Effects of Light Intensity and Girdling Treatments on the Production of Female Cones in Japanese Larch (Larix kaempferi (Lamb.) Carr.): Implications for the Management of Seed Orchards

To ensure sustainable forestry, it is important to establish an efficient management procedure for improving the seed production capacity of seed orchards. In this study, we evaluated the effects of girdling and increasing light intensity on female cone production in an old L. kaempferi (Lamb.) Carr. seed orchard. We also evaluated whether there is a genotype-specific reproductive response to these factors among clones. The results showed that female cone production was augmented by girdling and increasing light intensity. There was a difference in the effectiveness of girdling treatment levels, and the probability of producing female cones increased markedly at higher girdling levels. At light intensities where the relative photosynthetic photon flux density was higher than 50%, more than half of the trees tended to produce female cones, even in intact (ungirdled) trees, and the genotype-specific response to light intensity was more apparent in less-reproductive clones. These findings suggested that girdling less-reproductive trees combined with increasing light intensity was an effective management strategy for improving cone production in old seed orchards

Effects of Girdling Intensity, Pruning Season and Thinning on Tree Growth, Crown Vigor and Wound Recovery in Japanese Larch

To ensure sustainable forestry, it is important to establish efficient management procedures for seed orchards. We evaluated the effects of thinning, pruning season and girdling intensity on tree growth and vigor in an old Larix kaempferi seed orchard. Even after four years, tree size (crown width and tree height) increased, resulting in light intensity of an un-thinned class decreasing. Thinning counteracted the decrease in light intensity associated with tree growth, but it had no effect on promoting tree growth. Tree crown status was scored based on vigor and health. No significant difference in crown vigor was observed between unpruned and winter-pruned trees, but the summer-pruning class showed significantly lower vigor. Five years after girdling, trees with low and moderate girdling levels maintained high crown vigor, similar to intact trees, while the crown vigor of trees subjected to severe girdling was significantly lower. This is the first study to quantitatively model trends in remaining girdling depth over time, and to show that the half decay period was ca. 2–3 years. Our findings suggested that management procedures that combine moderate-level girdling, winter pruning and thinning to maintain rPPFD at 50% are well-suited to balancing tree vigor and reproduction in seed orchards

Optimizing the size of root cutting in Melia volkensii Gürke for improving clonal propagation and production of quality planting stock

Melia volkensii is a tree species growing in semi-arid regions of East Africa, and is recognized as one of the most valuable forestry species in such regions of Kenya. The use of root cutting is an easy method for its clonal propagation, but the most appropriate conditions have not been systematically examined. In this study, the relationship between diameter of root cut edge or fresh weight and formation frequency of adventitious bud were assessed. In addition, roots were divided into two fragments, and formation frequency of adventitious bud was compared between cross-sections roots without root tip and roots with root tip. Both the diameter of the cut edge and fresh weight of roots forming adventitious buds were significantly higher than in those not forming them (unpaired t-test, p<0.01). Formation frequency of adventitious bud was 77.0% in roots satisfying the criteria of cut edges diameter >15 mm and fresh weight >20 g, but it decreased (37.2%) in roots that did not meet this criteria. Based on anatomical analysis, an effect of the developmental stage of root fragments on adventitious bud formation was suggested, and root size is thought to reflect the stage of root development. The formation frequency of adventitious buds was 72% even in cross-sectioned roots, and the proportion was not significantly different from that of normal root tip (p>0.05). Therefore, it is concluded that root cutting using cross-sectioned roots are also available for clonal propagation.Keywords: Clonal forestry, anatomical analysis of root, availability of cross sectioned root

Efficient Calculation Method for Tree Stem Traits from Large-Scale Point Clouds of Forest Stands

With the use of terrestrial laser scanning (TLS) in forest stands, surveys are now equipped to obtain dense point cloud data. However, the data range, i.e., the number of points, often reaches the billions or even higher, exceeding random access memory (RAM) limits on common computers. Moreover, the processing time often also extends beyond acceptable processing lengths. Thus, in this paper, we present a new method of efficiently extracting stem traits from huge point cloud data obtained by TLS, without subdividing or downsampling the point clouds. In this method, each point cloud is converted into a wireframe model by connecting neighboring points on the same continuous surface, and three-dimensional points on stems are resampled as cross-sectional points of the wireframe model in an out-of-core manner. Since the data size of the section points is much smaller than the original point clouds, stem traits can be calculated from the section points on a common computer. With the study method, 1381 tree stems were calculated from 3.6 billion points in ~20 min on a common computer. To evaluate the accuracy of this method, eight targeted trees were cut down and sliced at 1-m intervals; actual stem traits were then compared to those calculated from point clouds. The experimental results showed that the efficiency and accuracy of the proposed method are sufficient for practical use in various fields, including forest management and forest research

Data from: A novel growth model evaluating age-size effect on long-term trends in tree growth.

1.One of the major problems in understanding growth trends in long-lived trees is the difficulty of separately quantifying the effects of tree size and age. Careful statistical control of the axiomatic age×size covariation is therefore required to identify long-term trends in tree growth and their drivers, and to predict forests’ responses to environmental changes reliably. 2.To address this issue, we present a novel tree growth model: a ‘two-dimensional lognormal growth model’. This is an extension of the one-dimensional lognormal growth model, in which tree growth is modelled primarily as a function of size. Our model assesses the trend in tree growth over time by explicitly partitioning the effects of age and size, controlling the covariation. The model is then extended to incorporate the effects of neighbourhood crowding and individual tree variation. 3.To demonstrate our model, we apply it to long-term monitoring data from a mature (104-year- old) plantation of Japanese cedar. Thinning operations of various intensities have been applied to this plantation, and the diameter of each individual tree has been measured repeatedly. 4.We observed a pronounced age-related decline in diameter growth. However, at each age, greater tree size was associated with a higher growth rate. The growth-size curve predicted from the model became flatter with tree age, and the curve's peak shifted rightwards as tree age increased. The model reveals that the sensitivity of a target tree to neighbourhood crowding depends strongly on neighbours’ size, and also provides an estimate of among-tree variation in growth performance. 5.Although the relationships between growth, size and age in long-lived trees are very complex, our growth model supports the conclusion that it is possible to predict long-term trends in tree growth reliably with respect to both age and size. In addition, the model's flexibility will facilitate more robust testing of species-specific responses to long-term environmental changes