continental, Alpine and Mediterranean. Stem discs were sampled from downed DW and categorized into five decay classes, from 0 (raw wood) to 4 (very decayed DW). In total, we collected 446 DW samples evenly distributed between tree species and decay classes. Samples were analysed for DW density (DWD) and C concentrations (CC). DWDs showed decreasing trend with respect to decay class, while for CC no trend regarding decay classes was observed. For each tree species group, DWDs by decay classes were compared between different BGR. In ring-porous group, a significant difference was observed in DWD between samples collected in Mediterranean and Continental BGR for decay classes 0-2, while in non-porous group DWDs significantly differ between samples collected in Alpine and Mediterranean BGR for decay classes 2-4. By using obtained volume conversion factors from this study, we provided new estimate of downed DW C stocks in Croatia. Also, we performed a comprehensive literature search on DWDs by decay classes for genera investigated in our study and observed differences in DWDs reduction patterns.

Šumski ekosustavi imaju važnu ulogu u ublažavanju klimatskih promjena uklanjajući značajnu količinu atmosferskog ugljika (C) vežući ga u tlo i svoju drvnu i lisnu biomasu. U šumskom ekosustavu postoji pet glavnih pohraništa C: nadzemna i podzemna živa biomasa, mrtvo drvo (MD), šumska prostirka i organski ugljik u tlu (engl. Soil Organic Carbon, SOC). MD i šumska prostirka imaju važnu ulogu u kruženju hraniva i očuvanju bioraznolikosti, dok SOC predstavlja najveće pohranište C u šumskom ekosustavu. Cilj ovog istraživanja je pridonijeti unaprjeđenju procjene zaliha i promjena zaliha C za navedena pohraništa. Za unaprjeđenje procjena zaliha C u MD postavljen je terenski pokus za glavne vrste drveća na četiri lokacije raspoređene u tri biogeografske regije Hrvatske, dok će se za unaprjeđenje procjene zaliha C u šumskoj prostirci objediniti i analizirati dostupni nacionalni podaci. Nadalje, istražit će se primjenjivost procesnog modela Biome-BGCMuSo za procjenu zaliha i promjena zaliha SOC-a. U tu svrhu provedeno je treće uzorkovanje mineralnog dijela tla u pokusu kronosekvence hrasta lužnjaka koje će zajedno sa prethodne dvije izmjere poslužiti za validaciju modeliranih promjena zaliha SOC-a. Istraživanjem će se dobiti nacionalni faktori konverzije volumena MD po stupnjevima raspadanja, sveobuhvatnija i reprezentativnija nacionalna baza podataka o zalihama C u šumskoj prostirci i prva procjena promjena zaliha C u tlu šuma hrasta lužnjaka u Hrvatskoj. Dobiveni rezultati mogu poslužiti pri izradi Nacionalnog izvješća o inventaru stakleničkih plinova.

Resource allocation to different plant tissues is likely to be affected by high investment into fruit production during mast years. However, there is a large knowledge gap concerning species-specific differences in resource dynamics. We investigated the influence of mast years on stem growth, leaf production, and leaf carbon (C), nitrogen (N), and phosphorus (P) concentrations and contents in Fagus sylvatica, Quercus petraea, and Q. robur at continental and climate region scales using long-term data from the International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) and similar datasets. We discussed the results in the light of opposing resource dynamics hypotheses: (i) resource accumulation before mast years and exhaustion after mast years (resource storage hypothesis), (ii) shifting resources from vegetative to generative compartments (resource switching hypothesis), and (iii) investing resources concurrently in both vegetative and generative compartments (resource matching hypothesis). Linear mixed-effects modelling (LMM) showed that both stem growth and leaf production were negatively influenced by weather conditions which simultaneously lead to high fruit production. Thus, the impact of generative on vegetative growth is intermixed with effects of environmental factors. Superposed epoch analyses and LMM showed that for mast behaviour in F. sylvatica, there are indicators supporting the resource storage and the resource switching hypotheses. Before mast years, resources were accumulated, while during mast years resources switched from vegetative to generative tissues with reduced stem and leaf growth. For the Quercus species, stem growth was reduced after mast years, which supports the resource storage hypothesis. LMM showed that leaf C concentrations did not change with increasing fruit production in neither species. Leaf N and P concentrations increased in F. sylvatica, but not in Quercus species. Leaf N and P contents decreased with increasing fruit production in all species, as did leaf C content in F. sylvatica. Overall, our findings suggest different resource dynamics strategies in F. sylvatica and Quercus species, which might lead to differences in their adaptive capacity to a changing climate. Nasl. z nasl. zaslona. Opis vira z dne 15. 7. 2021. Skupno št. avtorjev: 25. Avtor iz Slov.: Tom Levanič. Bibliografija: str. 14-17.

Mrtvo drvo (eng. Dead Wood, DW) važan je segment šumske biomase i na području Europe obuhvaća oko 13% ukupne biomase (FRA 2020). Osim što doprinosi produktivnosti i bioraznolikosti ekosustava (Harmon et al. 1986, Norden et al. 2004), jedan je od pet pohraništa ugljika (eng. Carbon, C) šumskog ekosustava, obračunatog u Nacionalnom izvješću o inventaru stakleničkih plinova (eng. National Inventory Report, NIR) (IPCC 2006). Za izvješćivanje o DW biomasi i C, nužni su faktori konverzije biomase, tj. gustoća DW (eng. Dead Wood Density, DWD) i koncentracija C (eng. C Concentration, CC) po stupnjevima raspadanja drva (Slika 1). Svrha ovog istraživanja je dati nacionalne vrijednosti za navedene faktore kako bi se u NIR-u omogućio prijelaz na više razine proračuna (Di Cosmo 2013), budući da su parametri svojstveni za pojedinu državu poželjni (UNFCCC 2021). Istraživanje je provedeno na deset vrsta šumskog drveća koje predstavljaju glavne šumske ekosustave u Republici Hrvatskoj (RH). Analizirano je 454 uzorka. Volumen uzoraka procijenjen je metodom istisnute vode, zatim su uzorci osušeni u sušioniku, vagani te im se utvrdio sadržaj ugljika elementarnim analizatorom Leco CNS 2000. Preliminarni rezultati pokazuju očekivano smanjenje DWD porastom stupnja raspadanja, dok za CC nije uočen trend s obzirom na iste. Uzevši u obzir da RH u svom NIR-u koristi faktore konverzije biomase neovisno o stupnjevima raspadanja, primjena DWD dobivenih u ovoj studiji mogla bi unaprijediti procjene DW u RH.

Magnetic susceptibility (MS) of soils and paleosols indicates the formation of secondary ferrimagnetic minerals (SFM) and pedogenic processes. MS measurements can relatively fast and non-destructively characterize the concentration, mineralogy, and grain size of magnetic minerals present in samples (HATFIELD, 2014 ; PETERS & DEKKERS, 2003). The soil characteristics are influenced by variations in iron mineral forms, and it can give clue to the processes of pedogenesis (DEARING, 1996). Topsoil has been identified as an environment in which ferrimagnetic materials are actively produced. Secondary magnetic minerals (magnetite/maghemite) are mostly ultrafine grained and contain a significant superparamagnetic (SP) component (

In the last 10 years, photogrammetric methods have gained a lot of attention in the forest inventory research and applications. This is caused by several factors. The first factor is advancement in the Computer Vision (CV) algorithms that neglected the usually complex and time-consuming photogrammetric workflow. The second factor is an advancement in sensor technology that consequently made the UAVs (photogrammetric platforms) more affordable. Due to the flexibility of use, price and accuracy of the products, UAV based photogrammetry has recently attracted great attention in many environmental applications, including forest inventory. Algorithms that brought photogrammetry to applicable level in forest inventory are Dense Image Matching (DIM) algorithms. They are allowing the user to produce a high- density point cloud (match each pixel) that represents the forest canopy and that can be used for further production of the Digital Surface Model (DSM) and the forest parameter estimation in combination with precise Digital Terrain Model (DTM). However, this is the most time-consuming process in the photogrammetric workflow, therefore automatically downsampled images are usually used in this process. This study aims to test point clouds of the different densities (produced with the different pyramid level of input images). Up to four pyramid levels of the images were used to produce point clouds by utilizing the algorithm implemented in the Agisoft PhotoScan software. The first test was conducted with the full resolution images (Level 0), the second with 1/2 (Level 1), the third with 1/4 (Level 2), the fourth with 1/8 (Level 3), and the last test was conducted with the 1/16 of the image resolution (Level 4). The study was conducted in the lowland pedunculate oak (Quercus robur L.) forests of Pokupsko Basin (Central Croatia). Point clouds were generated for the 54 circular plots with the radius ranging from 8 to 20 m. The UAV imaging was done using Trimble UX5 HP with Sony Alpha ILCE-R7 on 30 and 31 May 2017. Finally, 1441 images with the Ground Sample Distance (GSD) of approximately 8 cm were acquired. A high end- lap of 90% and side-lap of 80% were defined by the flight plan. UAV-based point clouds of different densities were tested on the tree- and plot-level using field reference data. Namely, for both tree- and plot-level, tree heights obtained from point clouds were compared with field-measured tree heights. Additionally, UAV-based point clouds were compared with the available Light Detection and Ranging (LIDAR) point cloud at the selected vertical profile of the 430 m length throughout the forest stand. The results of the conducted tests suggest that for the metric information extraction, the highest pyramid level and the most time-consuming process is not justified to use since benefits of such process are insignificant.

Magnetic susceptibility (MS) of soils and paleosols indicates the formation of secondary ferrimagnetic minerals (SFM) and pedogenic processeses. Comprehensive analysis of surface (0-10 cm depth) and sub-surface soils (20-30 cm depths) from over 750 locations in Croatia have been performed through measurements of low field mass specific MS (Xlf) and mass specific and percentage of frequency-dependent MS (Xfd) to determine spatial distribution of MS that can be used for provenance studies of soil, erosional processes as well as evaluation of soil pollution by heavy metals. It is also needed for the landmine-affected regions because it of the effects of soil magnetic susceptibility on metal detectors. Maps of soil MS in Croatia show two clearly differentiated distributions – Pannonian region versus karst area of Croatia. Differences are linked to geological sub-division of Croatia and its associated main soil types: the Mesozoic carbonate rocks of the Dinaric-Coastal karstic region with dominant red soils and kalkocambisols versus Pannonian region with dominant cambic, eluvial illuvial and gleyic soils mostly developed on clastic Neogene and Quaternary sediments. Soils developed on carbonate rocks have higher values of MS and Xfd compared to soils of Pannonian region. Magnetic properties of soils in karstic area are dominated by the presence of nanoscale superparamagnetic (SP) SFM grains produced in situ. Soil-derived magnetite gives major contribution to the magnetic enhancement in red soils. Primary ferrimagnetic minerals derived from geological sources dominate magnetic properties in only a minority of localities (mountainous areas composed of magmatic and metamorphic rocks). This is the first attempt to produce a soil magnetic susceptibility map Croatia that covers all dominant soil types in Croatia.

Soil survey and monitoring are becoming increasingly important in fulfilling reporting obligations to the United Nations Framework Convention on Climate Change (UNFCCC). Carbon stocks and stock change, status and trends of SOC, total N and C:N ratio, have to be reported annually in relation to GHG emissions. Land use and land management practices on national level, and not only for agricultural land, are also the key issues that need to be taken into account in SOC measurements and soil parameters analyses. In order to fulfill national reporting obligations and improve environmental monitoring data, in 2014, Croatian Agency for the Environment and Nature initiated the project “Change of soil organic carbon stocks and the calculation of total N and SOC trends, and C:N ratio”. Soil was sampled at 725 locations of representative land uses and depths from 0 to 30 cm. Soil sampling, physical and chemical laboratory analyses and data analyses are conducted in accordance to 2006 IPCC Guidelines for National Greenhouse Gas Inventories. All project results are included in GIS database containing spatial data, physical and chemical soil properties and analyzed data. Project results can be viewed or downloaded at ENVI Environment Atlas.

Potrajno gospodarenje šumama zahtijeva prostorno i vremenski određene informacije o stanju šume koje se još uvijek u mnogim zemljama svijeta, uključujući i Hrvatsku, prikupljaju na tradicionalan način, terenskom izmjerom. Iako terenska izmjera pruža informacije zadovoljavajuće točnosti, ona zahtijeva dugotrajan i intenzivan rad. Stoga se u novije vrijeme intenzivno istražuju mogućnosti upotrebe laserskih skenera i fotogrametrijskih metoda kao brza i efektivna alternativa klasičnom pristupu izmjere šuma. U ovom je radu prikazan algoritam za ekstrakciju opsega i modeliranje debla iz fotogrametrijskog oblaka točaka baziran na RANSAC (engl. Random Sample Consensus) algoritmu i metodi rastavljanja na glavne komponente (engl. PCA – Principal Component Analysis). Analizirana je točnost ekstrakcije opsegā na jednom deblu u ovisnosti o tipu kalibracije kamere (predkalibrirana, samokalibracija s inicijalnim parametrima, samokalibracija). Najmanja pogreška dobivena je predkalibriranom kamerom (RMSE=1,23 cm), slijede samokalibracija s inicijalnim parametrima (RMSE=1,35 cm) i samokalibracija (RMSE=1,63 cm). Predstavljeni algoritam pokazuje veliki potencijal primjene fotogrametrijskih mjerenja pri određivanju opsega debla, uz određene preinake u pristupu., Diameter at the breast height is one of the most important parameters used in the forestry. In practice, field measurement of the test plots is an intensive and time-consuming process that requires specialized equipment. Recently, the application of terrestrial laser scanner and photogrammetry in forestry, are being investigated as a fast and effective approach to forest plot measurement. In this paper, we present the algorithm for modelling and tree stem perimeter extraction based on the RANSAC (RANdom Sample Consensus) algorithm and PCA (Principle Component Analysis). The accuracy of the tree perimeters extraction is tested on the three tree models differing on the reconstruction type (self-calibration, self-calibration with initial parameters and self-calibration without initial parameters). The smallest error is acquired by estimating perimeters on the model reconstructed with the precalibrated camera (RMSE=1.23 cm), self-calibration with initial parameters (RMSE=1.35 cm) and self-calibration (RMSE=1.63 cm) follow. The presented algorithm indicates the great potential of photogrammetric methods application in tree perimeter estimation, with some changes in the approach.

Potrajno gospodarenje šumama zahtjeva prostorno određene informacije o stanju i razvoju šume koje se uglavnom prikupljaju u okviru inventure šuma, i to tradicionalno, terenskom izmjerom koja pruža točne informacije, ali zahtijeva dugotrajan i intenzivan rad. Upravo iz tog razloga prepoznat je potencijal upotrebe metoda daljinskog istraživanja pri izmjeri šuma. NaHrvatskom šumarskom institutu se od 2008. g. kontinuirano provode istraživanja o mogućnostima primjene digitalneaerofotogrametrije u izmjeri šuma, koja su posebice intenzivirana u okviruprojekata Hrvatske zaklade za znanost (EFFECtivitiy i 3D-FORINVENT). U ovom radu prikazan je i evaluiran brz i jednostavan način procjene volumena sastojina hrasta lužnjaka (Quercus robur L.) Pokupskog bazena na temelju dostupnih fotogrametrijskih materijala (aerosnimke, digitalni podaci terena) i postojećih modela procjene volumena. Fotogrametrijskim procesiranjem aerosnimaka prostorne rezolucije ≈30 cm snimljenih tijekom redovnog topografskog snimanja Republike Hrvatske (ljeto 2015.g.) izrađen je rasterski digitalni model površine krošanja (DMP) veličine piksela 5×5 m. Na temelju digitalnih podataka terena (prijelomnice, linije oblika, markantne točke terena, pravokutne mreže visinskih točaka) izrađena je mreža nepravilnih trokuta koja je potom linearnom interpolacijom pretvorena u rasterski digitalni model reljefa (DMR) veličine piksela 5×5 m. ‘Oduzimanjem’ DMR-a od DMP-a izrađen je digitalni model visine sastojina (DMV) veličine piksela 5×5 m. Na temelju podataka dobivenih iz DMV-a (maksimalna visina, 25. i 90. percentili visine, odnos površine krošanja na 30 m visine i površine odsjeka), podatka o starosti sastojine iz Osnove gospodarenja i parametara postojećeg modela za procjenu volumena lužnjakovih sastojina (Spačvanske šume), procijenjen je volumen za ukupno 89 lužnjakovih sastojina na području g.j. Jastrebarski lugovi. U odnosu na podatke Osnove gospodarenja, volumen sastojina procijenjen je fotogrametrijskom metodom s korijenom srednje kvadratne pogreške (RMSE) od 82, 42 m3 (26, 16%), srednjom pogreškom (SE) od 29, 65 m3 (9, 41%) i koeficijentom determinacije (R 2) od 0, 57. U usporedbi s prijašnjim istraživanjima provedenima na području šuma Spačvanskog bazena, dobiveni su rezultati slabije točnosti, što je i razumljivo zbog činjenice da je i na području šuma Pokupskog bazena korišten model (jednadžba procjene volumena) izrađen za područje šuma Spačvanskog bazena. Korištenjem modela izrađenog za Spačvanske šume, dolazi do značajnog precjenjivanja volumena sastojina Pokupskog bazena (9, 41%), što proizlazi iz različite kvalitete lužnjakovih šuma u Spačvanskom i Pokupskom bazenu. Naime, šume Spačvanskog bazena uglavnom pripadaju I bonitetnom razredu, dok šume Pokupskog Bazena pretežno pripadaju II bonitetnom razredu. Dobiveni rezultati ukazuju na potencijal fotogrametrijskih metoda u izmjeri šuma, ali isto tako ukazuju i na potrebu izrade lokalnih modela procijene strukturnih elemenata sastojina.

Digital aerial photogrammetry by using an Unmanned Aerial Vehicle (UAV) has recently attracted great attention in forest inventory research. By photogrammetric processing of UAV images, dense point clouds and digital surface models (DSMs) can be derived. To obtain data that can be useful for forest inventory, i.e. normalized point cloud (height above ground) or rasterized canopy height model (CHM), a highly accurate digital terrain model (DTM) is required. In combination with field reference data and using established prediction models, the normalized point clouds and CHMs could serve to estimate various forest inventory attributes. Although, a number of recent studies emphasize the great potential of UAV- images for tree and forest attributes estimation, further research is required to prove its practical applicability over different forest types. Moreover, the UAV technology (hardware and software) rapidly progresses and constant validations of results are needed. This study aims to investigate the capability of UAV-based CHMs generated at different spatial resolutions (10 cm, 30 cm, 50 cm) for use in forest inventory, with a special focus on estimation of plot-level mean tree height and mean diameter at breast height (dbh) of even-aged pedunculate oak (Quercus robur L.) forests. Tree height and dbh are two of the more fundamental measurements in forest inventories and provide the basis for many other computations The study was conducted in the lowland forest complex of Pokupsko Basin located 35 km southwest of Zagreb, Central Croatia. Field measurements of tree structural parameters were collected from the systematic sample of 165 circular plots with radii of 8, 15 or 20 m, which depended on the stand age. Dbh was measured for all trees with dbh≥10 cm. Tree height was measured for at least 50% of trees per plot, while heights of other trees in the plots were estimated using the constructed height curves (height-dbh models). The mean dbh and mean height for each plot were calculated. The positioning (x, y, z) coordinates of the sample plot centres were recorded using the GNSS receiver Stonex S9IIIN connected with the Croatian Positioning System (CROPOS). The UAV images were acquired using the Trimble UX5 HP with Sony Alpha ILCE-R7 on 30 and 31 May 2017. The study area (≈1500 ha) was covered by 1441 images with the ground sampling distance (GSD) of ≈8 cm. The images were collected in 4 flights with endlap of 90% and sidelap of 80%. DSMs of different spatial resolution (10 cm, 30 cm, 50 cm) were generated using the Dense DSM (Semi- Global Matching) algorithm of PHOTOMOD UAV 6.3 software. Finally, raster CHMs images with spatial resolution of 10 cm, 30 cm and 50 cm were then generated by subtracting LiDAR DTM from corresponding DSMs. For each plot, various height (mean, standard deviation, max, min, mod, percentiles) and density metrics (ratio between area of canopy above certain height threshold and plot area) were extracted and calculated from each CHM. These metrics were then further considered in the statistical modelling (i.e., for development of plot-level models of mean height and mean dbh) as potential independent variables. The findings suggest the clear potential of UAV-based photogrammetry when used for plot-level forest inventory, with reasonable accuracy for all tested spatial resolutions. Acknowledgment: This research has been supported by the Croatian Science Foundation under the projects IP-2016-06-7686 “Retrieval of Information from Different Optical 3D Remote Sensing Sources for Use in Forest Inventory (3D-FORINVENT)” and IP- 2016-06-5621 “Geospatial Monitoring of Green Infrastructure by Means of Terrestrial, Airborne and Satellite Imagery (GEMINI)”. The authors wish to thank Hrvatske vode, Zagreb, Croatia, for providing LiDAR DTM data.

Predmet ovog izvještaja su rezultati određivanja ukupnog dušika i organskog ugljika, opis postupaka i metoda koje su primijenjene u sklopu izrade izvješća Agencije za zaštitu okoliša (AZO) sukladno potrebama izvješćivanja prema Intergovernmental Panel on Climate Change (IPCC) i UNFCCC za kalkulaciju zaliha organskog ugljika u tlima Republike Hrvatske . Obrada podataka i izračuni za potrebe izvješćivanja prema UNFCC Konvenciji i Protokolu iz Kyota (sektori LULUCF i Agriculture), sukladno IPCC metodologiji i smjernicama za unapređenje izvješćivanja obuhvaćaju sljedeće: • Izračun organskog ugljika u tlu, rekalkulacija zaliha ugljika u tlu (C stock change) načinjenih 2012. godine sa novim podacima za ugljik i fizikalnim parametrima • Izračun organskog ugljika u organskom sloju za šumska tla (FL) • Izračun ukupnog dušika i odnosa ugljika i dušika (C:N ratio) • Definiranje i smanjenje najčešćih izvora nesigurnosti pri procjeni zaliha organskog ugljika u tlu kao što su nesigurnost kod procjene gustoće tla i kamenitosti, odnosno skeleta u tlu. Izrada i valorizacija regionalnih pedotransfernih funkcija koje bi omogućile bolju procjenu i kontrolu gustoće tla i skeleta iz ostalih dostupnih podataka. • Procjena nesigurnosti svih podataka • Opis i obrazloženje korištenih metoda izračuna podataka

When we talk about risks for Mediterranean forests we put forest fires on first place and on second storm winds. On European level damages caused by forest fires make 16% and storm winds 51% of all forest damages (assessment for period 2005-2010) but for Mediterranean part the ratio of damages caused by forest fires is much more higher than one caused by storm winds. This is also the case for Mediterranean part of Croatia which stretches along the Adriatic coast. Forest fires represent most serious and constant danger for forests which destroys the forest and forest land and caused degradation of habitats, worsen the forest soil quality, caused erosion and changes in ecological stability and loss of biodiversity. They can destroy waste areas of forests and by this caused serious and no reversal changes in landscape reduce attractiveness of touristic destinations, also they endanger human lives, houses and infrastructure, causing damages and losses in economy. Storm winds also caused lot of damages in forests and it seems that their impact and importance will only grow over the time under the influence of climate changes. Damages caused by storm winds have serious economic and social consequences and of most importance is to prevent them whenever is possible or to manage those which we can’t prevent. As they are part of natural dynamics in forest ecosystems they can seriously influence and change the stand structure and evolutionary processes related to regeneration and succession in forest stands. Smaller damages can even increase dynamic and diversity in small groups of trees which can stimulate regeneration, increase amount of dead wood in forests and influence microclimatic conditions, also it can increase biodiversity and at the same time stay on acceptable economic level of damage. Management of forest fires’ risks are in first place connected to forest management measures, starting from guarding, monitoring of forests and education of users in sense of prevention, and in sense to enable fast reaction in forest fires fighting and forest regeneration after forest fires. Risk management related to storm winds are connected to forest management measures, distribution of risks inside the forest complex and acceptance of losses when costs of prevention exceed damages. Paper present methodology for assessment of damages caused by those two main causes and also measures for prevention, risks reduction and regeneration.

The aim of this research was to investigate the applicability of canopy height models (CHMs) derived from digital aerial images for estimation of the main forest stand attributes (mean diameter, mean height, stand density, basal area, volume) of even-aged pedunculate oak forests. The research was conducted in the management unit Topolovac in Spačva basin (eastern Croatia), one of the largest coherent complex of lowland pedunculate oak forests in Europe. A CHM of the research area was generated by subtracting ground from surface elevations, i.e., by subtracting a digital terrain model (DTM) from corresponding digital surface model (DSM). For the DTM generation, a national digital terrain data were used. First, a triangular irregular network was created from the digital terrain data, which was then converted through linear interpolation into a raster DTM of 1 m grid size. For DSM generation, the colour infrared digital stereo aerial images collected as a part of the regular national survey in 2011 were used. A DSM of 1m grid size was generated using Dense DTM image matching algorithm (PHOTOMOD 5.24 software). In order to develop models for estimation of forest stand attributes, the data from field surveys conducted within regular forest inventory in 2011 were used as dependent variables, whereas metrics extracted from raster CHM were used as independent variables with addition of several variables from forest management plan (stand age, soil type, site class). A large number of potential independent variables were extracted from raster CHM, and only variables with the strongest correlation with field stand data were used in statistical modelling (multivariate linear regression). In total, 60 stands were used for models development, while 30 stands were used for models validation. The validation of stand-level models resulted with the following R2 values between observed and predicted estimates: 0.86, 0.91, 0.76, 0.71 and 0.80 for mean diameter, mean height, stand density, basal area and volume, respectively. The obtained results indicate that CHM derived from digital aerial images and national digital terrain data has potential for operational use in forest inventory of lowland pedunculate oak forests.

In Croatia, Common beech (Fagus sylvatica L.) is also a dominant tree species. With 901, 848 ha, beech forests (comprising mono-dominant beech forests as well as mixed forests with other tree species) cover 34.9 % of the total forest area (1). Because it is so widespread in Europe it plays an important role in the multiple forest function framework and in fulfilling ecological, social and economic requirements (2, 3). Results of multivariate regression analysis show that tree diameter at breast height almost completely explain variability of crown diameters (Fig 2a). Including tree height, stand age and site quality in model do not improve explained variability (for only 0.0036). Influence of tree height and stand age are expressed indirectly across dbh, while site quality has no shown influence on crown diameter. An irregular and multi-aged stand structure of beech forests in Croatia comprise more than one quarter of total beech forests, while stand structures of the forests potentially related to multi-aged forest management, considerably deviate from the theoretical. Due to high potential of the forests, environmental and social reasons, this close-to-nature type of forestry should be supported with an appropriate research and management approaches on forward.

Mikorizne makrogljive iznimno su značajne za fiziološko stanje biljnog simbionta te ga u određenoj mjeri štite od biotskih i abiotskih uzročnika stresa, ali i patogenih organizama. Na području istraživanja u Istri, patogena gljiva Sphaeropsis sapinea (Fr.) Dyko et Sutton uzrokovala je značajna sušenja kultura crnog bora (Pinus nigra J. F. Arnold) tijekom posljednjih 25 godina, a odnos ektomikoriznih gljiva i S. sapinea do sada nije istraživan. Ovo se istraživanje nastavlja na prijašnja istraživanja predispozicije crnog bora na zarazu gljivom S. sapinea, prilikom kojih je utvrđen utjecaj staništa i stresa na zarazu. Cilj ovog istraživanja je bio analizirati mikocenozu kultura crnog bora, kako bi se odredila ovisnost pojavljivanja različitih ektomikoriznih vrsta i njihovih plodišta u odnosu na prisutnost S. sapinea na iglicama. Uzorci gljiva sakupljani su tijekom tri godine (2011–2013.) na tri trajne plohe od 36. do 50. tjedna u godini. Određeni su udjeli ektomikoriznih vrsta i njihovih plodišta u ukupnom broju vrsta i plodišta te su izdvojene vrste koje imaju indikativnu vrijednost za zdravstveno stanje borovih kultura. Rezultati pokazuju jasnu ovisnost pojavljivanja S. sapinea o udjelu ektomikoriznih vrsta i njihovih plodišta. Povećanjem udjela ektomikoriznih vrsta i plodišta na 60 % ili više, značajno se smanjuje prisutnost patogena na iglicama. Također, mikocenoze zdravih i oštećenih kultura značajno su se razlikovale po sastavu vrsta.

Constant development of modern remote sensing methods, primarily digital photogrammetry, opens new possibilities for their application in forest management, with the aim of faster, simpler and cheaper ways of collecting data. Since the remote sensing methods have not yet reached wider practical application in Croatian forestry, focus of our work was on researching the potential application of digital photogrammetry on the tasks of creating management division. For selected part of the privately owned, multi- aged forests of 'Donja Kupčina - Pisarovina' management unit, comparison of results obtained by classical terrestrial (stand mapping) and photogrammetric method (strata delineation) of creating management division were performed, as well as comparison of costs of their application. Terrestrial stand mapping was conducted within regular inventory of the management unit. Strata delineation, i.e. photointerpretation was carried out in the stereomodels of colour infrared digital images of spatial resolution (GSD) of 30 cm and 10 cm, using digital photogrammetric workstation and PHOTOMOD software. Comparison between results (subcompartments area) obtained by different methods showed no statistically significant difference. In comparison to terrestrial mapping of stands, greater number of strata and subcompartments were delineated when using the photointerpretation of aerial images. That indicates the possibility of very detailed stands delineation by photointerpretation of aerial images. Regarding the costs of application, digital aerial images of GSD 30 cm proved to be the most favourable method. In contrast, all performed calculations revealed the application of aerial images of GSD 10 cm as financially the least favourable method. Finally, it can be concluded that photointerpretation of digital images GSD 30 cm has proven to be the most suitable method for operational use in creating management division, i.e. the method that provides the most favourable ratio of costs and accuracy of obtained results.

Problematika koju rad istražuje je sušenje obične jele u bukovo-jelovim šumama s proizvodnog stajališta. Proizvodnjom šumskih drvnih sortimenata jele u sastojinama različitih kategorija zdravstvenog stanja, ostvaruje se sortimentna struktura koja vrlo često značajno odstupa od planirane strukture, a time i od planiranih prihoda proizvodnje. Navedene razlike između planirane i ostvarene proizvodnje, koje su značajne za sastojine u kojima je jela umjereno do izrazito narušenog zdravstvenog stanja, ponajprije promatrajući osutost krošanja, glavna su tema ovoga rada. Područje istraživanja određeno je granicama Uprave šuma Podružnice Delnice, s naglaskom na one gospodarske jedinice, odnosno odjele zahvaćene intenzivnim sušenjem stabala jele. U skladu s tim, te uz stručnu pomoć Ekološkog i Proizvodnog odjela navedene Podružnice, prikupljanje podatka obavljeno je na području gospodarskih jedinica "Brloško" i "Široka Draga". Osnovna razlika na temelju koje su te jedinice odabrane je u kategoriji općeg zdravstvenog stanja stabala jele. Terensko istraživanje provođeno je u skladu s operativnim proizvodnim planom Podružnice za svaku godinu istraživanja, na način da je odabrano nekoliko odjela/odsjeka predviđenih za prebornu sječu tijekom godine. Na terenu su prikupljani podaci o oborenim jelovim stablima i to osnovne mjerne veličine prsni promjer i ukupna visina stabla, te mjere svakog izrađenog i klasiranog sortimenta iz stabala uzorka. Prikupljeni terenski podaci obrađivani su Microsoft Excel 2007, te SPSS programom za statističku obradu podataka. Analizom su potvrđene statistički značajne razlike između planirane i ostvarene proizvodnje drvnih sortimenata jele u odjelima sa značajnim sušenjem jele, a dokazane su značajne razlike između proizvodnje istovrsnih sortimentnih klasa pridobivenih iz jelovih sastojina različitih kategorija zdravstvenoga stanja.

Net Ecosystem Productivity (NEP) of 35-year-old pedunculate oak (Quercus robur L.) stand was investigated during 2008 and 2009 at eddy covariance (EC) site located in Jastrebarsko pedunculate oak forest, currently undergoing the process of joining FLUXNET network. Two independent methods for assessing NEP were used: 1) eddy covariance ; and 2) the "combined" method, using difference between Net Primary Productivity (NPP), assessed with biometric measurements, and heterotrophic respiration (Rh) estimated from soil respiration (SR) measurements. Maximal measured daily NEP from eddy covariance was 10, 7 gC m−2 day−1 in 2008., and 12, 2 gC m−2 day−1 in 2009. The annual NEP ranged from 384 gC m−2 yr−1 in 2008 to 584 gC m−2 yr−1 in 2009 indicating that the stands around the tower were actively storing carbon during both years. Using weekly measurements of stem increment on 640 dendrometer bands, annual height increment and litter production we obtained an estimate of the NPP of the stands in the footprint of 777 gC m−2 yr−1 in 2008 and 846 gC m−2 yr−1 in 2009. Heterotrophic respiration (Rh) , estimated from soil respiration measurements was 438 gC m−2 yr−1 in 2008 and 441 gC m−2 yr−1 in 2009. By subtracting Rh from NPP, we obtained NEP of 339 and 405 gC m−2 yr−1 in 2008 and 2009, respectively. Comparison of results for NEP during vegetation season reveals that agreement between the two methods was very good until July. Later in the summer and autumn, discrepancy occurs when stem growth ceases but trees continue to actively store carbon. This leads to the underestimation of NEP from combined method during that period, leading to the overall lower values of NEP when compared with NEP values from eddy covariance. Results of our measurements are compared with other forest sites in FLUXNET network. Further research is needed that would provide better estimates of Rh, R:S ratio, and related uncertainties in carbon fluxes in pedunculate oak forests.

U radu je procijenjena neto produktivnost ekosustava (NEP) i neto bilanca ugljika (NECB) u mladoj sastojini hrasta lužnjaka (Quercus robur L.) pomoću dvije neovisne metode i to: a) mikrometeorološke metode vrtložne kovarijance (EC) te, b) kombinirane metode koja je uključivala biometrijsku izmjeru šumske biomase i periodičko mjerenje respiracije tla (SR). Maksimalni NEP zabilježen vrtložnom kovarijancom iznosio je 10, 7 gC m−2 dan−1 u 2008., odnosno 12, 2 gC m−2 dan−1 u 2009. godini. Godišnje vrijednosti NEP kretale su se od 384 gC m−2 god−1 u 2008. do 584 gC m−2 god−1 u 2009. godini iz čega je razvidno da su sastojine u dohvatu mjerne stanice u obje godine bile neto spremnik ugljika. Biometrijskom metodom praćenja prirasta i produkcije listinca i sitnog drvnog otpada dobivena je neto primarna produktivnost (NPP) od 777 gC m-2 god-1 u 2008., odnosno 846 gC m-2 god-1 u 2009. godini. Udio heterotrofne respiracije (Rh) procijenjen je na 50% od izmjerene ukupne SR pa je Rh procijenjena na 438 gC m−2 god−1 u 2008. odnosno 441 gC m−2 god−1 u 2009. godini. Kombiniranom metodom NEP je dobivena kao razlika NPP i Rh, a iznosila je 339 i 405 gC m-2 god-1 u 2008., odnosno 2009. godini. Usporedba dvaju metoda procjene NEP-a daje dobro slaganje do srpnja za obje promatrane godine. Do odstupanja dolazi u drugom dijelu ljeta i jeseni kada prestaje debljinski prirast, ali stabla očito i dalje aktivno spremaju ugljik. Kombinirana metoda daje manje vrijednosti NEP-a u odnosu na metodu vrtložne kovarijance za što je moguće više razloga, npr.: udio Rh je manji od 50%, omjer podzemnog i nadzemnog dijela biomase ; R:S je veći od 0, 257, i sl. Potrebna su daljnja istraživanja koja bi empirički odredila udio Rh u SR, omjer R:S te istraživanja količine ugljika u sastavnicama tla.