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41.
Radial increment of beech (Fagus sylvatica L.) Is under a strong impact of climate in the continental biogeographical region of Croatia
Tom Levanič, Damir Ugarković, Ivan Seletković, Mladen Ognjenović, Mia Marušić, Robert Bogdanić, Nenad Potočić, 2023, original scientific article

Abstract: European beech (Fagus sylvatica L.) is an important component of forests in the alpine and continental biogeographical regions of Croatia. This study aimed to (1) analyze the long-term response of beech to climate, (2) identify potentially critical climatic conditions that could negatively affect the radial increment (RI) and vitality of beech, and (3) evaluate differences in the response of beech between the two biogeographical regions in Croatia. We used the 16 × 16 km Croatian ICP Forests Level 1 network. On a total of 25 plots, we cored between 5 and 24 trees for dendrochronological analysis. Tree-ring widths (TRW) were measured and standardized using cubic spline. TRW chronologies for the two regions were calculated and correlated to the temperature and precipitation data and Standardized Precipitation and Evapotranspiration Index (SPEI) using bootstrapped correlations. Continental region precipitation from April to August and alpine region precipitation from June to August were significantly important for RI. Temperature was less important for RI than precipitation in both regions, but the importance of the negative impact of above-average temperatures in the continental region and the positive impact of above-average precipitation in the alpine region has increased over the last two decades. A comparison with the 3-month SPEI confirmed the significant influence of high temperatures and the lack of precipitation in August on the RI of beech trees in both regions.
Keywords: climate change, tree growth, forest productivity, drought, European beech
Published in DiRROS: 28.06.2023; Views: 401; Downloads: 201
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42.
Causes and consequences of large-scale windthrow on the development of fir-beech forests in the Dinaric mountains
Matjaž Čater, Ajša Alagić, Mitja Ferlan, Jernej Jevšenak, Aleksander Marinšek, 2023, original scientific article

Abstract: We investigated several aspects of windthrow that are relevant to our understanding and management of forest ecosystems. As an example, we used an extreme event in December 2017, when the strongest storm in recent history occurred in the Slovenian Dinaric High Karst. We examined influential factors such as soil properties, wind speed, precipitation and ecological consequences for the affected forests. Soil properties were measured around standing and fallen silver fir trees at all three research sites. Tree species composition in the regeneration was observed on plots with chemical and acoustic ungulate deterrents and on control plots without deterrents. Economic estimates of yield loss due to damage were calculated at the national level. A model of the potential threat from windthrow was also developed based on data collected from windthrow events and meteorological data over the past 20 years. Our results indicate that soil depth and mineral fraction depth were similar at sites with and without damaged trees and were not the determining factors for tree toppling. Plots with acoustic deterrents showed the most effective regeneration development, the least decline in silver fir and the greatest increase in noble hardwood seedlings, while plots with chemical deterrents showed the least browsing damage. The estimated economic loss of €16.1 million is 6.6% less than the harvest under normal conditions. The economic loss was relatively low due to the nature of the storm, with the predominant type of damage being uprooted trees with no damaged trunks. The windthrow hazard model revealed that a large number of consecutive events with strong winds in each section weakened the stand, which was subsequently knocked down during the next extreme wind and rainfall event.
Keywords: natural forest regeneration, windthrow, economic loss, browsing, ungulate deterrents, forest soil properties, potential threat model
Published in DiRROS: 27.06.2023; Views: 1058; Downloads: 505
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44.
Forest managers’ perspectives on environmental changes in the biosphere reserve Mura-Drava-Danube
Marcus Sallmannshofer, Rok Damjanić, Harald Vacik, Marjana Westergren, Tjaša Baloh, Gregor Božič, Mladen Ivanković, Gyula Kovács, Miran Lanšćak, Katharina Lapin, Laszlo Nagy, Silvija Krajter Ostoić, Saša Orlović, Srđan Stojnić, Peter Železnik, Milica Zlatković, Silvio Schueler, 2023, original scientific article

Abstract: Riparian forests are particularly vulnerable to environmental change and anthropogenic influences because they are highly dynamic ecosystems, thus proper adaptation measures are crucial. The implementation of these measures, however, strongly depends on the actors’ perceptions of the specific problems occurring in such forests. For understanding the constraints of specific interest groups toward different adaptation activities, information in this field is essential. By conducting a questionnaire survey we explore how different types of forest managers, i.e., forestry professionals, forest owners, and conservation managers, perceive the effects of environmental change on forest management in the recently established Transboundary Biosphere Reserve Mura-Drava-Danube. We show that these forest managers are highly aware of ongoing environmental changes and appraise deteriorating forest conditions, especially after observing changes themselves. Abiotic damage is expected to increase the most, followed by biotic damage, the spread of non-native species, and tree dieback. Nearly 80% of the survey respondents expect further changes and almost all of them intend to adapt their management of forests to mitigate or prepare for these changes. Nevertheless, we show differences in sensitivity to change and willingness to initiate adaptation actions by assessing adaptation thresholds: conservation managers appear generally more tolerant to changes, which results in higher thresholds to initiate management adaptation than forestry professionals
Keywords: biosphere reserve Mura-Drava-Danube, forest management, sensitivity to environmental change, stakeholder perception, adaptation thresholds, riparian forest tree species
Published in DiRROS: 31.05.2023; Views: 331; Downloads: 257
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45.
Contrasting responses of alien and ancient forest indicator plant species to fragmentation process in the temperate lowland forests
Mirjana Šipek, Lado Kutnar, Aleksander Marinšek, Nina Šajna, 2022, original scientific article

Abstract: Fragmentation is one of the major threats to biodiversity. In a fragmented landscape, forest specialists are losing suitable forest habitats with specific site and microclimate conditions, which results in their local extinction. Conversely, the invasion of alien species is facilitated by open forest areas and increased boundaries between forest fragments and adjacent land. We studied the effect of fragmentation in terms of fragment size impact on overall plant species richness and on selected ecologically important groups' richness, composition, and diversity. We surveyed vegetation in the interior of 47 fragments of various sizes and one unfragmented reference forest. Our results reveal that the effect of fragmentation is complex and differs for studied plant groups. Decreasing fragment size negatively affects the overall plant richness and richness of native and ancient forest indicator plants as well as their diversity, while the effect is positive for alien plants. The highest proportion of ancient forest indicator plant species and the lowest proportion of alien plants in the unfragmented forest underline the great conservation value of forest fragments. At the same time, our results reveal that large and diverse forest ecosystems are susceptible to biological invasions as well.
Keywords: forest fragment, indicator plants, invasion, diversity, habitat modification, habitat conservation
Published in DiRROS: 15.05.2023; Views: 305; Downloads: 167
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46.
Are ecological niche optimum and width of forest plant species related to their functional traits?
Janez Kermavnar, Lado Kutnar, Aleksander Marinšek, Valerija Babij, 2023, original scientific article

Abstract: The ecological niche is one of the central concepts in plant ecology. Understanding which biological traits influence plant niches remains limited, preventing large-scale generalizations. Using a representative pool of 94 herb-layer species frequently occurring in the Slovenian forest vegetation types and an extensive suite of 28 plant functional traits, we tested whether traits serve as predictors for the optimum and width of plant species ecological niche. Niche optimum (mean) and niche width (standard deviation) of each species were derived from community-level ecological indicator values for six environmental gradients, i.e., light, temperature, continentality, moisture, soil reaction and nutrients. We investigated relationships between niche parameters and functional traits through a random forest analysis to account for relatively high trait correlations. Our results suggest that niche optimum and width of forest plant species are related to their functional traits. The two niche parameters were best explained by similar set of traits; however, the relative importance of traits differed substantially. Traits associated with disturbances (frequency and severity), plant dispersal (seed mass, dispersal syndrome), leaf economics spectrum (specific leaf area) and life strategy (CSR scores) showed the highest overall significance in predicting niche optimum and width. Functional traits were, on average, better predictors for niche optimum (average variance explained across all six environmental factors: 20.2%) than for niche width (average variance explained: 7.7%). Intraspecific trait variability, not considered in this study, likely plays an important role in case of niche width. The analyses suggest that, while not all traits impact niche parameters to the same degree, it is crucial to consider traits representing different ecological dimensions and revealing leading patterns of trait coordination. We recommend that the relative importance of traits for species niche parameters should be tested on a larger spatial scale using broader pool of forest understory plants across Europe.
Keywords: ecological gradients, Ellenberg indicator values, Slovenian forest types, trait-environment relationship, understory plants
Published in DiRROS: 09.03.2023; Views: 436; Downloads: 243
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47.
Assessing the heterogeneity and conservation status of the Natura 2000 priority forest habitat type Tilio–Acerion (9180*) based on field mapping
Janez Kermavnar, Erika Kozamernik, Lado Kutnar, 2023, original scientific article

Abstract: Priority habitat types (HTs) within the Natura 2000 network are of the highest importance for conservation in Europe. However, they often occur in smaller areas and their conservation status is not well understood. One such HT is that of the Tilio–Acerion forests of slopes, screes and ravines (9180*). The Natura 2000 study site, Boč–Haloze–Donačka gora, in the Sub-Pannonian region of eastern Slovenia is characterized by a matrix of European beech forests and includes rather small, fragmented areas covered by Tilio–Acerion forests. The goal of this research was to examine the heterogeneity and conservation status of the selected HT through field mapping, which was performed in the summer of 2020. As the conservation of HT calls for a more detailed approach, we distinguished between the following four pre-defined habitat subtypes: (i) Acer pseudoplatanus-Ulmus glabra stands growing mostly in concave terrain, (ii) Fraxinus excelsior stands growing on slopes, (iii) Tilia sp. stands with thermophilous broadleaves occurring on ridges and slopes, (iv) Acer pseudoplatanus stands occurring on more acidic soils with an admixture of Castanea sativa. Field mapping information was complemented with the assessment of habitat subtype characteristics using remote sensing data. The results showed that habitat subtypes differed significantly in terms of area, tree species composition, forest stand characteristics, relief features and the various threats they experienced (e.g., fragmentation, tree mortality, ungulate browsing pressure). The differences between subtypes were also evident for LiDAR-derived environmental factors related to topography (i.e., terrain steepness and Topographic Position Index). This study provides a baseline for setting more realistic objectives for the conservation management of priority forest HTs. Due to the specificities of each individual habitat subtype, conservation activities should be targeted to the Natura 2000 habitat subtype level.
Keywords: forest habitat subtype, monitoring, biodiversity conservation, LiDAR, Slovenia, NATURA 2000
Published in DiRROS: 03.02.2023; Views: 936; Downloads: 241
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48.
Climate–growth relationships in Laurus azorica - a dominant tree in the Azorean Laurel forest
Diogo C. Pavão, Jernej Jevšenak, Lurdes Borges Silva, Rui Bento Elias, Luis Silva, 2023, original scientific article

Abstract: Forests on oceanic islands, such as the Azores archipelago, enable interesting dendroclimatic research, given their pronounced climatic gradients over short geographical distances, despite the less pronounced seasonality. The Lauraceae play an essential ecological role in Macaronesian natural forests. An example is Laurus azorica (Seub.) Franco, a relevant species given its high frequency and physiognomic dominance in Azorean laurel forests. This study aims to quantify climate–growth relationships in L. azorica using a dendroecological approach. We sampled four stands at São Miguel and two stands at Terceira islands, for a total of 206 trees. Following standard dendrochronological methods and rigorous sample selection procedures, we obtained relatively low rbar values and high temporal autocorrelation. Using a stepwise Random Forest analysis followed by Generalized Linear Models calculation, we found prominent effects of present and previous year temperature, but a low precipitation signal on growth rings, with some model variation between stands. Our results agreed with previous observations for broad-leaved species with diffuse porous wood, contributing to increase the baseline dendroecological knowledge about Azorean forests. Due to the high levels of within- and between-stand variation, and to refine the climatic signal analysis, complementary approaches should be explored in the future.
Keywords: Azores, dendroclimatology, generalized linear models, laurel forest, Macaronesia, random forest
Published in DiRROS: 18.01.2023; Views: 328; Downloads: 243
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49.
Forest subsidy distribution in five European countries
Elena Haeler, Andreas Bolte, Rafael Buchacher, Harri Hänninen, R. Jandl, Artti Juutinen, Katharina Kuhlmey, Mikko Kurttila, Gun Lidestav, Raisa Mäkipää, Lydia Rosenkranz, Matevž Triplat, Urša Vilhar, Kerstin Westin, Silvio Schueler, 2023, original scientific article

Abstract: Forest subsidies are widely used to achieve policy objectives aimed at maintaining and supporting the provision of the various ecosystem services provided by forests. In the European Union, an important instrument is the European Agricultural Fund for Rural Development (EAFRD) within the EU's Common Agricultural Policy (CAP), but countries also have national subsidy systems. In both cases, individual countries determine which objectives they want to achieve with the subsidy schemes and which measures are supported. In this comparative study, we investigate which forest-related measures are subsidized across Europe and which forest owners, representing a very heterogeneous group, are involved in the activities of the subsidy systems. We collected data on subsidies paid out for forest-related measures from Austria, Finland, Germany, Slovenia and Sweden from the EAFRD funding period 2014–2020 for a comparison of the funded activities. Further, we analysed how subsidies were distributed among private forest owners with forest holdings of different sizes by performing G-tests to compare the observed with the expected subsidies received by forest owners in the different size categories. The results show that through the flexibility given by the CAP for countries to adjust their subsidy programmes to the specific national needs, EAFRD funds and equivalent national subsidies are indeed used for a wide range of activities instead of only a few following one common European goal. Reflecting the different needs and various forest functions, the subsidized activities range from the more ecology-oriented “investment to increase resistance and the ecological value of forests” to the more management-oriented “purchase of new machinery and new equipment for forestry operations”. In all five countries, small-scale forest owners with holdings smaller than 200 ha are the largest owner group and manage a large share of the forest area in private hands (from 47% in Austria to 97% in Slovenia). However, especially owners of the smallest holdings (< 20 ha) rarely use the funding scheme of the EAFRD framework and thus receive a disproportionately low share of subsidies. There might be several reasons for this. Small-scale forest owners are generally less involved regarding policy issues (including subsidy schemes) than owners of larger forest holdings and may not be aware of all funding opportunities. In addition, the considerable effort to apply, including project preparation, administration and documentation may be perceived as a barrier. It became clear that the current subsidy systems of the countries focus on different forest policy objectives. Our study further revealed that the documentation of subsidy distribution is partly unclear and inconsistent across countries hampering European comparisons. However, understanding current subsidy distribution is urgently needed for increasing the effectiveness of subsidy systems to achieve European policy goals of vital multifunctional forests.
Keywords: European agricultural fund for rural development, EAFRD, policy, incentives, multifunctional forests, small-scale forest owners, bioeconomy
Published in DiRROS: 05.01.2023; Views: 478; Downloads: 296
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50.
Hoverflies (Diptera: Syrphidae) as biodiversity indicators for assessing urban forest habitats
Maarten De Groot, Primož Simončič, Andrej Verlič, Urša Vilhar, 2022, original scientific article

Abstract: Urban and peri-urban forests are important habitats for maintaining biodiversity in cities. In this paper, we report a method for using hoverflies as biodiversity indicators in urban forest habitats. As a case study, forest habitats in three peri-urban and urban forests were assessed and compared to rural forests in Slovenia. Rožnik (Ljubljana) was chosen as the urban forest site, Mestni log (Ljubljana) and Brdo (Kranj) were chosen as the peri-urban sites, and eight sites were chosen in rural forests in different ecoregions in Slovenia. Forest hoverfly species richness and the species composition of different biological traits were compared between the peri-urban forests, urban forest and rural forest sites. In addition, species richness was assessed for changes in response to weather conditions between years. The number of species with the investigated traits in the urban and peri-urban forests was within the range of the number of species observed in the rural forests. The number of saproxylic species was higher in the urban forest but lower in the peri-urban forests compared to the rural forests. The proportions of species with different feeding modes and different development times were similar between the peri-urban, urban and rural forests. The proportions of species with development times of less than 2 months or more than 1 year and of predatory species were similar in the urban and peri-urban forests but higher in the rural forests. The species composition of the other biological traits differed between the peri-urban, urban and rural forests. Species richness and abundance displayed large differences in phenological patterns between 2012 and 2013; these differences are related to differences in the minimum temperature for these years. The results are discussed in relation to forest management in urban forests, the usefulness of hoverflies as a biodiversity indicator and possible extrapolation to other species groups.
Keywords: biological traits, ecosystem services, forest management, saproxylic species, Syrphidae, urban forest
Published in DiRROS: 30.12.2022; Views: 1416; Downloads: 668
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