Understorey vegetation in spruce-dominated forests in eastern Finland and Russian Karelia: Successional patterns after anthropogenic and natural disturbances

Abstract

This study compares the succession of understorey vegetation at semi-natural and managed mesic sites dominated by Norway spruce ( Picea abies (L.) Karst.). The area concerned is situated in the middle boreal forest zone on both sides of the border between Finland and Russia. The data were collected at 39 sites representing open/burned, sapling, young, mature and over-mature/old-growth forests. The coverage and number of species representing ground lichens, mosses, liverworts, grasses, herbs, dwarf shrubs and tree seedlings were recorded and analysed separately. The vegetation represented different stages of the succession and management history (managed versus semi-natural). The vegetation was ordered along two multivariate (DCA) axes, the first related to successional stage and the second to human influence. The total number of plant species was dependent on the successional stage and the diversity pattern was similar both after semi-natural and man-made disturbance. The plant life-form groups exhibited specific patterns in their occurrence and in their responses to natural and anthropogenic disturbances. The coverage of grasses and dwarf shrubs, in particular, followed quite different patterns after man-made and natural disturbances. Grasses were abundant in managed forests after clear-cutting, but almost absent from young natural forests, while dwarf shrubs occurred more commonly in the old managed forests than in the younger ones. The coverage of seedlings in semi-natural forests peaked in the sapling stage, decreased towards the mature stage and increased again in the old-growth stage, while tree recruitment was relatively low in the older managed successional stages. The results highlight especially the characteristic vegetation features of young natural forests, which differ considerably from the corresponding managed forests.