Epsilon Archive for Student Projects

Abstract

Browsing by ungulates can strongly constrain forest regeneration and thereby influence future stand structure, species composition and forest resilience. Downed deadwood has been suggested to reduce browsing pressure by increasing structural complexity and limiting herbivore access to regenerating seedlings, but this relationship has not previously been synthesised as a distinct review topic. The aim of this thesis was therefore to systematically review the scientific literature on the effects of downed deadwood on browsing pressure in regenerating forest vegetation.

The review was conducted using a systematic literature review approach based on PRISMA 2020 and PRISMA-EcoEvo. Searches were carried out in Web of Science, Scopus, and PubMed and records were screened in three stages: title, abstract, and full text. A total of 64 records were identified, of which 36 remained after deduplication and 15 were included in the final synthesis.

Most included studies (14 of 15) reported reduced browsing in the presence of downed deadwood. Reduced browsing was reported across several deadwood forms, including downed logs, coarse woody debris, slash, windthrow structures and deadwood patches. Across the reviewed studies, the protective effect of deadwood appeared to depend more on structural complexity and the spatial configuration of logs than deadwood type alone. The most frequently reported mechanism of deterrence was physical obstruction of herbivore movement, although one study suggested that reduced accessibility, lower seedling visibility, and favourable microsites may also contribute. One study reported context-dependent effects, indicating that the effectiveness of deadwood may vary with local environmental conditions such as stand structure and microclimate.

Overall, the available evidence suggests that downed deadwood can function as a natural browsing deterrent and may represent a promising nature-based complement to conventional browsing mitigation strategies. However, the evidence base is geographically and taxonomically narrow, and relatively few studies explicitly examined structural variables such as deadwood density, spatial arrangement of logs or threshold levels. Further research is therefore needed to clarify the mechanisms involved and to quantitatively support the development of practical forest management applications.