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.

Predation and aridity slow down the spread of 21-year-old planted woodland islets in restored Mediterranean farmland

“…Other studies, however, have documented the spatial patterns and effects of long-distance oak dispersal at the landscape scale and hence the importance of isolated oaks as seed sources (Gómez 2003;Purves et al 2007). Acorn physical protection against predators is needed in Mediterranean environments to ensure oak establishment after seeding (Adams et al 1992;Castro et al 2015), as other methods such as chemical repellents have been shown to be unsuccessful (Leverkus et al 2013).…”

Effectiveness of Diesel as a Mammal Repellent for Direct Seeding of Acorns

“…Thus, rather than deterring mammal predators, it is possible that diesel attracted them, which is in opposition with the study upon which we based our hypotheses [20]. This effect-or lack of an effect-of diesel, however, could vary with the identity of acorn predators, as do several other acorn-protector methods [2,8,19,23]. Instead, our results show that the lack of a reduction in acorn predation by diesel application was consistent across the two levels of acorn predators (Figure 1; diesel × exclosure interaction: χ 2 = 0.91, p = 0.34).…”

“…Previous studies have documented high rates of acorn predation in this area, both by rodents and wild boars [21][22][23]. We used two fenced plots of ca.…”

“…3000 m 2 (some 200 m apart from each other) built in 1997 where ungulates were excluded [24], as well as three unfenced plots of similar dimensions located just beside the fenced plots (snow precluded the use of a third exclosure). The exclosures generated two levels of acorn predators: rodents only (inside exclosures), and rodents plus ungulates (outside) [23]. The main rodent species in the area are wood mice (Apodemus sylvaticus) and Mediterranean pine voles (Microtus duodecimcostatus), whereas ungulates include Iberian ibex (Capra pyrenaica) and wild boars (Sus scrofa).…”

“…To assess the potential effects of diesel on seedling emergence and initial development, we conducted a nursery experiment under outdoor conditions in a nursery located 1 km from the University of Granada, at an elevation of 735 m. We sowed 78 acorns of each diesel treatment in 300 mL plastic containers filled with 50% local soil (44.8% sand, 41.8% silt, 13.3% clay, and 0.8% organic matter [23]) and 50% peat (Kekkila Garden Brown 025W; Kekkila Group, Vantaa, Finland). The acorns were placed 1 cm below the soil surface and protected from domestic rodents with a 0.5 cm wire mesh screen.…”