Our new paper is published about the effects of steppe mice on the vegetation of agroecosystems

Our new paper by Laura Godó et al. has recently been published in Agriculture, Ecosystems and Environment about the effect of mound-building and caching activities of the steppe mouse.

Reference

Godó, L., Valkó, O., Borza, S., Ferencz, A., Kiss, R., Lukács, K., Deák, B. (2024) Effects of mound building and caching by steppe mouse (Mus spicilegus Petényi) on the vegetation in agroecosystems. Agriculture, Ecosystems and Environment 379: 109359. https://doi.org/10.1016/j.agee.2024.109359.

The paper is open access and can be downloaded from here.

To analyse the complex effects of caching rodents on agroecosystems, we selected the steppe mouse (Mus spicilegus Petényi, 1882), a small outdoor mouse, as a model species. It is a common herbivorous rodent inhabiting grasslands and agroecosystems from eastern Austria to western Russia. Its most well-known and spectacular habitat transformation effect is mound building: in autumn, a group of mice gather and build a mound above their burrow that provides protection against harsh environmental conditions and weather elements during the winter period. The mound consists of a thick layer of piled up inflorescences, fruits, and spikes covered by shallow bare soil layer. Therefore, these mounds are very interesting objects for vegetation dynamics: they contain huge amount of seeds, and they provide small distinct patches for plant establishment.

Our study sites in East Hungary (A), and pictures of a steppe mouse mound (B) and the studied agroecosystems: old-fields (C), alfalfa fields (D) and annual crop fields (E).

Our findings suggest that small-scale disturbances, like mound-building by the steppe mouse, contribute to maintaining plant diversity in otherwise uniform agroecosystems. The mounds provide low-competition sites with unique resources, creating small vegetation patches that differ from surrounding areas. The steppe mouse may act as a "facultative engineer" species, influencing vegetation based on habitat type. However, the mounds are often short-lived due to agricultural activity, leading to a constantly shifting pattern of mound sites, which temporarily facilitate plant establishment.

Seed analysis of the mouse's caches showed a preference for a few weed species, but only a few of these appeared in the vegetation on mounds. This finding suggests that while mounds provide good conditions for cached weeds, they don’t result in significant weed growth, which may help change farmers' perceptions of these rodents as pests. As a common species adapted to disturbed habitats and expanding across Europe due to milder winters, the steppe mouse may increasingly affect agroecosystem structure and function in the region.

Abstract

Several rodent species are considered ecosystem engineers. They exert profound changes in agroecosystems by disturbing the soil during their activities. The steppe mouse (Mus spicilegus) inhabits various agroecosystems and constructs conspicuous mounds for overwintering using piled up plant material and soil. These mounds are widespread in many agroecosystems and may significantly affect the vegetation. In our study, we evaluated the effect of mound building activity of the steppe mouse on the vegetation of agroecosystems in Hungary. We sampled the cache content of 90 mounds in total located in old fields, alfalfa fields, and annual crop fields, and surveyed the aboveground vegetation of the mounds and their surrounding undisturbed matrix in 39 paired plots. Mice cached large amounts of seeds belonging mostly to weeds. In total we found 50,413 germinable seeds of 30 species in the cache content samples. However, the mound vegetation and the cache shared only a few species, suggesting that seeds cached by the mice do not contribute to the regenerating vegetation on the mounds. Soil disturbance by mice created distinct vegetation patches with species composition and structure different from the neighbouring undisturbed matrix. Early secondary successional vegetation patches on mounds introduced small-scale heterogeneity into the homogenous agricultural landscape, increased plant diversity and provided distinct flower resources for pollinators. The detected differences in the aboveground vegetation between the mound and the matrix in the studied habitats suggest that the steppe mouse acts as a facultative engineer species in agroecosystems.

New paper about the population dynamics of an endangered geophyte, Colchicum bulbocodium

Our new paper by Réka Kiss et al. has been published today about the population dynamics of the spring meadow saffron in Scientific Reports.

The paper is open access and can be downloaded from the journal homepage (please click here).

Reference:

Kiss, R., Lukács, K., Godó, L., Tóth, Á., Miglécz, T., Szél, L., Demeter, L., Deák, B., Valkó, O. (2024) Understanding the effects of weather parameters on the population dynamics of an endangered geophyte supports monitoring efficiency. Scientific Reports 14: 25974. https://doi.org/10.1038/s41598-024-76942-5

This paper is a result of a six-year-long monitoring study and one of the final results of the PD OTKA project of Réka. The study of the population dynamics of this beautiful and endangered early-spring geophyte plant has important implications for species conservation. The species has an interesting life cycle and the different life stages have different detectability. The beautiful flowers are easy to detect, but the plants have low detectability in the leaf and capsule production stages, and it is completely hidden underground thereafter. Therefore it is crucial to understand the transitions between the stages to give reliable population estimations. In the paper we describe the transitions between these life stages and the effects of various climatic parameters on the population dynamics of Colchicum bulbocodium.

In early spring, the flowers are well visible.

And it is easy to find them :)

When only the leaves are visible, it is not easy to spot the plants.

Especially not in such kind of understorey vegetation...

Abstract

Due to their complex life cycles geophytes are often neglected in conservation programs, despite theyare important elements of early spring communities. Their life cycle is strongly affected by weatherparameters, i.e. temperature, precipitation, and light, but the effects of these parameters are oftencontradictory and show high intra-annual variability even within species. Deeper knowledge about theabiotic factors affecting the population dynamics of geophytes is needed to support the designationof effective conservation plans. We aimed to explore the link between weather parameters andpopulation dynamics of Colchicum bulbocodium, an endangered and strictly protected geophyte. Wemonitored three life cycle stages (flowering, growing, fruiting) of 1069 individuals in permanent plotsfor six consecutive years. Our results showed that life cycle of C. bulbocodium was strongly relatedto the actual weather parameters; the lagged effect of the previous year was weaker. Increasingtemperature and lack of cold periods had negative effect on all life stages. We highlighted thatpopulation estimation based on the number of flowering individuals in a single year can underestimatepopulation size by 40–83%. Monitoring in years following wet and cold springs and cold winters couldincrease the accuracy of population estimations of the flowering individuals.

Cultural and natural values of sacred sites - our new paper in Human Ecology

In our study recently published in Human Ecology, we aimed to explore the cultural values associated with ancient burial mounds, provide an overview of the landscape changes on and around the kurgans during the past 280 years, and explore the plant biodiversity of the kurgans. Based on our results, we evaluated factors that can support or endanger the grasslands on kurgans and assess whether there are synergies or trade-offs between cultural and natural values.

The citation of the paper:

Deák, B., Bede, Á., Süveges, K., Dózsai, J., Ormsby, A.A., Dixon, A., Valkó, O. (2024): Synergies and trade-offs between cultural and natural values of sacred sites – A case study of ancient burial mounds in Central Europe. Human Ecology https://doi.org/10.1007/s10745-024-00515-3

The paper is open access and can be downloaded from the journal homepage (please click here).

Kurgans, ancient burial mounds, hold significant cultural and spiritual value across the Eurasian steppes, reflecting a deep connection of local societies and these important landscape elements. These mounds, built by various steppe cultures like the Yamnaya, Sarmatians, Avars, and Hungarians, have served as cultural and spiritual landmarks for millennia. Their enduring cultural significance is evident through archaeological finds and the continued use of these sites for religious and communal activities.

Humka Kalvarija (‘Calvary Mound’; Kanjiža; Serbia)

Our study focusing on kurgans in Hungary, Romania, and Serbia reveals that these mounds are still regarded as sacred by local communities, who maintain graves and other spiritual objects on them. This cultural respect has helped preserve the kurgans, preventing destructive land use changes that could have altered their original state. In the past, kurgans also served practical purposes, such as acting as sentinel points, border markers, or flood refuges, further contributing to their preservation.

Despite significant landscape changes over the past three centuries, with much grassland converted to agricultural or urban use, the grasslands on kurgans have often remained intact. This preservation is likely due to the cultural importance of the kurgans, as land users consciously chose to protect these sites as part of their cultural heritage. Similar patterns of preservation due to cultural significance have been observed in other sacred sites around the world, such as sacred groves in India or land around monasteries in Italy. Kurgans are valuable for biodiversity, acting as refuges for grassland species that have become rare or endangered in surrounding landscapes. The relatively undisturbed state of these mounds, combined with their cultural significance, allows them to maintain high levels of plant species diversity. This makes kurgans important biodiversity hotspots in otherwise human-transformed landscapes. The microclimates created by the varying slopes and aspects of the kurgans contribute to this biodiversity by providing different habitats for various plant species.

Temető-halom (‘Cemetry Mound’, Iratoșu, Romania)

However, the maintenance of cultural values on kurgans can also lead to trade-offs. The construction of new religious and cultural structures can reduce the area of natural grassland, and the introduction of non-native or invasive species can threaten the existing biodiversity. In some cases, the lack of maintenance can lead to the accumulation of litter and an increased risk of fire, further endangering the natural values of the kurgans.

The study suggests that the cultural recognition of kurgans by local communities plays a crucial role in their preservation. This ‘bottom-up’ approach, driven by respect for historical and cultural heritage, can be more effective than formal protection measures. The findings highlight the importance of maintaining traditional cultural practices associated with kurgans to support the conservation of both their cultural and natural values. In conclusion, kurgans are essential biocultural hotspots that contribute to landscape-scale biodiversity conservation. Their preservation is vital not only for their cultural heritage but also for maintaining the ecological integrity of the landscapes they inhabit. By fostering a deeper understanding of the cultural and natural values associated with kurgans, we can better protect these ancient mounds and the biodiversity they support.

Humka Kalvarija (‘Calvary Mound’; Kanjiža; Serbia)

Abstract

In the Eurasian steppes, ancient burial mounds called ‘kurgans’ are among the most widespread manmade structures. These sacred sites hold cultural values and often provide safe havens for grassland-related plant species. We established links between kurgans' cultural and natural values through a comprehensive multi-layered evaluation of human and landscape history, cultural attributes, and botanical composition on selected mounds in Hungary, Romania, and Serbia. We evaluated factors that can support or endanger the grasslands on kurgans and assessed whether there are synergies or trade-offs between the presence of cultural and natural values. We found that kurgans act as cultural hotspots in transformed landscapes, and we found the following evidence for the synergies between cultural and natural values: i) Extensive land use and management connected to the cultural functions could considerably contribute to the preservation of grassland specialist plants on the mounds. ii) Over the past three centuries, most grasslands we studied were converted to cropland, but the cultural importance of the kurgans could hinder their destruction through ploughing or construction works. However, we also found that built cultural objects decreased the grassland cover area and supported the establishment and spread of several weedy and invasive species. Consequently, to preserve the valuable biocultural systems, it is essential to focus efforts on the maintenance of the already existing traditional cultural functions and not the establishment of new objects.

Our new paper about grassland restoration by topsoil removal and topsoil transfer - published in BMC Ecology and Evolution

Our latest paper about grassland restoration by topsoil removal and topsoil transfer  has been recently published in BMC Ecology and Evolution.

The paper is open access and can be freely downloaded from the journal homepage (please click here).

The citation of the paper:

Valkó, O., Kelemen, A., Kiss, O., Bátori, Z., Kiss, R., Deák, B. (2024): Grassland restoration on linear landscape elements – comparing the effects of topsoil removal and topsoil transfer. BMC Ecology and Evolution 24: 112. https://doi.org/10.1186/s12862-024-02299-y 

Here we compared the effectiveness of the two methods for the restoration of alkaline grasslands. We surveyed vegetation development after topsoil transfer and topsoil removal after the elimination of former linear landscape scars. Topsoil removal supported a rapid vegetation recovery and several rare halophyte species became established in the restored site. Topsoil transfer was less succesful and the developing vegetation was characterised by fewer target species and several weeds. Since these methods are rarely applied in Hungary, our results can provide new insights for the planning and implementation of restoration projects that involve the elimination of landscape scars.

This figure shows the initial conditions (in 2015): the positive landforms (embankments) and negative landforms (channels) that were eliminated in 2019. Below, you can see the recovering vegetation in the two sites in year 2 (2020).

Abstract

Artificial linear landscape elements, including roads, pipelines, and drainage channels, are main sources of global habitat fragmentation. Restoration of natural habitats on unused linear landscape elements can increase habitat quality and connectivity without interfering with agricultural or industrial development. Despite that topsoil removal and transfer are widely applied methods in restoration projects, up to our knowledge these were previously not compared in the same study system. To address this knowledge gap, we compared spontaneous vegetation recovery after the elimination of positive (embankments) and negative landscape scars (drainage channels) in lowland alkaline landscapes in South Hungary. The novelty of our study is that we compared the fine-scale and landscape-scale results of both methods. At the fine scale, we monitored the spontaneous vegetation development on the created open surfaces in the first, second and fourth year after restoration in 160 permanent plots per year. For characterizing the habitat changes on the landscape scale, we prepared habitat maps and assigned naturalness scores to each patch before and after the restoration activities. Both restoration methods resulted in a rapid vegetation recovery at the fine scale, progressing toward the reference state. In the topsoil removal treatment, a large part of the soil seed bank was removed; therefore, the colonization of the bare surface was a slower process. Seeds of halophytes, including the endemic and protected Suaeda pannonica, were probably present in the deeper soil layers, and these species became established in the restored surfaces, despite being absent in the surrounding vegetation. For restoring vegetation cover, topsoil transfer was a more rapid option; however, vegetation closure and competition by generalist species and weeds hampered the establishment of target species. The removal of the landscape scars by both methods made the sites accessible for grazing. At the landscape scale, the two methods had different effects: there was a slight increase in the habitat naturalness in the topsoil removal site, and a slight decrease in the topsoil transfer site because of weed encroachment. Spreading an upper layer of nutrient-poor soil with low amounts of weed seeds, direct propagule transfer, and targeted grazing regimes could enhance restoration success.

Our new review about urban grassland restoration has been published in Journal of Environmental Management.

Our latest paper, a global review about urban grassland restoration has been published in Journal of Environmental Management. This is a result of a nice cooperation between our research group and Valentin Klaus (ETH Zürich) and Leonie Fisher (University of Stuttgart).

The paper is open access and can be freely downloaded from the journal website (please click here).

Citation

*Fekete, Réka, *Valkó, Orsolya, Fischer, Leonie, **Deák, Balázs **Klaus, Valentin (2024): Ecological restoration and biodiversity-friendly management of urban grasslands – a global review on the current state of knowledge. Journal of Environmental Management 368: 122220.

 *, **: equal contributions.

Urban grasslands, like parks, meadows, vacant lots and other green spaces, play a crucial role in enhancing biodiversity in cities. However, as urbanization accelerates, these green spaces are increasingly threatened by factors like habitat degradation, pollution, and human activities. Our recent review explores the best strategies for restoring and managing urban grasslands to support biodiversity, focusing on lessons learned from various global studies.

The results of the review in numbers - location of the reviewed studies, and data on city population, site type, studied taxa, and main interventions.

The review found that restoration efforts in urban grasslands can indeed boost biodiversity, but the outcomes vary depending on factors such as the methods used to prepare the soil, the types of species introduced, and the specific conditions of each site. For instance, some sites benefit from introducing native plants, while others may need specific soil treatments or adjustments to local management practices. The success of these efforts also depends on maintaining diverse habitats, reducing mowing frequency, and avoiding the use of chemicals, all of which can create a more favourable environment for a wide range of species.

One key recommendation from our review is to create a network of interconnected green spaces across cities. This could involve enhancing connectivity between parks, vacant lots, and even small patches of green space that act as "stepping stones" for wildlife. Maintaining spontaneous vegetation in unused areas, like vacant lots, can also provide valuable habitats for various invertebrate species, which are essential for the overall ecosystem. Additionally, evaluating soil conditions before starting restoration projects is crucial, as the existing soil's seed bank and nutrient levels can significantly impact the success of the restoration.

The review also highlights the importance of shifting towards low-intensity, biodiversity-friendly management practices in urban grasslands. For example, reducing the frequency of mowing and eliminating the use of fertilizers and chemicals can significantly enhance biodiversity while also reducing maintenance costs. Using native, drought-tolerant species that require little to no irrigation is another cost-effective strategy, particularly as cities face the challenges of climate change.

However, we also identified several knowledge gaps that need to be addressed in future research. For instance, more studies are needed to understand the large-scale effects of urban grassland restoration, such as how these efforts impact entire cities or regions. Additionally, research is lacking in certain parts of the world, particularly in the Global South, and in cities of particulars sizes (especially small cities and mega-cities). Understanding how different local factors interact to influence restoration outcomes is essential for developing more widely applicable guidelines for urban grassland management.

In conclusion, while there is clear evidence that urban grassland restoration can enhance biodiversity, the success of these efforts depends on a variety of factors, including local conditions, management practices, and the specific methods used. By addressing the identified knowledge gaps and continuing to refine our approaches, we can better support biodiversity in urban environments, ultimately contributing to healthier and more resilient cities.

This photo collection shows the large variety of urban grasslands with native plant species in different greenspaces: A) garden meadow (Zürich, Switzerland), B) vacant lot (Detmold, Germany), C) right-off-way infrastructure (Zürich, Switzerland), D) tallgrass meadow in an urban park (Gödöllő, Hungary), E) mini-meadows in containers (Weesen, Switzerland), and F) roadside verge (Zürich, Switzerland)

Abstract

In the face of the global biodiversity decline, ecological restoration measures to actively enhance urban biodiversity and options for biodiversity-friendly greenspace management are high on the agenda of many governments and city administrations. This review aims to summarize and advance the current knowledge on urban grassland restoration by synthesizing research findings on restoration approaches and biodiversity-friendly management measures globally. Indeed, we found restoration approaches to be generally effective in increasing biodiversity; yet, there were variations in the outcomes due to the difference in soil disturbance methods, management regimes, the set of species introduced to a site, and the specific local setting. Based on the reviewed studies, we formulated recommendations for maximizing restoration success of urban grasslands through: i) creating a network of heterogeneous urban greenspaces and enhancing connectivity between them; ii) maintaining the spontaneous vegetation in vacant lots and wasteland sites that can provide habitats for various invertebrate species; iii) evaluating actual soil conditions, soil seed bank, and seed rain before restoration efforts take place since these seed sources could considerably affect the restoration outcomes, iv) preserving nutrient-poor conditions in urban greenspaces instead of introducing nutrient-rich topsoil; v) shifting to less intensive, biodiversity-friendly management in urban greenspaces by reducing mowing frequency and avoiding the use of chemicals; and vi) utilizing native dry grassland species for climate adaptation without irrigation. We further identified knowledge gaps regarding i) city-scale and regional-scale effects of restoration, ii) effects of interventions on multiple taxa and multiple ecosystem services, iii) restoration in small versus mega-cities, and iv) in the global south. These gaps should be addressed in future studies for making general guidelines for urban grassland restoration broadly applicable.

Our new paper about plant trait - environment relationships at the meso-scale published in the Science of the Total Environment

Our new paper by Balázs Deák et al. about the plant trait distributions in topographically heterogeneous dry grasslands has recently been published in the Science of the Total Environment.

The paper is open access, and can be freely downloaded from the website of the journal (please click here).

Reference:

Deák, B., Botta-Dukát, Z., Rádai, Z., Kovács, B., Apostolova, I., Bátori, Z., Kelemen, A., Lukács, K., Kiss, R., Palpurina, S., Sopotlieva, D., Valkó, O. (2024): Meso-scale environmental heterogeneity drives plant trait distributions in fragmented dry grasslands. Science of the Total Environment 947: 174355.

For studying trait-environment relationships, we selected our favourite study system, kurgans (millenia-old ancient burial mounds built by nomadic steppe tribes) that are among the most widespread man-made landmarks in the Eurasian steppe and forest steppe zone (please see our previous publications on these mounds here). We have shown that even at the scale of a few meters, the environmental heterogeneity can considerably shape the distribution of plant traits. Since these small landmarks are characterised by various different microsites, the large trait variation on the mounds can considerably increase community resilience.

Abstract

Environmental heterogeneity shapes the patterns of resources and limiting factors and therefore can be an important driver of plant community composition through the selection of the most adaptive functional traits. In this study, we explored plant trait–environment relationships in environmentally heterogeneous microsite complexes at the meso-scale (few meters), and used ancient Bulgarian and Hungarian burial mounds covered by dry grasslands as a model habitat. We assessed within-site trait variability typical of certain microsites with different combinations of environmental parameters (mound slopes with different aspects, mound tops, and surrounding plain grasslands) using a dataset of 480 vegetation plots. For this we calculated community-weighted means (CWMs) and abundance models. We found that despite their small size, the vegetation on mounds was characterized by different sets of functional traits (higher canopy, higher level of clonality, and heavier seeds) compared to the plain grasslands. North-facing slopes with mild environmental conditions were characterized by perennial species with light seeds, short flowering period, and a high proportion of dwarf shrubs sharply contrasted from the plain grasslands and from the south-facing slopes and mound tops with harsh environmental conditions. Patterns predicted by CWMs and abundance models differed in the case of certain traits (perenniality, canopy height, and leaf dry matter content), suggesting that environmental factors do not necessarily affect trait optima directly, but influence them indirectly through correlating traits. Due to the large relative differences in environmental parameters, contrasts in trait composition among microsites were mostly consistent and independent from the macroclimate. Mounds with high environmental heterogeneity can considerably increase variability in plant functional traits and ecological strategies at the site and landscape levels. The large trait variation on topographically heterogeneous landscape features can increase community resilience against climate change or stochastic disturbances, which underlines their conservation importance.

PhD defence of Katalin Lukács

Congratulations to Kata Lukács, who last week defended her PhD thesis entitled "The mechanism and ecological importance of human-vectored seed dispersal" with summa cum laude. We wish you all the best for the future and continue happy sciencing :)

Kata's PhD topic was the ecological significance of human-vectored seed dispersal. This is a very interesting, new, diverse and human-centered topic :) Kata has carried out her doctoral research with maximum dedication, enthusiasm, and precision.

Start of our first experiment related to human-vectored dispersal in 2017...

And continuation of the same experiment a few years later :)

The dissertation is based on the following articles:

Lukács, K., Tóth, Á., Kiss, R., Deák, B., Rádai, Z., Tóth, K., Kelemen, A., Bátori, Z., Hábenczyus, A.A., Tölgyesi, C., Miglécz, T., Godó, L., Valkó, O. (2024). The ecological footprint of outdoor activities: Factors affecting human-vectored seed dispersal on clothing. Science of the Total Environment 906: 167675. PDF

Valkó, O., Lukács, K., Deák, B., Kiss, R., Miglécz, T., Tóth, K., Tóth, Á., Godó, L., Radócz, S., Sonkoly, J., Kelemen, A. & Tóthmérész, B. (2020). Laundry washing increases dispersal efficiency of cloth-dispersed propagules. NeoBiota, 61, 1. PDF

Lukács, K., & Valkó, O. (2021). Human-vectored seed dispersal as a threat to protected areas: Prevention, mitigation and policy. Global Ecology and Conservation, 31, e01851. PDF

Lukács, K., & Valkó, O. (2022). Magterjedés az emberi ruházaton: megelőzési és védekezési lehetőségek. Természetvédelmi Közlemények, 28, 74–85. [in Hungarian] PDF

If you are interested in the topic, read the doctoral thesis, available here (in Hungarian and English). 

.. or the slightly shorter summary of the doctoral thesis, below:

The doctoral dissertation consists of three chapters aiming to provide an in-depth understanding of epianthropochory and to investigate further details of this process. In the first chapter, we collected data in a multi-site field experiment in three Central-European countries. We collected the diaspores (seeds, fruits) from 88 volunteer participant’s shoes and socks and we studied the effects of landscape-, vector- and plant characteristics. In total of 251 samples (and 2008 subsamples) we identified 229 plant species and we were the first to report the ability for cloth-dispersal in case of 137 species. Most of the identified species were weeds and disturbance tolerant species, which might cause serious environmental problems worldwide. We have shown that site characteristics and vector characteristics strongly influence the human-vectored seed dispersal (HVD) on clothing. In the second chapter, we tested the germination potential after the laundry washing in case of diaspores of 18 plant species. In addition, the adhesion potential of the diaspores was tested on three different clothing and fabric types (blue jeans, polar sweater and cotton socks) before and after the laundry washing. Our results show that washing temperature was the most significant factor affecting germination. Gentle washing at 30 C did not affect the germination potential, while intensive washing (60 C) decreased the seedling number in half of the species. Washing at 60 C desynchronized the germination of eight species. In desynchronized germination, diaspores start germination at different times. If germination is desynchronized, there is a higher chance some diaspores will germinate in a perfect time and establish in a new environment. We found that the lowest proportion of diaspores remained attached on blue jeans. Some of the diaspores may remain on clothing after the laundry washing and may even spread over long distances. In the third study, our aim was to collect biosecurity measures related to HVD on clothing. The biological measures were grouped according to the categories in force: information, self-regulation, legislation, quarantine measures, monitoring, interception and visitor management. Based on the literature, we added useful suggestions to guide to development of future directives.