Forestal vegetation of northern Velebit is the most variable of all. When approaching the park from the coastal side, towards the mountain's crest, firstly there's a degradated forest of pubescent oak and Oriental hornbeam (Querco-Carpinetum orientalis). This phytocenosis covers large areas of the mountain's western (coastal) exposures. Through centuries, maybe even milleniums, these forests were intensively exploited - harvested, irradicated, devastated by cattle etc. That is the reason for their present degradation. Although economically worthless, they are highly important for protection of soil against erosion. Apart from the mentioned species, the most wide-spreaded plants on the coastal side are paliurus (Paliurus aculeatus) and flowering ash (Fraxinus ornus). On higher altitudes, this phytocenosis is replaced with forests of pubescent oak and flowering ash (Ostryo-Quercetum pubescentis), which also degradated from its original form. They mostly grow on carbon soils, in a form of small, scatterd forests or shrubs. These forests have tremendous importance in soil conservation. Except for flowering ash and pubescent oak, there are also common European ash (Fraxinus excelsior), Italian maple (Acer opalus), Turkey oak (Quercus cerris) , Norway maple (Acer platanoides) , sessile oak (Quercus petraea) and common hornbeam (Carpinus betulus).

The next forestal phytocenosis in vertical succesion is Seslerio-Fagetum sylvaticae, a coastal beech forest, which is the first in a belt of beech forests of the mountain. It is marked by a typical thermophile species - Sesleria autumnalis, a kind of grass, which blossoms in autumn and covers entire forest floor like a carpet.

This forest dwells on altitudes between 700 and 1300 meters, and together with the indigenous forests of the Illirian black pine (Pinetum nigrae submediterranum) is the last of the submediterranean thermophile group of forestal phytocenosis. The continental slopes of Velebit are covered with a belt of alpine beech forests - Fagetum montanum. This phytocenosis streches between altitudes of 600 and 900 metres, and it containes a wide variety of plant species. It's areal extends quite low on the continental side, so it sometimes descends to the edges of karst plains. Besides beech, there are also sycamore (Acer pseudoplatanus), mountain elm (Ulmus glabra) and others.

Following the coastal beech forests belt from the western side, and the alpine beech forests belt from the continental side, proceed beech and fir forests - Abieti-Fagetum dinnaricum . These forests inhabit altitudes between 1200 and 1400 meters and consist mainly of beeches and firs. Further up, there is a sub-alpine beech forest - Homogyno sylvestris - Fagetum sylvaticae . This phytocenosis inhabits the highest altitudes of north Velebit - over 1600 meters. It is a pure beech forest with many alpine plant species. The trees of this forest are specific for their lower part of the trunk which is more or less arched, due to the extreme climate - strong winds and lots of snow.

The Park is covered with some of the most beautiful and well-preserved spruce forests. Humid type of spruce forests (Aremonio Piceetum) is best developed in Štirovača, while different types of spruce forest (Listero - Piceetum and Calamagrostio - Piceetum) inhabit higher altitudes, usually above 1400 meters.

The upmost parts of northern Velebit, as forestal vegetation is concerned, are covered with the indigenous virgin forests of dwarf mountain pine - Pinetum mughi illyricum . Dwarf mountain pine is the dominant species. Its branches are very long and laid to the ground, thus forming vaste impassable areas, due to the extreme climate of high mountain peaks.