Forest rodents provide directed dispersal of Jeffrey pine seeds.
ABSTRACT Some species of animals provide directed dispersal of plant seeds by transporting them nonrandomly to microsites where their chances of producing healthy seedlings are enhanced. We investigated whether this mutualistic interaction occurs between granivorous rodents and Jeffrey pine (Pinus jeffreyi) in the eastern Sierra Nevada by comparing the effectiveness of random abiotic seed dispersal with the dispersal performed by four species of rodents: deer mice (Peromyscus maniculatus), yellow-pine and long-eared chipmunks (Tamias amoenus and T. quadrimaculatus), and golden-mantled ground squirrels (Spermophilus lateralis). We conducted two caching studies using radio-labeled seeds, the first with individual animals in field enclosures and the second with a community of rodents in open forest. We used artificial caches to compare the fates of seeds placed at the range of microsites and depths used by animals with the fates of seeds dispersed abiotically. Finally, we examined the distribution and survival of naturally establishing seedlings over an eight-year period. Several lines of evidence suggested that this community of rodents provided directed dispersal. Animals preferred to cache seeds in microsites that were favorable for emergence or survival of seedlings and avoided caching in microsites in which seedlings fared worst. Seeds buried at depths typical of animal caches (5-25 mm) produced at least five times more seedlings than did seeds on the forest floor. The four species of rodents differed in the quality of dispersal they provided. Small, shallow caches made by deer mice most resembled seeds dispersed by abiotic processes, whereas many of the large caches made by ground squirrels were buried too deeply for successful emergence of seedlings. Chipmunks made the greatest number of caches within the range of depths and microsites favorable for establishment of pine seedlings. Directed dispersal is an important element of the population dynamics of Jeffrey pine, a dominant tree species in the eastern Sierra Nevada. Quantifying the occurrence and dynamics of directed dispersal in this and other cases will contribute to better understanding of mutualistic coevolution of plants and animals and to more effective management of ecosystems in which directed dispersal is a keystone process.
SourceAvailable from: Xianfeng Yi[Show abstract] [Hide abstract]
ABSTRACT: We examined the effects of soil water content (SWC) on scatter-hoarding decisions of Siberian chipmunks, Tamias sibiricus, when caching acorns of Quercus mongolica. We hypothesized that higher SWC, which favours germination in this and similar oaks, would also be favoured for caching and cache recovery in this rodent. We conducted three sets of experiments: one in small arenas, a second in larger seminatural enclosures, and a third in the field with free-ranging chipmunks in a temperate forest of the Xiaoxing’anling Mountains of northeast China. Siberian chipmunks selectively cached acorns in soil of higher SWC and recovered more observer-made artificial caches where SWC was higher. We argue the selective scatter hoarding in soil of higher SWC represents a form of directed dispersal that may be relatively common in other systems, especially where SWC is unevenly distributed, and further suggest that this may represent an important rodenteseed interaction that varies with climate.
[Show abstract] [Hide abstract]
ABSTRACT: Recent studies have demonstrated the higher likelihood of regeneration in forest gaps compared with the understory for the dominant species in pine-oak mixed forest. Here, we tested whether rodent seed predation or dispersal was beneficial for gap regeneration. We tracked the seed predation and dispersal of Quercus aliena var. acuteserrata and Pinus armandii using coded plastic tags in the forest understory close to gaps. Our results demonstrated that the proportions of initial buried seeds of both species were significantly more abundant in the forest understory compared with gaps. After seed caching, however, significantly lower proportions of the seeds of both species survived in the forest understory compared with gaps during the 30-day observation period. The final survival proportions of the seeds cached in the forest understory were lower than those cached in the gaps the next spring, which indicated that small rodents rarely retrieved scatter-hoarded seeds from forest gaps. Our findings suggest that rodent seed predation patterns contribute to the regeneration of the dominant species in gaps compared with the understory in a pine-oak mixed forest. In the study area, reforestation usually involves planting seedlings but direct sowing in forest gaps may be an alternative means of accelerating forest recovery and successional processes.Acta theriologica 10/2014; 59(4). DOI:10.1007/s13364-014-0192-y · 1.16 Impact Factor
African Zoology 04/2013; 48(1):152-158. DOI:10.3377/004.048.0115 · 0.85 Impact Factor