Effects of granivorous rodents on direct seeding of oak and beech in relation to site preparation and sowing date

Abstract:To facilitate the reintroduction of five native late-successional Taiwanese Fagaceae species into Japanese cedar (Cryptomeria japonica (D.) Don) plantations, we experimented with methods to alleviate their establishment limitations. We tested different combinations of tree species, seedling development stages, and site preparation techniques. First, we directly sowed both fresh and germinated acorns under both closed and opened (thinned) canopies. Both fresh and germinated acorns survived only six months at most. Wildlife consumption was the most critical factor hindering their survival. We subsequently experimented with different methods for increasing establishment rates, such as thinning in combination with understory control, applying chemical animal repellents to seeds, using physical barriers against seed predators, and using seedlings of different ages. Among the methods experimented, none was effective. The effects of silvicultural treatments to deter seed consumption lasted only the first few weeks after sowing, whereas the effects of physical barriers were inconsistent. We also tested planting 3-month and 1-year-old seedlings. Seedling survival after 9 months was about 20% on average for 3-month-old seedlings but reached 80% for 1-year-old seedlings. Our results suggest that planting seedlings older than six months or establishing physical obstacles to prevent seed predation will be the most effective strategies to reintroduce late-successional hardwood Fagaceae species into Japanese cedar plantations.

Section: Preventing Seed Predationmentioning

confidence: 99%

Bringing the Natives Back: Identifying and Alleviating Establishment Limitations of Native Hardwood Species in a Conifer Plantation

Lin

et al. 2018

“…Direct seeding of acorns, besides allowing the normal development of the root system, provides greater flexibility in terms of the timing and the location of sowing [8], as well as important economic advantages [9], as compared to planting. However, many species of mammal predators, including rodents, lagomorphs and ungulates, prey on acorns [10][11][12][13][14]. As a consequence, direct sowing of acorns is usually avoided due to the large losses to predators and the uncertainty that it generates despite its many advantages [2,8,15,16].…”

Section: Introductionmentioning

confidence: 99%

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

Leverkus

Carrión

Molina‐Morales

et al. 2017

Abstract:The assisted regeneration of oaks can be achieved through seeding or planting. Whereas direct seeding of acorns has several advantages over planting nursery-grown seedlings, the problem of seed predation by mammals precludes its widespread application. We investigated the potential of diesel as a mammal repellent to prevent the consumption of Holm oak acorns. We tested the effect of submerging acorns in diesel for 0, 6, 12, and 24 h on acorn predation in a field experiment in the Sierra Nevada Natural Park (Granada province, Spain), and the potential effect of the same treatments on seedling emergence and growth in a nursery experiment. The field experiment showed no reduction in acorn predation through diesel. On the other hand, submersion in diesel hindered the germination of one in every four sown acorns regardless of submersion time. Our results are in line with many failed attempts to protect acorns with chemical repellents and suggest that an effective, universally-abundant, inexpensive, and easy-to-apply acorn protector to enhance the success of seeding operations is yet to be found.

“…Planting oaks in rows in high initial densities (between 5000 and 10,000 seedlings·ha −1 ) is the common way to establish oak forests [1]. However, it is expensive due to the high costs associated with the purchase of seedlings, protective measures against browsing and extensive site preparation, particularly on wind-thrown sites [13][14][15]. In southwest Germany, for example, planting 5000 seedlings per ha in rows would cost between 15,000 and 18,000€ (including fencing).…”

Section: Introductionmentioning

confidence: 99%

“…20 oak seedlings per group with 1 m initial spacing between the trees. The oak trees planted in groups are often surrounded by a varying number (8)(9)(10)(11)(12)(13)(14)(15)(16) of planted shade-tolerant trainer trees (Carpinus betulus L., Tilia cordata Mill., Fagus sylvatica L.). The purpose of the trainer trees is to accelerate self-pruning of oaks, and to maintain the desired branch free bole length (at least 25% of tree height) by preventing the formation of epicormic branches.…”

Section: Introductionmentioning

confidence: 99%

Oak Group Planting Produces a Higher Number of Future Crop Trees, with Better Spatial Distribution than Row Planting

Skiadaresis

Saha

Bauhus

2016

Recent studies have reported superior tree quality and comparable tree growth of oaks planted in group compared with row planting. However, a comparative assessment of the potential future crop trees (PFCTs) between group and row planting is still lacking. Here, we compared the density and tree quality of planted oaks and other naturally regenerated trees between group and row planting. We assessed whether the distribution of PFCTs fulfills the goal of maintaining a spatially homogenous distribution of such crop trees at the stand level by geospatial analysis. We selected 10 group and row planting stands that were either 14 to 15 or 21 to 22 years old. Tree density in group plantings was significantly higher than in row plantings. Stand basal area was higher in row planting in younger stands but comparable to group planting in older stands. The proportion of trees with straight stems and monopodial crowns was higher in groups than in rows. The density and species' richness of the PFCTs was significantly higher but the number of oak PFCTs was lower in group than in row plantings. In group plantings, naturally regenerated PFCTs contributed to 43% of total PFCTs, but to only 19% in row plantings. Also, the spatial distribution of PFCTs in group plantings was more uniform than in row plantings. Uniform and homogeneous distribution of the PFCTs in group planting stands can facilitate design and conduct of tending operations. Thus, the group planting technique offers not only cost savings in the establishment phase but also additional benefits, including spreading of risks through increased tree species diversity.