Monitoring the conservation state of target habitat types: 91F0 – flooded mixed forests of Quercus robur, Ulmus leavis, Ulmus minor, Fraxinus angustifolia, and 9340 – evergreen holm oak forests (Quercus ilex)

In 2023, the company Prosilva d.o.o. performed research in the territory of Krka National Park to determine the state of two Natura 2000 habitat types: 91F0 – flooded mixed forests of Quercus robur, Ulmus leavis, Ulmus minor, Fraxinus angustifolia, and 9340 – evergreen holm oak forests (Quercus ilex), and the measures required for their conservation

For this purpose, extensive field surveys were performed and their results analysed. The methodological approach to establishing the state and measures to be take encompassed determining the structural and functional elements of the habitat type at transects laid at appropriate locations.

On each transect, the structural elements of the habitat type were determined: composition and share of typical, undesirable and standard (common) species for that habitat type, while the area of the survey (width of the transect) is relevant for assessing the functional elements of the habitat type (presence and abundance of dead trees and intensity of stressors). Additionally, the degree of presence and influence of abiotic (flood, fire) and biotic (phytogenic, zoogenic, anthropogenic) factors was determined, particularly if they pose a threat to the conservation of the habitat type in a favourable state. All these parameters were analysed to give the final assessment of the conservation status of the habitat type, to identify the pressures in place, and to recommend protection measures to be taken to preserve the habitat in a favourable state.

The habitat type 91F0 includes wet, occasionally flooded forests dominated by hygrophyte (water-loving) species, and the key tree species are narrow-leaved ash, field elm, black alder and white willow. In Krka National Park, this habitat type is distributed predominantly in the riparian zone and on the terraces along the Krka and Čikola Rivers, covering an area of 63.78 hectares. The most significant localities are Skradinski buk, Krka monastery, Miljacka mill, and Bilušića buk along the Krka River, and Ključica along the Čikola River.

Habitat type 9340 includes holm oak forests with Mediterranean species, which in addition to holm oak are particularly privets (Phillyrea sp.), manna ash, scorpion senna, mastic tree, smilax and others. Type 9340 is distributed in the area of Mačkovica, covering an area of 17.25 ha.

At four localities of the habitat type 91F0 (Skradinski buk, Krka monastery, Miljacka mill, and Bilušića buk) it was found to be in good condition. The area of this habitat type in good condition is 51.32 ha. This assessment is based above all on the share and cover of species typical for this habitat type, including the particularly important species Fraxinus angustifolia, Alnus glutinosa, Ulmus minor, Salix alba and, in the shrub layer, Cornus sanguinea and Crataegus monogyna, while Humulus lupulus is rare. In the ground layer, these are Aristolochia rotunda, Lysimachia nummularia and Berula erecta, while other hydrophytes are rarer. A relatively large number of species from the surrounding dry forest habitats in the Mediterranean area are found all the way down to the river. This is due above all to the phytoclimate and the plant species that tolerate dry conditions throughout most of the year. In parts of the localities, there are invasive alien species that are currently not a threat to the survival of the habitat type, though their abundance and cover are certain to increase in the future. Dry dead wood is present in moderate to high amounts. An important factor for the survival of this habitat type in Krka National Park is the fact that a favourable trend of ground water has been recorded at the hydrology station at Skradinski buk over the past 30 years. At the locality Skradinski buk, the impact of visitors is highly significant, while at the locality Krka monastery, domesticated animals have a strong impact.

At the locality Ključica (Čikola River) the state of the habitat type is assessed as very poor (12.55 ha). The reason for this is primarily the weak presence of ash and the widespread drying of elm, which has led to a more thicket-like appearance of the habitat, with the lack of regeneration of typical species, and the presence of unfavourable alien species with part of the locality covered in problematic native though ruderal species.

The state of habitat type 9340 at the locality Mačkovica is good. Many of the typical species are present in nearly all transects and areas of the locality, particularly Quercus ilex, Fraxinus ornus, Phillyrea latifolia, Pistacia lentiscus, Coronilla emerus ssp. emeroides, Smilax aspera and others. There are no invasive species that would pose a threat to the habitat type. Dead wood is present in a moderate and satisfactory ratio throughout the entire locality.