17E3

E. Herbaceous communities and communities of lichens and mosses

Humid riverside clover (Trifolium spp.) meadows

Relationships with habitat classifications. EUNIS: E3.31 Helleno-Moesian riverine and humid [Trifolium] meadows, E3.34 Illyrio-Moesian riverine and humid [Trifolium] meadows; PAL. CLASS.: 37.61 Helleno-Moesian riverine and humid clover meadows, 37.64 Illyrio-Moesian riverine and humid clover meadows; HD 92/43: 6510 Lowland hay meadows (Alopecurus pratensis, Sanguisorba officinalis); Bondev (1991): 148 Mesophytous grass communities (meadows) (Festuceta pratensis, Poaeta sylvicolae, Alopecureta pratensis, Lolieta perennis, Agrostideta stoloniferae etc.) replacing forests of elm and field ash, Querceta roboris and Q. peduculiflorae, etc.

Conservation status. BDA, HD.

Category. Endangered [EN - A1, 2 D3 E2 F2 G2 H2 J L2].

General characteristics. The humid riverside clover meadows (Trifolium spp.) occur mainly in the lowlands (mostly below 200 m alt.), along small rivers and in small valleys in areas with transitional Mediterranean climate. The main areas of distribution of this habitat are in SE Bulgaria, the Thracian Lowlands and SW Bulgaria (Petrich region). In the past, these plant communities used to cover larger areas, but consequently they had been ploughed and turned into arable land. The areas are flat or slightly slanting, with very humid and seasonally flooded alluvial soils (Fluvisols). The soil acidity varies from slightly acid to pronounced alkaline in most places. Thin water layer stays often in spring and consequently dries up. In some places, due to prolonged drought in summers and water evaporation, the soils become slightly saline. Usually, the soils are eutrophic and relatively rich, with a well-developed humus horizon.

The projective cover of the vegetation is usually high, 90–100%. Due to the Mediterranean features of the climate the floristic structure of these meadow coenoses include many annual species (20–30%). Perennials are dominating among grasses: Anthoxanthum odoratum, Cynosurus cristatus, Elymus repens, Festuca pratensis, Holcus lanatus, Poa sylvicola, more rarely Phacelurus digitatus (= Rottboellia digitata) and Beckmannia eruciformis. However, some terrophytes such as Alopecurus rendlei (= Alopecurus utriculatus), Hordeum hystrix, Hordeum secalinum, and Vulpia myuros also occur. Most frequent dominant sedges are Carex distans, C. hirta, Eleocharis spp., Holoschoenus vulgaris.One of the most typical characteristics of the coenoses under consideration is the participation as dominants or co-dominants of legumes, particularly clovers: Trifolium hybridum, T. incarnatum subsp. molinerii(= T. molinerii), T. michelianum, T. ochroleucon, T. patens, T. pratense, T. repens, T. resupinatum,etc. More frequently occurring annual legumes are Lathyrus aphaca, L. hirsutus, Medicago arabica, Trigonella procumbens, and Vicia striata. The following species also frequently occur: Crepis setosa, Galium debile, Geranium dissectum, Gratiola officinalis, Inula britannica, Lysimachia nummularia, Moenchia mantica, Oenanthe silaifolia, Ononis arvensis, Ophioglossum vulgatum, Orchis laxiflora subsp. elegans, Potentilla reptans, Prunella vulgaris, Ranunculus sardous, Rhinanthus rumelicus, Rumex acetosa,and Verbena officinalis. When the soils are slightly saline some halophytes occur although their abundance is not high, such as Hordeum hystrix, Juncus gerardii, Mentha pulegium, Puccinellia convoluta etc.

There are almost no endemics or relics in these communities but mainly widely distributed species. There are few rare and endangered species for the country that need to be protected such as Trifolium squarrosum, Leucojum aestivum etc.

In most places the primary vegetation of this habitat used to be of forest type, but as a result of human activities it was turned into meso- to xerophytic vegetation. In most places these meadows are mowed, but in some places near urban areas, they are intensively grazed and trampled by domestic animals. Thus the conditions in the habitat become drier and the number of ruderals increases (Centaurea calcitrapa, Achillea millefolium, Cichorium intybus,etc.). These meadow coenoses belong to class Molinio-Arrhenatheretea,order Trifolio-Hordeetalia and alliance Trifolion resupinati.The following associations from this alliance have been registered so far in Bulgaria: Hodeeto-Caricetum distantis and Cynosureto-Caricetum hirtae that occur in Strandzha-Aitos region. It is very likely that the syntaxonomical diversity is much higher.

Characteristic taxa.

Distribution in Bulgaria. In the lowlands of South Bulgaria: the valley of Struma river, and the northern slopes of Belasitsa Mts. (Petrich area), Thracian Lowland (Plovdiv and Karlovo areas), South-East Bulgaria (South Black Sea coast, Strandzha and Sakar Mts., Toundzha Hilly plain, etc.); up to 300 m alt.

Conservation importance. The habitat is threatened by extinction. It has an important role in water protection, soil protection and soil formation. Some of the rare and endangered species in Bulgaria are also protected in this habitat type: Leucojum aestivum, Oenanthe angulosa, O. lachenalii, and Trifolium squarrosum.

Threats. Ploughing for arable lands, overgrazing, changes in the hydrological regime of the rivers, construction of dikes, and draining of the riverside flooded areas, pollution with synthetic fertilizers, herbicides, general aridisation of the climate, etc.

Conservation measures taken. The habitat is in Annex № 1 of BDA. Some of the areas with such meadows are in sites of the European Ecological Network NATURA 2000.

Conservation measures needed. Detailed study and mapping of the present state of these meadows in Bulgaria, monitoring, proclamation of the most representative areas as protected areas, restoration of the hydrological regime.

References. Ganchev et al. 1964; Sopotlieva 2008; Hájek et al. 2008.

Authors: Rossen Tzonev, Veska Roussakova


Humid riverside clover (Trifolium spp.) meadows (distribution map)