Združba gradna in navadnega črnilca se pojavlja na različnih nekarbonatnih kamninah, ki so v glavnem sedimenti z močnim silikatnim deležem in imajo več ali manj karbonatnih veziv in vložkov. Prevladuje sorazmeroma sušna in topla mikroklima. Tla so zelo kisla in slabo nasičena z bazami; ponekod so lahko psevdooglejena, včasih se pojavlja distrični ranker ali pobočni psevdoglej. Združba uspeva na nadmorskih višinah med 150 in 750 m, letna količina padavin je od 1000 do 1500 m.

Diagnostična kombinacija rastlinskih vrst
Drevesna plast: graden (Quercus petraea), pravi kostanj (Castanea sativa).
Grmovna plast: Quercus petraea, Frangula alnus, Juniperus communis.
Zeliščna plast: Calluna vulgaris, Chamaecytisus supinus, Festuca heterophylla, Genista germanica, Hieracium racemosum, H. sabaudum, H. sylvaticum, Lathyrus niger, Lembotropis nigricans, Luzula luzuloides, Melampyrum pratense subsp. vulgatum, Pteridium aquilinum, Quercus petraea, Solidago virgaurea subsp. virgaurea, Vaccinium myrtillus.
Mahovna plast: Hypnum cupressiforme, Leucobryum glaucum, Pleurozium schreberi, Polytrichum formosum, Thuidium tamariscinum.

Združba gradna in navadnega črnilca je sekundarna združba na rastišču združbe bukve in pravega kostanja. Pretežno je nastala na opuščenih pašnikih.

Večinoma so to kmečki gozdovi, ki so bili v preteklosti pretirano izkoriščani, saj so v njih tudi steljarili in pasli.

Združbo gradna in navadnega črnilca uvrščamo v zvezo Quercion roboris-petraeae.

The Melampyo vulgati–Quercetum petraeae occurs on various noncalcareous stones that consist mainly of deposits with a significant portion of silicate having more or less calcareous binders and inserts. The microclimate is predominantly dry and warm. Dystric soils have poor base saturation. There is Planosol in places, and dystric Leptosols or slope Planosol occur sometimes. The association grows at an altitude between 150 and 750 meters, and the annual rainfall ranges from 1,000 to 1,500 meters.

Diagnostic combination of plant species
Tree layer: Quercus petraea, Castanea sativa.
Shrub layer: Quercus petrea, Frangula alnus, Juniperus communis.
Herb layer: Calluna vulgaris, Chamaecytisus supinus, Festuca heterophylla, Genista germanica, Hieracium racemosum, H. sabaudum, H. sylvaticum, Lathyrus niger, Lembotropis nigricans, Luzula luzuloides, Melampyrum pratense subsp. vulgatum, Pteridium aquilinum, Quercus petraea, Solidago virgaurea subsp. virgaurea, Vaccinium myrtillus.
Moss layer: Hypnum cupressiforme, Leucobryum glaucum, Pleurozium schreberi, Polytrichum formosum, Thuidium tamariscinum.

The Melampyo vulgati–Quercetum petraeae is a secondary association on the site of the Castaneo–Fagetum. It is predominantly found on abandoned meadows.

These are mainly rural forests that were excessively exploited in the past when they were used for litter and grazing.

The Melampyo vulgati–Quercetum petraeae is classified in the alliance Quercion roboris–petraeae.

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Puncer I. & M. Zupančič 1979: Novi združbi gradna v Sloveniji (Melampyro vulgati-Quercetum petraeae ass. nova s. lat.). Scopolia 2, 47 s.
Zupančič M. 1994: Popravki imen nekaterih rastlinskih združb v luči novega kodeksa. Hladnikia 2: 33–40.