Aconalni gozdovi bukve in črnega gabra pokrivajo v predalpskem in preddinarskem območju velike strnjene površine. Poraščajo kopaste grebene in strma, predvsem prisojna, gladka pobočja, v katera so vrezani globoki jarki. Uspevajo od nižin do približno 1000 m nad morjem. Na dolomitni matični podlagi prevladujejo srednje globoke, zelo skeletne rendzine, na grebenih prehajajo v inicialne rendzine, v jarkih pa so rjave rendzine, mestoma tudi plitva rjava tla. Toploljubni bukovi gozdovi uspevajo, v navadno humidnih razmerah Slovenije, le na izrazito prisojnih legah, kjer so posebne ekološke razmere. Vendar črni gaber, kljub svoji toploljubni naravi, uspeva le v krajih, kjer letno pade vsaj 1100 do 1200 mm padavin in poletja niso presuha, v nasprotnem primeru se umika izrazitejšim toploljubnim vrstam, kot sta na primer puhasti hrast in cer.

Diagnostična kombinacija rastlinskih vrst
Drevesna plast: črni gaber (Ostrya carpinifolia), bukev (Fagus sylvatica), mali jesen (Fraxinus ornus), beli javor (Acer pseudoplatanus), mokovec (Sorbus aria), maklen (Acer campestre), graden (Quercus petraea).
Grmovna plast: Berberis vulgaris, Clematis vitalba, Cornus mas, C. sanguinea, Corylus avellana, Crataegus monogyna, Daphne mezereum, Euonymus verrucosa, Ligustrum vulgare, Lonicera xylosteum, Rosa arvensis, Viburnum lantana.
Zeliščna plast: Aposeris foetida, Aremonia agrimonoides, Buphthalmum salicifolium, Calamagrostis varia, Carex alba, C. digitata, C. flacca, Cirsium erisithales, Cyclamen purpuracens, Digitalis grandiflora, Euphorbia amygdaloides, Fragaria vesca, Galium laevigatum, Hacquetia epipactis, Helleborrus niger subsp. niger, Hepatica nobilis, Hieracium sylvaticum, Melittis melissophyllum, Mercurialis perennis, Peucedanum oreoselinum, Polygala chamaebuxus, Primula vulgaris, Pteridium aquilinum, Salvia glutinosa, Sanicula europaea, Solidago virgaurea, Vincetoxicum hirundinaria, Viola reichenbachiana.

Biocenotska zgradba toploljubnih bukovih gozdov je precej labilna. Po večjih presvetlitvah prevladajo izrazito toploljubne vrste: črni gaber, mali jesen in druge. Razvojne smeri na opuščenih pašnikih na potencialno naravnem rastišču združbe bukve in črnega gabra potekajo predvsem preko navadnega brina, navadne leske in rdečega bora.

Gospodarski pomen gozdov bukve in črnega gabra je relativno majhen. Čistih bukovih gozdov boljše kakovosti je na teh rastiščih zelo malo. Največjo skupino predstavljajo degradirana grmišča in gozdovi, ki so zelo primerni za pašo drobnice. V isto skupino spadajo tudi zaraščajoči pašniki.

Združbo bukve in črnega gabra uvrščamo v zvezo Aremonio-Fagion.

Azonal beech forests with Ostrya carpinifolia cover large closed areas in the prealpine and predinaric regions. They grow on ridges and steep, mainly sunny slopes with deep gullies cut in the slopes. They are found on sites from the lowlands up to an altitude of around 1,000 meters. The dolomite is covered by medium deep and skeletal rendzic Leptosols that on ridges change to initial rendzic and lithic Leptosols. In gullies, there are brown rendzic Leptosols and shallow chromic Cambisol in places. Thermophilous beech trees thrive in generally moist conditions in Slovenia only on conspicuously sunny sites with specific ecological conditions. In spite of its thermophilous characteristics, Ostrya carpinifolia thrives only on sites where there is more than 1,100 to 1,200 mm of rainfall. It also does not require overly dry summers; in this case, it yields to thermophilous species such as Quercus pubescens and Q. cerris.

Diagnostic combination of plant species
Tree layer: Ostrya carpinifolia, Fagus sylvatica, Fraxinus ornus, Acer pseudoplatanus, Sorbus aria, Acer campestre, Quercus petraea.
Shrub layer: Berberis vulgaris, Clematis vitalba, Cornus mas, C. sanguinea, Corylus avellana, Crataegus monogyna, Daphne mezereum, Euonymus verrucosa, Ligustrum vulgare, Lonicera xylosteum, Rosa arvensis, Viburnum lantana.
Herb layer: Aposeris foetida, Aremonia agrimonoides, Buphthalmum salicifolium, Calamagrostis varia, Carex alba, C. digitata, C. flacca, Cirsium erisithales, Cyclamen purpuracens, Digitalis grandiflora, Euphorbia amygdaloides, Fragaria vesca, Galium laevigatum, Hacquetia epipactis, Helleborrus niger subsp. niger, Hepatica nobilis, Hieracium sylvaticum, Melittis melissophyllum, Mercurialis perennis, Peucedanum oreoselinum, Polygala chamaebuxus, Primula vulgaris, Pteridium aquilinum, Salvia glutinosa, Sanicula europaea, Solidago virgaurea, Vincetoxicum hirundinaria, Viola reichenbachiana.

The biocenotic structure of thermophilous beech forests is rather unstable. After several removals, conspicuously thermophilous species predominate such as Ostrya carpinifolia, Fraxinus ornus, and others. The succession on abandoned meadows on potentially natural sites of the association Ostryo–Fagetum develops over stages with common juniper (Juniperus communis), hazel (Corylus avellana), and Scotch pine (Pinus sylvestris).

The Ostryo–Fagetum forests are of minor economic significance. There are only a few pure beech stands of higher quality on these sites. Degraded shrubs and forests suitable for sheep and goat grazing represent the largest group. Overgrown meadows belong to the same group.

The association Ostryo–Fagetum is classified in the alliance Aremonio–Fagion.

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Wraber M. 1966: Über eine thermophile Buchenwald-Gesellschaft (Ostryo-Fagetum) in Slowenien. Angewandte Pflanzensoziolologie 18–19: 279–288.
Marinček L. 1987: Bukovi gozdovi na Slovenskem. Delavska enotnost, Ljubljana. 153 s.
Marinček L. 1996: Prispevek k poznavanju asociacije Ostryo-Fagetum M. Wraber ex Trinajstić 1972. Razprave IV. razreda SAZU 37(6): 119–146
Dakskobler I. 1996: Comparison between beech forest of suballiances Ostryo-Fagenion Borhidi 1963 and Cephalanthero-Fagenion Tx.1955 ex Tx. & Oberd. 1958. Annali dei Musei Civici di Rovereto 11: 175–196.