Vegetacijsko-strukturna obilježja sastojina obične smreke (Picea abies Karst.) u prašumi Smrčeve doline na sjevernom Velebitu | Vegetation and Structural Features of Norway Spruce Stands (Picea abies Karst.) in the Virgin Forest of Smrčeve Doline in Northen Velebit

Detailed research into the virgin forest of Smrčeve Doline, situated in Northern Velebit National Park, was undertaken in the vegetation period of 2010 (Fig. 1). The virgin forest covers an area of 488 ha, of which spruce forests account for 300 ha, beech forests for 125 ha, while the rest is without any forest vegetation. The altitude ranges between 1,279 m and 1,607 m. The virgin forest mainly extends in the north-south direction. Over half of the spruce stands are distributed in sinkholes, as well as on northern and northwestern slopes ascending towards the tops. In the geomorphological sense, this is an exceptionally richly developed Dinaric karst relief, where the parent material is made of limestone breccias and limestone-dolomite blocks, which often resurface. The soil is organogenic and organomineral calcomelanosol in a mosaic with calcocambisol. The average annual temperature is 3.5 °C and the amount of the average annual precipitation is 1,898mm (meteorological station Vučjak, 1954m above sea level, period 1961-1990, data of the DHMZ). Phytocoenological research based on the standard Central European method of the Zürich-Montpellier School has shown that stands of Norway spruce are distributed in two forest communities (Table 1): spruce forest with Laserpitium krapfii (Laserpitio krapfii-Piceetum abietisVukelić, Alegro et Šegota 2010) and spruce forest with Hypericum richerii grisebachii (Hyperico grisebachii-Piceetum abietis /Bertović 1975/ Vukelić, Alegro, Šegota et Šapić 2010). The floral composition with their differences justifies their classification into independent associations in relation to other sub-alpine phytocoenoses of the Dinaric region. Compared with them, spruce forests of the sub-alpine belt of northern Velebit are differentiated by the presence and the higher cover of species Campanula velebitica, Melampyrum velebiticum, Hypericum richeri grisebachii, Laserpitium krapfii, Valerianamontana, Euphorbia carniolica, Geranium sylvaticum,Adenostyles alliariae and other, as well as the absence of the species of the Alpine-boreal and the south Balkan region (Vukelić et al. 2010a, Vukelić et al. 2010b). These results are of exceptional importance because, in combination with other research, they will be indispensable for defining forest communities of spruce in the Gorski Kotar area, which, according to preliminary comparisons, show more similarities with the communities of the Dinaric and pre-alpine area of Slovenia. The structural features of the stands were established in two sample plots situated in the most representative part of the virgin forest.