Preliminary Work on Generative Seedling Production and Clone Selection of European Black Poplar (Populus nigra L.)

European black poplar (Populus nigra L.) is a pioneer species that belongs to the Salicaceae family and occurs in riparian ecosystems. It is one of the most endangered forest species in its entire distribution area. In Croatia, black poplars are considered an economically important forest species, but mostly clones originate from crossing combinations with American and European black poplar (Populus × canadensis Moench), while a small number of clones are native black poplar. Studies on native black poplar are quite rare and the generative propagation has not been used. The aim of this study was to gain knowledge on the production of high-quality black poplar seedlings and to carry out the selection of genotypes with the aim of establishing a base for future breeding. The female black poplar tree was selected on phenotypic characteristics in the area of Forest Administration Osijek, Forest Office Valpovo. The tree was cut down in April 2019, and branches with half-open seed capsules on catkins were collected. The branches were transferred to the Croatian Forest Research Institute’s greenhouse, where the catkins opened under the influence of the high temperature. Sowing was done in different substrates to test their effectiveness. Black poplar seedlings were selected and transplanted with regard to development and height growth. The results showed differences in height growth between plants sown in two different substrates and the occurrence of fungal diseases only on plants sown in pure sand. With subsequent multiple propagation using cuttings and selection by genotype, it is expected that it will be possible to identify several clones of native black poplar that will be introduced for use in forestry in Croatia. The use of quality plants grown from seeds will increase the genetic diversity and preserve the native black poplar gene pool

Diversity of Ectomycorrhizal Fungi in Young Pedunculate Oak Stand from Morović, Serbia

Although oaks belong to the economically most important hardwood tree species in Europe, data on the diversity of ectomycorrhizal (ECM) fungi on pedunculate oak in the Republic of Serbia are deficient. The aim of our study was to give the first insight into the diversity of ECM fungi in the young stand of pedunculate oak in Morović, Serbia. The combination of morpho-anatomical characterization and molecular analysis was used for determination of ECM fungi on penduculate oak. Studied parameters included: (i) counting of vital ECM root tips, (ii) calculation of diversity indices and (iii) classification of morphotypes of ectomycorrhizae into the exploration types. Eighteen ECM fungal taxa were recorded in the studied young pedunculate oak stand. Seven of them were identified to the level of species, eight fungi to the genus, two to the family level, and one ECM fungus remained unidentified. ECM communities consisted of a small number of abundant taxa and a bigger number of rare taxa. The most abundant ECM fungi were Entoloma sp., Thelephoraceae sp., Russula cf. odorata and Russula lilacea, which made association with the majority of ECM root tips. Short-distance exploration type (ET) dominated, followed by medium-distance smooth ET and contact ET, while long-distance ET and medium-distance fringe ET were rare at the Morović site. Values of diversity indices obtained in the studied pedunculate oak stand were comparable to the ones recorded in different oak stands over Europe. In order to get a deeper insight into the diversity of ECM fungi on pedunculate oak there is a need to continue research on increased number of sites and also to include seasonal dynamics

Acorn Yields and Seed Viability of Pedunculate Oak in a 10-year Period in Forest Seed Objects across Croatia

Quercus robur L. exhibits not only a large inter-annual variability in seed production but also considerable variability among locations and individuals within the same year. The differences in how individual trees and populations of oaks invest in acorn production, both in terms of the yield size and the acorns quality, is of interest both ecologically and economically. For this research we used data collected from harvesting which has been organised and executed by the largest forestry company in Croatia - public enterprise Croatian Forests Ltd. According to the Act on Forest Reproductive Material, Croatian Forest Research Institute is designated as the Official Body that supervises production and provides analysis of quality of forest reproductive material. Regarding that, we summarized data of 10-year long records (from 2009 to 2018) of submitted seed samples and seed quality testing from 119 Q. robur forest seed objects across Croatia. Our aim was to investigate seed yield and effects of seed size and seed moisture content on seed viability. In the study period there were four years with higher quantity of collected seeds than other years (2010, 2011, 2015 and 2017). There was no significant difference in seed viability among forest seed objects. However, variations among years within forest seed objects were highly significant. It was also found that seed size (indicated by the number of acorns per kg) and seed moisture content were significantly related to seed viability. Bigger seed dimensions, i.e. lower mean number of acorns per kg, correlated with higher viability. Lower moisture content affected decrease in acorn viability. On average, viability dropped below 70% when acorn mean moisture decreased below 36%. Thus, it can be concluded that bigger seeds and seeds with moisture content of 40-44% have better viability

Preservation of the Gene Pool of Protected and Significant Trees in the Republic of Croatia

Hrvatski šumarski institut (HŠI) već više od 10 godina se bavi projektima očuvanja genofonda zaštićenih i znamenitih stabala na području Republike Hrvatske (RH). Značaj ovakvih projekata prepoznat je od strane brojnih javnih ustanova, lokalne samouprave i udruga za zaštitu prirode koje žele sačuvati genetski materijal takvih stabala za sva vremena. Diljem RH nalaze se brojna znamenita stabla koja nose povijesnu, kulturnu i estetsku simboliku pojedinog kraja, a neka se nalaze i na popisu zaštićenih stabala. Djelatnici HŠI-a obavljaju stručne poslove vezane uz proizvodnju klonskog materijala koji obuhvaćaju: proizvodnju podloga (biljke na koje se cijepe plemke), sakupljanje plemki (grančice od matičnog stabla koje se klonira), vegetativno razmnožavanje (cijepljenje vegetativnog materijala na pripremljene podloge) u plasteniku te uzgoj, školovanje, njegu i zaštitu biljaka u rasadniku instituta. Navedeni postupci dovode do stvaranja genetski identičnih „novih stabala“ čime se omogućuje trajno zadržavanje starih, izvornih stabala na lokalitetima pojedinog kulturnog dobra.The Croatian Forest Research Institute (CFRI) has been involved in projects for the preservation of the gene pool of protected and significant trees in Croatia for more than 10 years. The importance of this projects has been recognized by numerous public institutions, local governments and nature conservation associations that want to preserve the genetic material of significant trees for future generations. In Croatia, there are numerous trees that have the historical, cultural and aesthetic value of a particular area, and some of them are on the list of protected trees. CFRI employees perform professional work related to the production of clonal material, which includes: root-stocks production (plants on which scions are grafted), scions collection (twigs from the mother tree), vegetative propagation (grafting of vegetative material on prepared root-stocks) in the greenhouse and the cultivation, schooling, care and protection of plants in the institute’s nursery. These procedures lead to the creation of genetically identical “new trees”, which allows the permanent retention of old, original trees in the localities of individual cultural assets

Micropropagation of Forest Tree Species in the Laborator for Plan Tissue Culture of the Croatian Forest Research Institute

Hrvatski šumarski institut od 2018. godine kroz Laboratorij za kulturu tkiva radi na razvitku protokola za mikropropagaciju najvažnijih i najugroženijih vrsta šumskog drveća u Republici Hrvatskoj. Sve intenzivnije klimatske promjene negativno utječu na stabilnost šumskih sustava, dok u isto vrijeme pogoduju pojavi novih, ali i pojačanom širenju već postojećih šumskih štetnika i patogena. Pronalazak i očuvanje superiornih genotipova koji bi mogli opstati u novonastalim okolnostima postaje sve važnije za očuvanje šuma, dok se uz pomoć mikropropagacije ovaj proces može višestruko ubrzati.Since 2018, the Laboratory for Plant Tissue Culture of Croatian Forest Research Institute has been working on the development of protocols for micropropagation of the most important and most endangered forest tree species in the Republic of Croatia. Increasing climate changes negatively affect forest systems stability, favouring the emergence of new and increasing the spread of existing forest pests and pathogens. Finding and preserving superior genotypes that could survive in the changed conditions is becoming increasingly important for forest conservation. By applying the micropropagation technique, this process can be accelerated any times

Research Projects of the Croatian Science Foundation on the Conservation of Genetic Resources and Dynamic of Fructification of Penduculate Oak (Quercus robur L.) and European Beech (Fagus sylvatica L.) in Croatia

Cilj rada je predstaviti dva istraživačka projekta Hrvatske zaklade za znanost pod naslovima „Očuvanje genetskih resursa šumskog drveća u svjetlu klimatskih promjena“ – ConForClim IP-2013-11-8131 i „Dinamika plodonošenja i očuvanja genofonda hrasta lužnjaka (Quercus robur L.) i obične bukve (Fagus sylvatica L.) u svjetlu klimatskih promjena“ – CropForClim IP-2018-01-8189. Oba projekta imaju za cilj na projektnim vrstama, hrastu lužnjaku i običnoj bukvi, istražiti genetsku varijabilnost i prilagodljivost sa svrhom davanja smjernica za poboljšanje i unapređenje očuvanja genetskih resursa. Projekti se provode na lokalitetima Hrvatskih šuma d.o.o. pod vodstvom dr.sc. Mladena Ivankovića, predstojnika Zavoda za genetiku, oplemenjivanje šumskog drveća i sjemenarstvo na Hrvatskom šumarskom institutu. Istraživački tim oba projekata čine znanstvenici sa Hrvatskog šumarskog instituta i Fakulteta šumarstva i drvne tehnologije Sveučilišta u Zagrebu, dok su na projektu ConForClim bili uključeni i znanstvenici sa Šumarskog instituta Baden-Württenberg i Katedre za fiziologiju drveća Instituta za šumarstvo koji je u sklopu Albert–Ludwigs Sveučilišta Freiburg.The aim of this paper is to present two research projects of the Croatian Science Foundation entitled „Conservation of genetic resources of forest trees in light of climate changes“ - ConForClim IP-2013-11-8131 and „Dynamic of fructification and conservation of genetic resources of pedunculate oak (Quercus robur L.) and european beech (Fagus sylvatica L.) in light of climate changes“ - CropForClim IP-2018-01-8189. Both projects aim to investigate genetic variability and adaptability on project species, pedunculate oak and european beech, with the purpose of providing guidelines for improving and advancing the conservation of genetic resources. The projects are being implemented at the sites of Croatian Forests Ltd. leading by Mladen Ivanković,PhD head of Division for genetics, forest tree breeding and seed science at Croatian Forest Research Institute (CFRI). The research team of both projects consists of scientists from the CFRI and the Faculty of Forestry and Wood Technology, University of Zagreb, while scientists from the Forest Research Institute Baden-Wuerttemberg and the Department of tree physiology at the Albert-Ludwigs-University Freiburg, were also involved in the ConForClim project

Variability of seed yield, seed and seedling traits from selected European beech (Fagus sylvatica L.) seed stands

Razumijevanje dinamike i varijabilnosti uroda šumskog drveća, uključujući i običnu bukvu (Fagus sylvatica L.), na brze promjene u okolišu postalo je vodeći izazov u gospodarenju šumama. Promjene u količini sjemena koje obična bukva proizvede variraju tijekom godina, a ovise o brojnim čimbenicima uključujući stanišne i vremenske uvjete tijekom prethodne i tekuće godine u kojima sjeme sazrijeva. Jedan od ciljeva ovog istraživanja bio je istražiti povezanost lokalnih AB (sažetak) meteoroloških uvjeta s dinamikom plodonošenja u četirima odabranim sjemenskim sastojinama obične bukve na području Uprava šuma podružnica Bjelovar, Karlovac, Ogulin i Požega. Procjena uroda sjemena prije opadanja vrlo je važna informacija za šumarsku operativu jer dostupna količina sjemena znatno utječe na planiranje obnove šuma. Stoga je drugi cilj istraživanja bio uspostaviti metodologiju vizualne procjene uroda za primjenu u gospodarenju šumskim sastojinama, odnosno utvrditi točnost vizualne procjene kategorijalnim ocjenama s postavljanjem zamki za sakupljanje sjemena, odnosno sjemenomjera. Količinska procjena uroda obične bukve obavljena je metodom sistematskoga postavljanja sjemenomjera i velikih mreža za sakupljanje čitavoga uroda pojedinog stabla. Cilj je bio utvrditi povezanost količine uroda i čimbenika poput visine i promjera stabala, veličine i kvalitete krošnje, kvalitete forme stabala te zdravstvenoga stanja stabla. Također, jedan od ciljeva bio je utvrditi kvalitetu sjemena odnosno istražiti utjecaj sadržaja vlage i veličine sjemena na klijavost i vitalitet sjemena te povezati klijavost s lokalnim vremenskim uvjetima u odabranim sjemenskim sastojinama. Rasadnički test potomstva osnovan je radi potvrde pretpostavke da istraživane sastojine posjeduju visoku razinu unutarpopulacijske genetske raznolikosti kao i da postoji genetska diferencijacija populacija. Rezultati istraživanja ukazuju da običnu bukvu karakterizira visoka varijabilnost u produkciji sjemena. Između godina u kojima je urod zabilježen, kao i između istraživanih ploha i stabala unutar plohe utvrđene su značajne razlike u intenzitetu uroda. Prevladavajući faktori koji su utjecali na pojavu i količinu uroda bili su lokalni meteorološki uvjeti, visina stabala te veličina i kvaliteta krošnje. Usporedba vizualne procjene intenziteta uroda i prikupljene količine sjemena ukazuje na potrebu za nastavkom monitoringa i razvijanja pouzdanije vizualne procjene uroda. Također, za buduća istraživanja predlaže se primjena različitih načina postavljanja sjemenomjera. Rezultati su pokazali da na kvalitetu sjemena utječu vremenski uvjeti u razdoblju prije sakupljanja sjemena. Razlike u kvaliteti sjemena, ovisno o godini uroda i između istraživanih populacija, mogle su se barem djelomično objasniti količinom oborina i temperaturama zraka, koje su utjecale na vlagu sjemena i time na njegovu klijavost. Analizom rasadničkoga testa s potomstvom iz odabranih sastojina utvrđena je visoka razina unutarpopulacijske genetske raznolikosti i genetska diferencijacija populacija za svojstvo početka listanja. Za svojstvo visinskoga rasta i prirasta utvrđena je značajna unutarpopulacijska raznolikost, dok genetske diferencijacije populacija nije bilo.Understanding the dynamics and variability of forest tree yields, including European beech (Fagus sylvatica L.), with regard to rapid environmental changes has become a major challenge for forest management. The variation in the amount of seeds produced by European beech fluctuates between years and depends on numerous factors including site and weather conditions during the year of seed maturation and the preceding year. One of the objectives of this study was to investigate the relationship of local meteorological conditions with the dynamics of seed yield in four selected European beech seed stands in the Forest Administration Bjelovar, Karlovac, Ogulin and Požega. Estimating seed yield before seedfall, is very important information for forestry operations because the amount of seeds available significantlyinfluences forest regeneration planning. Therefore, thesecond goal of the IV research was to establish a methodologyfor visual assessment of yield for application in forest stand management, namely, to determine the accuracy of visual assessment by categorical assessments by setting traps for seed collection, i.e., seed traps. Quantitative assessment of beech yield was performed using the method of systematic placement of seed traps and large nets to collect the entire yield of an individual tree. The aim was to determine the relationship between yield quantity and other factors, such as tree height and diameter, crown size and quality, tree shape quality, and tree health. Moreover, one of the goals was to determine the quality of seeds, namely, to investigate the influence of moisture content and seed size on seed germination and viability, and to examine the connection of germination and local weather conditions in the selected seed stands. The nursery progeny test was established to confirm the assumption that the studied stands possess a high level of intrapopulation genetic variation as well as the existence of genetic differentiation of populations. Theresults of the research show that European beech is characterized by high variability in seed production. Significant differences in the amount of seed yield were found between the years in which the yield was recorded, as well as between the examined plots and trees within the plot. The predominant factors influencing the occurrence and the amount of yield were local meteorological conditions, tree height, crown size and quality. A comparison of visual assessments of yield intensityand seed collection indicates the need to continue the monitoring and to develop a more reliable visual assessment of yield. Also, for future research, it is proposed to employ different methods of setting seed traps. The results showed that seed quality is affected by weather conditions in the period before seed collection. Differences in seed quality, depending on the year of seed yield and between the studied populations, could be at least partially explained by the amount of precipitation and air temperature, which affected seed moisture and, consequently, its germination. Analysis of the nursery progeny test with offspring from the selected stands revealed a high level of intrapopulation genetic variation and genetic differentiation of populations for the phenology trait. Significant intrapopulation variation was determined for the trait of height growth and increment, while there was no genetic differentiation of population

Variability of seed yield, seed and seedling traits from selected European beech (Fagus sylvatica L.) seed stands

Razumijevanje dinamike i varijabilnosti uroda šumskog drveća, uključujući i običnu bukvu (Fagus sylvatica L.), na brze promjene u okolišu postalo je vodeći izazov u gospodarenju šumama. Promjene u količini sjemena koje obična bukva proizvede variraju tijekom godina, a ovise o brojnim čimbenicima uključujući stanišne i vremenske uvjete tijekom prethodne i tekuće godine u kojima sjeme sazrijeva. Jedan od ciljeva ovog istraživanja bio je istražiti povezanost lokalnih AB (sažetak) meteoroloških uvjeta s dinamikom plodonošenja u četirima odabranim sjemenskim sastojinama obične bukve na području Uprava šuma podružnica Bjelovar, Karlovac, Ogulin i Požega. Procjena uroda sjemena prije opadanja vrlo je važna informacija za šumarsku operativu jer dostupna količina sjemena znatno utječe na planiranje obnove šuma. Stoga je drugi cilj istraživanja bio uspostaviti metodologiju vizualne procjene uroda za primjenu u gospodarenju šumskim sastojinama, odnosno utvrditi točnost vizualne procjene kategorijalnim ocjenama s postavljanjem zamki za sakupljanje sjemena, odnosno sjemenomjera. Količinska procjena uroda obične bukve obavljena je metodom sistematskoga postavljanja sjemenomjera i velikih mreža za sakupljanje čitavoga uroda pojedinog stabla. Cilj je bio utvrditi povezanost količine uroda i čimbenika poput visine i promjera stabala, veličine i kvalitete krošnje, kvalitete forme stabala te zdravstvenoga stanja stabla. Također, jedan od ciljeva bio je utvrditi kvalitetu sjemena odnosno istražiti utjecaj sadržaja vlage i veličine sjemena na klijavost i vitalitet sjemena te povezati klijavost s lokalnim vremenskim uvjetima u odabranim sjemenskim sastojinama. Rasadnički test potomstva osnovan je radi potvrde pretpostavke da istraživane sastojine posjeduju visoku razinu unutarpopulacijske genetske raznolikosti kao i da postoji genetska diferencijacija populacija. Rezultati istraživanja ukazuju da običnu bukvu karakterizira visoka varijabilnost u produkciji sjemena. Između godina u kojima je urod zabilježen, kao i između istraživanih ploha i stabala unutar plohe utvrđene su značajne razlike u intenzitetu uroda. Prevladavajući faktori koji su utjecali na pojavu i količinu uroda bili su lokalni meteorološki uvjeti, visina stabala te veličina i kvaliteta krošnje. Usporedba vizualne procjene intenziteta uroda i prikupljene količine sjemena ukazuje na potrebu za nastavkom monitoringa i razvijanja pouzdanije vizualne procjene uroda. Također, za buduća istraživanja predlaže se primjena različitih načina postavljanja sjemenomjera. Rezultati su pokazali da na kvalitetu sjemena utječu vremenski uvjeti u razdoblju prije sakupljanja sjemena. Razlike u kvaliteti sjemena, ovisno o godini uroda i između istraživanih populacija, mogle su se barem djelomično objasniti količinom oborina i temperaturama zraka, koje su utjecale na vlagu sjemena i time na njegovu klijavost. Analizom rasadničkoga testa s potomstvom iz odabranih sastojina utvrđena je visoka razina unutarpopulacijske genetske raznolikosti i genetska diferencijacija populacija za svojstvo početka listanja. Za svojstvo visinskoga rasta i prirasta utvrđena je značajna unutarpopulacijska raznolikost, dok genetske diferencijacije populacija nije bilo.Understanding the dynamics and variability of forest tree yields, including European beech (Fagus sylvatica L.), with regard to rapid environmental changes has become a major challenge for forest management. The variation in the amount of seeds produced by European beech fluctuates between years and depends on numerous factors including site and weather conditions during the year of seed maturation and the preceding year. One of the objectives of this study was to investigate the relationship of local meteorological conditions with the dynamics of seed yield in four selected European beech seed stands in the Forest Administration Bjelovar, Karlovac, Ogulin and Požega. Estimating seed yield before seedfall, is very important information for forestry operations because the amount of seeds available significantlyinfluences forest regeneration planning. Therefore, thesecond goal of the IV research was to establish a methodologyfor visual assessment of yield for application in forest stand management, namely, to determine the accuracy of visual assessment by categorical assessments by setting traps for seed collection, i.e., seed traps. Quantitative assessment of beech yield was performed using the method of systematic placement of seed traps and large nets to collect the entire yield of an individual tree. The aim was to determine the relationship between yield quantity and other factors, such as tree height and diameter, crown size and quality, tree shape quality, and tree health. Moreover, one of the goals was to determine the quality of seeds, namely, to investigate the influence of moisture content and seed size on seed germination and viability, and to examine the connection of germination and local weather conditions in the selected seed stands. The nursery progeny test was established to confirm the assumption that the studied stands possess a high level of intrapopulation genetic variation as well as the existence of genetic differentiation of populations. Theresults of the research show that European beech is characterized by high variability in seed production. Significant differences in the amount of seed yield were found between the years in which the yield was recorded, as well as between the examined plots and trees within the plot. The predominant factors influencing the occurrence and the amount of yield were local meteorological conditions, tree height, crown size and quality. A comparison of visual assessments of yield intensityand seed collection indicates the need to continue the monitoring and to develop a more reliable visual assessment of yield. Also, for future research, it is proposed to employ different methods of setting seed traps. The results showed that seed quality is affected by weather conditions in the period before seed collection. Differences in seed quality, depending on the year of seed yield and between the studied populations, could be at least partially explained by the amount of precipitation and air temperature, which affected seed moisture and, consequently, its germination. Analysis of the nursery progeny test with offspring from the selected stands revealed a high level of intrapopulation genetic variation and genetic differentiation of populations for the phenology trait. Significant intrapopulation variation was determined for the trait of height growth and increment, while there was no genetic differentiation of population

Variability of seed yield, seed and seedling traits from selected European beech (Fagus sylvatica L.) seed stands

Razumijevanje dinamike i varijabilnosti uroda šumskog drveća, uključujući i običnu bukvu (Fagus sylvatica L.), na brze promjene u okolišu postalo je vodeći izazov u gospodarenju šumama. Promjene u količini sjemena koje obična bukva proizvede variraju tijekom godina, a ovise o brojnim čimbenicima uključujući stanišne i vremenske uvjete tijekom prethodne i tekuće godine u kojima sjeme sazrijeva. Jedan od ciljeva ovog istraživanja bio je istražiti povezanost lokalnih AB (sažetak) meteoroloških uvjeta s dinamikom plodonošenja u četirima odabranim sjemenskim sastojinama obične bukve na području Uprava šuma podružnica Bjelovar, Karlovac, Ogulin i Požega. Procjena uroda sjemena prije opadanja vrlo je važna informacija za šumarsku operativu jer dostupna količina sjemena znatno utječe na planiranje obnove šuma. Stoga je drugi cilj istraživanja bio uspostaviti metodologiju vizualne procjene uroda za primjenu u gospodarenju šumskim sastojinama, odnosno utvrditi točnost vizualne procjene kategorijalnim ocjenama s postavljanjem zamki za sakupljanje sjemena, odnosno sjemenomjera. Količinska procjena uroda obične bukve obavljena je metodom sistematskoga postavljanja sjemenomjera i velikih mreža za sakupljanje čitavoga uroda pojedinog stabla. Cilj je bio utvrditi povezanost količine uroda i čimbenika poput visine i promjera stabala, veličine i kvalitete krošnje, kvalitete forme stabala te zdravstvenoga stanja stabla. Također, jedan od ciljeva bio je utvrditi kvalitetu sjemena odnosno istražiti utjecaj sadržaja vlage i veličine sjemena na klijavost i vitalitet sjemena te povezati klijavost s lokalnim vremenskim uvjetima u odabranim sjemenskim sastojinama. Rasadnički test potomstva osnovan je radi potvrde pretpostavke da istraživane sastojine posjeduju visoku razinu unutarpopulacijske genetske raznolikosti kao i da postoji genetska diferencijacija populacija. Rezultati istraživanja ukazuju da običnu bukvu karakterizira visoka varijabilnost u produkciji sjemena. Između godina u kojima je urod zabilježen, kao i između istraživanih ploha i stabala unutar plohe utvrđene su značajne razlike u intenzitetu uroda. Prevladavajući faktori koji su utjecali na pojavu i količinu uroda bili su lokalni meteorološki uvjeti, visina stabala te veličina i kvaliteta krošnje. Usporedba vizualne procjene intenziteta uroda i prikupljene količine sjemena ukazuje na potrebu za nastavkom monitoringa i razvijanja pouzdanije vizualne procjene uroda. Također, za buduća istraživanja predlaže se primjena različitih načina postavljanja sjemenomjera. Rezultati su pokazali da na kvalitetu sjemena utječu vremenski uvjeti u razdoblju prije sakupljanja sjemena. Razlike u kvaliteti sjemena, ovisno o godini uroda i između istraživanih populacija, mogle su se barem djelomično objasniti količinom oborina i temperaturama zraka, koje su utjecale na vlagu sjemena i time na njegovu klijavost. Analizom rasadničkoga testa s potomstvom iz odabranih sastojina utvrđena je visoka razina unutarpopulacijske genetske raznolikosti i genetska diferencijacija populacija za svojstvo početka listanja. Za svojstvo visinskoga rasta i prirasta utvrđena je značajna unutarpopulacijska raznolikost, dok genetske diferencijacije populacija nije bilo.Understanding the dynamics and variability of forest tree yields, including European beech (Fagus sylvatica L.), with regard to rapid environmental changes has become a major challenge for forest management. The variation in the amount of seeds produced by European beech fluctuates between years and depends on numerous factors including site and weather conditions during the year of seed maturation and the preceding year. One of the objectives of this study was to investigate the relationship of local meteorological conditions with the dynamics of seed yield in four selected European beech seed stands in the Forest Administration Bjelovar, Karlovac, Ogulin and Požega. Estimating seed yield before seedfall, is very important information for forestry operations because the amount of seeds available significantlyinfluences forest regeneration planning. Therefore, thesecond goal of the IV research was to establish a methodologyfor visual assessment of yield for application in forest stand management, namely, to determine the accuracy of visual assessment by categorical assessments by setting traps for seed collection, i.e., seed traps. Quantitative assessment of beech yield was performed using the method of systematic placement of seed traps and large nets to collect the entire yield of an individual tree. The aim was to determine the relationship between yield quantity and other factors, such as tree height and diameter, crown size and quality, tree shape quality, and tree health. Moreover, one of the goals was to determine the quality of seeds, namely, to investigate the influence of moisture content and seed size on seed germination and viability, and to examine the connection of germination and local weather conditions in the selected seed stands. The nursery progeny test was established to confirm the assumption that the studied stands possess a high level of intrapopulation genetic variation as well as the existence of genetic differentiation of populations. Theresults of the research show that European beech is characterized by high variability in seed production. Significant differences in the amount of seed yield were found between the years in which the yield was recorded, as well as between the examined plots and trees within the plot. The predominant factors influencing the occurrence and the amount of yield were local meteorological conditions, tree height, crown size and quality. A comparison of visual assessments of yield intensityand seed collection indicates the need to continue the monitoring and to develop a more reliable visual assessment of yield. Also, for future research, it is proposed to employ different methods of setting seed traps. The results showed that seed quality is affected by weather conditions in the period before seed collection. Differences in seed quality, depending on the year of seed yield and between the studied populations, could be at least partially explained by the amount of precipitation and air temperature, which affected seed moisture and, consequently, its germination. Analysis of the nursery progeny test with offspring from the selected stands revealed a high level of intrapopulation genetic variation and genetic differentiation of populations for the phenology trait. Significant intrapopulation variation was determined for the trait of height growth and increment, while there was no genetic differentiation of population

Seed Quantity and Quality Variation in European Beech (Fagus sylvatica L.): A Comparative Analysis of Different Crop Years

European beech (Fagus sylvatica L.) is characterized by inter-annual cycles of seed production (masting), with synchronized high seed production between sites in some years. The importance of both seed quantity and quality monitoring stems from its role in sustaining the ecological balance, promoting biodiversity, and ensuring the long-term viability of forest ecosystems. This study aimed to (1) describe seed production from 2015 to 2022, (2) identify the potential factors that could affect the yield appearance and seed quantity, and (3) compare the quality of beechnuts from different crop years in Croatia. At each of the six forest seed objects located in the area of forest administrations Bjelovar, Karlovac, Ogulin, Požega, and Delnice, we selected 5 trees for seed collection. Seeds were collected with large PVC nets covering total projection area of the tree crowns. Seed quality testing was performed according to the International Rules for Seed Testing (ISTA Rules). Our results indicate a consistent biennial beechnut cycle. The crop was completely absent in 2015, 2017, 2019 and 2020, while 2016, 2018, 2020 and 2022 were fruitful years. Weather plays a key role in triggering masting. We found that beechnut production is influenced by summer weather conditions (from June to August) in the previous two years. Abundance of beechnut production varies on an annual level, population level and on individual trees. Factors that partially explain the variability in yield are tree height and crown size. No significant differences in viability were found across different years and sites, though the results should be approached with caution due to limited sample representation. The study identified a positive correlation between seed weight and viability, as well as the impact of precipitation on moisture content. The results emphasize the need for continued monitoring and further research to understand the factors influencing beechnut production and quality, crucial for sustainable forest management in the face of climate change