Differential effects of acorn burial and litter cover onQuercus rubrarecruitment at the limit of its range in eastern North America

Abstract

Primary predators or dispersers such as birds and rodents cache acorns of northern red oak (Quercus rubra L.). A proportion of these acorns are not retrieved, and thus, animals may favour oak regeneration by placing acorns in microsites suitable for recruitment. We experimentally investigated the effects of acorn burial and litter cover on red oak recruitment at two sites at the northern limit of the species' range in North America. Laboratory experiments also tested the effects of acorn burial and litter cover on desiccation and germinability and the influence of soil moisture on germination. Burial and litter protected acorns against predation by deer in the field. Germination was promoted by burial both in field and laboratory experiments. Germination was proportional to acorn water content and to soil moisture. Seedling emergence in the field was enhanced by burial but reduced by litter cover. Acorns buried but uncovered by litter had the highest probability of recruiting a seedling. A potential effect of seed predators or dispersers on red oak regeneration and expansion is suggested, as acorn caching by birds and rodents may actually enhance population recruitment, despite high mortality through acorn consumption.

Dispersal timing, palatability and caching of acorns of Aesculus turbinata Bl

“…Burial of seeds saves them from mammalian predators, at lest in the case of Quercus rubra (Garcia et al 2002). Seed burial into caches is likely to confer advantages of both seed germination and saving from predators.…”

Temperature effect on seed germination of four plants in sand from coastal sand dunes in Greece

“…Many studies on sand dunes have reported that very small seeds showed a high germination rate because of the small amount of moisture required for inhibition (Stairs 1986;Zheng et al 2005). In sand dunes, seed germination is strongly related to available moisture (García et al 2002).…”

The Relevance of Burial to Evade Acorn Predation in an Oak Forest Affected by Habitat Loss and Land Use Changes

“…Nevertheless, most studies on acorn consumption have been focused on acorns exposed on the soil surface, evaluating how vertebrates contribute to reduce their availability in oak forests (e.g., Li and Zhang, 2003;Guzmán-Guzmán and Williams-Linera, 2006;Puerta-Piñero, 2010;Bustamante et al, 2012;Andresen, 2012). On the other hand, studies conducted with buried acorns have been mainly focused in assessing whether burial promote germination and seedling recruitment (e.g., García et al, 2002;Gómez, 2004;Flores-Cano et al, 2012), or whether acorn burial by scatter-hoarding mammals is a mechanism that promote dispersal beyond parental trees (Smallwood et al, 2001;Steele et al, 2001). Therefore, the relevance of acorn burial as a mechanism to evade predation by mammals has received less attention (Haas and Heske, 2005;Muñoz and Bonal, 2011).…”

“…Different letters accompanying the curves indicate statistical differences in acorn removal rates after performing the respective pairwise comparisons (χ 2 critical α = 0.05). evade seed predation in forest ecosystems (Janzen, 1971;Andersen, 1989;García et al, 2002;Pinto et al, 2009). Nevertheless, these results also suggest that the outcome of the interactions that take place between acorns and their consumers, as well as the relevance of acorn burial may change across the different habitats composing forest ecosystems that were affected by human activities (see Figure 3B).…”