The Tisa Superioara Site includes the area of the floodplain and the terraces on the left of the upper Tisa valley, which forms the border between Romania and Ukraine in the sector where the river crosses the Maramureş Depression from East to West. To this is added a territory in the east, which includes the forest massif between the mountain upper Tisa and the upper Ronişoara, the most important and compact forest area remained in the Romanian southern half of the Maramureş Depression.
The site is important primarily for the protection of ichtyofauna (11 priority species of fish), out of which huchen and striped chub stand out as very rare species, in danger of extinction in the Romanian fauna. In addition, amphibians (Triturus cristatus, Triturus montandoni) and the European pond turtle (Emys orbicularis) have populations still very strong in the site, despite recent destructions caused by abusive hydraulic works. In the Tisa floodplain, the priority forest habitat 91E0* Alluvial forests is very important, with role as ecological corridor, yet fragmented. In addition, there are at least three other important hygrophilic and hydrophilic habitats that are to be investigated.
In the Ronișoara forest massif there is an important area for large mammals, with populations of bear, wolf, lynx and deer, overlapping the homonymous forest reserve. The flora and fauna of this forest massif located in the high hill area (600 – 900 m) are still little researched and deserve special attention. In this area, there is a mosaic of at least three Natura 2000 forest habitats, in which beech forests dominate.
“Ronişoara Forest” protected area represents a 62-ha seed reserve, located on the territory of Rona de Sus commune, within Sighetu Marmaţiei Forest District. The reserve can be reached from Hera Pass, at approx. 1 km on the National Road 18, on the left side. Ronişoara Forest consists of seed stands of sessile oak, characterized by very good straightness, cylindricity and pruning, qualities that betray an exceptional genetic conformation, which resulted in the identification of a very valuable origin, unanimously recognized as the “Ronişoara Sessile Oak”. Due to the conformation of trees, the forest has also a great aesthetic value and it was declared a nature reserve by Law no. 5/2000 on the approval of the National Territory Arrangement Plan, Section III-Protected Areas, under the functional group I (protection), subgroup 5C – forests established as nature reserves.
The sessile oak forests in Maramureş include areas from the lowest elevation in the Historical Maramureş (the Tisa leaves Maramureş at 204 m) and climb the sunny slopes up to 600 m, rarely up to 700 m, until the 8˚C isotherm, the average annual temperature. In Rona de Sus, the average annual temperature is 8˚C, the average annual rainfall reach 742 mm, and the vegetation period of sessile oaks is of 166 days per year. The tree layer consists of two co-dominant species, alternatively predominant, namely sessile oak (Quercus petraea), which is more competitive in sunny habitats, and hornbeam (Carpinus betulus), which is more present in shaded areas.
As regards the ornithological fauna, the forest lies in the Columbidae area, very rich in avian species due to abundant plant and animal nutrition.