Marshland vegetation of the class <Emphasis Type="Italic">Phagmito-Magnocaricetea</Emphasis> in Croatia

The marshland vegetation of the class Phragmito-Magnocaricetea in Croatia is presented in a single place for the first time. All the available relevés from the literature have been assembled and supplemented with the results of field research. Thirty-three communities have been established, shown in a synoptic table drawn up on the basis of 486 relevés. The communities are understood according to the traditional syntaxonomic system based on the dominant or diagnostic species. For the purposes of comparison, the marshland vegetation is classified using numerical methods as well. The results obtained show that most clusters correspond to specific associations, but do not confirm the division into vegetation alliances and orders. The marshland communities with the most relevés in the dataset, and that therefore can be considered the most widespread in Croatia, are: Phragmitetum australis, Caricetum gracilis, and Galio palustris-Caricetum ripariae. The marshland vegetation is also analysed from the standpoint of nature conservation. In the dataset studied, 59 taxa from the Red Book of Vascular Flora of Croatia are identified as threatened, the 15 most endangered marshland communities are separated, and 10 neophytes and one neophyte association are registered. The diversity of marshland vegetation, and of the associated plant species, is considerably higher in inland Croatia than along the Adriatic coast, which is probably a result of the geological bedrock, climate and, in some places, halophile conditions.     

Variability of the <Emphasis Type="Italic">Molinion</Emphasis> meadows in Slovakia

Nine vegetation types were distinguished using cluster analysis within Molinion meadows in Slovakia. Vegetation of cluster 1 occurs on most acidic soils and is characterized by the occurrence of species of the Caricion fuscae alliance and of the Nardus grasslands. Vegetation of cluster 2 is also found on rather acidic soils but in contrast to cluster 1 vegetation it contains species of base-rich sites, such as Betonica officinalis, Galium boreale or Serratula tinctoria. Vegetation of cluster 3 occurs in wet base-rich habitats and often contains species of the Caricion davallianae alliance. Species of dry and Nardus grasslands are typical for vegetation of cluster 4, which is found at the driest sites and is confined to oligotrophic sandy soils. Vegetation of clusters 5 and 6 occurs on moist mesotrophic soils. Their species composition is quite similar, the main difference being that the former includes species-poor relevés and the latter includes species-rich relevés. Relevés of cluster 7 include species of dry grasslands and some ruderal species and represent degraded types of inundated floodplain meadows of the Deschampsion alliance. Vegetation of clusters 8 is characterized by species of the Phragmito-Magnocaricetea class and of the Deschampsion alliance, and occurs in wet nutrient-rich habitats. Vegetation of cluster 9, which usually develops from vegetation of cluster 8 due to decrease in the ground-water table, often contains species of dry grasslands and mesic meadows. Except for relevés of clusters 1 and 7, all others can be assigned to the Molinietum caeruleae Koch 1926 association. Cluster 1 corresponds to the Junco effusi-Molinietum caeruleae Tüxen 1954 association. Average Ellenberg indicator values for relevés, which were passively projected on the ordination biplot of detrended correspondence analysis, showed that the first ordination axis correlates with nutrients, soil base status and temperature, and second axis with moisture.     

The Balkan wet grassland vegetation: a prerequisite to better understanding of European habitat diversity

The knowledge of broad-scale floristic variation in wet grasslands, which are endangered throughout Europe, is still limited and some regions have remained unexplored so far. In addition, hitherto published phytosociological studies were concentrated at the national level and therefore national vegetation classifications are not consistent with each other. In order to overcome these shortcomings of traditional phytosociology, we gathered original data from Bulgaria and analysed them together with the data from Central Europe. We further analysed major compositional gradients within Bulgarian wet grasslands and changes in species richness along them. We sampled 164 wet grassland vegetation plots throughout Bulgaria. We further prepared a restricted data set of wet grasslands from Central-European phytosociological databases. Both data sets were merged and classified by modified TWINSPAN. Four distinct vegetation types were differentiated. Even if they correspond with traditional alliances, which are primarily drawn as geographically defined units in Western and Central Europe (sub-Mediterranean Trifolion resupinati, sub-continental Deschampsion cespitosae and Molinion caeruleae and sub-oceanic Calthion palustris), they all occur in Bulgaria. When more precise classification was applied, two types of sub-Mediterranean wet grasslands and one high-altitude type of Calthion grasslands were detected solely in Bulgaria. DCA analysis showed that altitude is a dominant gradient controlling variation in Balkan wet grasslands. The second DCA axis was interpreted as the gradient of nutrient availability. Species richness shows skewed-unimodal trends along both major gradients, with the highest species richness in intermittently wet nutrient-limited grasslands. Tukey post-hoc test of altitudinal differences amongst vegetation types is significant for all pairs of clusters, suggesting that altitudinal differentiation is responsible for co-occurrence of nearly all European types of wet grasslands in Bulgaria. Our results suggest that (1) climate is an important factor for the diversity of wet grasslands; (2) Balkan vegetation of middle altitudes matches with that of Central Europe, whereas that of the lowest altitudes corresponds rather to the sub-Mediterranean region and high mountains are specific; (3) upward shift of Central-European vegetation types in southern Europe, so often described in forest vegetation is also evident for grassland vegetation and (4) the high diversity of Balkan vegetation is determined by a diverse relief enabling confluence of habitats possessing different climatic conditions.     

Campylobacter,salmonella and chlamydia in free-living birds of Croatia

Campylobacteriosis, salmonellosis and avian chlamydiosis are zoonotic diseases in which birds have been suggested to play an important role as reservoirs. We have investigated the prevalence of Campylobacter and Salmonella spp. and Chlamydophila sp. in 107 free-living birds belonging to 25 species from 13 families from Croatia in order to examine the natural infections caused by these agents. Campylobacter jejuni-like organisms were isolated from 2 of 107 free-living bird species examined (1.9%). Salmonella was isolated from 8 fresh fecal specimens from free-living bird species (7.4%). These isolates were identified as S. typhimurium in 4 (3.7%), and S. enteriditis in 4 (3.7%) free-living birds. These samples originated from feral pigeons (Columba livia domesticus; n=14; 28.6%), rook (Corvus frugilegus; n=13; 15.4%), buzzard (Buteo buteo; n=12; 16.7%), black-headed gull (Larus ridibundus; n=8; 12.5%) and tawny owl (Strix aluco; n=8; 12.5%). The presence of Chlamydophila sp. was not detected in the free-living birds examined during this study. Epidemiological aspects and possible significance of the examined birds as a source of infections for domestic animals and humans are discussed.     

Syntaxonomic update on the relict groves of Mirbeck's oak (Quercus canariensis Willd. and Q. marianica C. Vicioso) in southern Iberia

As relict traces of the Tertiary period, Quercus canariensis Willd. and the forests it forms comprise one of the most interesting woodlands, which prevails in southern Iberia with very particular edaphoclimatic envelopes. Combining phytosociological methodology with hierarchical cluster analyses, we aim to update the syntaxonomic scheme of the forests related to this species and the complex matrixes it forms with the hybrid species Quercus marianica C. Vicioso. We propose one new association from Portugal, in a total of four types of Mirbeck's oak woodlands, in Southern Iberia. We conclude the necessity to maintain high standards on taxonomic and geobotanical surveys, with major biogeographic knowledge; it is indissociable from an accurate analysis and comprehension on the functional ecology and structure of these woodlands, regarding its dynamics. Therefore, their high conservation value, related to its relict status, supports the integration of these forests in Habitat 9240 (Annex B-I from Council Directive 92/43/EEC) in order to ensure its preservation.     

Limitations to seedling establishment in a mesic Hawaiian forest

While invasive species may be visible indicators of plant community degradation, they may not constitute the only, or even the primary, limitation to stand regeneration. We used seed-augmentation and grass-removal experiments under different canopy conditions to assess the relative importance of dispersal limitation, resource availability, and competition on seedling establishment in the understory shrubs Sophora chrysophilla, Dodonea viscosa, and Pipturus albidus in a montane mesic forest in Hawaii. The study location was an Acacia koa-Metrosideros polymorpha forest at 1000–1500 m elevation on the leeward side of Hawaii Island; it is a closed-canopy forest historically subject to logging and grazing by cattle and sheep and currently dominated by the exotic grass, Ehrharta stipoides, in the herb layer. Seedling establishment after 1 and 2 years was strongly dispersal limited in Sophora and Dodonea, but not in Acacia, a non-augmented species in which abundant seedlings established, nor in Pipterus, in which only one seedling established in 2 years. Grass cover reduced seedling establishment in Acacia, Sophora, and Dodonea and, for the latter two species, seedling establishment was substantially greater in the warmer, more moist forest at the lowest elevation. Light, moisture, and resin-captured N and P were more strongly affected by elevation and canopy composition than by grass cover, but in most cases seedling establishment was not positively correlated with resource availability. Limitations to the establishment of woody seedlings in this forest-grassland mixture vary among species; however, both dispersal limitation and competition from a shade-tolerant grass are important deterrents to regeneration in these forests.     

Ecological impact of marine plant harvesting in the northwest Atlantic: a review

The ecological impact of marine plant harvesting is related to the intensity of exploitation, the harvesting technique, and the vulnerability of the species or habitat to perturbation. In eastern Canada information was available on four levels of impact: long-term changes in the target species and direct loss or damage to non-target species, direct or indirect impact on the habitat or community, indirect effects of changes in habitat or community structure, and trophic level impact. Near monoculture stands of Chondrus crispus have associated with them up to 36 animals species and 19 major species of algae that are vulnerable to removal as by-catch. Indirect effects of changes in macrophyte cover were not observed in fish species utilization of Ascophyllum nodosum beds on rising tides. Subtidal areas devoid of all macrophyte cover had lower levels of the preferred foods for Homarus americanus than kelp-covered areas; however, barren grounds are not created by macrophyte exploitation rates of 20% to 80% in eastern Canada. Long-term harvesting has altered the population structure and population ecology of C. crispus and A. nodosum in some areas. In general both target species and associated communities are resistant to perturbation.     

Pattern analysis in Belgian limestone grasslands

Pattern analyses were made in several limestone grasslands of Belgium. Vegetation has been sampled in continuous transects. Monospecific patterns are defined by means of two non-parametric indices; multivariate analysis (reciprocal averaging) completed the analysis. The following kinds of pattern are described and explained: random, aggregate, clump, gap, stationary density variation, non-stationary density variation, gradient and many complex patterns. The multivariate analysis leads to a careful phytosociological study of the transects and to the definition of floristically homogeneous regions. Some particular points of pattern analysis, the problem of vegetation sampling and some perspectives are discussed.     

Vegetation on avalanche paths in the alps

Vegetation pattern on avalanche paths in the Nordkette Mountains near Innsbruck (Tyrol, Austria) was studied using transect sampling. The plant communities represent a gradient from alpine grassland (Seslerio-Caricetum sempervirentis, via grassland with Trisetum distichophyllum) and nutrient-poor grassland (Carlino-Caricetum sempervirentis) to an avalanche grassland proper. Along this gradient disturbance decreases from higher to lower elevations. The topography of the avalanche path suggests a gradient from the central zone to the edge of the path, although a floristic zonation or grouping of species across the path cannot be detected. Disturbance and local topography are the dominant factors for the vegetation pattern on the avalanche paths investigated.Abbreviations DCA= detrended correspondence analysis     

Recent changes in mountain grasslands: a vegetation resampling study

Understanding how land‐use changes affect different facets of plant biodiversity in seminatural European grasslands is of particular importance for biodiversity conservation. As conclusions of previous experimental or synchronic observational studies did not converge toward a general agreement, assessing the recent trends in vegetation change in various grassland systems using a diachronic approach is needed. In this resurvey study, we investigated the recent changes in grassland vegetation of the French Jura Mountains, a region with a long tradition of pastoralism. We compared the floristic composition of 150 grassland plots recorded between 1990 and 2000 with new relevés made in 2012 on the same plots. We considered taxonomic, phylogenetic and functional diversity as well as ecological characteristics of the plant communities derived from ecological indicator values and life strategies of the species. PCA of the floristic composition revealed a significant general trend linked to the sampling year. Wilcoxon paired tests showed that contemporary communities were generally more dominated by grass species and presented a higher tolerance to defoliation, a higher pastoral value, and a higher nutrient indicator value. Comparisons revealed a decrease in phylogenetic and functional diversity. By contrast, local species richness has slightly increased. The intensity of change in species composition, measured by Hellinger distance between pairs of relevés, was dependent on neither the time lag between the two surveys, the author of the first relevé nor its location or elevation. The most important changes were observed in grasslands that previously presented low pastoral value, low grass cover, low tolerance to defoliation, and high proportion of stress‐tolerant species. This trend was likely linked to the intensification of grassland management reported in the region, with a parallel increase in mowing frequency, grazing pressure, and fertilization level. More restrictive specifications should be applied to agricultural practices to avoid overexploitation of mountain species‐rich grasslands and its negative consequences on their biodiversity and resilience.     

Light distribution in mesic grasslands: Spatial patterns and temporal dynamics

Abstract. Spatial patterns and temporal dynamics of light distribution were investigated using lacunarity analysis, a multi‐scale measure of spatial heterogeneity, in three mesic grasslands with different disturbance regimes. Frequency distributions of relative light intensity (RLI) were similar for the two non‐disturbed grasslands, despite different composition (forbs vs. caespitose grass) resulting from different historical disturbance regimes prior to 1985, and different from the annually disturbed grassland. Spatial heterogeneity of light distribution was greater at all scales in the native, annually disturbed grassland than in the two non‐disturbed grasslands. The disturbance regime affected temporal dynamics of the spatial patterns of light distribution in each grassland. The annually disturbed grassland exhibited a dramatic decrease in lacunarity (heterogeneity) from early to late April, likely the result of considerable growth of a cool‐season grass. A general decrease in lacunarity occurred in the native, non‐disturbed grassland, although the magnitude was much less than in the annually disturbed grassland. The reverted, non‐disturbed grassland did not exhibit an appreciable change in lacunarity until later in the growing season, and then only at smaller scales. Combining the frequency distribution of RLI and the lacunarity curves provided an effective approach to assess relationships between the dynamics of spatial pattern of light distribution and ecological processes as influenced by different disturbance regimes. Integrating lacunarity analysis with more traditional measurements of grassland ecosystems (plant spatial distribution and arrangement and plant species composition and architecture) may be an effective way to assess functional consequences of structural changes in grassland ecosystems.     

Classification of South Swedish Isoetid vegetation with the help of numerical methods

Relevés of Isoetid vegetation from 60 lakes in southern Sweden have been classified with the help on numerical methods. A community system is constructed, at the variant level by clustering with the TABORD program, and at the community and subcommunity levels by reference to traditional floristic characteristics. The diagnostic species were selected with the help of PCA. Isoëtes lacustris, Lobelia dortmanna and Littorella uniflora determined the community composition together with Eleocharis acicularis. The differentation of the syntaxa along the first three ordination axes of a PCA was clear. The complex water depth factor determines clearly the position of the small syntaxa (variants) in the PCA ordination space. At high levels of similarity the relevés were grouped effectively with the TABORD program, so that the clusters are floristically homogeneous and easy to identify on the basis of floristicsociological criteria. At higher syntaxon levels a selective use of diagnostic species was made.     

Linkage between seasonal gas exchange and hydraulic acclimation in the top canopy leaves of Fagus trees in a mesic forest in Japan

We investigated how leaf gas exchange and hydraulic properties acclimate to increasing evaporative demand in mature beech trees, Fagus crenata Blume and Fagus japonica Maxim., growing in their natural habitat. The measurements in the top canopy leaves were conducted using a 16-m-high scaffolding tower over two growing seasons. The daily maxima of net photosynthetic rate for the early growing season were close to the annual maximum value (11.9 mol m^–2 s^–1 in F. crenata and 7.7 mol m^–2 s^–1 in F. japonica). The daily maxima of water vapor stomatal conductance were highest in the summer, approximately 0.3 mol m^–2 s^–1 in F. crenata and 0.15 mol m^–2 s^–1 in F. japonica. From the early growing season to the summer season, the leaf-to-air vapor pressure deficit increased and the daily minima of leaf water potentials decreased. However, there was no loss of leaf turgor in the summer as a result of effective osmotic adjustment. Both the soil-to-leaf hydraulic conductance per unit leaf area and the twig hydraulic conductivity simultaneously increased in the summer, probably as a result of production of new vessels in the xylem. These results suggest that both osmotic adjustment and increased hydraulic conductance resulted in the largest diurnal maximum of stomatal conductance in the summer, resulting in the lowest relative stomatal limitation on net photosynthetic rate, although the leaf-to-air vapor pressure deficit was highest. These results indicate that even in a mesic forest, in which excessive hydraulic stress does not occur, the seasonal acclimation of hydraulic properties at both the single leaf and whole plant levels are important for plant carbon gain.     

高寒干旱草原披针叶黄华植物群落土壤种子库与地上植被的关系

以祁连山高寒干旱退化草地披针叶黄华(Thermopsis lanceolate)群落为研究对象,采取野外调查取样和室内分析相结合的方法,对群落土壤种子库与地上植被的关系进行了对比研究。结果表明:地上植被物种共调查出15种,土壤种子库检测出植物18种,地上植被阿尔泰针茅(S.krylovii)、赖草(A.dasystachys)和扁穗冰草等可食草以及不食草披针叶黄华和阿尔泰狗哇花(H.altaicus)优势度明显,其它物种不明显;土壤种子库与地上植被物种组成的相似性程度较低;土壤种子库与地上植被中可食草的物种数多于不食草,土壤种子库的物种数均不小于地上植被中的物种数,地上植被中存在而未在土壤种子库中检测到的可食草物种有阿尔泰针茅和赖草,土壤种子库中存在而地上植被中未被发现的物种有早熟禾(P.annua)、灰绿藜(C.glaucum)、碱韭(A.polyrhizum)、酸模(R.patientia)、独行菜(L.apetalum)和秦艽(G.macrophylla);原生禾草物种在可食草功能群中生物量所占比例较低,毒杂草物种生物量所占比例增加显著,而土壤种子库的数量百分含量较低;可食草与不食草的生物量在植被梯度下的变化呈显著负相关(r=-0.940,P=0.018),而土壤种子库密度变化无相关性;可食草生物量变化与其土壤种子库密度变化不相关,不食草生物量变化与其土壤种子库密度的增加呈显著正相关(r=0.902,P=0.036)。     

Habitat matters – Strong genetic and epigenetic differentiation in Linum catharticum from dry and wet grasslands

Plant species differ in their ecological amplitude, with some species occurring in very different habitats under strongly differentiated environmental conditions. We were interested in to what extent the occurrence of Linum catharticum in dry calcareous grasslands (Bromion) and wet litter meadows (Molinion), two habitats on opposing ends concerning, for example, moisture level, is reflected on the genetic and epigenetic level. Using AFLP (amplified fragment length polymorphisms) and MSAP (methylation sensitive amplification polymorphisms) analyses, we studied the genetic and epigenetic variation of L. catharticum from calcareous grasslands and litter meadows. From each habitat, we included five study sites with 16 individuals per sampling location. We observed lower genetic than epigenetic diversity, but considerable differentiation among habitats, which was stronger on the genetic than the epigenetic level. Additionally, we observed a strong correlation of genetic and epigenetic distance, irrespective of geographic distance. The dataset included a large portion of fragments exclusively found in individuals from one or the other habitat. Some epigenetic fragments even occurred in different methylation states depending on the habitat. We conclude that environmental effects act on both the genetic and epigenetic level, producing the clear differentiation among plant individuals from calcareous grasslands and litter meadows. These results may also point into the direction of ecotype formation in this species.     

Effects of ants on plant diversity in semi-natural grasslands

Ants (L. niger and L. flavus) build conspicuous mounds that are covered with vegetation. The aim of this study was to investigate whether the vegetation on ant mounds in semi-natural grasslands differed from that around the mounds. Another aim was to investigate whether the changes in the vegetation on ant mounds were influenced by grazing management or by habitat characteristics, semi-dry versus moist. Here, the total number of plant species and total plant cover were lower on ant mounds than in patches off-mound. The plant cover of perennials that form rosettes was twice as high on mounds inhabited by L. niger than on those inhabited by L. flavus. Only a few plant species were restricted to either ant mounds or adjacent field and the effects of ants on the plant diversity in semi-natural grasslands seemed to be low. Grazing management did not affect the differences in the vegetation on ant mounds and in equal-sized patches off-mound, whereas habitat characteristics affected ant-induced changes in vegetation cover of some plant species.     

On community structure in high alpine grasslands

Previously published data on production biology, energy use efficiency, nutrient availability and vulnerability were reinterpreted for the explanation of community processing and structure in high altitude grasslands of the Alps. The final goal of the approach was to present a characterization of these plant communities in generalized terms.The keystone-concept was applied, and the alpine grasslands then defined as plant communities with one or a few keystone species. Associated species show a varying degree of interdependence from these keystones. They form guilds exploiting resources not needed by the latter. As many of these species belong to these groups, and alpine grasslands are commonly species rich, a high functional redundancy is typical for these communities.