Species selection – A fundamental silvicultural tool to promote forest regeneration under high animal browsing pressure

Abstract

Abstract Heavily disturbed post-mining sites are often difficult to restore to forestland due to chemical and physical soil limitations, as well as frequent animal herbivory of planted tree seedlings. Forest tree species differ in how they allocate resources to defensive compounds or growth in order to resist abiotic and biotic stresses after outplanting. However, the influences of plant nutrition and secondary metabolite production on browse susceptibility and recovery are not well understood within and among species, especially for temperate deciduous forest trees. We investigated foliar tannin and nutrient responses under fenced (to exclude white-tailed deer, Odocoileus virginianus) and non-fenced environments on an abandoned mine land in southwestern Indiana, USA. Using field fertilization (15N-9P-10K controlled-release fertilizer at 0, 30 g, and 60 g per seedling), we also created a gradient of nutrient availability for planted black cherry (Prunus serotina Ehrh.), bur oak (Quercus macrocarpa Michx.), northern red oak (Quercus rubra L.), and white oak (Quercus alba L.) seedlings. Fencing improved growth relative to non-fenced seedlings; fertilization improved growth for all species except northern red oak, but only when combined with fencing. Fertilization reduced foliar tannin concentrations for black cherry and white oak, but did not change browsing preference or browse recovery for any species. Without fencing, browsing selection was solely driven by tree species, whereby black cherry had a higher likelihood of being browsed compared to all oak species. This response was likely associated with differences among species in resource allocation patterns; black cherry prioritizes structural growth and recovery, while oaks allocate resources to both growth and secondary metabolite production. As fencing is often considered cost-prohibitive for mine reclamation and other restoration efforts, species selection is perhaps the most fundamental silvicultural tool to promote forest regeneration success under conditions of high animal browsing pressure.