A new device to foster oak forest restoration via seed sowing

Abstract

Seed sowing may be a cheap and efficient reforestation method that can yield high-quality seedlings for many woody species, but this option is usually discarded against seedling planting due to the high seed losses to mammal predators. The search for methods to reduce seed predation is therefore a key issue to broaden reforestation options and restoration success. In this study we tested (1) the effectiveness of a new device to prevent small mammals from consuming large seeds such as acorns and (2) its effect on initial seedling performance. The device consists of a capsule made of two truncated pyramids joined at the bases, with two small openings at the top and the bottom where the stem and root can exit but rodents cannot enter. We conducted a field seed-predation experiment using fenced plots (only rodents present) and unfenced plots (rodents + wild boar present) and a nursery experiment to check seedling emergence and growth. Acorn predation by rodents was almost nil when protected by the device (1.1 vs. 53.4 % without seed shelter), whereas predation by wild boar in the unfenced plots was not reduced by the device (12.4 %). In the nursery experiment there was no effect of the device on seedling emergence or growth. These results suggest that physical protectors like the one used in this study could represent a cheap method to foster the restoration of tree cover via seed sowing, especially if used in combination with fences or habitat features to reduce predation by large animals.