24 priority habitats have been identified in the Măcin Mountains National Park, 1 of them being unique in the world! (The Dobrogean beech forest).
Out of the 8 groups of European ecosystems (according to the Corine Biotopes Project classification), 6 are represented in the Măcin Mountains: forests, shrubs and lawns, rivers, swamps, rocks and debris, and archaeological sites.
The most representative and wide forest ecosystems are identified in the Moesian-Western Black Sea oak, hornbeam and silver lime forests, with Fraxinus coriarefolia, Nectaroscordum siculum ssp. bulgaricum, which for a complex with oak trees, oriental hornbeam, silver lime and other xerothermal forests (situated at altitudes over 250 m), and with the Western Black Sea pubescent oak, oriental hornbeam and flowering ash forests, which include Paeonia peregrina, Asparagus verticillatus and Pyrus elaeagrifolia (150 – 250 m).
In the park there are frail lawn habitats, meadows with forests and siliceous rocks, characterized by a wide variety of rare and vulnerable species, which vegetate in biotopes with extreme conditions (climate, soil, etc.), or are situated at the edge of vegetation, needing conservation by the establishment of new protected areas. The forest ecosystems which are situated at the limit of the vegetated area can also be considered frail, due to the differential natural regeneration of arboretums, caused by unfavorable climate, abusive grazing and the continuous dwindling of the valuable autochthonous species (Sessile oak, oak, ash, etc.) The greatest threat to biodiversity is the destruction of the rocky areas where rare species live, because of granite quarrying.
According to the CORINE classification, inside the Măcin Mountains National Park there are two greater types of habitats:
1. Rocky habitats: in the composition of saxicolous vegetation there are a series of species which are adapted to ecologic conditions specific to rocky areas, such as: Alyssum saxatile, Moehringia grisebachii, Campanula romanica, Dianthus nardiformis, Sempervivum ruthenicum Polypodium vuIgare, Asplenium trichomanes, Asplemium. ruta muraria, Cystopteris fragilis, Silene compacta etc. This type of habitat is spread over most of Pricopan Heights and the Western and Southern part of Măcin Heights.
2. Steppe habitats: herbaceous species representative of steppe habitats (most living on a rocky under-layer): Allium rotundum, Artemisia austriaca, Botriochloa ischaemum, Convolvulus canthabrica, Dianthus nardiformis, Festuca valesiaca, Kochia prostrata, Poa bulbosa etc. Vegetal associations (phytocoenoses) found in this habitat: Festucetum valesiacae, Poaetum bulbosae and Teucrium polium – Scleranthus perennis (on the slopes and at the base of Pricopan Heights, the SW of Măcin Heights), Kochietum prostratae (at the base of the slopes of Pricopan Heights), Andropogonetum ischaemi ( on Pricopan Heights and in the steppe and forest-steppe areas on the Măcin Heights), Agropyretum cristatae (at the base of Cheia Hill) and Sambucetum ebuli (on the place of the former sheepfolds in the area of Pricopan Heights).
3. Forest habitats: the forest habitats around the perimeter of the national park can be framed within the layer of mesophilic Balkan forests. Associations are composed of the species Quercus petraea, Q. dalechampii, Q. polycarpa, mixed with lime species (Tilia cordata, T. tomentosa, T. platyphylos), ash (Fraxinus excelsior, F. ornus), hornbeam (Carpinus betulus) şi oriental hornbeam (Carpinus orientalis). The associations characteristic to this type of habitat are Galantho (plicatae) – Tilietum (tomentosae), Nectaroscordo – Tilietum (tomentosae), Querco (pedunculiflorae) – Tilietum (tomentosae), Tilio (tomentosae) – Carpinetum (betuli) and the Dobrogean beech-hornbeam associations with Carex pilosa (this last type is limited to the Beech/Fagilor Valley area)
4. Forest-steppe habitats: transitional habitats between the forest-steppe areas and mesophilic forests are represented by xerothermal sub-Mediterranean forests (these generally having a fragmented structure). The association specific to this transition habitat is Paeonio (peregrinae) – Carpinetum (orientalis). Typical forest-steppe habitats are characterized by an alternation of patches of forest and steppe meadows/rocky areas. The associations of this type of habitat are Achilleo (coarctatae) – Quercetum pubescentis and Gymnospermio (altaicae) – Celtetum glabratae.
5. Humid areas: this type of habitat is localized in the spring areas and along streams (most of these temporary). The species characteristic to humid areas are: Phragmites australis, Solanum nigrum, Potentilla reptans, Heleocharis palustris, Juncus gerardi, Lythrum thymifolia, L. salicaria, etc.