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

The effects of deer browsing and slash removal on vegetation succession wer e studied on 20 clearcuts in southern Sweden. The experiment was establishe d over a 5-year period (1989-1993). Each clearcut was divided into two part s: On one part 80% of the slash was removed, while on the other it was reta ined and evenly distributed. Field vegetation was studied on 0.5 m(2) plots on which the plant species present were identified, and biomass was measur ed 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 outs ide 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 wei ght) of biomass per hectare. Total plant biomass was higher inside exclosur es, but was not influenced by slash removal. Neither slash removal nor excl osure affected the biomass of grasses and sedges, which dominated the veget ation. 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 th e biomass of dwarf shrubs was not influenced by exclosure or slash removal. However, on the oldest clearcuts there were more dwarf shrubs on areas whe re slash had been removed and there were also signs of browsing influence o n dwarf shrubs. In total, about 50 plant species were recorded. However, th e 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), accoun ted for up about 75% of the plant biomass. Total biomass was higher and pla nt succession tended to occur faster inside exclosures. The average number of plant species was not influenced, and frequencies of common plant specie s was affected relatively little by the exclosures. Slash removal had no in fluence 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 bee n removed, and the frequencies of several common species were strongly infl uenced by slash removal. (C) 1999 Elsevier Science B.V. All rights reserved .