THE NUTRITIONAL STATUS OF COMMON BEECH (FAGUS SYLVATICA L.) AND SILVER FIR (ABIES ALBA MILL.) ON MEDVEDNICA

U Hrvatskoj se od 1995. godine provode istraživanja na plohama intenzivnog motrenja (Razina II) u sklopu i po metodama Međunarodnog programa za procjenu i motrenje utjecaja zračnog onečišćenja na šume (UN-ECE ICP Forests). U radu se daje usporedba višegodišnjeg niza podataka (1999.–2004.) o stanju ishrane obične bukve (Fagus sylvatica L.) i obične jele (Abies alba Mill.) na plohi intenzivnog motrenja 103 «Sljeme» sa stanjem ishrane na drugim plohama u sastojinama obične jele i obične bukve na području Medvednice. U uzorcima lišća i iglica određene su ukupne koncentracije dušika, fosfora, kalija, kalcija i magnezija koje su uspore|ene s graničnim vrijednostima (GV). Ti su podaci tako|er stavljeni u kontekst klimatskih prilika područja. Istraživani lokaliteti na području Medvednice razlikuju se u pogledu uvjeta za ishranu drveća, a na stanje ishrane utjeću i antagonizmi iona.The research on intensive monitoring plots (Level II) as a part and according to the methods of the International Co-operative Programme for Assessment and Monitoring of Air Pollution Effects on Forests (UN-ECE ICP Forests) has been conducted in Croatia since the year 1995. In this paper a comparison is given of data on foliar composition of Common beech (Fagus sylvatica L.) and Silver fir (Abies alba Mill.) in the years 1999 to 2004 on intensive monitoring plot No. 103, «Sljeme» with their nutritional status on beech-fir plots in other parts of Medvednica mountain. The total concentrations of nitrogen, phosphorous, potassium, calcium and magnesium were determined in the samples of foliage, and these data were put in the context of climate properties in the area of research. The investigated localities differ regarding the conditions they provide for the nutrition of trees, and the nutritional status further depends on ion antagonisms

The Charismatic Movement: Identity, Sources and Premises of action

Katolički karizmatski pokret ili Pokret obnove u Duhu Svetom danas je vrlo razvijen i, osobito među mladim vjernicima, popularan oblik okupljanja radi zajedničkog ostvarivanja određenih segmenata duhovnog života. Katolička Crkva se prema ovom obliku okupljanja i djelovanja u posljednjim desetljećima često određivala, ali i korigirala i usmjeravala njegova očitovanja i načine djelovanja. Danas je to pokret općenito prihvaćen i podržan. No, kao i svaki drugi oblik okupljanja s ciljem duhovno-vjerskog rasta i napretka osoba i zajednica, ni ovaj oblik nije pošteđen različitih opasnosti i zastranjenja. Stoga je za pastoralno djelovanje izuzetno važno na teološko-pastoralni prosudbeni način odrediti i prepoznati vlastitosti i izvorišta ovog pokreta danas. Upravo je to cilj ovog rada. Te vlastitosti i ta izvorišta sagledavaju se na temelju povijesnih oznaka te posebno na temelju odrednica učiteljstva Crkve. K tomu, ovo je sagledavanje obogaćeno i teološkim prilozima nekih istaknutijih teologa.The Catholic Charismatic Movement or the Movement of Renewal in the Holy Spirit is a highly developed and popular form of gathering for the common realization of certain segments of the spiritual life, especially among young believers. In the last decades, the Catholic Church has often reflected about this form of gathering and action, and has also corrected and offered guidelines for its manifestations and its way of doing things. Today, this movement is generally accepted and supported. But, like any other form of gathering with the purpose of spiritual and religious growth and progress of persons and communities, this form is not spared of various dangers and anomalies. It is therefore of utmost importance for pastoral action to determine and identify, in theological-pastoral discernment, the properties and sources of this movement today. This is precisely the aim of this paper. These properties and sources are examined on the basis of historical designations, and especially on the basis of the instructions of the Magisterium of the Church. In addition, the examination is enriched with theological contributions of some prominent theologians

The Charismatic Movement: Identity, Sources and Premises of action

Katolički karizmatski pokret ili Pokret obnove u Duhu Svetom danas je vrlo razvijen i, osobito među mladim vjernicima, popularan oblik okupljanja radi zajedničkog ostvarivanja određenih segmenata duhovnog života. Katolička Crkva se prema ovom obliku okupljanja i djelovanja u posljednjim desetljećima često određivala, ali i korigirala i usmjeravala njegova očitovanja i načine djelovanja. Danas je to pokret općenito prihvaćen i podržan. No, kao i svaki drugi oblik okupljanja s ciljem duhovno-vjerskog rasta i napretka osoba i zajednica, ni ovaj oblik nije pošteđen različitih opasnosti i zastranjenja. Stoga je za pastoralno djelovanje izuzetno važno na teološko-pastoralni prosudbeni način odrediti i prepoznati vlastitosti i izvorišta ovog pokreta danas. Upravo je to cilj ovog rada. Te vlastitosti i ta izvorišta sagledavaju se na temelju povijesnih oznaka te posebno na temelju odrednica učiteljstva Crkve. K tomu, ovo je sagledavanje obogaćeno i teološkim prilozima nekih istaknutijih teologa.The Catholic Charismatic Movement or the Movement of Renewal in the Holy Spirit is a highly developed and popular form of gathering for the common realization of certain segments of the spiritual life, especially among young believers. In the last decades, the Catholic Church has often reflected about this form of gathering and action, and has also corrected and offered guidelines for its manifestations and its way of doing things. Today, this movement is generally accepted and supported. But, like any other form of gathering with the purpose of spiritual and religious growth and progress of persons and communities, this form is not spared of various dangers and anomalies. It is therefore of utmost importance for pastoral action to determine and identify, in theological-pastoral discernment, the properties and sources of this movement today. This is precisely the aim of this paper. These properties and sources are examined on the basis of historical designations, and especially on the basis of the instructions of the Magisterium of the Church. In addition, the examination is enriched with theological contributions of some prominent theologians

Challenges and Fruits of the Work of Charismatic Movement Today

Katolički karizmatski pokret ili Pokret obnove u Duhu Svetomu jedan je od najraširenijih i danas duhovno-pastoralno najaktivnijih pokreta unutar Katoličke Crkve. U posljednjih nekoliko desetljeća, a osobito od vremena Drugoga vatikanskog sabora naovamo, ovo je duhovno i pastoralno gibanje doživjelo različite faze vlastitog razvitka i konsolidiranja. Danas su jasno profilirani njegovi temeljni teološko-pastoralni okviri postojanja i djelovanja, kao i uporišna težišta aktivnosti pojedinaca i zajednica koje su vezane za to gibanje. U ovome radu sagledavaju se i razlučuju izazovi, tj. oni aspekti djelovanja ovog pokreta koji osobito u duhovnom i pastoralnom smislu predstavljaju poteškoću. Uz to, sagledavaju se i razlučuju i pozitivne strane te perspektive djelovanja ovog pokreta preko kojih njegovi pripadnici obogaćuju ukupni život i djelovanje Crkve, a osobito djelo evangelizacije.The Catholic Charismatic Movement or the Movement of Renewal in the Holy Spirit is one of the most widespread and today spiritually-pastorally most active movements within the Catholic Church. In the last few decades, and especially from the time of the Second Vatican Council onwards, this spiritual and pastoral movement has experienced various stages of its own development and consolidation. Nowadays, its basic theological-pastoral frameworks of subsistence and activity are clearly profiled, as well as the strongholds of the activities of individuals and communities related to this movement. This paper examines and distinguishes the challenges, i.e. those aspects of the activities of this movement that are especially difficult in the spiritual and pastoral sense. Furthermore, the positive aspects and perspectives of the activities of this movement are considered and distinguished, through which its members enrich the overall life and activities of the Church, and especially the work of evangelization

Climate and relief properties influence crown condition of common beech (Fagus sylvatica L.) on the Medvednica massif

Background and Purpose: Common beech is a dominant broadleaved tree species in European forests, and also on the Medvednica massif. Since climate is a decisive factor in the development of a certain type of vegetation, it might have an equally important role in its survival. The influence of relief properties on the crown condition of common beech (Fagus sylvatica L.) can also be significant, since beech stands on Medvednica vary in their elevation and exposition. Materials and Methods: Twelve common beech research plots, with complete defoliation data sets in the period 2004–2006 were chosen to represent the variety of environmental conditions present on the Medvednica massif in the western Pannonian region of Croatia. Climate parameters used in the model included annual precipitation (AP), precipitation in the vegetation period (VP), mean annual air temperature (AT), and mean air temperature in the vegetation period (VT). The elevation (EL) of the experimental plots and data from the meteorological station of Puntijarka were used to obtain an estimate of the AT, VT, AP and VP on each research plot. Results: The share of moderately to severely damaged trees (crown defoliation over 25%) was highest in 2004, an expected result of the 2003 drought. This value was significantly higher than in the following two years. The determining climate parameter explaining the changes in defoliation was VP, and the most decisive relief parameter was EL. Defoliation was higher with low VP and higher EL. D was higher predominantly on southern expositions. Conclusions: Climate and relief properties were found to significantly influence the crown condition of beech trees. Although there is a significant positive trend of temperature change on Medvednica, in the period 2004–2006 precipitation in the vegetation period had the dominant effect on the crown condition

DEFOLIATION OF FOREST TREES IN CROATIA IN THE PERIOD 2001-2011

Međunarodni program za procjenu i motrenje utjecaja zračnog onečišćenja na šume (International Cooperative Programme on Assessment and Monitoring of Air Pollution Effects on Forests, skraćeno ICP Forests) osnovan je 1985. godine u okviru UNECE Konvencije o dalekosežnom prekograničnom onečišćenju zraka (CLRTAP), s mandatom da motri utjecaj antropogenih čimbenika (pogotovo zračnog onečišćenja) i prirodnih čimbenika stresa na stanje i razvoj šumskih ekosustava u Europi te da doprinese boljem razumijevanju uzročno-posljedičnih veza u šumskim ekosustavima Europe. Hrvatska se projektu priključila 1987. godine. Značajna se osutost krošanja šumskog drveća u Hrvatskoj u razdoblju od 2001. do 2011. godine kretala u rasponu od 20,6 (2002.) do 27,7 % (2010.). U razdoblju od 2001. do 2005. godine značajna osutost listača kretala se u rasponu od 14,4 do 19,2 %, a kontinuirani rast bilježimo od 2006. godine. Kod četinjača značajna je osutost naglo porasla u 2003. godini, nakon čega se zadržava iznad 70 % do 2006. godine, s maksimumom u 2005. godini (79,5 %). Isto tako, kod nekih je vrsta (obična bukva, poljski jasen, hrast kitnjak) zabilježeno povećanje značajne osutosti nakon sušnih godina, dok kod npr. hrasta lužnjaka takva pojava nije primijećena. Rezultati ovog istraživanja pokazuju kako se osutost krošanja šumskog drveća, u ovisnosti od vrste, može povezati s klimatskim svojstvima kako tekuće, tako i prethodnih godina.The International Cooperative Programme on Assessment and Monitoring of Air Pollution Effects on Forests - ICP Forests started in 1985 in the framework of the UNECE Convention on Long-Range Transboundary Air Pollution (CLRTAP), with the mandate to monitor the effects of anthropogenic factors (in particular air pollution) as well as natural stress factors on the condition and development of forest ecosystems in Europe and to contribute to a better understanding od cause-effect relationships in forest ecosystem functioning in various parts of Europe. Croatia joined the programme in 1987. The share of moderately to severely defoliated trees in the period 2001-2011 ranged from 20,6 % (2002) to 27,7 % (2010). For broadleaves, the share was between 14,4 % and 19,2 %, and a continuous growth of defoliation is recorded since 2006. The share of moderately to severely defoliated conifers sharply grew from 2003 to 2006, with a maximum in 2005 (79,5 %). With some single species (common beech, narrow-leaved ash, sessile oak) also a rise in defoliation is recorded after dry years, while with others, such as pedunculate oak, dry years have no discernible effect on the crown condition. The results of monitoring show that crown defoliation can, depending on the species, be linked to climate properties of either current, or past years

Habitat Characteristics of Bracken-Covered Areas Intended for Afforestation in Ličko Sredogorje

Background and Purpose: Forest cultures in continental part of Croatia are mainly based on bracken-covered areas and moors on deserted agriculture soils and pastures. Successful afforestation i.e. establishment of forest cultures depends among other things on the understanding of habitats and ecology of forest trees. The choice of best species of forest trees for afforestation needs to be based on the research in soil and climate characteristics of target habitats. The aims of this research were to show mesoclimatic characteristics of Ličko sredogorje and microclimatic and pedological characteristics of Ličko polje. Also, based on habitat characteristics and ecology of forest trees, the aim was to determine species of forest trees suitable for afforestation of bracken-covered areas. Materials and Methods: Climate, microclimate, pedological and plant nutrition researches were done at the area of Lika highlands. Climate analysis was done according to air temperatures, amount of precipitation, relative air humidity and other climate elements and appearances. Composite soil samples were taken from the depth of 0-30 cm in order to determine plant nutrition potential. Samples were prepared for further analysis in the laboratory. Results: The highest average annual air temperature of 9.6 °C was found at weather station Gračac and the lowest at Korenica station (8.1 °C). Average amount of precipitation for this region was around 1500 mm. Monthly rain factors were ranging from arid to perhumid. Considering thermal character of the climate, the area has moderately warm climate. Average volumetric soil humidity is 14.2 %. Soil has strong acid reaction, is very humus, good to richly supplied with total nitrogen, content of physiologically active phosphorus and potassium is low, and C/N ration normal. Conclusions: According to habitat characteristics in the area of Ličko sredogorje and ecological demands of forest tree species, forest cultures of Common birch (Betula pendula Roth.), Common spruce (Picea abies Karst.), Eastern white pine (Pinus strubus L.), Black pine (Pinus nigra subsp. austriaca Asch i Gr.), Common pine (Pinus sylvestris L.) and European trembling aspen (Populus tremula L.) can be established

Defoliation of Forest Trees in Croatia in the period 2006 – 2009

S obzirom na stav da je najvažniji uzročnik propadanja šuma zračno onečišćenje, 1985. godine je u okviru UNECE Konvencije o dalekosežnom prekograničnom onečišćenju zraka (CLRTAP) osnovan Međunarodni program za procjenu i motrenje utjecaja zračnog onečišćenja na šume (International Cooperative Programme on Assessment and Monitoring of Air Pollution Effects on Forests, skraćeno ICP Forests), u koji se Hrvatska uključila 1987. godine. Prednost monitoringa (trajnog motrenja) u odnosu na jednokratna istraživanja je u dobivanju vremenskog niza podataka koji omogućuje ispravnije zaključivanje o stanju pojava koje, u ovome slučaju, variraju na godišnjoj razini. Motrenje se provodi na mreži točaka Razine 1 (bioindikacijske točke razmaka 16 km) i osnovnoj mreži točaka (točke razmaka 4 km), a ključnu ulogu u Programu ima vizualna procjena osutosti krošanja. Vrijednosti značajne osutosti su vrlo visoke u Upravama šuma Podružnicama Vinkovci, Zagreb, Delnice i Buzet, a niske u UŠP Bjelovar i Koprivnica.Visok postotak značajne osutosti u UŠP Delnice i Vinkovci posljedica je visokeosutosti obične jele, odnosno hrasta lužnjaka. U UŠP Buzet, visok postotak značajne osutosti posljedica je visokih vrijednosti značajne osutosti gotovo svih promatranih vrsta. Porast značajne osutosti svih vrsta traje od 2002. godine, a listača od 2003. godine. Kod četinjača od 2006. godine bilježimo lagan pad osutosti.In response to widespread concern that air pollution could affect forest condition, the International Co-operative Programme on the Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) was established by the Convention on Long-range Transboundary Air Pollution (CLRTAP) under the United Nations Economic Commission for Europe in 1985. Croatia joined the Programme in 1987. The advantage of monitoring is in obtaining a time series of data that enables correct deduction on the phenomena that, in this case, vary on annual basis. Monitoring is conducted on two networks: Level I (so called bioindication plots at 16 x 16km distance) and basic network (4 x 4 km distance of plots). Defoliation, the key parameter for assessing forest ecosystem condition, is assessed according to ICP Forests Manual on methods and criteria for harmonized sampling, assessment, monitoring and analysis of the effects of air pollution on forests. Defoliation is high in Forest Branch Offices Vinkovci, Zagreb, Delnice and Buzet, and low in Bjelovar and Koprivnica (Fig. 5). The high percentage of moderately to severely damaged trees in Forest Branch Office Delnice and Vinkovci is the result of intensive dieback of silver fir and pedunculate oak, respectively. In Forest Branch Office Buzet, a high percentage of moderately to severely damaged trees is the result of high defoliation values in almost all surveyed species. In Forest Branch Offices Gospić and Senj, moderate to severe damage of silver fir trees in year 2009 is significantly lower that the corresponding value in the bioindication and basic plot network in Croatia, while it is somewhat higher in Forest Branch Offices Delnice and Ogulin. Very high values of percentages of moderately to severely damaged trees of pedunculate oak in the year 2009 were present in Forest Branch Offices Požega, Zagreb, Našice and Osijek, and very low in Bjelovar and Koprivnica. Moderate to severe damage of beech is significantly higher than the value for Croatia in Forest Branch Offices Zagreb, Delnice and Senj, and lower in Bjelovar, Sisak, Karlovac and Našice. The rising percentage of moderately to severely damaged trees of all species started in 2002, and for broadleaves in 2003. Conifers, on the other hand, have a decreasing trend of defoliation since 2006 (Tabs. 2–4)

Nova automatska metoda za poboljšanje točnosti fotogrametrijskog DTM-a u šumama

Accuracy of a Digital Terrain Model (DTM) in a complex forest environment is critical and yet challenging for accurate forest inventory and management, disaster risk analysis, and timber utilization. Reducing elevation errors in photogrammetric DTM (DTMPHM), which present the national standard in many countries worldwide, is critical, especially for forested areas. In this paper, a novel automated method to detect the errors and to improve the accuracy of DTMPHM for the lowland forest has been presented and evaluated. This study was conducted in the lowland pedunculate oak forest (Pokupsko Basin, Croatia). The DTMPHM was created from three-dimensional (3D) vector data collected by aerial stereo-photogrammetry in combination with data collected from existing maps and field surveys. These data still present the national standard for DTM generation in many countries, including Croatia. By combining slope and tangential curvature values of raster DTMPHM, the proposed method developed in open source Grass GIS software automatically detected 91 outliers or 3.2% of the total number of source points within the study area. Comparison with a highly accurate LiDAR DTM confirmed the method efficiency. This was especially evident in two out of three observed subset areas where the root mean square error (RMSE) values decreased for 8% in one and 50% in another area after errors elimination. The method could be of great importance to other similar studies for forested areas in countries where the LiDAR data are not available.Digitalni model reljefa (DTM, engl. Digital Terrain Model) ima široku i važnu primjenu u mnogim djelatnostima, uključujući i šumarstvo. Međutim, precizno modeliranje terena, odnosno izrada DTM-a u šumama, bilo korištenjem terenskih metoda ili metoda daljinskih istraživanja, izazovan je i vrlo zahtjevan zadatak. U većini razvijenih zemalja svijeta, zračno lasersko skeniranje (ALS, engl. Airborne Laser Scanning) bazirano na LiDAR (engl. Light Detection and Ranging) tehnologiji trenutno predstavlja glavnu metodu za izradu DTM-a. Uslijed mogućnosti laserskog zračenja da penetrira kroz krošnje drveća, LiDAR tehnologija se pokazala kao efektivna i brza metoda za izradu DTM-a u šumskim područjima s vrlo velikom točnošću. Međutim, u mnogim zemljama svijeta, uključujući i Hrvatsku, zračno lasersko skeniranje nije u potpunosti provedeno, tj. samo su manji dijelovi zemlje pokriveni s podacima zračnog laserskog skeniranja. U tim slučajevima, DTM temeljen na stereo-fotogrametrijskoj izmjeri aerosnimaka potpomognut s terenskim podacima najčešće predstavlja glavni izvor informacija za izradu DTM-a. Poznato je da tako izrađen DTM u šumskim predjelima ima manju točnost od DTM-a dobivenog na temelju zračnog laserskog skeniranja zbog pokrivenosti terena vegetacijom. Također, u okviru nedavno provedenog istraživanja (Balenović i dr., 2018) utvrđeno je da takvi službeni fotogrametrijski digitalni podaci terena u šumskim predjelima sadrže određen broj tzv. grubih grešaka, koje mogu značajno utjecati na točnost izrađenog DTM-a. Nakon vizualnog detektiranja i manualnog uklanjanja tih pogrešaka, Balenović i dr. (2018) utvrdili su značajno poboljšanje točnosti fotogrametrijskog DTM-a.Stoga je glavni cilj ovoga rada razviti automatsku metodu za detekciju i eliminaciju vertikalnih pogrešaka u fotogrametrijskim digitalnim podacima terena te na taj način poboljšati točnost fotogrametrijskog DTM-a u nizinskim šumskim područjima Hrvatske. Ideja je razviti brzu, jednostavnu i učinkovitu metodu koja će biti primjenjiva i za druga šumska područja sličnih karakteristika, a za koja ne postoje DTM dobiven zračnim laserskim skeniranjem. Istraživanje je provedeno u nizinskim šumama na području gospodarske jedinice Jastrebarski lugovi, u neposrednoj blizini Jastrebarskog (Slika 1). Istraživanjem je obuhvaćena površina od 2.005,74 ha, na kojoj su u najvećoj mjeri zastupljene jednodobne sastojine hrasta lužnjaka (Quercus robur L.), a u ma­njoj mjeri jednodobne sastojine poljskog jasena (Fraxinus angustifolia L.) te jednodobne sastojine običnoga graba (Carpinus betulus L.). Nadmorska visina područja istraživanja kreće se u rasponu od 105 do 121 m.Fotogrametrijski DTM (DTMPHM) je izrađen iz digitalnih vektorskih podataka terena (prijelomnice, linije oblika, markantne točke terena i pravokutne mreže visinskih točaka) nabavljenih iz Državne geodetske uprave (Slika 2). Ti podaci predstavljaju nacionalni standard i jedini su dostupni podaci za izradu DTM-a u Hrvatskoj. Detaljan opis vektorskih podataka dan je u radu Balenović i dr. (2018). Prvo je iz digitalnih terenskih podataka izrađena nepravilna mreža trokuta, koja je potom linearnom interpolacijom pretvorena u rasterski DTMPHM prostorne rezolucije (veličine piksela) 0,5 m. Automatska metoda za detekciju i eliminaciju vertikalnih pogrešaka fotogrametrijskog DTM-a u nizinskim šumskim područjima razvijena je u slobodnom programskom paketu Grass GIS (Slika 3). Kombinacijom vrijednosti nagiba i tangencijalne zakrivljenosti terena rasterskog DTMPHM (Slika 4), automatskom metodom su detektirane 91 grube greške (engl. outliers). Drugim riječima, utvrđeno je da 91 točkasti vektorski objekt pogrešno prikazuje stvarnu visinu terena. Navedeni broj čini 3,2 % od ukupnog broja točkastih objekata korištenih za izradu DTMPHM-a. Nakon eliminacije detektiranih pogrešaka izrađen je novi, korigirani fotogrametrijski DTM (DTMPHMc). Za ocjenu vertikalne točnosti izvornog (DTMPHM) i korigiranog DTM-a (DTMPHMc) korišten je visoko precizni DTM dobiven zračnim laserskim skeniranjem (DTMLiD). U tu svrhu su izrađeni rasteri razlika između DTMPHM i DTMLiD, te između DTMPHMc i DTMLiD. Kako je preliminarnom analizom utvrđeno da vertikalne razlike između DTMPHM i DTMLiD nisu normalno distribuirane (Slika 5), za ocjenu točnosti su uz normalne mjere točnosti korištene i tzv. robusne mjere točnosti (Tablica 2). Dobiveni rezultati ukazuju na poboljšanje vertikalne točnosti fotogrametrijskog DTM-a primjenom razvijene automatske metode. To je posebice uočljivo na podpodručjima 2 i 3 (Slika 6 i 7) u kojima se nakon uklanjanja detektiranih grešaka, korijen srednje kvadratne pogreške (RMSE, engl. root mean square error) smanjio za 8 % odnosno 50 % (Tablica 2). Na temelju dobivenih rezultata i usporedbe s DTMLiD, može se zaključiti da predložena metoda uspješno detektira i eliminira vertikalne pogreške fotogrametrijskog DTM-a u nizinskim šumskim područjima, te slijedom toga poboljšava njegovu vertikalnu točnost

Accuracy Assessment of Digital Terrain Models of Lowland Pedunculate Oak Forests Derived from Airborne Laser Scanning and Photogrammetry

Digital terrain models (DTMs) present important data source for different applications in environmental disciplines including forestry. At regional level, DTMs are commonly created using airborne digital photogrammetry or airborne laser scanning (ALS) technology. This study aims to evaluate the vertical accuracy of DTMs of different spatial resolutions derived from high-density ALS data and existing photogrammetric (PHM) data in the dense lowland even-aged pedunculate oak forests located in the Pokupsko basin in Central Croatia. As expected, the assessment of DTMs’ vertical accuracy using 22 ground checkpoints shows higher accuracy for ALS-derived than for PHM-derived DTMs. Concerning the different resolutions of ALS-derived (0.5 m, 1 m, 2 m, 5 m) and PHM-derived DTMs (0.5 m, 1 m, 2 m, 5 m, 8 m) compared in this research, the ALS-derived DTM with the finest resolution of 0.5 m shows the highest accuracy. The root mean square error (RMSE) and mean error (ME) values for ALS-derived DTMs range from 0.14 m to 0.15 m and from 0.09 to 0.12 m, respectively, and the values decrease with decreasing spatial resolution. For the PHM-derived DTMs, the RMSE and ME values are almost identical regardless of resolution and they are 0.35 m and 0.17 m, respectively. The findings suggest that the 8 m spatial resolution is optimal for a given photogrammetric data, and no finer than 8 m spatial resolution is required. This research also reveals that the national digital photogrammetric data in the study area contain certain errors (outliers) specific to the terrain type, which could considerably affect the DTM accuracy. Thus, preliminary evaluation of photogrammetric data should be done to eliminate possible outliers prior to the DTM generation in lowland forests with flat terrain. In the absence of ALS data, the finding in this research could be of interests to countries, which still rely on similar photogrammetric data for DTM generation