Selection of the optimal spatial resolution of image-based digital surface models for use in forestry—example from the area of Lowland oak forests [Odabir optimalne prostorne rezolucije fotogrametrijskih digitalnih modela površine za primjenu u šumarstvu-primjer s područja nizinskih šuma hrasta lužnjaka]
Balenovic I.,Hrvatski sumarski institute |
Marjanovic H.,Hrvatski sumarski institute
Nova Mehanizacija Sumarstva | Year: 2016
In recent years, digital aerial photogrammetry has emerged as an alternative method to airborne laser scanning in three-dimensional modelling of forest areas, especially for the generation of digital surface models (DSMs). In forest inventory, DSM is usually used in combination with the corresponding digital terrain model for the generation of canopy height model (CHM), which is then used as a basis for deriving various tree and forest attributes. The main aim of this research was to examine the vertical accuracy of DSMs of different spatial resolutions over the forest area, and with new findings contribute to the application of digital photogrammetry in forest science and practice. For that purpose, DSMs with spatial resolution (pixel size) of 0.3 m (DSM0.3), 0.5 m (DSM0.5), 1 m (DSM1), 2 m (DSM2) and 5 m (DSM5) were generated by image matching of digital aerial images for the area of lowland pedunculate oak forests (management unit Kunjevci, Forest Administration Vinkovci). The vertical accuracy of DSMs was evaluated by comparing manually stereo measured elevations of 294 tree tops with the elevations of planimetrically corresponding DSMs points. As expected, the highest accuracy was obtained for DSM0.3 (root mean square error, RMSE = 0.76 m; mean error, ME =-0.03 m). Almost equal accuracy was obtained for DSM0.5 (RMSE = 0.76 m; ME =-0.05 m) and DSM1 (RMSE = 0.76 m; ME =-0.07 m), slightly lower for DSM2 (RMSE = 0.84 m; ME =-0.16 m), whereas the lowest accuracy was obtained for DSM5 (RMSE = 1.31 m; ME =-0.54 m). The accuracy comparison showed that the decreasing of spatial resolution (pixel size) of raster based DSMs from 0.3 m to 1 m, does not significantly affect their vertical accuracy. With further decreasing of spatial resolution to 2 m, and especially to 5 m, the vertical accuracy of DSMs also decreases. In the light of the obtained results, further studies should be focused on research of possibilities of application of DSMs of different spatial resolution in forest inventory, namely: DSM0.3 and DSM0.5 for obtaining information at tree level, DSM0.5 and DSM1 at plot level, and DSM1, DSM2 and DSM5 at stand level. © 2016, University of Zagreb. All rights reserved.
Matosevic D.,Hrvatski Sumarski Institute |
Pajac Zivkovic I.,University of Zagreb
Sumarski List | Year: 2013
Alien species are defined as species living outside of their natural range and outside of their natural dispersal potential. When an alien species enters a novel environment and has negative ecological and economical impact it becomes invasive species. Alien species are considered as one of the major threats to biodiversity after habitat destruction and enormous damage is done by them to ecosystems and economies. They have been described as an outstanding global problem. Economic damages associated with alien species in several countries in the world amount to about 5 % of the world GNP. Numerous alien insect species, many introduced only in the last 200 years, have become successfully established in various ecosystems in Europe, 1541 species of alien invertebrates are already present, 94 % of them are arthropods and 90 % of them are insects. More than half of the alien invertebrates are phytophagous (52 %) and 30 % of them infest trees and shrubs. Basic knowledge of the identity, origin, pathway, time of introduction of alien species is essential for assessing the threats from alien species and the first requirement when assessing the impact of alien species on ecosystems is to make an alien species inventory of a certain territory or country. Such studies are needed to assess which taxonomic or bio-ecological groups of alien insects are more successful invaders or more harmful to environment and economy. Croatia lacks such an inventory. Even though Croatia was included in most recent and comprehensive study of alien terrestrial arthropodes in Europe, Croatian references with first records were totally missing. There is no up-to-date list of phytophagous alien insect species on woody plants in Croatia. The aim of this paper is to provide up-to-date comprehensive list of known phytophagous alien insect and mite species on woody plants in Croatia with all relevant Croatian references. The starting point for compiling the list of alien species of phytophagous insects on woody plants in Croatia was a book "Alien Terrestrial Arthropodes of Europe" and database DAISIE. These are primary online resources on alien insect species available to the public and first qualified reference system on invasive alien species for the European region. We compiled the list by searching many sources of forestry, agricultural and taxonomic entomological peer-reviewed literature in Croatia, checklists and primary research publications on alien insect species. The references in these sources were examined for additional relevant publications. A total of 101 phytophagous alien species (98 insect species from 6 orders and 3 mite species form subclass Acarina) on woody plants were recorded (Table 1) and they are already present in Croatian entomofauna. They were dominated by Hemiptera (56.4 %), Lepidoptera (14.9 %), Hymenoptera (12.9 %), followed by Diptera (5.9 %) and Coleoptera (5.9 %), Acarina (3 %) and T ysanoptera (1 %)(Figure 1). One third (33.7 %) of the alien species in Croatia originate from Asia, 26.7 % from North America while 12.9 % are of tropical origin (Figure 2). From the 101 established alien insect species in Croatia, an increase in the number of introductions can be noted in the first decade of 21st century (Figure 3). Agricultural lands are the most frequently invaded habitats by alien phytophagous insects in Croatia (56.4 %), followed by parks and gardens (28.7 %) and woodlands and forests (14.9 %)(Figure 4). Order Hemiptera clearly dominates as it includes some of the most successful invaders (57 %) on woody plants in Croatia. Similar results were obtained at a country level for Hungary, Great Britain, Italy, Slovenia and Europe in general. T is outcome can be attributed to the fact that species of this order remain undetected and are easily transported due to their tiny size in concert with the intensive trade in agricultural commodities. The occurrence of other orders (Lepidoptera 14 %, Hymenoptera 13 %, Diptera 6 %, Coleoptera 6 %, and T ysanoptera 1 %) is slightly different from other European countries. Results from several investigations have shown strong positive correlations between the number of alien insects per European country and the volume of manufactured and agricultural imports, road network size, the GDP and the geographic size. In contrast, alien species richness was not correlated with the total or percentage of forest cover. The number of alien insects is positively correlated with country surface area, and bordering the sea does not influence the number of alien insect species which is quite important for Croatia. There is a strong correlation between the number of alien insect species and the total amount of imports and level of international trade of the country. It can be predicted that the number of established alien insect species will grow as Croatia shows constant increase of traded commodities with other European and non-European countries. In this review we have listed alien insect species that have not yet been recorded for Croatia on European level. These are Oxycarenus lavaterae; Massilieurodes chitendeni; Adelges (Dreyfusia) nordmannianae; Pineus (Eopineus) strobi; Protopulvinaria pyriformis; Dryocosmus kuriphilus; Platygaster robinae; Aproceros leucopoda; Rhyzobius lophanthae; Rodolia cardinalis; Harmonia axyridis; Xylosandrus germanus; Caloptilia roscipennella; Caloptilia azaleella; Phyllocnistis citrella; Argyresthia thuiella; Cydalima perspectalis; Dasineura gleditchiae; Ceratitis capitata; Rhagoletis cingulata and Drosophila suzukii. Some of them are novel and only recently introduced alien species whereas some of them are present for decades in Croatia but due to the lack of a comprehensive and regularly updated inventory of alien species they have not been listed before. T is also makes this up-to-date list of alien phytophagous insects in Croatia valuable. Our results have shown that Asia is the main region of origin of alien insects established in Croatia (33 %), followed by North America (27 %). The trends are similar in other European countries and Europe in general. A rapid increase in the number of new alien species introduction per year in Croatia is noticeable from the years 2007-2012 (6.4 species/year) compared to 2002-2007 (1.8 species/year) (Figure 3). In Europe, an average of 17.5 new species of insects per year was recorded between 2000 and 2007, while this value was only 8.1 from 1950 to 1974. In Europe twice as many new insect species were observed per year on trees and shrubs during the period 2000-2007 (6.3 species) compared to 1960-1979 (3.4 species). The differences between the number of new alien species/year in Europe and Croatia are probably due to differences in sampling efforts, country surface, volume of traded goods etc but the rapidly increasing trend is obvious. More than 80 % of alien insect species in Croatia (57 % on agricultural lands and 28 % in parks and gardens) have been established in man-made habitats (Figure 4). Only 15 % of alien insect species in Croatia have established themselves in natural environments (forests and woodlands) which is almost the same percentage as on European level. It is a common observation that simple, disturbed, man-made habitats are more easily invaded by insects and other invaders than complex, undisturbed, natural habitats. Alien insects linked to human environments and activities (e.g. ornamental plants, bonsais, seeds, large potted trees, cut flowers, vegetables, fruits) are more likely to be carried by human transports into a new region than insects living in natural areas. A study has shown that bonsais carry a more diverse alien insect fauna then timber and that ornamental plants constitute "miniature" ecosystems which may host a large variety of insects that have the potential to damage other woody plants as well. Almost 90 % of alien invertebrates in Europe were introduced unintentionally through human activities, mostly as contaminants of a commodity. In Europe, ornamental plant trade contributes significantly more than forestry products to the invasion of alien forest insects. As interception data have not been analysed in this paper, a research of such data for alien insect species and trade volumes in horticultural plants in Croatia isstrongly needed. There is a strong suspicion that ornamental plants are one of main pathways of introduction of alien insects to Croatia due to the increase of the imported volumes from year to year. Alien insect species are known for being serious pests worldwide and they can impact habitats which they invade in several ways. Alien insects can affect native biodiversity through direct actions: phytophagous insects feeding on plants, a predator or a parasitoid attacking host, an alien species hybridizing with a native species or indirect actions: vectoring diseases, competing for food, or sharing natural enemies with native species. T is research has shown that dangerous pests that can cause direct economic costs have invaded and are spreading in Croatia (Table 1). Due to high percentage of alien insect on agricultural lands (outdoor and in glasshouses) in Croatia (Figure 4) the yield losses of alien insect species on agricultural crops in Croatia must be considerable. Alien insects can have serious negative impact on forests, woodlands and urban parks. Some potentially damaging forest and urban pests have already established themselves in Croatia. In countries where the percentage of forest cover is high (Croatia around 44 %) the damage from alien insects is expected to be considerable. Most introductions of alien insects are unintentional and unpredictable.
Matosevic D.,Hrvatski Sumarski Institute |
Melika G.,Budapest Pest Diagnostic Laboratory
Sumarski List | Year: 2012
Leaf miners support rich parasitoid assemblages and majority of these parasitoid species are generalists. Alien and invasive species are global problem and pose direct and indirect threat to ecosystem stability. Leafminers are very successfull invaders and they build up their populations soon aft er establishment in an new area. Invaders escape from their native parasitoids and have competitive advantage over native species in new area. Native parasitoids adapt to new host and new parasitoid assemblages are established. Croatia has rich native leafminer fauna with recently added alien and invasive species. Phyllonorycter roboris, Phyllonorycter quercifoliella, Tischeria ekebladella on Quercus robur and Q. petraea, Phyllonorycter klemannella on Alnus glutinosa are native leafminers. Phyllonorycter robiniella, Parectopa robinella on Robinia pseudoacacia, Phyllonorycter platani on Platanus sp., Cameraria ohridella on Aesculus hippocastanum and Phyllonorycter leucographella on Pyracantha coccinea are recently introduced invasive species in Croatia. In this research we tested the following hypotheses: a) native parasitoids have adapted to new hosts, b) these parasitoid species are generalists, c) native and alien species of leafminers with similar bioecological characteristics have similar parasitoid assemblages. The sites of research were chosen according to the host plant sites, in forests and parks in Croatia. The research was carried out from 2004-2006. Leaves with mines were collected and kept in glass containers in outside insectary until emergence of parasitoids. For each parasitoid assemblage the diversity indices were calculated: Domination index (D), Shannon's diversity index H and evenness of species E. Cluster analyses for comparison of similarities of parasitoid assemblages was done. In total, 28 taxa of parasitoids from the superfamily Chalcidoidea and 4 taxa from the superfamily of Ichneumonoidea have been found (Table 1). Table 1 shows domination index (D) for parasitoid species found for a host leaf miner. Th is research compares the parasitoid assemblages of diff erent species of leafminers, the results have been obtained aft er mass rearings of parasitoids from diff erent localities and diff erent collection times and it does not give detailed insight into parasitism percentages and the seasonal distribution of parasitoid species within a parasitoid assemblage. Table 2 shows values of Shannon's diversity index H and evenness of species E, and Figure 1 shows dendrogram from cluster analyses grouping leaf miner species according to the similarities of their parasitoid assemblages. The majority of parasitoid species found are generalist species found on other species of leaf miners from the order Lepidoptera. P. roboris/P. quercifoliella have the most diverse parasitoid assemblage (the highest H value) (Table 2) followed by T. ekebladella. Oaks support rich fauna of taxonomicaly and ecologicaly similar leaf miner species and free exchange of parasitoids is enabled among them. All the parasitoid species found on these leafminers are generalist. They also have the highest E value (Table 2) because they lack specifi c monophagous parasitoid species. P. klemannella has lower diversity indices H and E because of the dominance of specifi c parasitoids from Encyrtidae family. P. platani has two dominant parasitoid species Minotetrastichus platanellus and Pediobius saulius. Dendrogram shows that P. roboris/P. quercifoliella, P. robiniella, P. leucographella, Pa. robiniella i T. ekebladella have similar parasitoid assemblages. Very similar are T. ekebladella and Pa. robiniella, both host species grow on the same sites together (oak and black locust) and generalists can search for similar mines: white upper surface leaf mines. The greater linkage distance between P. klemannella i P. platani can be explained with the dominance of specifi c monophagous parasitoid species in the assemblage. The similarities between parasitoid assemblages of native (P. roboris/P. quercifoliella, T. ekebladella) and alien (P. leucographella, P. robiniella, Pa. robiniella, C. ohridella) leaf miner species show that the native generalist parasitoids have adapted to new hosts. Ten species of parasitoids have been found on C. ohridella, with Pediobius saulius and Minotetrastichus frontalis as two dominant species (Table 1). Th is research has shown that invasive leaf miner species in Croatia have recruited a parasitoid community similar to the native leaf miner species and that this process has occurred quite rapidly.
Matosevic D.,Hrvatski Sumarski Institute |
Pernek M.,Hrvatski Sumarski Institute
Sumarski List | Year: 2011
Alien species are intentionaly or unintetionaly introduced species into new area. When an alien species succefully invades and impacts a new ecosystem it becomes an invasive species. Until today, 109 invasive insects on woody plants (57 from North America, 52 form Asia) have been introduced and established in forest ecosystems in Europe (MATTSON et al. 2007). Introduction and dispersal of new species is increasing from year to year due to globalization of trade and ever increasing tourist traffic between continents. The aim of this research was to identify most important alien and invasive insect species in Croatian forests and give an estimate od their damage and prognosis of their future spread. The research has lasted for 5 years (2006 to 2010) and potential host plants in continental, submediterranean and mediterranean parts of Croatia were researched. For each invasive species found a prognosis for their future spread and damages is given according to their biology, ecology, researches on natural enemies and data from the literature. Seven (7) insects species from the orders Lepidoptera, Hymenoptera, Diptera and Hemiptera were found and they can be cosidered as alien or invasive species in Croatian forest ecosystems (Table 1). For each insect species a host plant, locality where the insect was found and prognosis of damage on the scale from 1 to 4 (1-no influence on host plant, 4-serious forest pest) is given. Parectopa robiniella, Phyllonorycter robiniella, Phyllonorycter issiki, Obolodiplosis robiniae, Leptoglossus occidentalis, Metcalfa pruinosa, Dryocosmus kuriphilus are alien or invasive insects established in Croatian forests. Introduction and spread of these species and their intensity of occurence has been very similar to the same pattern of spread and occurence in other Europaean countries. Several other invasive species on woody ornamental plants in urban areas have also been recorded in Croatia: Phyllonorycter leucographella, Dasineura gleditchiae, Argyresthia thuiella, Cameraria ohridella, Anoplophora chinensis. Knowledge on insect origin, biology, ecology, pathways of introduction and spreading are very important for providing pest risk analysis and making relevant prognosis of dangers that a new pest is posing for forest ecosystems.
Past, present and future of application of remote sensing methods in Croatian forest inventory [Prošlost, sadašnjost i budućnost primjene metoda daljinskih istraživanja pri inventuri šuma u Hrvatskoj]
Benko M.,Hrvatski Sumarski Institute |
Balenovic I.,Hrvatski Sumarski Institute
Sumarski List | Year: 2011
Making correct decision in forest management is based on the quality of the collected information. Collection information from forests is the main task of the forest inventory. Due to the rapid development of technology, in the second half of the 20 th century, there have been major changes in the way of data collection, particularly in developed countries. In addition to conventional terrestrial methods of data collection, data on forests is increasingly being collected with remote sensing methods. Using remote sensing methods leads to reducing the scope of the fieldwork, and opens the possibility of saving time and money. In this paper was given the review of previous research and results of application of remote sensing methods in Croatian forest inventory. Previous researches presented in this paper will give insight into the current status and role of remote sensing in Croatian forest inventory, and along with some new findings may serve as guidelines for future research and application of new methods of remote sensing in forest inventory. Various researches about applicability of remote sensing methods in forest inventory operations, primarily on aerial photographs and more recently on satellite images, were conducted in Croatia in the last 30 and more years. In all previous studies of forest damage assessments with photointerpretation on CIR aerial photographs it was proved that this method is to be equally in comparison with terrestrial methods regarding to accuracy, and much more efficient regarding to achieved speed and objectivity. Methodology suitable for operational use in inventory of forest damage was made. Periodic inventories of forest health with using remote sensing methods enable easy monitoring of changes of forest between two inventories, identification of new foci of dying trees or other damage, which is especially important in today's changed and altered environmental conditions. Forest management inventory requires information of greater accuracy. Therefore, aerial photographs of higher spatial resolution have more important applications in relation to satellite imagery in forest management inventory. Some researches of using aerial photographs for photogrammetric measurements of stands parameters shown in this paper gave good results. Despite the above, the application of remote sensing methods in practical forest inventory has not been sufficiently utilized. Development of digital photogrammetry and 'new' remote sensing methods and systems such as lidar, and improving existing ones, increasing the possibilities and scope of remote sensing methods. Therefore is necessary to continuously monitor the latest developments and explore new additional possibility of their application in forest inventory.
Phenotypic stability and adaptability of families of common walnut (Juglans regia L.) in progeny tests [Fenotipska stabilnost i adaptabilnost familija običnog oraha (Juglans regia L.) u testovima potomstava]
Littvay T.,Hrvatski Sumarski Institute
Sumarski List | Year: 2011
Common walnut (Juglans regia L.) belongs to the most important tree species in the world. With the origin in central Asia it is widespread worldwide except in tropical and subtropical regions. Its broad applications in nourishment, medicine, pharmacology and food processing, wood and leather industry makes it one of the most valuable plant species. The distribution of common walnut in Croatia is more a result of favorable climatic and soil conditions than the organized cultivation. In Croatian common walnut is mostly spread in the hilly terrains around Hrvatsko Zagorje around Požega, Koprivnica, Bjelovar, Daruvar, Kutina, Sisak, Jastrebarsko Ozalj; in Eastern Slavonia around Vukovar and Ilok in Baranja. In Dalmatia around Split, Drniš, and Zadar hinterland, in Primorje in the hinterland of Novi Vinodolski, Crikvenica, Senj, in Istria and part of Herzegovina. This paper presents the results of work on the selection of individual trees and the establishment of halbsib-progeny tests, over the five-year research of quantitative and morphometric traits in progeny tests of common walnut, tested in two habitats. Research sites are located at two locations that were most suitable for testing due to the ecological and soil characteristics of selections in continental part of Croatia. These sites are: Zabrdica, under forestry office Sokolovac and Kozarevac I under the forestry office Kloštar Podravski. The study of interaction between heritage and environment is based on the assumption that environment must be controlled (similar growing conditions) and phenotypes must be known, as done in these experiments, devoting the special attention to environmental factors. In such planned and conducted experiments, relationship between genotype and environment can be studied through so-called phenotypic stability. Analysis of phenotypic stability of common walnut families in the localities (habitats) was conducted in the model of regression analysis in which the phenotypic values (growth and fruit mass) of specific families are shown as a linear function of the environment. For the independent variable it is selected the mean value of the corresponding phenotypic characteristic of families, ie diameter growth and fruit mass of the center tree at the locality. Results are listed in Table 1, 2 and shown in Figure 4, 5. Below average growth stability and specific adaptability to high-yield environment (Zabrdica) showed families Stain 2, 4 and 6, while Stains 12, 13 and 18 showed above average stability and specific adaptability to adverse environment (Kozarevac I). Other families showed the average stability and good adaptability to all environments (Zabrdica and Kozarevac I) (Table 1 and Figure 4). Below average fruit mass stability and specific adaptability to high-yield environment (Kozarevac I) showed only Stain 16, while Stains 1, 3, 4, 6, 15, 17, and 18 showed above average stability and specific adaptability to adverse environment (Zabrdica). Other families showed the average stability and good adaptability to all environments (Zabrdica and Kozarevac I) (Table 2 and Figure 5). Based on adaptation capacity and production potential of the particular genotype can be determined its use-value for plantation raising. Genotypes with good adaptation ability and high productivity are the best solution for growing the common walnut in plantations. The research results provide a good basis for creating the Croatian variety of walnut same as the opportunities for permanent preservation of genetic resources for the common walnut.
Ostoic S.K.,Hrvatski sumarski Institute |
Vuletic D.,Hrvatski sumarski Institute
Sumarski List | Year: 2016
Ecosystem services including forest ecosystem services are hot topic globally among scientists and practitioners for decades. In Croatia there is a long tradition of discussing forest ecosystem services in terms of how to systemise them, assess and value, as well as how to secure payment for their provision. However, literature review showed discrepancy between scientific and professional production and importance of this topic for forestry sector in Croatia. This is especially a fact when it comes to research related to citizen perceptions and attitudes and whether they are informed about the topic. Therefore, the purpose of this paper is to analyse the role of information in better understanding of the topic with the assumption that being informed leads to better understanding of the topic. Survey questionnaire was applied on the sample of three student populations of the University of Zagreb - Faculty of Forestry (FoF), Faculty of Mechanical Engineering and Naval Architecture (FMENA) and Centre for Croatian Studies(CCS) (Table 1). The hypothesis was made that respondents from FoF would have better understanding of the topic since they are more informed through their study programme in comparison to respondents from other two faculties. The sample was purposeful and convenient at the same time, and included 247 respondents. Statistical Package for Social Sciences (SPSS) was used for statistical data analysis that included Chi-square and Kruskal-Wallis non-parametric tests beside descriptive statistics. Results showed that respondents from FoF in their own opinion were more informed about the topic of forest ecosystem services and payment for ecosystem services in comparison to respondents from other faculties (Figures 1 and 2). However, questions concerning their actual knowledge on the topic showed that even them had problems with recognising forest ecosystem services and purposes of the payment for forest ecosystem services (Tables 2 and 4). However, there was always statistically significant difference in answers between respondents from FoF and other two faculties (Table 3). When asked about who has the obligation to pay for forest ecosystem services respondents provided various answers, while only 29.2% of respondents from FoF, 9.9% of respondents from FMENA and 15.2% of respondents from CCS provided correct answer to this question (Figure 3). Similarly respondents were asked about the institution responsible for distribution of resources collected as payment for forest ecosystem services. Correct answer was given only by 41.5% of respondents from FoF, 26.8% from FMENA and 19.7% from CCS (Figure 4). Furthermore, respondents were asked to express their agreement with four statements related to payment for forest ecosystem services in terms of purposeful and transparent money spending, whether it contributes to the better state of forests in Croatia or it should be abolished (Figures 5-9). Results showed that rather high share of respondents does not have opinion, especially respondents from FMENA and CCS. The conclusion is that information has a role in better understanding of the topic of forest ecosystem services, but there are probably other factors that were not included in this research. In future it is important to continue studying understandig and attitudes of various segments of citizens. The purpose of these studies would be to contribute to creation and implementation of proper forest policy instruments that would help in better understanding of the topic and eliciting positive attititude towards forestry activities related to forest ecosystem services by citizens.
Matosevic D.,Hrvatski Sumarski Institute |
Pernek M.,Hrvatski Sumarski Institute |
Hrasovec B.,University of Zagreb
Sumarski List | Year: 2010
Oriental chestnut gall wasp (Dryocosmus kuriphilus Yatsumatsu) (Hymenoptera: Cynipidae) is new invasive species in Europe and important pest on sweet chestnut (Castanea sativa Mill.). It is on quarantine species lists in Europe as well as in Croatia. The species originates from China and it was first introduced to Europe to Italy in 2002. It has also been recorded in Slovenia, France, Hungary and Switzerland. In May 2010. it was recorded in Croatia for the first time. Oriental chestnut gall wasp has one generation per year (Figure 1). Adult wasps (only females are known) emerge from galls from mid June until the end of July and lay eggs in the buds. The wasp overvinters as early larval instar in buds and cannot be detected without large magnification lense. In spring when new shoots and leaves emerge the galls develop on the leaf midveins (Figure 2) or shoots. The galls, 5-20 mm in diameter, contain one or usually several chambers with white larvae, later pupae. Young galls are green, later rose-coloured and can be easily detected on sweet chestnut shoots. Old galls are brown, woodlike and remain attached to the tree up to two years (Figure 3). The spread of oriental gall wasp occurs mainly by transport of infected plant material (scions for grafting, plants for planting) into new areas. Locally, the wasps spreads by active flight or passive (aided by wind or human dispersal) transport. The galls disrupt twig growth and reduce fruiting. Various authors consider it as a seroius pest on sweet chestnut trees. Several control measures against this pest have prooved themselves uneffective. Pruning of infested shoots can be done in small orchards but this method is uneffective in forests. Some parasitoid species, e.g. Torymus sinensis, can reduce populations of oriental chestnut gall wasp and this species has already been introduced as biological control agent in Japan, Korea and Italy. Oriental sweet chestnut gall wasp was first recorded in Croatia on 21 May 2010 in Lovran and after that in several other sweet chestnut forests (Table 1, Figure 5). According to the number of galls per shoot it can be estimated that on the localities Lovran, Samobor and Ozalj (single galls per leaf/shoot) the pest has recently been introduced. Localities in Zagreb had high infestation rates (numerous galls per leaf/shoot) and it can be estimated that the pest is here present since 2007 or 2008. The spread forecast for Croatia for the following years is given. Intensive spread can be expected in all areas where sweet chestnut is grown, lower intensity in Istria, surroundings of Karlovac and Banija, and much higher intensity and quicker spread in Zagreb area, Hrvatsko zagorje and Samoborsko gorje. The trasport of infested planting material to uninfected zones (region of hills in Slavonia) shoudbe strongly avoided.
The influence of powdery mildew (Microsphaera alphitoides Griff. et Maubl.) on growth and survival rate of Oak seedlings [Utjecaj pepelnice (Microsphaera alphitoides Griff. et Maubl.) na rast i preživljenje Hrastova ponika]
Liovic B.,Hrvatski Sumarski Institute
Sumarski List | Year: 2011
Powdery mildew as plant disease caused by the fungus species Microsphaera alphitoides Griff et Maubl., has major impact in process of oak trees dieback. Most threatened are seedlings and saplings. Experiences from professionals in last few decades proved that within the habitat of Pedunculate oak, powdery mildew is one of important factors that affects survival rate of oak's saplings, therefore rejuvenation of oak forests. Although fungus highly pathogenic, the researches of its influence on development and dieback of saplings in order to justify the investments in protection are relatively few. The researches targeted to determine the level of dependence between the height increment and diameter increment in relation with the survival rate of seedlings and the intensity of contamination caused by mildew, are set on research plots according to the block distribution in fenced surfaces, under the Forest District Bjelovar of the Croatian Forests Ltd. The experiment is set on the same model also in the Croatian Forest Research Institute's nursery. The acorns collected were treated with fungicides and sawn in rows in fenced surface. In experiment two variants were tested in four repetitions; seedlings treated with anti-mildew fungicides and seedlings without any protection. After germination in one-month intervals the plots were cleaned from weed and the height increment was measured, whilst based on the surface of leaves covered with mycelia the infection caused by powdery mildew was estimated on 50 leaves sample in every plot. Fungicides were applied every 15-20 days depending of weather conditions. For the protection three fungicides were used: Artea 330 EC (0.5 l/ha), Anvil 5 SC (0.5 l/ha) and Punch 10EW (0.3 l/ha) all with 250 l/ha of water and 0.2 % Sandovit surfactant. Fungicides were used in forest nurseries seven times and five times in forest. The intensity of photosynthesis was measured on infected and non-infected leaves with portable gas-exchange system Li-Cor LI-6400. On seedlings treated with fungicides at 10.00 hours was measured 8,31 μmol of CO2 m-2s-1 while at 14.00 hours was measured 6,76 CO2 m-2s-1. On infected seedlings at 10.00 hours was measured significantly lesser value 5,38 μmol of CO2 m-2s-1 while at 14.00 hours 3,75 CO2 m-2s-1. The research results show the direct relationship between the infestation by powdery mildew and the intensity of photosynthesis with the height increment and the survival rate of seedlings. This relationship is particularly denoted inside the forest, under the canopy where average height of seedlings (Graf 4) is significantly lesser at the infected seedlings (22,62 cm) compared with the seedlings treated by fungicides (25,57 cm). At the infected seedlings appeared massive defoliation 12 days earlier than at the uninfected. The survival rate of infected seedlings (Graf 7) in the forest at the end of the 1st year is 78 % while the survival of treated seedlings is 94 %. In opposition inside the nursery (Graf 5) the infected plants have average height of 24,82 cm at the end of first vegetation, while treated are relatively smaller 22,56 cm. The survival rate in the nursery (Graf 6) is approximately equal in both treatments, at the infected seedlings 92 % comparing to 95,5 % at the uninfected.
Vrbek B.,Hrvatski Sumarski Institute
Sumarski List | Year: 2013
In the Croatian Forestry Institute a collection of monoliths of the most important forest soils was produced during the period from 2011 to 2013. The collection was made by means of a new method of attachment and preparation with the use of epoxy resin. Aft er digging the pedological pit, the profile is prepared and a prism of soil, measuring 20 cm × 100 cm and 5 cm thick, is made. With a sharp tool it is then separated from the soil and placed horizontally so that the monolith can be analysed and fixed onto the base. In the case of skeletal soils we gradually move the soil from the marked prism in the pedological profile into the frame according to marked parts. Aft er drying the monolith is fixed with clear matte varnish, following which it can be presented in a vertical position or on the wall of an exhibition area. The new method is less complicated and faster because it does not require a massive monolith in a large box, which is occasionally difficult to transport to the first communication road.