Iva Apostolova

Diversity of wetland vegetation in the Bulgarian high mountains, main gradients and context-dependence of the pH role

We fill a gap in understanding wetland vegetation diversity and relationship with environmental determinants in Bulgarian high mountains. A total of 615 phytosociological samples were taken from springs, mires, wet meadows and tall-forb habitats throughout Bulgaria, of which 234 relevés are from mire and spring vegetation above timberline. The vegetation was classified by TWINSPAN and the resulting vegetation types were reproduced by the formal definitions using the combination of Cocktail species groups based on phi-coefficient of joint co-occurrence of the species. Nine vegetation types of springs and fens have been clearly delimited above the timberline. All vegetation types include Balkan endemic species, the representation of which varies. Fens generally harbour more Balkan endemics than do springs, with the exception of species-poor high-altitude Drepanocladetum exannulati. The gradient structure of the vegetation was revealed by DCA and by CCA with forward selection of environmental factors. The major determinants of vegetation variation strongly differ above and below the timberline and likewise between springs and fens. The base-richness gradient controls the floristic variation of Bulgarian submontane fens, whereas the complete data set including both submontane and subalpine fens is governed by the altitude gradient from lowland and basin fens to subalpine fens rich in Balkan endemics. When focusing on sites above the timberline only, the first DCA axis separates fens from springs without organic matter. The major species turnover in springs follows the variation in water pH and mineral content in water, whereas fen vegetation variation is primarily controlled by succession gradient of peat accumulation. Altitude remains an important factor in all cases. Weak correlation between water pH and conductivity was found. This correlation was even statistically insignificant in fens above the timberline. Water pH is not influenced by mineral richness in Bulgarian high mountains, since it is buffered by decomposition of organic matter in fens. In springs, pH reaches maximum values due to strong aeration caused by water flow. The plant species richness decreases significantly with increasing altitude. The increase of species richness towards circumneutral pH, often found in mires, was not confirmed in Bulgarian high mountains. The correlation between species richness and pH was significant only when arctic-alpine species and allied European high-mountain species were considered separately. The richness of boreal species was independent on pH. Some of them had their optima shifted to more acidic fens as compared to regions below the timberline. Our results suggest that subalpine spring and fen vegetation should be analysed separately with respect to vegetation-environment correlations. Separate analysis of fens below and above timberline is quite appropriate.

Effect of land abandonment on the vegetation of upland semi-natural grasslands in the Western Balkan Mts., Bulgaria

Abstract The area of semi-natural grasslands in Bulgaria has decreased tremendously in the past century due to agricultural intensification or abandonment. As these grasslands host valuable biodiversity, conservation measures are needed for their sustainable maintenance. We studied the effect of pastureland abandonment on plant communities at the Ponor Mt., a part of the Balkan Mts., Bulgaria. Data on floristic composition, vegetation structure and several abiotic parameters were collected in 137 randomly located 16-m2 plots in 2008. Canonical correspondence analysis (CCA) was used to analyse how species composition is related to abiotic and land use factors. Analyses of covariance (ANCOVAs) were used to test for the effects of sheep grazing vs. abandonment on vegetation structure and composition. The main environmental factors explaining the compositional variation were related to the altitude, sheep grazing and soil depth. Pastureland abandonment led to an increase in vegetation height and of the richness of mesophytes and leafy plants, and red-list species. Grazed plots had higher total species richness, more xerophytes, rosette forming and spring-flowering species. To ensure the persistence of the species of both the open grasslands and mid-successional grassland communities, the management should be carried out in an extensive way and with a zonation regime.

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.

Disjunct Occurrences of Plant Species in the Refugial Mires of Bulgaria

Many mire vascular plant and bryophyte species have disjunct occurrences in Bulgaria despite that most of south-eastern Europe is not suitable for the occurrence of permanently waterlogged and nutrient-limited wetlands due to the current and glacial dry climate conditions as well as prevailing limestone bedrock. Unfortunately, such important distributional data are scattered throughout numerous papers and reports, and are not adequately provided even by national checklists and floras. No attempt to summarize them has been done yet. Therefore, the main aim of this paper is to review and enlarge such data, and to use the resulting data set to address the question whether the disjunctly occurring rare species are concentrated in certain mire complexes or even in particular vegetation plots and if they do characterize such localities. Our current research shows that the phenomenon of isolated occurrences of mire plants in Bulgaria is even more widespread than previously thought. Seventeen species were found as new for Bulgaria with their distribution range limits there, and distributional data of many other species, including some previously considered extinct, were enlarged. Fifty-four mire species were found at only three or fewer sites. Our analyses showed a conspicuous concentration of rare, disjunctly occurring species at a few sites, which are, however, largely unexplored in terms of palaeoecology or ecology, not legally protected and currently threatened by human activities. The distributions of target rare species within Bulgarian mires were significantly nested, which means that more species-poor assemblages were subsets of richer ones. Nestedness was significantly related to the estimated area of mire complex, but not all high-diversity mires were large. Disjunctly occurring rare species were more concentrated in particular vegetation plots at lower altitudes and in mineral-rich fens. Fragmentary data about the ecology and history of Bulgarian refugial mires suggest that these mires harbour specific ecotypes and genotypes, contain specifically distributed biogeographic groups of species, provide an opportunity to test biogeographical hypotheses and shelter crucial information about the history of European mires. Thus, these sites have a potential to become a source of very important information for biogeographical, palaeoecological, and phylogeographical analyses.

A review of Potentillo ternatae-Nardion strictae alliance.

A Review of Potentillo Ternatae — Nardion Strictae Alliance A classification of the Nardus stricta dominated communities in the Balkan Range is presented. Two associations are identified: Nardetum strictae and Campanulo alpinae — Nardetum strictae nom. nov. The alliance Potentillo ternatae — Nardion strictae is typified and some comments on its distribution range and syntaxonomical affiliation to the higher units are presented. A synopsis is included of all available associations referred to Potentillo ternatae — Nardion strictae. Pregled zveze Potentillo ternatae - Nardion strictae V članku je predstavljena klasifikacija združb z dominantno vrsto Nardus stricta na Balkanu. Prikazali smo dve asociaciji: Nardetum strictae and Campanulo alpinae - Nardetum strictae nom. nov. Zvezo Potentillo ternatae - Nardion strictae smo tipizirali in predstavili njeno razširjenost in sintaksonomsko uvrstitev v višje enote. Prikazan je sinopsis vseh opisanih asociacij, ki jih uvrščamo v zvezo Potentillo ternatae - Nardion strictae.

Mollusc communities in Bulgarian fens: predictive power of the environment, vegetation, and spatial structure in an isolated habitat

Mollusc communities of previously unexplored Bulgarian fens were studied in order to determine and generalise the patterns of species richness and composition along the mineral richness gradient. The aim was also to compare predictive values of the environment, vegetation and spatial structure. Altogether, 44 mollusc species were recorded at 40 treeless fen sites. Species richness varied from 0 to 18 species per site, and it was positively associated with the mineral gradient and negatively with altitude. However, the best predictor was obtained using plant species composition. All explanatory variables had higher effect on land snails than on the entire mollusc assemblage (including aquatic species). Species richness and abundance were significantly and positively correlated with the species composition turnover; the communities were highly nested, with poor sites having subsets of the fauna found in the richest. The main direction of mollusc species turnover was highly associated with that observed for vegetation, and the main gradient of plant species composition was able to explain nearly 20% of total variation in mollusc data. We found that spatial structure explained by far the highest proportion of independent variation, which reflected the high level of geographical isolation of Bulgarian fens and regional differences independent of any environmental variation. Our results demonstrate (1) the general role of mineral richness gradient for structuring mollusc communities in fens, (2) the pivotal indicator role of plant species composition in predicting species composition of mollusc communities, despite being trophically independent and (3) the effect of isolation and origins of the habitat on species composition: most species have wide geographical distributions within the habitat type, and geographical patterns within Bulgaria may have a stochastic element.

The Association Erysimo - Trifolietum Micev. 1977 in Bulgaria and Some Remarks on its Mediterranean Character

The Association Erysimo - Trifolietum Micev. 1977 in Bulgaria and Some Remarks on its Mediterranean Character We endeavor to enlarge the knowledge about Bulgarian vegetation diversity. Data on seminatural grasslands containing 344 relevés, collected in Southeast Bulgaria were analyzed by the combine method, using TWIN-SPAN and the Cocktail method. The Erysimo diffusii-Trifolietum angustifolii association and the alliance Trifolion cherleri were established for the first time in Bulgaria. So far the presence of this association was known for Macedonia. The aims of our study are to present more data about the Erysimo-Trifolietum in Bulgaria and to make some comments about its affiliation to Helianthemetea guttati. The association is characterized ecologically and floristically. Analysis of the floristic elements shows that the most numerous are sub-Mediterranean species. Analysis of the life forms shows that these communities are hemicryptophyte-therophytic. A review of syntaxonomical systems and association assignment to higher syntaxa were made. According to current European vege-tation surveys the association should be related to class Helianthemetea guttati. Our results reveal an intermediate character of the studied vegetation - closed dry grasslands, with distinct presence of Festuco-Brometea species with a high percent of therophytes and Mediterranean floristic elements related to Helianthemetea guttati as well. Članek je prispevek k poznavanju raznovrstnosti vegetacije Bolgarije. Podatke, ki obsegajo 344 popisov, nare-jenih v jugovzhodni Bolgariji, smo analizirali s kombinacijo metod TWINSPAN in Cocktail. Asociacija Erysimo diffusii-Trifolietum angustifolii in zveza Trifolion cherleri sta prvič omenjeni v vegetaciji Bolgarije. Do sedaj je bila prisotnost te asociacije poznana le v Makedoniji. Namen raziskave je predstaviti dodatne podatke o asociaciji Erysimo-Trifolietum v Bolgariji in podati nekaj komentarjev o njeni uvrstitvi v razred Helianthemetea guttati. Asociacija je označena ekološko in floristično. Analiza flornih elementov je pokazala, da so submediteranske vrste najštevilnejše. Analiza življenjskih oblik pa, da je to hemikriptofitsko-terofitska združba. Opravljen je pregled sinataksonomskega sistema in uvrstitev v višje sintaksone. Po trenutnem pregledu evropske vegetacije jo uvrščamo v razred Helianthemetea guttati. Naši rezultati pa razkrivajo vmesni značaj obravnavane vegetacije - sorodnost s suhimi travniki s prisotnostjo vrst Festuco-Brometea in visokim odstotkom terofitov in z razredom Helianthemetea guttati, ki ga označujejo mediteranski elementi.

The insecure future of Bulgarian refugial mires: economic progress versus Natura 2000

Bulgarian mires acted as refugia during the dry phases of ice ages and contain a high number of rare and disjunct species. In this study we ranked all known mire and spring complexes in Bulgaria according to the occurrence of rare and threatened plant and mollusc species. This analysis shows a conspicuous concentration of rare species at several sites, and no correspondence between the importance of individual mires for biodiversity and their legal protection. Of the 10 mire complexes of highest priority only one is effectively protected. The remaining unprotected mires have either been destroyed or are threatened by ongoing development. Destruction of mire habitats proceeds faster than the approval of Natura 2000 sites. There is a possibility that unique Bulgarian mires will be lost before the Natura 2000 system begins to perform its role. Only effective and timely protection of the mire remnants, together with appropriate management, will ensure the future of these unique habitats.

Grasslands in North-Eastern Bulgaria – tradition and changes

North-Eastern Bulgaria is a region which combines significant agricultural areas with grasslands, forest and shrub communities that support a rich biodiversity. Intensive agriculture has resulted in considerable fragmentation of the natural and semi-natural habitats. This represents a potential threat to the conservation of biodiversity. The main cultivated crops include wheat, maize, barley, sunflower and recently rape. The stock rearing is related to cattle, sheep, pig and poultry-farming. The grassland community diversity reflects the diversity of natural habitats. Some that occur in the studied region have high conservation value and are listed in the Habitats Directive 92/43 EEC. The regional floristic diversity numbers 1,950-2,000 species, which is about 50% of the Bulgarian flora. Situated in an area of heavy anthropogenic impacts and in a period of complex changes, grasslands require the implementation of practical measures for their maintenance and rational use.Keywords: floristic diversity; Habitats Directive 92/43 EEC; natural habitats; North-Eastern Bulgaria grasslands

Is penetration of non-psammophytes an underestimated threat to sand dunes? - a case study from western Pontic coast

The aim of this study was to identify how far the different dune types from one of the largest dune complexes at the Bulgarian Black Sea Coast are affected by the penetration of non-psammophytes and if there is an upward trend in their number. We studied the Kamchia dune system during 2013–2015. Vegetation was sampled at 162 plots along 12 transects systematically situated to cover three different habitats: embryonic, white and grey dunes. All vascular plants as well as cover percentage of each species and total vegetation cover were registered within each plot. The overall species list of the different dune types was additionally completed for the whole study area. A total 207 plant species were registered. They were classified into five groups as follows: psammophytes – 38, weeds and ruderals – 36, plants typical of grasslands and shrublands – 95, plants typical of forests – 18 and alien (including invasive) species – 20. Number and cover of defined groups were calculated in respect to their distribution in different dune habitats. Results show that grey dunes contain the highest percentage of non-psammophytic plants, which decrease towards white and embryonic dunes. The studied coastal area is still less influenced by non-psammophytes. It represents an example of a Bulgarian Black Sea coastal dune complex that is relatively unaffected by urbanization. The high floristic and habitat diversity deserve further effective protection.