Deer browsing and slash removal affect field vegetation on south Swedish clearcuts

The effects of deer browsing and slash removal on vegetation succession were studied on 20 clearcuts in southern Sweden. The experiment was established over a 5-year period (1989-1993). Each clearcut was divided into two parts: On one part 80% of the slash was removed, while on the other it was retained and evenly distributed. Field vegetation was studied on 0.5 m(2) plots on which the plant species present were identified, and biomass was measured by destructive harvesting in the late summers of 1989-1996. The effects of browsing by roe deer (Capreolus capreolus L). and moose (Alces alces L.) were assessed by comparing vegetation inside exclosures to that found outside them. The exclosures were established in both slash-retained and slash-removed areas in the winter of 1992-1993. On 1-year-old clearcuts there was almost no vegetation, whereas 6-year-old ones contained about 4 t (dry weight) of biomass per hectare. Total plant biomass was higher inside exclosures, but was not influenced by slash removal. Neither slash removal nor exclosure affected the biomass of grasses and sedges, which dominated the vegetation. Herbs, trees and shrubs showed more growth inside exclosures and on areas where the slash had been retained. For the study period as a whole the biomass of dwarf shrubs was not influenced by exclosure or slash removal. However, on the oldest clearcuts there were more dwarf shrubs on areas where slash had been removed and there were also signs of browsing influence on dwarf shrubs. In total, about 50 plant species were recorded. However, the most common species, that is, Deshampsia flexuosa (L.) Trin., Betula spp., Rubus idaeus (L.), and Calluna vulgaris (L.) Hull, made up more than 95% of the total biomass and one species, Deshampsia flexuosa (a grass), accounted for up about 75% of the plant biomass. Total biomass was higher and plant succession tended to occur faster inside exclosures. The average number of plant species was not influenced, and frequencies of common plant species was affected relatively little by the exclosures. Slash removal had no influence on the total plant biomass, and the effect on plant succession was less pronounced than the effect of exclosure. There were more plant species on areas where slash had been retained than on areas from which it had been removed, and the frequencies of several common species were strongly influenced by slash removal. (C) 1999 Elsevier Science B.V. All rights reserved.