Thermophilous Oak Forests Research Articles

Invasive behaviour of oak lace bug in forest ecosystems: a comparative analysis between thermophilous and mesophilous oak forests

Forest ecosystems provide invaluable ecological, economic, and social benefits, making them essential for global well-being. However, these ecosystems face various threats, including biological invasions by alien species. Among these, the oak lace bug (OLB), an invasive North American insect, has rapidly spread in Europe, impacting oak forests and raising concerns about its adaptation to new environments. OLB feeds on the undersides of oak leaves, extracting sap and causing chlorotic discoloration. Severe infestations lead to premature defoliation, increased susceptibility to diseases or pests and can also result in a substantial reduction in photosynthesis activity. This study aims to analyse OLB’s invasive behaviour in Romanian forest ecosystems, with a specific focus on the differences between thermophilous and mesophilous oak forests. The analysis covers 6 years of data and reveals critical insights. In the initial 4 years, OLB predominantly inhabited the extracarpathian regions of Romania, with concentrated presence in the southern, western, and northwestern areas. Forest ecosystems mainly affected between 2017 and 2020 were characterized by thermophilous oak forests in southern and western regions. However, in the last 2 years (2021–2022), OLB presence increased, particularly in lowland ecosystems, albeit with reduced damage intensity. The analysis also unveiled an adaptation and expansion of OLB in mesophilous forest ecosystems. Climatic factors, specifically temperature and precipitation, significantly influenced OLB’s behaviour, points with severe attacks exhibiting specific climatic conditions. In summary, this study provides crucial insights into OLB’s behaviour, emphasizing the role of climatic and environmental factors in its invasive tendencies.

Glebowy bank nasion zbiorowisk leśnych Wielkopolskiego Parku Narodowego – badania wstępne

The aim of this study is to examine the soil seed banks of the following plant communities: the complex of lakeside plant communities (Carici elongate-Alnetum, Fraxino-Alnetum); the Central European oak-hornbeam forest (Galio sylvatici-Carpinetum); the thermophilous oak forest (Potentillo albae-Quercetum), in the course of transformation into the oak-hornbeam forest; the fresh coniferous mixed forest (Querco roboris-Pinetum) and the subcontinental pine forest (Leucobryo-Pinetum). All of these plant communities are located in protected areas of the Wielkopolska National Park. The soil seed banks of an individual communities are compared according to the species richness and species diversity as well as species similarity between the herb-layer and the seed bank. The soil seed banks are mainly composed of autochthonous species. The studied communities differ in size and species richness of the soil seed bank as well as in its species diversity. The indicated parameters decrease along with the decrease in the fertility and humidity of the communities. A statistically significant, moderate, positive correlation of species richness between the herb layer and the soil seed bank is observed. Nevertheless, the species similarity between the herb layer and the seed bank is relatively low, which can be attributed to the following: 1) the dominance of single species is greater in soil seed banks than in herb layer; 2) woody species whose seedlings were not recorded in the herb layer or were recorded very rarely, have a large share in seed banks; 3) seeds of some clonal plants were not recorded in seed banks as these species invest only small resources in generative reproduction.

Traditional human practices protect diversity of open forests threatened by ticking nutrient time bomb

Open forests are among the world's most species-rich ecosystems but these are now suffering from strong environmental pressure. With the increasing frequency of drought events accompanying climate change, open forests are now at high risk of canopy openness, an associated increase in nutrient load, and a consequent reordering of the plant community. Based on an 11-year field manipulative experiment, we examined whether the reintroduction of traditional forest uses, in particular the regular removal of litter which has been practiced for many centuries in Europe, may mitigate eutrophication and protect the ancient plant diversity of open forests. We examined vascular plant composition in 64, 3 × 3 m plots in 32 randomized blocks, each consisted of one litter-removal and one control plot in a subcontinental thermophilous oak forest dominated by Quercus petraea (Czech Republic, Central Europe). We analyzed how regular litter removal influenced the changes in topsoil nutrients and diversity and abundances of perennial, short-lived monocarpic and open oak forest plant species after eleven years of the annual application of this management. The regular litter removal significantly mitigated eutrophication by a reducing total nitrogen, and significantly decreased the amounts of base cations Ca2+ and Mg2+ in the topsoil. The studied plant species groups responded differently. Perennial and open oak forest species significantly increased their richness and abundances in the litter-removal plots and at the same time their diversity did not change significantly depending on inter-annual weather conditions. In contrast, litter removal negatively affected abundances of short-lived monocarpic species, whose richness was also considerably influenced by weather conditions (decreased the most in years with spring droughts). Moreover, we have found a protective effect of regular litter removal on drought-sensitive open oak forest species that survived in the litter-removal plots, whereas some completely disappeared from control sites during the period of repeated drought events. Our study thus demonstrates that litter removal is a tool with high potential in maintaining biodiversity in open forests affected by climate change.

Comparative study of Central and Eastern European alliances of thermophilous oak forests (Quercion petraea, Betonico-Quercion, and Lathyro-Quercion) within the temperate zone of Europe

Abstract In this paper we carried out a comparative analysis of three alliances, namely Quercion petraea, Betonico-Quercion and Lathyro-Quercion, which span Central and Eastern European thermophilous oak forests. The main goal was to find out floristic and ecological differences as well as to assess specificities in the phytosociological and layer structure across the syntaxa in different regions of Europe. Cluster analysis was performed based on the Bray-Curtis distance matrix and the flexible beta algorithm. A phytoindication method was applied to determine ecological relationships. Variability in the phytosociological structure was studied by shares of species of different classes of vegetation. The layer structure features were investigated by comparing species with the highest constancy value within each layer. Analysis of the distribution boundaries of differentiating species allowed the geographical boundaries of the three identified syntaxa clusters to be delineated. In the phytosociological structure, the greatest differences were found in the proportion of species of Quercetea pubescentis and Brachypodio-Betuletea classes. The Central and Eastern European syntaxa groups were shown to be significantly different in the constancy-ranked series of major layer-forming species.

Dwindling coppice woods in Central Europe – Disappearing natural and cultural heritage

Coppicing has gradually declined in recent decades in many European countries after centuries of upswing. Although the abandonment of this traditional forest management method was forced by changes in social and economic conditions and is rational, it results in losses of many natural and cultural-historical values. Due to the speed of the decline, it is an appropriate time to appraise ancient coppice woodlands as a part of European cultural heritage, map their remnants, and try to save at least some of the most preserved and valuable ones.Only 7.5% of the coppice woodland area in the Czech Republic remains when compared to the extent in the middle of the nineteenth century and currently, according to available data. Although research in the field shows that the current numbers are underestimated (56% of the real extent of coppice woods in the study area remain unnoticed in official reports, mostly because stored coppices are already marked as high forests), the majority of coppice woodland remnants face overmaturity, subsequent felling and replacement by high forests.Considering that the locations of the remnants are unknown, it is useful to develop tools to make the search more effective. Predictive indices of the likelihood of coppice woodland occurrence, which were tested in the South Moravian Region, represent an example of such a tool. Additionally, the results of this study show even more effective and accessible predictors. Due to the long-term development of ancient coppice woodlands, resulting in man-made natural ecosystems with high ecological values, it is possible to target many valuable remnants with the help of habitat mapping data. Specifically, the spatial distribution of Acidophilous thermophilous oak forest habitat, Hercynian oak-hornbeam forest habitat and Dry acidophilous oak forest habitat proved to be the most useful in the study area.As the example in the Czech Republic shows, some of the oldest and most valuable ancient coppice woods may still occur in areas where they are no longer listed in forest evidence as a coppice because of current neglect. The issue is that the time required to understand this phenomenon is limited.

Succession of Xeric Calcareous Grassland Toward Thermophilous Oak Forest: The Case of Abava Valley, West Latvia

Abstract The succession of semi-natural xeric calcareous grassland plant communities toward deciduous forest communities is poorly studied in Latvia. There is insufficient knowledge on the natural transformation of dry calcareous grasslands of Festuco-Brometea into thermophilous quasi-climax oak forest communities of Quercetea pubescentis that are very rare in Latvia. In this paper, a geobotanical study is presented that included studies of soils, tree age, spatial pattern of trees, vegetation composition of different succession stages, and analysis of environmental factors. The study was conducted in the Abava Valley, West Latvia, an area that is unique with species-rich xeric calcareous Festuco-Brometea grasslands, thermophilous oak forests dominated by Quercus robur, and intermediate secondary succession stages with young to medium-aged Juniperus communis and Pinus sylvestris formations.

Secondary Serpentine Forests of Poland as a Refuge for Vascular Flora

The aim of present study was to determine the role of secondary, serpentine forests in Poland in the protection of rare vascular plant species. On the basis of 95 phytosociological relevés collected between 2009 and 2020, we identified the main types of serpentine forest communities and assessed their diversity indices. Ordination methods were used to determine the relationship between the degree of transformation of forest communities (reflected by the occurrence of alien and nitrophilic species) and the presence of endangered species in their undergrowth including the environmental background. We distinguished four types of communities: thermophilic and mesophilic pine plantations (both secondary in origin) as well as thermophilous oak forest and acidophilous oak–hornbeam forest (semi-natural and close to natural in character, respectively). Rare and endangered species were unevenly distributed and concentrated in oak forest (16 species) and thermophilic pine plantation (nine species). The endangered species mainly preferred sites at higher altitudes and with higher slope inclination, light availability, and soil reaction. We did not confirm that the presence of alien or nitrophilic species negatively influenced the ability of studied forests to preserve rare plants. As secondary forests can still harbor endangered species, they should fulfil complementary functions in the nature protection system.

Thermophilous oak forests in Slovakia

Thermophilous oak forests in Slovakia

Разнообразие широколиственных и сосново-широколиственных лесов на восточной границе их распространения

Разнообразие широколиственных и сосново-широколиственных лесов на восточной границе их распространения

Restoring diversity of thermophilous oak forests: connectivity and proximity to existing habitats matter

The habitat fragmentation and isolation threaten populations of rare species. Organisms become endangered because of the primary habitat loss, but also due to limited dispersal capacity. Whether threatened species are limited more by their dispersal capacity or by lack of suitable habitats is an unresolved question critical to effective conservation. To address the question, we investigated patterns of colonisation by light demanding woodland plants in patches (clearings) of broadleaf forest where open canopy conditions were restored by partial cutting. Six pairs of identically sized (40 × 40 m) clearings were created in closed canopy thermophilous oak forest. Each pair included a clearing isolated in the closed forest and a clearing connected to an alluvial meadow and migration corridor along a river. Within each clearing, we followed colonization success by threatened and common species for 8 years. To assess the relative role of species pool, dispersal limitation and niche-based competition processes (viewed through the plant functional traits), we compared vegetation composition of the clearings to that of surrounding habitats (closed forest, open forest, meadow, forest edge). Clearings hosted more threatened species than closed forests, forest edges and meadows. Existing patches of open forest harboured the highest diversity of threatened species. Their proximity increased colonization success of threatened plants in clearings. Higher colonization rates by threatened plants were associated with shorter distances to source habitats and higher light, higher pH and lower moisture values in the clearings. Clearing type affected composition and ecological strategies of threatened species. Connected clearings were colonized by taller light-demanding species with higher seed mass, more suitable for establishment in a highly competitive environment, while the isolated clearings were colonized by shorter species with higher specific leaf area, better equipped for a more shaded environment. Species richness of threatened species increased in the first 3 years and decreased in last years, indicating that forest thinning creates only a short-term regeneration window with tree and shrub canopy closing back relatively fast. Active intervention should be therefore repeated in short intervals, preferably as shifting mosaics of differently aged stands. Our results bring novel information on the relative importance of habitat quality, isolation, and biotic filtering on communities of threatened species and their colonization success.

An Efficient Tool for the Maintenance of Thermophilous Oak Forest Understory—Sheep or Brush Cutter?

Research Highlights: Thermophilous oak forests are among the most species-rich forest ecosystems in Central Europe. In the temperate zone, they evolved from mixed deciduous forests due to centuries-long livestock grazing. The abandonment of traditional forms of landscape use resulted in a constant decline in the number of patches of these communities, their area and species richness, which has been ongoing for decades and calls for their urgent conservation. The commonly used approaches to the conservation of this community are the reestablishment of grazing or mechanical removal of undergrowth. However, there are a limited number of works comparing their effects on the forest herb layer separately and in combination. Background and Objectives: The purpose of our research was to evaluate the effectiveness of grazing, mechanical brush removal and their combination for the conservation of the oak forest herb layer. Materials and Methods: Our work was based on a fully crossed experimental design set in a 60-year-old oak forest. The individual and combined influences of sheep grazing and brush cutting on forest floor vegetation were compared to control plots. We surveyed plant species twice—before the application of treatments and one year later on 600 one-square-meter subplots selected randomly in the limits of twelve fenced 20 m × 20 m treated and untreated study plots. Results: Both grazing by sheep and mechanical removal served well for total plant species richness and their cover, if applied separately. But these effects were not additive—plant species richness and plant cover on plots with combined treatment did not differ from plots, where just a single treatment was applied. Application of both treatments (but separately) had positive influence on species cover of the target group of plants typical to xerothermic oak forests and non-target species of mixed deciduous forests. Mechanical removal allowed also for successful control of woody species. Active conservation measures resulted also in negative effects—we observed increase in the species richness and cover of ruderal species on grazed plots. Conclusions: Both tested methods can be used for active conservation of open oak forest understorey vegetation. The method of active conservation should be chosen depending on the goal and the species composition of the forest floor and undergrowth found at the beginning of the restoration process, however, combining of these treatments does not bring any extra advantage. In our opinion a monitoring of the reaction of vegetation on treatments is of paramount importance.

Winter Geometrid Moths in Oak Forests: Is Monitoring a Single Species Reliable to Predict Defoliation Risk?

Species within the group of winter moths (Geometridae) are important oak defoliators in European forests. Adults of these species emerge either in late autumn (‘autumn species’) or in early spring (‘spring species’), and caterpillars of both ‘autumn’ and ‘spring’ species appear in spring. The abundance of adults assessed by regular monitoring allows the prediction of the defoliation intensity in trees by caterpillars in the following spring. ‘Autumn species’ (mostly a single one, Operophtera brumata) are monitored by forestry practices as pests, whereas ‘spring species’ are often not paid any attention. We hypothesised that ‘spring species’ could also have an important share in caterpillar assemblages in oak forests. We aimed to study the proportions between ‘autumn’ and ‘spring’ species in adult and larval stages. In a xeric thermophilous oak forest in southern Slovakia, Central Europe, we collected adult moths using sticky bands set up on trunks of Quercus pubescens during the winter of 2014–2015 and caterpillars from other trees belonging to the same oak species over the following spring. We also captured caterpillars from several oak species in various areas and over different years in Slovakia and Bulgaria, and we compiled relevant literature data. ‘Spring species’ recorded from a unique forest as adults during winter and as caterpillars in the following spring were significantly more abundant than ‘autumn species.’ Moreover, ‘spring species’ from Slovakian forests, regardless of the locality, the oak species and the year of sampling, reached high proportions, mostly over 50% of individuals in caterpillar assemblages. The ‘spring species’ Agriopis leucophaearia was the most abundant, followed by the ‘autumn species’ Operophtera brumata. ‘Spring species’ accounted for more than 50% of individuals in caterpillar assemblages in the Balkan Peninsula (Bulgaria) concerning one case, and they were of little importance in northern Greece. We recommend monitoring all winter moth adults (‘autumn’ and ‘spring’ species together) continuously in forestry practices, using sticky bands on oak trees from late autumn to early spring.

Thermophilous oak forests of the steppe and forest-steppe zones of Ukraine and Western Russia

We present a formal classification of thermophilous oak forests of the steppe and forest-steppe zones of Ukraine and Russia. Using 45 sources (synoptic tables; some from Central and Western Europe were also included for comparative purposes), we classified the data using cluster analyses, followed by post-classification tools aimed at formal identification of the optimal number of clusters and fidelity-based table sorting. Db-RDA ordination and a CART were used to identify the lead putative climatic drivers of the vegetation patterns. Of the six clusters identified by our classification procedures, two clusters are interpreted here as new alliances (Betonico-Quercion, Scutellario-Quercion). Some new associations classified into these alliances were also either validated or described as new. We further show that the Quercion petraeae is of heterogenous nature and the position of the units previously classified as the Potentillo albae-Quercion should be re-evaluated. NMDS was used to analyse the patterns of the phytocoenologic elements (diagnostic species of relevant syntaxonomic classes) in the six clusters. This analysis revealed that the classification of the Ukrainian and Russian thermophilous oak forests into the Quercetea pubescentis class is untenable and remains open to further scrutiny.

Soil moisture and a legacy of prehistoric human activities have contributed to the extraordinary plant species diversity of grasslands in the White Carpathians

The factors that determine the unique species richness and composition of some temperate grasslands are poorly known. Uniqueness of the extraordinarily species-rich grasslands in the White Carpathian mountain range (Czech Republic, Slovakia), with many disjunct occurrences of species, have been previously attributed to intermittently wet deep soils, which facilitate the co-occurrence of steppe and wet-grassland species, and Holocene continuity of open land, resulted in large species pools. Based on a detailed investigation of 23 well-preserved regularly mown grasslands differing in their vegetation composition and species richness, we tested the relative importance of the hypothetical determinants of compositional variability within semi-dry grasslands. For the first time we included measurements of seasonal moisture at different soil depths and landscape differences in the intensity of the effect of prehistoric humans. Soil moisture was measured using the frequency-domain reflectometry based Profile Probe PR2 sensor at depths of 10, 20, 30, 40 and 60 cm in the soil, repeatedly every four weeks from April to November. Soil samples were taken from the same depths in order to determine soil basicity and nutrient content. As a proxy of the intensity of the effect of prehistoric human activities, mean distances between sampled localities and the five nearest Neolithic or Aeneolithic settlements were used. The species richness was best explained by mean soil moisture, which increased towards the most species-rich grasslands, whereas the distance from prehistoric settlements had no effect. Basicity, moisture and the distance from prehistoric settlements had significant conditional effects on species composition. There was a high frequency of species of intermittently wet soils, thermophilous oak forests and forest fringes in the most valuable grasslands, which are located mostly in the south-western part of the area where the soils were moister and closer to prehistoric settlements, but the seasonal variation in moisture was not high. We conclude that coexistence of species from different habitats is dependent on regular management and high soil moisture throughout the growing season. Due to intermediate moisture conditions that are tolerated by multiple ecological groups of species, many species may locally coexist and form a species-rich grassland community of unique species composition. In addition, prehistoric human activities contributed to landscape openness and helped maintain a forest-steppe species pool during the Holocene forest optimum. Our results indicate that although this historical determinant shapes predominantly the species composition pattern, the extraordinarily species-rich spots are determined rather by abiotic factors, such as intermediate moisture and biotic interactions resulting from the type and duration of management practices.

НОВЫЕ АССОЦИАЦИИ ТЕРМОФИТНЫХ ДУБРАВ СОЮЗА LATHYRO PISIFORMIS-QUERCION ROBORIS SOLOMESHCH ET GRIGORIEV IN WILLNER ET AL. 2016 В ЮЖНО‑УРАЛЬСКОМ РЕГИОНЕ

New plant communities of thermophilous oak forests of the associations Omphalodo scorpioidis-Quercetum roboris ass. nova hoc loco and Lasero trilobi-Quercetum roboris ass. nova hoc loco. belonging to the alliance Lathyro pisiformis-Quercion roboris Solomeshch et Grigoriev in Willner et al. 2016 are described. These plant communities are floristically affluent and contain a large number of meadows-steppe and forest fringe species. In the territory of the Southern Ural region, these communities have the fragmented range and limited to relatively small patches near the tops of ridges and on the steep southern slopes of mountains and hills. Based on the comparison of floristic composition of these communities and other syntaxons of oak forests early described in the region, the combinations of diagnostic species of new associations are proposed.

Phytosociological classification of the thermophilous oak forests in Bulgaria: new interpretations and gaps in knowledge

Phytosociological classification of the thermophilous oak forests in Bulgaria: new interpretations and gaps in knowledge

Effects of a host tree on movement and distribution of winter geometrid moths (Lepidoptera): thickness of trunks and branches

Abstract Adult moths from an ecological group of winter geometrid species look for trees where they copulate and females lay eggs. We investigated how tree trunk and lower branch thickness affects the occurrence of females on trunks and branches and how the density of females and tree trunk thickness affects the occurrence of males on trunks. The research was carried out in a xeric thermophilous oak forest in southern Slovakia (Central Europe) in the winter season 2014–2015. The moths were obtained from Quercus pubescens trees by sticky bands. Three autumn species Operophtera brumata, Erannis defoliaria, Alsophila aceraria and four spring species Agriopis leucophaearia, Agriopis marginaria, Apocheima hispidaria, Phigalia pilosaria were recorded. We have found out that females had not exclusively negative geotactic behaviour as they (except for the rare P. pilosaria) occurred also on lower branches. Tree trunk and lower branch thickness had a positive effect on abundance of females of the three most abundant species (A. leucophaearia, O. brumata, E. defoliaria) on trunks and lower branches. Tree trunk thickness had a positive effect on density of the females of A. leucophaearia on trunks but not on O. brumata and E. defoliaria. The abundance of the males of O. brumata, E. defoliaria and A. leucophaearia on trunks was positively affected by tree trunk thickness and the density of their females.

Comparison of habitats of the rare fungus Pluteus fenzlii between Białowieża Virgin Forest (Poland) and thermophilous forests (Slovakia)

AbstractPluteus fenzlii is a rare Eurasian lignicolous fungus, an iconic bright yellow species that attracts attention. Its habitat in the Białowieża Virgin Forest, Poland, is dominated by Carpinus betulus with admixture of Quercus robur, Tilia cordata and Picea abies, with an herb layer typical for the Carpinion betuli alliance. In Slovakia, the country hosting the highest number of localities worldwide, P. fenzlii prefers closed canopy of thermophilous forest with dominance of Quercus cerris and adjacent Quercus robur agg., Q. petraea agg., Carpinus betulus and Tilia cordata. In the Natura 2000 classification this vegetation belongs to habitat 91M0, Pannonian-Balkanic Turkey Oak-Sessile Oak forests, and priority habitat 91G0, Pannonic woods with Quercus petraea and Carpinus betulus. The Slovak localities can be assigned to the mycosociological community Boleto (aerei)–Russuletum luteotactae, typical for thermophilous oak forests of Southern Europe and extrazonal areas in Central Europe. The presence of P. fenzlii at the isolated Białowieża locality could represent either a remote site of its present occurrence or a remnant of its former distribution, connected with the relict occurrence of thermophilous vegetation in Białowieża where continental oak forests have already disappeared.

Classification of the relict forest communities of Palla’s Black Pine (Pinus nigra subsp. pallasiana) in Bulgaria

Abstract New approach for the classification of the Black Pine forest communities in Bulgaria was made in the paper. The analysis of forest pytocoenoses from Vlahina, East and West Rhodopi and Balkan Range Mountains confirmed their separation into two classes – Quercetea pubescentis (low-altitudinal) and Erico-Pinetea (high-altitudinal). The second class is represented from one polymorphic association Seslerio latifoliae-Pinetum nigrae whereas the other group is represented from two new associations. The association Junipero deltoidi-Pineteum pallasianae is more related to the surrounding thermophilous oak forests as well as the association Lathyro laxiflori-Pinetum pallasianae is more similar to the hornbeam and beech forests.

Drivers of natural spread of invasive Impatiens parviflora differ between life-cycle stages

Impatiens parviflora is one of the most widely spread invasive species in central Europe, yet the factors affecting its spread are still subject to discussion. The aim of this study was to determine which factors affect the spread of I. parviflora. This was achieved by observing the natural spread of the species on 15 permanent transects, in six different habitats, found within the Czech Republic from 2012 to 2016. The transects were divided into 321 plots, whilst data on environmental conditions, as well as of the spread of I. parviflora and its performance, were collected in each plot. The results showed that individual stages of the I. parviflora life-cycle were affected by individual environmental conditions to different extents. The most important factor preventing seedling emergence and establishment was a high cover of herb layer. It did not, however, affect survival of older plants. Thus, I. parviflora can grow in sites with dense cover of herb layer in case the cover formed after I. parviflora seedlings established. Juvenile mortality was the highest in sites with low nutrient levels and low soil moisture. Canopy openness had a negative effect on I. parviflora performance. Impatiens parviflora performed better in neutral soils, in comparison to acidic soils. Oak-hornbeam forests were the most suitable habitat for I. parviflora, followed by acidophilous oak and mixed coniferous forests. However, I. parviflora was able to penetrate into even species-rich habitats, such as thermophilous oak forests, as well as steppe grasslands on rocks. This makes it a potential threat to biodiversity. Only heathlands found on former pastures proved to be unsuitable for I. parviflora, as these remained uninvaded until the end of the study.