Evaluation of Three-Dimensional Leaf Distribution within a Closed Canopy Based on Low-Cost Laser Scanning Data during Leafless Season

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Do Coarser Gap Mosaics in Conifer Plantations Induce More Seed Dispersal by Birds? Temporal Changes during 12 Years after Gap Creation

The creation of canopy gaps is thought to be an efficient silvicultural operation to diversify species composition of monoculture conifer plantations; however, the shortage of regeneration materials in overclosed plantations is one of the concerns related to this operation. Seed dispersal by frugivorous birds may play an important role in inducing the spread of native broad-leaved trees in canopy gaps in plantations in the warm temperate zone of central Japan because bird-dispersed woody species are abundant in this area. We monitored the dynamics of the abundance and species composition of bird-dispersed seeds over 12 years after gap creation in the canopy of a Japanese cypress (Chamaecyparis obtusa (Siebold et Zucc.) Endl.) plantation. We also studied the effects of gap-mosaic patterns (from many small gaps to fewer large gaps) on dispersal. We used a hierarchical Bayesian zero-inflated Poisson model to analyze the factors affecting seed dispersal by frugivorous birds. Seed dispersal by birds increased with gap age except for just after gap creation. Dispersal in coarser gap mosaics was more abundant than that in finer gap mosaics. The species diversity of dispersed seeds in each seed trap (α-diversity) and plot (γ-diversity) showed similar trends in terms of temporal changes and differences between plots related to seed dispersal abundance; β-diversity did not. These trends might have been caused by shrub-vegetation development after gap creation. The effects of shrub vegetation were classified into the attraction by fruits borne within the vegetation, as well as other effects related to vegetation, such as functions of perch availability and insect presence as a food source. The presence of bird-dispersed seeds was strongly promoted by vegetation in all seasons, but only marginally by the presence of fruit-bearing vegetation. However, fruits attracted seed dispersal by frugivorous birds in the winter season. Our results suggest that both vegetation development and fruiting are important for promoting seed dispersal by frugivorous birds, and those effects are different in different seasons according to vegetation conditions and shifting food resources

Leaf cluster morphology is altered along a local light gradient in different manners between young and old <i>Fagus crenata</i> crowns

Leaf cluster morphological variation within and among Fagus crenata crowns was examined by analysing hierarchical leaf cluster structure. Leaf clusters were defined as a continuous group of leafy voxels, where each voxel was classified as part of a cluster if its effective leaf area density (eLAD) exceeded a threshold value. This threshold value ranged from sparse (10−1.3 m2 m−3) to dense (101.2 m2 m−3). Compared with young crowns, old crowns had a smaller effective leaf area index, a higher proportion of leafless space, more highly fragmented leaf clusters, and thinner clusters at all hierarchal levels, from smaller clusters with higher eLAD to large clusters with lower eLAD. Leaf clusters exhibited structural adaptability to the local light gradient within the crowns. For instance, we observed a positive correlation between leaf cluster thickness and inclination with relative light intensity. We hypothesized that the leaf cluster responses represented adaptations to changes in the light environment within crowns, particularly the increased light interception in lower crowns and the corresponding responses of leaves and twigs. However, cluster adaptation to local light conditions differed between young and old crowns. In young crowns, cluster thickness markedly varied with local light conditions, whereas cluster inclination did not respond. In old crowns, cluster inclination clearly adapted to local light conditions, whereas cluster thickness had little response.</p

Do Coarser Gap Mosaics in Conifer Plantations Induce More Seed Dispersal by Birds? Temporal Changes during 12 Years after Gap Creation

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