The individual growth of tree diameter at breast height (dbh) is analyzed in an even-aged plantation of Cryptomeria japonica from stand age of 45 to 94 years, to examine how the growth of individual trees has been affected by the changes in spacing resulting from thinning operations. At any age, a significant proportion (0.37-0.46) of the variation in dbh growth during a 5-11-year period was explained by dbh at the beginning of the period, probably due to greater leaf mass of larger trees. Next, either one-sided or two-sided competition was added to the model, by calculating the basal area (BA) of neighboring trees around each tree within a given radius or BA for trees having larger dbh than the focal tree within the radius. After preliminary analyses, a radius of 8 m was selected as the critical range for tree competition. Although both types of competition explained a significant proportion (0.09-0.43) of growth variation, one-sided competition was not significant at ages greater than 54 years. Based on the model at 45 years of age, the initial deviation of growth rate for each tree from the predicted rate was calculated and added to the models as a third variable. This raised the coefficient of determination up to 0.50-0.74. These findings have practical significance for forest plantation management, particularly for controlling the growth of standing trees via thinning, to produce high-quality timber in the future.
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-yearold) 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 Accepted ArticleThis article is protected by copyright. All rights reserved. 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.
We have studied the photosynthetic production and growth of Thujopsis dolabrata var. hondai (hiba) seedlings under typical light conditions found in mixed forests, including constant shade, phenological gaps under broad-leaved trees with different lengths of foliation period, and in an open plot. Leaves sampled from the open plot had significantly higher rates of light-saturated gross photosynthesis and dark respiration, and a significantly lower specific leaf area than leaves from the other plots. The relative growth rate of whole plant biomass was significantly higher in plots that received larger amounts of light. The variations in these properties under the various light conditions are considered to reflect the ability of hiba seedlings to adapt to available light. In the late autumn, leaves sampled from the open and from the gap under deciduous trees indicated photoinhibition. However, the estimated value of monthly net photosynthesis of hiba seedlings was greater in these plots, indicating that the benefit of a greater light intensity for photosynthesis seems to be larger than the detriment of photoinhibition. The seasonal pattern of photosynthesis by understory hiba seedlings was affected by the phenology of canopy trees. Light availability under the canopy of deciduous trees associated with phenological gaps helped hiba seedlings to tolerate the relatively dark conditions during the subsequent foliation period. These results for reaction to the light regime and for the phenology of hiba seedlings are practicable for hiba forest management.
2016 Correlation between Height:diameter Ratio and Shoot Growth in Containerised and Bare-root Seedlings of Cryptomeria japonica. J Jpn For Soc 98: 139 145 Previous studies revealed that in terms of the stem height growth, containerised seedlings with an average height:diameter ratio HDR of ca. are superior to conventional bare-root seedlings and containerised seedlings with an average HDR of ca. are inferior to conventional bare-root seedlings. In this study, we focused on the correlation between the stem growth and HDR in individual seedlings. We measured the stem growth of-year-old containerised seedlings and-year-old conventional bare-root seedlings for four growth seasons. In each of the growth seasons, HDR showed a negative correlation with stem height growth rate and a positive correlation with the stem radial growth rate of an individual seedling; the strongest correlation was observed in the first and second growth seasons. Therefore, the seedling with a high HDR allocated resources to stem radial growth rather than to height growth. Regarding the stem height growth, we analysed the sequential data for four growth seasons using a linear mixed effects model. HDR showed a negative correlation with the stem height growth. In conclusion, high HDR had negative effects on not only the relative height growth rate but also on the actual height growth.
Mt. Hayachine in Iwate prefecture is characterized by serpentine site, which is known to have high concentrations of Ni. In general, few plants that can tolerate high concentrations of Ni can grow in serpentine soil. Thujopsis dolabrata var. hondai occurs naturally on Mt. Hayachine. In this study, we hypothesized that T. dolabrata var. hondai shows Ni tolerance due to detoxification by phenolics. We collected T. dolabrata var. hondai seedlings and root-zone soil from the Kadoma National Forest on Mt. Hayachine to analyze the concentrations of Ni, other heavy metals, and macronutrients. The seedling roots had high concentrations of Ni. Further, we conducted a pot experiment by using 1-month-old sterile seedlings grown in three types of sterilized soils-Kadoma soil (obtained from the Kadoma National Forest), Tsugaru forest soil, and nursery soil-and compared the concentrations of Ni, nutrients, and catechin, as well as the growth of seedlings in the different soils. The pot experiment indicated that the roots of seedlings grown in Kadoma forest soil contained high concentrations of Ni and catechin, which could act as an antioxidant and a possible Ni-chelating compound that detoxified Ni in the plant cells. We concluded that T. dolabrata var. hondai seedlings growing in the serpentine site of Mt. Hayachine accumulated Ni and could detoxify it by producing high concentrations of catechin.
We describe observed long-term adaptive responses to light conditions in the morphology of saplings of Thujopsis dolabrata var. hondai Makino, a shade-tolerant conifer species. Under stably bright conditions, the crown shape was slender and conical. In contrast, in stably dark conditions, the crowns had a highly distinctive broad, shallow, bowl-like shape, due to the formation of characteristic orthotropic lateral branches with higher apices than the stem. Leaf display by these branches may reduce self-shading and stem elongation requirements for leaf arrangement in dark conditions, thereby minimizing increases in maintenance costs associated with increasing tree size. Epicormic terminal leaders were frequently present on long branches in the lower part of the crowns. These branches did not show vigorous growth or contribute to crown expansion. However, the low-hanging branches in the lowest quarter of the crown may frequently touch the ground, particularly under snow pressure, and produce adventitious roots under these leaders, thereby increasing numbers of ramets. The snow pressure may also cause stem layering and restrain saplings from increasing their height to more than 1 m. These morphological and reproductive traits of lateral branches may contribute to shade tolerance and improve survival of the saplings.Key words: apical control, epicormic shoot, light intensity, longevity in shade, orthotropic end of a branch, vegetative reproduction. Résumé :Les auteurs décrivent les réponses adaptatives aux conditions de lumière observées à long-terme sur la morphologie des gaules de Thujopsis dolabrata var. hondai Makino, une espèce de conifère tolérante à l'ombre. En condition d'éclairage stable, la taille de la couronne était plus mince et conique. Par contre, en condition de noirceur stable, les couronnes présentaient une forme distinctive large et concave à cause de la formation de branches latérales orthotropes caractéristiques possédant des apex plus hauts que la tige. L'organisation des feuilles sur ces branches pourrait réduire l'auto-ombrage et les exigences relatives à l'allongement des tiges pour l'arrangement des feuilles en condition de noirceur, minimisant ainsi les augmentations de coûts de maintien associés à l'accroissement de la taille de l'arbre. Des pousses apicales épicormiques terminales étaient fréquemment présentes sur les branches longues de la partie inférieure des couronnes. Ces branches ne montraient pas de croissance vigoureuse ou ne contribuaient pas à l'expansion de la couronne. Cependant, les branches basses du quart inférieur de la couronne pouvaient souvent toucher le sol, particulièrement sous la pression de la neige et produire des racines adventices sous ces pousses apicales, augmentant ainsi le nombre de ramets. La pression de la neige pouvait aussi provoquer le marcottage des tiges et restreindre l'augmentation de la hauteur des gaules à plus qu'un mètre. Ces traits morphologiques et reproductifs des branches latérales pourraient contribuer à la tolérance à l'ombre et améliorer ...
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