TAGLIAMENTO RIVERBED SCI - VEGETATION

The Middle Tagliamento Valley SCI is a very important hub of the Friuli Venezia Giulia Natura 2000 Network as connection hinge between the Alpine region and the river and perifluvial lowland environments characterized by the presence of large gravel beds and the wet area of Osoppo fields. The latter is a sort of miniature plain, arised from sedimentary processes upstream of the morainic amphitheater.
Within a rather limited areal there is a mosaic of natural environments whose pieces are represented by large gravelly and permeable expanses where Tagliamento river flows with its characteristic braided paths walk. Here typically arise xeric (dry) habitats like the riverside woods, the pioneer herbaceous and shrubby vegetation, the primitive dry grasslands and the more evolved ones. In a more distal position are instead the wetlands on which flows the Ledra river, typical resurgence meandering river. The phenomena of spontaneous water surfacing feed wet and vegetation-rich habitats where dominate moor prairies (Molinia caerulea), Willow or White Poplar or Black Alders riparian woods (Alnus glutinosa formations).

In SCI there are natural environments deeply different, groupable into the following macro-categories:

• rocky habitats (especially on Mt. Cuar and Mt. Flagjel)
• steppe-like habitats (in Tagliamento edge grasslands)
• wet and spring habitats  (in the Osoppo plain).

Within the complex framework of this vast territory are co-existing very different vegetational conditions which, although in many anthitetical ways, are maintaining high levels of contiguity. In the mountainous part in a relatively small space there is the passage from the sub-Mediterranean vegetation to that with mountain connotations.
The Tagliamento riverbed includes a very wide area almost devoid of structured vegetation which is characterized by the presence of predominantly pioneer species with highly developed root systems. This situation is mainly due to the periodical floods, to the the consequent lack of soil and nutrients and finally to the extreme weather conditions among which, above all, stands out the strong excursion, not only thermal (both daily and seasonal), but also in terms of water availability. This represents a shift from an almost-daily situation of total surface dryness to more rare but paradoxical situation of total flooding.

Among the typical pioneer vegetation of the riverbed there is the association scientifically called Epilobio-Scrophularietum caninae whose characteristics species are represented by the two herbaceous species Epilobium dodonaei and Scrophularia canina. Within these populations there is often the presence of some alpine species transported from upstream to downstream by the river (rafting) such as Gentiana clusii and Scabiosa graminifolia. In areas less frequently subjected to flooding, the river terraces that are extended at an altitude slightly greater than the active riverbed one, there are the first primitive grasslands. The Tagliamento area has a high conservation value as reservoir of gravel-typical species, pioneer and rich of Illyrian-Balkan entities. A very special meaning is taken from the original and endemic species that is typical of the local area such as: Centaurea dichroantha, Euphorbia triflora kerneri, Knautia ressmanii e Polygala forojuliensis. On the vast riverbeds, the pioneer herbaceous formations alternate themselves  with shrubby ones dominated by Olive Willow (Salix eleagnos), hygrophil river woods with a predominance of White Willow and Black Poplar and arid stable meadows.

The peculiarity of the area close to Bars resurgences consists above all in the alternation of areas that are predominantly dry, that arise on gravelly soil and raised the average level of groundwater, and the wet surfaces on soaked soil much more organic-matter rich. This leads to a multiplication of small biotopes and habitats within a restricted area and overall diversified even if already very biodiversity rich. The resurgence phenomena then feed the presence of water streams crowned by the presence of riparian woods and wet meadows on one side and dry grassland on the gravelly surfaces of the ancient riverbed (the old bed where the river flowed) on the other side. These are the oldest bars of coarse material deposited by the Tagliamento river in recent times. On these fragments of permeable soil and bloom many species typical of the dry meadows including several wild orchids such as Ophrys holoserica, Cephalantera longifolia, Orchis militaris, Orchis tridentata e Orchis morio. The dry grassland belts  develop especially at the edge of the active riverbed of Tagliamento, in eastern areas most far from the resurgences. Conversely, in the center of the wetland area many stable meadows have been progressively fertilized and transformed into poliphita meadows used for the production of forage.

The particular sun exposure and the influence of the nearby Adriatic Sea creates instead the condition, rare and unique, of a thermophilic island on steep slopes north of Peonis. Here is a vegetation wreck of Illyrian-Mediterranean character which constitutes an enclave of Holm Oak (Quercus ilex). It is in fact one of the more northern stations of the natural occurrence of this species.
On the southern slopes of the Mt. Cuar and Mt. Flagel there is also the unique sequence from the Illyrian-prealpine arid woods constituted by Hop Hornbeam (Ostrya carpinifolia), by Manna Ash (Fraxinus ornus) and by thermophilic-character beech forests, replaced on the top by meadows and pastures.

COMMUNITY INTEREST HABITATS

In Middle Tagliamento Valley SCI there is a large number of different plant associations, both dry and wet, considered habitats of interest and as such protected by the European "Habitat" Directive. The following are listed in order of surface coverage compared to the total area. The habitats where there is an asterisk are considered priority habitats of Community interest because they are particularly rare, precious and protection-worthy.

• 91K0 llyrian Fagus sylvatica forests (Aremonio-Fagion) 32%
• 6170 Alpine and subalpine calcareous grasslands 15%
• 62A0 Eastern sub-mediterranean dry grasslands (Scorzoneretalia Villosae) 15%
• 9180 Tilio-Acerion forests of slopes, screes and ravines 5%
• 3240 Alpine rivers and their ligneous vegetation with Salix elaeagnos 5%
• 3230 Alpine rivers and their ligneous vegetation with Myricaria germanica 5%
• 3220 Alpine rivers and the herbaceous vegetation along their banks 3%
• 8210 Calcareous rocky slopes with chasmophytic vegetation 2%
• 8160 Medio-European calcareous scree of hill & montane level 2%
• 6430 Hydrophilous tall herb fringe communities of plains and of the montane to alpine levels 1%
• 91L0 Illyrian oak-hornbeam forests. (Erythronio-carpinion) 1%
• 0110 Rupicolous or basophilic association of vegetation called Alysso-Sedion 1%
• 5130 Juniperus communis formations on heaths or calcareous grasslands 1%