Cervid Exclusion Alters Boreal Forest Properties with Little Cascading Impacts on Soils

• Published in: Ecosystems (New York) 2018-08, Vol.21 (5), p.1027-1041
• Main Authors: Kolstad, Anders Lorentzen, Austrheim, Gunnar, Solberg, Erling J., Venete, Aurel M. A., Woodin, Sarah J., Speed, James D. M.
• Format: Article
• Language: English
• Subjects: Alces alces; Bayesian analysis; Biomedical and Life Sciences; Boreal forests; Browsing; Bulk density; Canopies; Carbon/nitrogen ratio; Clearcutting; Composition effects; Coniferous trees; Deciduous trees; Defecation; Ecology; Environmental impact; Environmental Management; Forests; Geoecology/Natural Processes; Herbivores; Hydrology/Water Resources; Life Sciences; Machine learning; Moose; Nitrogen; Northern Hemisphere; Original Articles; pH effects; Plant Sciences; Plant species; Soil density; Soil fertility; Soil properties; Soil structure; Soil temperature; Soils; Species composition; Taiga; Trampling; Zoology
• ISSN: 1432-9840; 1435-0629
• DOI: 10.1007/s10021-017-0202-4

Large herbivores are capable of modifying entire ecosystems with a combination of direct (for example browsing/grazing, trampling, defecation) and indirect (for example affecting plant species composition that then alters soil properties) effects. With many ungulate populations increasing across the northern hemisphere it is important to develop a general theory for how these animals can be expected to impact their habitats. Here we present the results of an 8-year experimental exclusion of moose (Alces alces) from 15 recent boreal forest clear-cut sites in Central Norway. We used standard univariate techniques to describe the treatment effect on multiple forest and soil properties and combined this with a multivariate Bayesian network structure learning approach to objectively assess the potential mechanistic pathways for indirect effects on soils and soil fertility. We found that excluding moose had predictable direct effects, such as increasing the ratio of deciduous to coniferous tree biomass and the canopy cover and decreasing soil bulk density and temperature. However, we found no treatment effects on any measures of soil processes or quality (decomposition, nitrogen availability, C/N ratio, pH, nutrient stocks), and furthermore, we found only limited evidence that the direct effects had cascading (indirect) effects on soils. These findings oppose the commonly held belief that moose exclusion will increase soil fertility, but still highlights the strong ability of moose to directly modify forested ecosystems.