Pestrost in pojavljanje domačih in tujerodnih drevesnih in grmovnih vrst na ploskvah nacionalne gozdne inventure v Sloveniji

Abstract

In Slovenia, the National Forest Inventory (NFI) is used to monitor the state and development of forests at the national level. In this paper, we analysed the diversity of tree and shrub species and assessed the presence of non-native tree species in Slovenian forests. According to the literature, Slovenia hosts 71 autochthonous tree species, of which 60 were found among the trees measured on the 2 x 2 km NFI density plot grid. The highest average number of trees and shrubs, as well as the Shannon-Wiener index of species diversity, were observed in sample plots located in the Pre-Alpine Ecological Region (H’ = 0.85), while the lowest values were found in the Alpine Ecological Region (H’ = 0.58). The total growing stock of trees and shrubs in Slovenia is 330.7 m3/ha ± 2.1%, with the growing stock of small trees and shrubs (less than 10 cm DBH for trees and shrubs) estimated at 9.7 m3/ha ± 5.9%. Common beech (Fagus sylvatica) (31.9%) and Norway spruce (Picea abies) (28.2%) dominate the growing stock of tree and shrub species, while common hazel (Corylus avellana) (85.0%) represents the highest proportion of shrub species. Ten different non-native tree species were identified across 138 NFI plots, with the highest distributions in the Sub-Mediterranean and Pre-Pannonian Ecological Regions. Black locust (Robinia pseudoacacia) dominates the growing stock of non-native tree species. Among small trees (those with a DBH of less than 10 cm), common beech represents 32.4%, with Norway spruce and manna ash (Fraxinus ornus) each contributing more than 10.0%. The growing stock of small shrub species (shrubs with a DBH of less than 10 cm) is dominated by common hazel (Corylus avellana) with 78.3%, while more than 2% is also represented by cornel (Cornus mas), old man’s beard (Clematis vitalba) and elderberry (Sambucus nigra). The results show that the combination of a panel system, a large number of sample plots (3027) and an improved coding system enabled the first comprehensive and objective assessment of tree and shrub species diversity, as well as the presence of non-native species in Slovenian forests.