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One of the research topics of the Pilis Forestry Systems Experiment is to investigate the effects of different silvicultural practices on understorey vegetation in an oak–hornbeam forest stand. In the experiment, interventions of two significantly different forest management modes were studied between 2014 and 2020. Three interventions modelled the conditions of the so-called clear-cut forest management applied in the largest area of Hungary: a cut area, a group of residual trees in the cut area, and a so-called cut stand where half of the trees were removed. In Hungary, the continuous cover forestry method is still only applied in a small area, one of the most important elements of it is the creation of a gap in the closed canopy by cutting a few trees. The continuous cover forestry mode was therefore modelled with gap cutting. In addition to the above interventions, the experiment also included a control area where no interventions were made. The effects of the five intervention types were observed in 6 replicates (blocks).

We studied how understorey attributes change in response to different forest management and how these responses change over time. Then we assessed the ability of treatments to maintain the forest character of the vegetation. One of the most important differences between the experimental sites was the behaviour of disturbance-tolerant and invasive species. The majority of indicator species associated with the cut areas were disturbance tolerant (Cirsium arvense, Calamagrostis epigeios) and invasive, light-demanding species (Erigeron annuus, Conyza canadensis, Solidago gigantea). None of these species were present in the area before the interventions. The disturbance-tolerant bushgrass (Calamagrostis epigeios) and the invasive giant goldenrod (Solidago gigantea) started to become more common in the areas after the third year of the interventions (2017). The goldenrod was dominant in only a few areas, but was still present in some areas six years after the interventions (2020). The average cover of bushgrass was 9% five years after the intervention and reached 25-50% in some of the cuttings. None of these species were present in the plots, and if some individuals appeared in one year, they disappeared the following year. Compared to the cuttings, the soil moisture and humidity were higher in the cuttings. These microclimatic factors were probably behind the phenomenon that the experimental stands retained the forest understory character better because they proved more resistant to disturbance and invasive species than the cuttings.

The study shows that areas managed under continuous cover forestry methods can be more resistant to disturbance-tolerant and invasive species than areas under clear-cut management, and that increasing the proportion of continuous cover forestry management in our country is important from both ecological and conservation perspectives.

Led by researchers from the University of Alberta in Canada, members of the CER ‘Lendület’ Seed Ecology Research Group also participated in an international study to find the key to the success of invasive grass species. The results of this research have recently been published in the journal Oikos. The three grass species studied were native species of Eurasian grasslands – smooth brome (Bromus inermis), narrow-leaved meadow-grass (Poa angustifolia) and crested wheat grass (Agropyron cristatum) – which are considered invasive species causing serious conservation problems on North American prairies. Our experiment sought to answer whether seed origin or soil-mediated effects contribute to the invasiveness of these three grass species. We collected seeds and soil from populations from non-native (Canada) and native (Hungary, Kazakhstan, Germany, Ukraine) ranges (47 populations in total), germinated seeds in all possible combinations (from their own population, from other populations in the native range, and on soil from invasive ranges) and compared the biomass of developing seedlings.

Although we have studied biologically and ecologically similar species, our results suggest that the key to success for each species is different, species-specific. In the case of the crested wheat grass, our results suggest that the species has become evolutionarily more successful since the invasion (i.e., larger plants have developed from seeds from Canadian populations, regardless of soil type) and that soil-mediated effects have contributed to its success (root biomass of plants was higher in soils from Canadian populations, regardless of seed origin). In the case of smooth brome, local adaptation may be the key to success. This means that within the invaded range, seeds from a given population developed the highest biomass in the soil of their own population, while smaller plants developed in soils from other Canadian populations. Overall, the study shows that the keys of success of invasive species are influenced by a number of factors, many of which act in concert and may reinforce each other. Targeted research on the key species of most conservation importance is therefore very important, as effective action against invasive species requires knowledge of the factors that determine their success.

In January 2024, the HUN-REN Ecological Research Centre’s Evolutionary Ecology Research Group launched a network of community science projects on conservation and ecology in Hungary. The SEEN (Social Engagement in Ecology Network) Conference, held in Tata on 18-19 January, aimed primarily to create a living link between Hungarian community science projects and the researchers working on them.

The community science method is about involving civilians at different stages of the scientific process. For example, in cases where researchers want to collect data from across the country on the occurrence of particular species, observations by civilians can multiply the effectiveness of the research. This can be particularly important in the case of invasive species, where up-to-date information on the distribution and abundance of species is of particular importance.

Several community science projects aimed at detecting and monitoring invasive species, such as ticks, mosquitoes or an ivy species, were presented at the SEEN conference. Several research groups from the Invasion Biology Division of the National Laboratory for Health Security were represented. In addition to the above-mentioned research on invasive ticks and mosquitoes, the research also covered alien plants escaping from gardens and an intensively spreading native species, the beaver. In this way, research into invasion biology has received considerable attention.

As well as presenting research, the conference focused on community science as a socially important method. Involving citizens in the scientific process is an opportunity to transfer knowledge, to raise awareness of ecological, health and social problems affecting our environment, and to increase trust in scientists and science. Last but not least, it can help to bridge the gap between scientists and society, which for many seems unbridgeable.

One of the main causes of biodiversity loss is biological invasion, which has negative impacts on the economy and society. As the invasion problem becomes more and more serious, there is an urgent need to develop more innovative, effective and proactive strategies to help improve the resilience of native communities to invasion by limiting the establishment and spread of invasive alien species. Developing effective prevention, mitigation and restoration strategies requires an understanding of the processes underlying biological invasion and resistance to invasion.

A systematic review and meta-analysis on seed-based ecological restoration experiments was conducted in collaboration with several research groups at the HUN-REN Ecological Research Centre, National Laboratory of Health Security, Division of Invasion Biology, to investigate the potential of functional similarity, seeding density and priority effects to increase resistance to invasion. A comparative analysis of 48 studies showed that ecological restoration based on seed sowing has the potential to limit the establishment and growth of invasive alien species. Providing priority to native species was found to be the best method to increase the resistance of plant communities to invasion, as it can reduce the performance of invasive alien species by more than 50%. Even the short-term (only one week) seeding advantage has been shown to be beneficial for native species, but the priority effect can be further enhanced by increasing the temporal advantage. Seeding functionally similar species generally had a neutral effect on invasive alien species. High-density seeding was effective in reducing invasive alien species, but there may be thresholds above which further increases in seeding density do not necessarily result in increased resistance to invasion.

The results of this publication suggest that priority should be given to the establishment of native species to prevent the spread of invasive alien species and reduce their impact. The study also highlights the need to integrate research across geographic regions, global invasive species and potential resistance mechanisms to improve the predictive capacity of invasive ecology and identify best restoration practices to prevent and control invasive alien species.

Nowadays, one of the most effective seed dispersal vectors are humans. The key our efficiency is the rapidly growing rate of global transport, trade and tourism, which enables us to move more and more easily and quickly between distant biogeographical regions, and even between continents. Based on the results of studies so far, nearly 500 species have been registered to be able to spread on clothing, and most of thes are weed and invasive species that cause serious conservation problems, especially in the isolated habitats.

In a study, published in the journal Science of the Total Environment, members of the HUN-REN Centre for Ecological Research, ‘Lendület‘ Seed Ecology Research Group, analysed the potential mechanisms that might affect the outcome of seed dispersal on clothing. Their research involved 88 volunteers in a multi-site field experiment with samples collected from Hungary, Romania, and the Czech Republic. Researchers accompanied volunteers on 39 sampling occasions during fieldwork or filed trips and provided each participants a new pair of socks at the beginning of the day. At the end of the outdoor activity, they collected the seeds from socks. They also collected seeds from the inside and outside of volunteers’ shoes (a total of 251 samples and 2,008 subsamples were collected). During the experiment, they also recorded the sampling date, distance walked, and time spent outside, a list of plants to characterise the species pool of the visited site and the participants’ clothing type.

Their results show that dispersal on clothing can play an important role in seed dispersal between habitats and regions. The process allows the spread of many species: researchers have found nearly 36,000 seeds from nearly 230 plant species. Nearly half of the dispersed species were disturbance-tolerant or weed species, but there were also large numbers of species associated with natural habitats. In total, researchers observed the spread of 11 invasive and adventive species. Interestingly, most seeds were spread by men and field biologists during visits to grassland habitats. The type of clothing and footwear also had a significant effect on the dispersal efficiency: wearing long pants and high-top shoes can decrease seed dispersal potential compared to wearing short pants and low-top shoes (e.g., sneakers). Based on the result, it is crucial to inform people about this phenomenon, as our individual habits and behaviour can reduce the spread of weeds and invasive plant species.

Community science based monitoring of invasive mammal and bird species of Hungary has begun in a cooperation between the Institute for Wildlife Management and Nature Conservation of Hungarian University of Agriculture and Life Sciences (MATE) and the Institute of Ecology and Botany, Centre for Ecological Research.

On the BeaverMap website [https://hodterkep.hu/upload-semiaquatic-mammals], maintained by the Centre for Ecological Research, researchers are collecting data about five semi-aquatic mammal species, which are the following: Eurasian beaver – a native species with community interest in the European Union; nutria, American mink and muskrat – invasive alien species; Eurasian otter – a strictly protected native species in Hungary. If the informant is unsure in the identification of the observed semi-aquatic mammal species, he can ask for help from the researchers. When submitting an observation, the informant has to upload at least one documentative photo, mark the location on the map, and fill out a short questionnaire. In the frame of the questionnaire, it is also possible to share experiences and opinions related to the activity and effects of the species.

The new website [https://invazivadak.uni-mate.hu/] of the MATE Institute for Wildlife Management and Nature Conservation aims to collect data about some invasive mammalian and bird species with game management interest. Informants can submit data about the raccoon, raccoon dog, muskrat, nutria, American mink, Canada goose and Egyptian goose. Based on photos and descriptions placed on the website, it is possible to recognize the observed species with a high certainty. On the basis of these, we expect registered users to provide data on species observations, supported by photos if possible.

This year, the Eurasian Grassland Conference was held in Szarvas, organized by the Lendület Seed Ecology Research Group of the HUN-REN Ecological Research Centre and the Körös-Maros National Park Directorate, where several research groups of the Invasion Biology Division presented their latest results. In the opening plenary lecture, Dr. András Kelemen, researcher of the Lendület Seed Ecology Research Group, talked about the invasive species threatening the grasslands of the Kiskunság region. He showed the results of a citizen science programme to survey naturalized cacti populations and a study to test the control of sand dropseed, and reported on the emergence of new invasive species such as the knotgrass (Paspalum distichum). Katalin Lukács, also a member of the research group, presented a poster showing that seeds remaining on clothing do not lose their germinative capacity even after washing and can therefore continue to spread. She was awarded the Best Young Investigator prize in the poster category for her high-quality work. The very first session of the conference was dedicated to invasive species. The first session of the conference was dedicated to invasive species. In it, Dr. Melinda Halassy, head of the Restoration Ecology Research Group of the HUN-REN Centre for Ecological Research, first presented the impact of the combined seeding of native competitor species on the establishment of invasive species. She was followed by Boglárka Berki, PhD student of the HUN-REN Ecological Research Centre’s Large-scale Vegetation Ecology Research Group, who presented the results of their research on the possible management of the common milkweed, one of the most common invasive species. During the post-conference programme f, led by Dr. András Kelemen, Dr. György Kröel-Dulay and experts from the Kiskunság National Park Directorate, participants were able to learn about the invasive species and possible management methods in Kiskunság.

Plant invasion and habitat fragmentation have adverse effects on biodiversity in almost all ecosystems. Our research explored the direct and indirect effects of common milkweed (Asclepias syriaca) invasion on plant and arthropod biodiversity. For our study, we selected 30 Hungarian forest-steppe fragments of different sizes. Each was sampled in a common milkweed-invaded area and a control area. We recorded vegetation structure, measured temperature and soil moisture, and collected data on arthropods with different ecological roles in the invaded and control areas of the fragments. We studied plants, bees, butterflies, flower-visiting wasps and flies, true bugs and spiders.

Temperature and soil moisture were lower in the invaded area than in the control area. Common milkweed had a positive effect on plant species richness and flower density. We found mainly indirect effects of invasion on arthropods through changes in habitat microclimatic characteristics and food sources. Pollinators responded positively to the abundance of native flowers, so that the common milkweed had an indirect positive effect on pollinators. Similarly, we found higher numbers of true bug species in invaded areas than in control areas, as the species richness of true bugs also increased with increasing diversity of native plant species. Predators were positively affected by complex vegetation structure, higher soil moisture and lower temperatures. Furthermore, increasing fragment size negatively affected spider species richness in control areas but did not affect areas invaded by common milkweed. Grassland specialist spiders were more sensitive to fragment size than generalists, while generalist spider species were more sensitive to invasion.

The positive effect of milkweed on generalist species may homogenise communities in the long term. The density of common milkweed and the success of its dispersal may increase with fragmentation, and we therefore recommend removing invasive plants from small habitat fragments to preserve native habitat. The study of generalist species and the indirect effects of invasion are essential to understanding the impact of invasive plant presence.

Urbanisation can contribute significantly to the spread of invasive mosquito species and the diseases they spread. Urbanised habitats provide access to large food sources (humans and domestic animals) and offer abundant breeding sites for mosquitoes. Although human-formed landscapes are often associated with the presence of invasive mosquito species, there still remains a lack of knowledge about the relationship between each species and the built environment. In the present study, the relationship between the extent of urbanisation and the presence of invasive mosquito species was investigated, with a focus on the distribution of the Asian tiger mosquito, the Japanese bush mosquito and the Korean mosquito. Data were collected using citizen science, within the framework of the mosquito monitor.hu, which collected invasive mosquito occurrence data between 2019 and 2022 with the contribution of the general public.

The research found that the relationship between each species and urbanized landscapes was found to be different. The presence of the Asian tiger mosquito showed a statistically significant and positive relationship with urbanization, while the presence of the other two invasive mosquito species showed no relationship with urbanization.

The results highlight the importance of citizen science in scientific research, as data collected using this approach can be used to better understand the drivers of invasion and the ecological needs of invasive species.

Publications:
Garamszegi, László Zsolt; Soltész, Zoltán; Kurucz, Kornélia; Szentiványi, Tamara: Using community science data to assess the association between urbanization and the presence of invasive Aedes species in Hungary Parasites & Vectors, 2023

Invasions of alien species are a major cause of biodiversity loss, threatening both natural and human-managed ecosystems. Ecological restoration of habitats is key to controlling invasion, and seeding restored habitats with appropriate species can increase their resistance to invasion. In this research, the Centre for Ecological Research’s Restoration Ecology Research Group sought to answer the question: is similarity of plant traits or higher seeding rates of native species more effective at reducing invasive species in the early stages of development?

Seeding experiments were set up in the National Botanic Garden with three alien invasive species that are widespread in Hungary: Common milkweed (Asclepias syriaca), Horseweed (Conyza canadensis) and European bur grass (Tragus racemosus).

The invasive species were grown in pots, sown separately and together with native species. Three dicotyledonous species (Yellow bedstraw Galium verum, Baby’s breath Gypsophila paniculata, Common soapwort Saponaria officinalis) were selected from the Pannonian sandy grassland flora, which have similar plant characteristics, and therefore are expected to have similar resource requirements and stronger competition with the selected invasive species. In addition, a fescue species (Festuca vaginata), the dominant grass species in sand grasslands, and a mixture of all species were also seeded in the experiment. All native species were sown in two different quantities: the same quantity as the invasive species (12-12 seeds) or five times that quantity (60 seeds of the native species).
There were no significant differences between the laboratory-tested germination and germination in pots of the native and alien invasive species. However, it was found that the germination rate of alien species, and consequently their establishment, was reduced when native species were sown at the same time as alien species in higher quantities, although to different extents depending on the species. Seeding of the sand grassland perennial grass (F. vaginata) instead of species with similar characteristics reduced germination the most for all invasive species studied.

These results confirm that invasive alien species can be effectively controlled by sowing native seeds at an early establishment stage, especially at higher densities and using competitive species. Invasion-resistant habitat restoration is best achieved through a combination of several factors. It is important that native species are sown in large quantities and that the seed mixes used include species, such as dominant grasses, that are competitive with invasive species at an early stage of development.