Mosaic Of Patches Research Articles

Plant biodiversity and soils in the Jebel Marra region of Darfur, Sudan

Jebel Marra, a volcanic complex in western Sudan, is an important site of early settled agriculture, with high plant diversity, supported by orographic rainfall. Vegetation types were examined in relation to habitat, altitude, soils, and land management. In 52 sites, 274 species, predominantly Fabaceae and Poaceae, were recorded (with 17 new records). Sites were clustered using TWINSPAN, and Detrended Correspondence Analysis (DCA), generating eight vegetation types, six new since the 1970s. Changes in the dominant species show that the savanna has become sparser, with annuals displacing perennials. Soils were mostly “sandy clay loams,” so vegetation types did not directly correspond to soil types, although Type VIII vegetation grew in soils with a higher clay content. The sand fraction that predominated in soils of all other vegetation types was, mainly (87%) “soft” or aeolian sand. Canonical Correspondence Analysis (CCA) separated communities and species along a first axis, associated with finer soil textures, higher Fe, and lower elevations. The second axis was positively associated with elevated phosphorus, and negatively with sandy loams. CCA showed that rainfall alone was less pertinent than soil texture, which determines plant-available water capacity. The region’s vegetation was not uniformly diverse; instead, a mosaic of patches of diverse terrain, associated with different vegetation “types,” collectively generates a diverse flora. Besides climate change, overgrazing and increasing human pressures due to conflict, local population growth and an influx of refugees place these (already stressed) plant resources at risk. Our survey provides a baseline to track changes and develop adaptive management strategies.

Topsoil removal in degraded open sandy grasslands: can we restore threatened vegetation fast?

Natural open inland sandy grasslands are a highly threatened habitat in Europe. The originally nutrient‐poor habitats have been affected by increased aerial N‐deposition and the spread of competitively strong plants. We investigated the restoration of degraded psammophilous vegetation in the southeastern part of the Czech Republic, central Europe, where the competitively strong grass Calamagrostis epigejos had formed a compact cover over many hectares formerly dominated by valuable psammophilous grasslands. To expose nutrient‐poor sand, the upper nutrient‐rich layer was scraped off down to a depth of 10–30 cm. Vegetation was recorded by phytosociological relevés annually in a total of 15 permanent plots (5 × 5 m) established between 2012 and 2014 (five plots in each consecutive year). Reference sites with target psammophilous vegetation and degraded sites were also sampled. The target psammophilous species colonized the open sand areas immediately from the adjacent well‐preserved vegetation fragments. Out of 101 vascular plant species recorded in total in restored sites, 34 species were classified as target species, out of which 25 species were classified as threatened. After 6 years, the species richness and number of threatened species in the restored plots approached those of the reference sites. The results of multivariate analyses revealed that spontaneous development of restored plots run fast towards psammophilous vegetation. The optimal restoration strategy of eutrophicated open sandy grasslands should consist in creating a mosaic of topsoil removal patches followed by disturbance after some time and preservation of still existing fragments of target vegetation.

Mapping forest age and characterizing vegetation structure and species composition in tropical dry forests

Land use changes generate a mosaic of forest patches with different ages of abandonment (i.e. succession) intermingled with other land uses. Mapping the successional age of vegetation is crucial to understand carbon accumulation patterns and the recovery of vegetation structure, diversity, and composition of forests over time. The overall objective of this research was to produce maps portraying secondary vegetation age classes and to assess how successional age classes can be related to vegetation structure, diversity and composition in two types of tropical dry forests (TDF) in the Yucatan Peninsula. We used a two-stage image classification process. First, SPOT-5 imagery were segmented and then classified using a Random Forests method. Second, the classified images were post-processed to rectify any classification errors. Additionally, we evaluated the association between the different forest age classes and vegetation structure, species richness and composition using a separate Random Forests classification of field plot data. Post-processing improved the accuracy of the Random Forests classifications by 14.19% and 16.28% for the tropical semi-deciduous and semi-evergreen forests, to attain final accuracy values of 91% and 88.37%, respectively. Vegetation structure, richness and composition were all strongly associated with successional age, accounting for 77.7% and 84.7% of the total variation among forest age classes for the tropical semi-deciduous and semi-evergreen forests respectively. Therefore, the forest age maps obtained can be related to attributes of vegetation structure, diversity and composition that are useful for biodiversity conservation, forest management and climate change mitigation.

Ecological Allee effects modulate optimal strategies for conservation in agricultural landscapes

One target of biological conservation is the protection of biodiversity in agricultural landscapes. However, in their land-use decisions, farmers are often challenged with balancing biodiversity maintenance and profit generation. Under the current agricultural system, this tends to result in intensive farming which destroys suitable habitat for wild species. Thus, the potential for land-use conflicts between agriculture and biological conservation is high. Previous studies that investigated the effects of subsidies and taxes suggest mild trade-offs between conservation and farming, thus favouring land-sharing solutions to biological conservation. However, many ecological-economic models that dealt with this issue neglect possible Allee effects, which have been found by ecologists to be a common phenomenon. The existence of Allee effects markedly alters predictions of ecological-economic models: we show that conservation success is accompanied by substantial losses in agricultural production. More suitable habitat is required to prevent extinction of the species of interest, and conservation measures should start before the population has declined to some critical value. We emphasize the effect of spatial fragmentation on population viability under an Allee effect, as a clumped area of suitable habitat protects a population much better from extinction than a fragmented mosaic of habitat patches.

Linking deforestation patterns to soil types: A multifractal approach

AbstractIn the three last decades, continental Ecuador biosphere reserves (CEBRs) have undergone important land cover transformations because of human‐managed systems such as agriculture, livestock, forestry, and urbanization. Thus, the native landscape structure has been altered, exhibiting a mosaic of patches with varying sizes and shapes. The resulting landscape could shape some patterns over time, reflecting the complex interactions between human activities and biotic‐abiotic factors, such as soil, climate, and water availability. Quantifying the landscape patterns and their dynamics is essential for the monitoring and assessment of the ecological consequences of land‐cover change in time. Based on the soil maps and raster land‐cover maps from 1990 to 2016 of two CEBRs, the spatial deforestation patterns were quantified through lacunarity and multifractal analysis. To conduct these analyses, the deforested areas were identified and overlapped to predominant soil types. The results showed that the deforestation process pattern and soil types interact through complex relations due to specific site characteristics. Thereby, both soil and land cover interacted in fractal structures. The patch area distribution of deforestation patterns linked to soil types reveals a power‐law relationship in which, as the area of the deforested patches increased, their frequency decreased. Also, this relation presents self‐similarity and multifractal behaviour over a wide range of scales from 46–2,674 pixels, with a pixel size of 30 m × 30 m. However, each CEBR showed varying degrees of heterogeneity and complexity, which were reflected through lacunarity and multifractal parameters. The dynamics of deforestation patterns linked to soil types can be spatially dependent on the initial patchiness state, the distance to the adjacent patches, and the suitability of the soil for agrarian activities. Altogether, these were the spatial underlying factors of the deforestation evolution in the two CEBRs.Highlights Deforestation patterns show spatial self‐similarity Deforestation patterns are linked to soil types Landscape ecology, lacunarity, and multifractal analyses are useful to understand deforestation patterns Initial patch location, distance to the nearest neighbour and soil suitability boost the deforestation expansion

MULTI-SCALE ANALYSIS OF JACK PINE SAPLINGS AFTER FIRE ACROSS BURN SEVERITIES

Abstract. Fire serves as a successional initiation in jack pine (Pinus banksiana) forests of North America, as jack pine reproduce using seratonous cones that open only in intense heat. Jack pine seedling resilience after fire is characterized by high numbers of mortality. The estimation of sapling survivability and density is useful for understanding dynamics of carbon sequestration, forest structure and dynamic, and supporting management of the landscape. Most studies concerning the interaction of forest disturbances occurs at moderate spatial resolution. These moderate resolution data analyses do not adequately capture the fine scale spatial variation of the landscape after fire for understanding sapling survival. Thus, high-resolution data, such as aerial photography may provide more detailed information to support decision-making. A key to the types of spatial patterns that emerge in these early years is the pre-fire stand condition. In heavily managed areas, the mosaic of forest patches may include extensive variety in disturbance conditions. In this current research we address the problem of scale in relation to understanding the influence of pre-fire condition on post-fire early recovery patterns. To do this, we combine data output from the LandTrendr algorithm in Google Earth Engine with spectral data from aerial photography collected by airplane and Unmanned Aerial System to perform a random forest classification. The result is a finer scale resolution map of forest conditions of varying sapling density.

Restoration of the shifting mosaic of floodplain forests under a flow regime altered by a dam

A braided gravel-bed river provides essential habitats for various plants and animals. However, human regulation of rivers, such as dams, channelization, and other engineering works, alter flow and sediment regimes, which generally cause the degradation of river and riparian ecosystems. One of the prominent changes prevailing in Japanese rivers is forest expansion over gravel bars, and many native plants and animals that depend on gravel-bar habitat are now endangered. The Satsunai River is typical of rivers experiencing forest expansion, so the Japanese government launched a restoration project in 2012 to partially restore its riparian ecosystems. This is a large-scale experiment developed jointly by an interdisciplinary science team and river managers, who conduct monitoring and evaluation under an adaptive management scheme. The main measure to restore gravel bed habitat was an artificial flood regime, releasing a maximum water volume of 120 m3/s, which was a 2-year return period flood before dam construction. A unique feature of the project is that we considered the role of high-magnitude floods with recurrence intervals greater than 20 years after dam construction. We hypothesize that the artificial floods can be timed seasonally to create sites for regeneration and nesting of riparian species, and the high-magnitude floods contribute to maintaining a shifting mosaic structure of floodplain forest and unvegetated gravel-bar patches. We also used critical non-dimensional shear stress analysis to define “flood-disturbance areas” that can be disturbed under the artificial flow regime created by a dam. Artificial floods have been initiated once a year since 2012 at the end of June, synchronized with the seed dispersal period of Salix arbutifolia, which is endangered and a high conservation priority in the project. Thus far, the idea of setting floodplain-disturbance areas and the strategy of using both artificial and high-magnitude floods to restore a shifting mosaic of floodplain habitat patches is appropriate, as we found successful regeneration of S. arbutifolia and an exponential decay curve of the age distribution of floodplain forest patches. However, the sediment regime regulated by the dam was not addressed in this research, so future monitoring should track changes in river morphology associated with reduced sediment supply caused by the dam.

Meta-replication, sampling bias, and multi-scale model selection: A case study on snow leopard (Panthera uncia) in western China.

Replicated multiple scale species distribution models (SDMs) have become increasingly important to identify the correct variables determining species distribution and their influences on ecological responses. This study explores multi‐scale habitat relationships of the snow leopard (Panthera uncia) in two study areas on the Qinghai–Tibetan Plateau of western China. Our primary objectives were to evaluate the degree to which snow leopard habitat relationships, expressed by predictors, scales of response, and magnitude of effects, were consistent across study areas or locally landcape‐specific. We coupled univariate scale optimization and the maximum entropy algorithm to produce multivariate SDMs, inferring the relative suitability for the species by ensembling top performing models. We optimized the SDMs based on average omission rate across the top models and ensembles’ overlap with a simulated reference model. Comparison of SDMs in the two study areas highlighted landscape‐specific responses to limiting factors. These were dependent on the effects of the hydrological network, anthropogenic features, topographic complexity, and the heterogeneity of the landcover patch mosaic. Overall, even accounting for specific local differences, we found general landscape attributes associated with snow leopard ecological requirements, consisting of a positive association with uplands and ridges, aggregated low‐contrast landscapes, and large extents of grassy and herbaceous vegetation. As a means to evaluate the performance of two bias correction methods, we explored their effects on three datasets showing a range of bias intensities. The performance of corrections depends on the bias intensity; however, density kernels offered a reliable correction strategy under all circumstances. This study reveals the multi‐scale response of snow leopards to environmental attributes and confirms the role of meta‐replicated study designs for the identification of spatially varying limiting factors. Furthermore, this study makes important contributions to the ongoing discussion about the best approaches for sampling bias correction.

Yottixel - An Image Search Engine for Large Archives of Histopathology Whole Slide Images.

With the emergence of digital pathology, searching for similar images in large archives has gained considerable attention. Image retrieval can provide pathologists with unprecedented access to the evidence embodied in already diagnosed and treated cases from the past. This paper proposes a search engine specialized for digital pathology, called Yottixel, a portmanteau for "one yotta pixel," alluding to the big-data nature of histopathology images. The most impressive characteristic of Yottixel is its ability to represent whole slide images (WSIs) in a compact manner. Yottixel can perform millions of searches in real-time with a high search accuracy and low storage profile. Yottixel uses an intelligent indexing algorithm capable of representing WSIs with a mosaic of patches which are then converted into barcodes, called "Bunch of Barcodes" (BoB), the most prominent performance enabler of Yottixel. The performance of the prototype platform is qualitatively tested using 300 WSIs from the University of Pittsburgh Medical Center (UPMC) and 2,020 WSIs from The Cancer Genome Atlas Program (TCGA) provided by the National Cancer Institute. Both datasets amount to more than 4,000,000 patches of 1000×1000 pixels. We report three sets of experiments that show that Yottixel can accurately retrieve organs and malignancies, and its semantic ordering shows good agreement with the subjective evaluation of human observers.

Six-year removal of co-dominant grasses alleviated competitive pressure on subdominant grasses but dominant shrub removal had neutral effects in a subalpine ecosystem

The ‘stress-gradient hypothesis’ predicts increasing facilitative interactions with increasing environmental stress, but it remains unclear if the prevailing type of interaction (i.e. facilitative or competitive) between dominant and subordinate plant species occurring in harsh environments is dependent on the plant functional type. In addition, most plant-species removal experiments in grasslands are short-term (1–2 years), which may imprecisely reflect transient effects arising from methodological limitations. We conducted a dominant species removal experiment in a subalpine ecosystem, containing a mosaic of grass-dominated and shrub-dominated community patches, both of which are common in the subalpine zone of the Qinghai-Tibetan Plateau. We examined the direction and magnitude of the effects of three co-dominant grass and a dominant shrub species on subordinate species richness and biomass over a 6-year period. Removal of the dominant grass species alleviated their competitive pressure on subdominant grasses, which resulted in similar total and grass biomass detected in the final year of the study. By contrast, shrub removal showed no effects on its subordinate species biomass. Furthermore, neither the removal of the dominant shrubs nor the grasses altered their respective subordinate species richness. Thus, in subalpine ecosystems that experience harsh environmental conditions, our results showed that the direction of interactive effects of dominant plant species on subordinate species may be dependent on the plant functional type and are not necessarily facilitative. Furthermore, we showed that longer-term plant-removal experiment observations may be required to better determine the effects of species removal for this subalpine and other montane ecosystem(s).

Modelling patch mosaic connectivity and ecological corridors with GraphScape

Out of many approaches to landscape connectivity, we choose patch-mosaic, flow-neutral framework for modelling. Our new software system GraphScape transforms a vector mosaic map into landscape graph, finds shortest paths and combines them into minimum spanning tree. The result is an optimal network of connections for a given set of patches. To capture mobile agent properties, we use two types of resistance assigned to patches and transfer resistance assigned to combinations of patch classes. Another alternative is step-model, when transfers occur as if on unweighted graph. Resulting MST is rendered by linear skeleton (binary), Transit Density measure assignable to patches (continuous), and summary statistics. A novelty is compete workflow from vector-based map to complex graph structures. We describe concepts and operation of software. GraphScape can be used for ecological corridors planning, identification of key areas of corridors overlap, identification of the role of particular mobility factors, assessment of patch isolation.

Patch Mosaic Burning: Traditional Knowledge Supporting Management Decision Making

Patch Mosaic Burning: Traditional Knowledge Supporting Management Decision Making

Agricultural Heritage Systems and Landscape Perception among Tourists. The Case of Lamole, Chianti (Italy)

The Globally Important Agricultural Heritage Systems (GIAHS) program, promoted by the Food and Agriculture Organization (FAO), recognizes the multifunctional role of agricultural heritage systems. Traditional terraced landscapes represent important touristic destinations, and Chianti is one of the most well-known areas of Italy for rural tourism. The high-quality landscape of Lamole, consisting of forests and terraced agricultural areas, is included in the Italian National Register of Historical Rural Landscapes thanks to local farmers who recently restored the traditional landscape, considering it important both for tourism and product quality. The main aim of this research was to investigate, using anonymous questionnaires, whether tourists are aware of the characteristics of the Lamole landscape in comparison with other parts of Chianti. Results show that tourists clearly express their preference for the traditional landscape, which is comprised of a mosaic of agricultural patches with dry-stone terraces and forests, and that the level of landscape diversification is similar to 180 years ago. As tourism is a major resource, public institutions should support farmers in preserving the traditional landscape, investing in paths and information, as requested by tourists. The methodology has proved to be useful for addressing local planning, and to help farmers to achieve sustainable development in well-known touristic rural areas.

Fragment shape and size, landscape permeability and fragmentation level as predictors of primate occupancy in a region of Brazilian Cerrado

Human activities result in the formation of a mosaic of forest patches within a non-habitat matrix. The response of the local biodiversity to changes in land-use may occur at different scales. It is important to evaluate the effects of the attributes of both the patches and the surrounding landscape on the occupancy of forest patches by animal populations. Here, we assessed the predictive potential of local (basal area, tree density), patch (size, shape) and landscape scale (total area of forest, number of patches, matrix permeability, patch proximity) variables on the occupancy of forest patches by the syntopic primates Alouatta caraya, Sapajus libidinosus and Callithrix penicillata in the city of Goiânia in the Cerrado region of central Brazil. We used playback to survey primate populations in 22 focal patches and assessed the landscape within a 1000 m buffer zone around each site. In A. caraya, occupancy was influenced by the shape of the focal patches, the amount of forest and fragmentation level of the landscape. Focal patch size and the permeability of the matrix were the principal determinants of the occupancy of S. libidinosus. None of the predictors influenced patch occupancy in C. penicillata, and the structure of the vegetation did not influence occupancy in any of the species. The preservation of as many forest patches as possible, both large and small, as well as gallery forests, and the enhancement of matrix permeability will be essential for the long-term conservation of the syntopic primates of the Cerrado of central Brazil.

Edge influence on understorey plant communities depends on forest management

AbstractQuestionsDoes the influence of forest edges on plant species richness and composition depend on forest management? Do forest specialists and generalists show contrasting patterns?LocationMesic, deciduous forests across Europe.MethodsVegetation surveys were performed in forests with three management types (unthinned, thinned 5–10 years ago and recently thinned) along a macroclimatic gradient from Italy to Norway. In each of 45 forests, we established five vegetation plots along a south‐facing edge‐to‐interior gradient (n = 225). Forest specialist, generalist and total species richness, as well as evenness and proportion of specialists, were tested as a function of the management type and distance to the edge while accounting for several environmental variables (e.g. landscape composition and soil characteristics). Magnitude and distance of edge influence were estimated for species richness per management type.ResultsGreatest total species richness was found in thinned forests. Edge influence on generalist plant species richness was contingent on the management type, with the smallest decrease in species richness from the edge‐to‐interior in unthinned forests. In addition, generalist richness increased with the proportion of forests in the surrounding landscape and decreased in forests dominated by tree species that cast more shade. Forest specialist species richness, however, was not affected by management type or distance to the edge, and only increased with pH and increasing proportion of forests in the landscape.ConclusionsForest thinning affects the plant community composition along edge‐to‐interior transects of European forests, with richness of forest specialists and generalists responding differently. Therefore, future studies should take the forest management into account when interpreting edge‐to‐interior because both modify the microclimate, soil processes and deposition of polluting aerosols. This interaction is key to predict the effects of global change on forest plants in landscapes characterized by the mosaic of forest patches and agricultural land that is typical for Europe.

The effect of microhabitat patch size on settlement differs among co-occurring coral reef fishes

Over small spatial scales, coral reefs represent a mosaic of suitable settlement microhabitat patches of varying size for late-stage larval reef fishes. Few studies have specifically examined how variation in patch size influences density of recently settled coral reef fishes (recruits). Using standardized units of coral rubble settlement substrate deployed on sandy bottom, we monitored the concurrent settlement of three reef fish taxa onto differently sized patches (0.28–1.68 m2) at 5-d intervals during a lunar settlement peak. We found marked differences among taxa in how recruit density scaled with patch size. Recruit density of a damselfish and a parrotfish decreased and increased, respectively, with the increase in patch size, while that of a wrasse was similar among patch sizes. Our results highlight the importance of the interaction between taxon-specific settlement behaviour and patch size in establishing initial spatial differences in density within and among coral reef fish taxa in a heterogeneous landscape.

The role of semi‐open habitats as dispersal corridors for plant species of woodlands and open habitats

AbstractQuestionsEuropean pasture landscapes have been shaped by grazing and alternate husbandry. They are structurally characterised by mosaics of open habitat patches, individual trees and groups of trees or shrubs. We investigated whether these semi‐open habitats may act as stepping stones and thus as dispersal corridors for both plants from woodlands and open habitats to mitigate habitat fragmentation effects. We (a) contrasted the plant communities in semi‐open habitats with those of woodlands and open habitats, and (b) explored which life‐history traits or environmental requirements are associated with the presence or absence of species in semi‐open habitats.LocationSwabian Jura, South Germany; Lueneburg Heath, North Germany.MethodsWe selected four study sites in two contrasting landscapes and conducted vegetation surveys and analysed canopy closure and soil chemical properties in four different habitat types: woodlands, semi‐open habitats with high and low canopy closure and open habitats. We tested whether habitat type affected species composition, identified habitat‐specific indicator species and compared Ellenberg indicator values for light and moisture and species’ dispersal and establishment traits across these habitat types.ResultsPlant communities of woodlands were significantly different from those of all other habitat types, whereas open habitats showed some similarities to semi‐open habitats. On average, 73% of open habitat and 39% of woodland species were present in semi‐open habitats. Habitat requirements as well as dispersal and establishment traits of woodland species were often more specialised and differed from those of species of the other habitat types, making them less capable to disperse into semi‐open habitats.ConclusionsSemi‐open corridors have the potential to connect patches of open habitats and to a lesser extent also of woodlands without creating new barriers for either habitat type. Thus, semi‐open corridors may counteract habitat fragmentation effects and are a promising tool for biodiversity conservation, particularly in fragmented pasture landscapes.

Competition modulates the response of growth to climate in pure and mixed Abies pinsapo subsp. Maroccana forests in northern Morocco

The effects of changes in structure and composition on the dynamics and responses of secondary forests to climate change are understudied. Secondary forests of Abies pinsapo var. maroccana are often a mosaic of patches of various development stages showing different stand structures and successional stages. We hypothesise that the structure, species composition and tree-to-tree competition of A. pinsapo stands in Talassemtane National Park (Riff in northern Morocco) modulate the potential response of these secondary forests to climate change. Nine plots representing three species mixtures were established in A. pinsapo-dominated forests, and dendrometric and dendroecological surveys were conducted. The two-parameter Weibull function was used to investigate the diameter distributions of Abies pinsapo, Pinus nigra subsp. mauritanica. Cedrus atlantica, Acer opalus, Juniperus oxycedrus and Quercus ilex for each site along the compositional gradient. We quantified changes in radial growth, response to climate and drought, and components of growth resilience. Finally, the influence of neighbourhood competition on individual tree growth was evaluated using the a competition index. Diameter distributions had an exponential, reverse-J character for A. pinsapo in pure and C. atlantica mixed stands. By contrast, A. pinsapo presented a positively-skewed diameter distribution dominated by small-sized trees in P. nigra mixed stands. There was a significant correlation between tree growth and climate on all forest types, with differing magnitudes per species. Significant precipitation-growth correlations were found for the previous autumn and winter (October, December) in A. pinsapo. Drought events reduced A. pinsapo’s resistance to subsequent droughts when growing in pure and mixed stands with C. atlantica. This decline was statistically significant by the end of the studied period (1999–2005). In contrast, mixed forests showed the highest recovery after drought. Successive drought events consistently reduced A. pinsapo‘s resilience to drought, regardless of species composition. In pure A. pinsapo and in A. pinsapo-C. atlantica mixed forests, competition reduced A. pinsapo’s growth, while in A. pinsapo-P. nigra mixed forests increased competition with P. nigra seemed to have a positive-to-neutral effect on A. pinsapo growth. Here, we showed that the response to climate and resilience of A. pinsapo forests could be severely influenced by structure, species composition, and competition, potentially influencing our expectations of long-term persistence of old-growth coniferous trees in the Riff mountains. Understanding forest resilience and response to changing climate has important implications towards managing and safeguarding the productivity and health of these old growth forests.

Long-Term Effects of Sheep Grazing in Various Densities on Marsh Properties and Vegetation Dynamics in Two Different Salt-Marsh Zones

For conservation management of grassland ecosystems, an important question is under which conditions large grazers induce compositional and structural variation in plant communities, which is a prerequisite for high biodiversity. Here we used two long-term projects on the mainland salt marshes of the Wadden Sea to test the hypothesis that long-term grazing management with different stocking densities results in plant communities with distinctively different plant species composition and vegetation structure. The two projects took place on a low clayey and a high sandy salt marsh with different stocking densities of sheep: 0, 1.5, 3.5, 4.5 and the initially 10 sheep ha−1, where measurements were collected 11, 15, 19 and 23 years after the start of the project. Moreover, grazers affect abiotic conditions by reducing soil-redox potential and surface elevation, thereby driving composition and structure of salt-marsh vegetation. On the low salt marsh, a continued high stocking density (10 sheep ha−1) resulted in succession from the early-successional Puccinellia maritima community to the late-successional Atriplex portulacoides community. On the high salt marsh, the early-successional Festuca rubra community was maintained under all stocking densities. Cessation of grazing resulted in succession to the Elytrigia atherica community in both salt-marsh types. Intermediate stocking densities (1.5, 3 or 4.5 sheep ha−1) resulted in a mosaic of tall vegetation and patches of lawn, i.e. short-grazed vegetation, where Puccinellia maritima lawn occurred interspersed with patches of the Festuca rubra and tall Elytrigia atherica communities in both salt-marsh types. Effects of grazers were influenced by the presence of watering points near the sea wall. To conclude, our results show how joint interactions between grazers and abiotic conditions drive vegetation diversity and heterogeneity, with implications for ecosystem functions and services such as wildlife biodiversity and coastal protection.

Active dispersion, habitat requirements and human biting behaviour of the invasive mosquito Aedes japonicus japonicus (Theobald, 1901) in Hungary.

Aedes japonicus japonicus is endemic in a number of countries in eastern Asia but has been accidently introduced into many regions of the world including Europe. It was first detected in Hungary in 2012. In 2017, robust populations of the species were found at Lake Balaton, one of the most important tourist destinations in Central Europe. Based on the experience gathered in the above localities, habitat requirements, dispersion abilities and human biting behaviour of the species were studied in western Hungary during 2017 and 2018. Our results show that (a) a few years after its detection at the Slovenian-Hungarian border, Ae. j. japonicus is widespread in at least two-thirds of the western half of Hungary; (b) the species spreads quickly in ecological corridors formed by mosaics of rural areas, detached houses, gardens and small forest patches; (c) Ae. j. japonicus occupies artificial containers; (d) expansion of the species into new areas is slowed by extensive closed forest patches.