This study aimed to clarify the relationship between tree dimensions and tree damage (stem tilting, stem snapping, and falling down) after weeding (cleaning cutting) in a non-weeded 8-year-old hinoki (Chamaecyparis obtusa) stand in a warm-temperate region of Kyushu, Japan. We also performed an analysis to identify which tree dimensional characteristics were likely to cause fatal stem tilting and falling down after weeding. The first weeding in the study site was conducted 9 years after planting. We analyzed the relationship between tree damage and different tree parameters. Five out of 37 hinoki trees (14%) died after being impacted by competing plants felled by weeding, which suggests that the survival of planted trees immediately after weeding was influenced by contingent factors. Trees with a large height-to-diameter ratio ( >137.2 m/m) and a tall height ( >3.9 m) immediately after weeding tended to suffer from severe tilting in the year after weeding, which suggests that vulnerability to stem tilting is related to tree size and shape. According to our results, height-to-diameter ratio can be used as a criterion with tree height for considering the timing of weeding on hinoki plantations to avoid fatal stem tilting and falling down.

This study aimed to examine the relationship between the ecosystem services of pollination offered by native honey bees (Apis cerana) and the distance to natural forests (as an indicator of landscape structure) in hyuganatsu (Citrus tamurana) orchards in Aya Town, Miyazaki Prefecture, Japan. Two statistical models were developed to predict the number of visits of native honey bees to hyuganatsu tree. The area-distaince model (AD-model) considered the area of natural forests and distance from natural forests and the area model (A-model) considered the total area of the surrounding natural forests, and the results of the two models were compared. The estimated parameters of both models suggested a positive effect of natural forests on pollination services. Further, the estimated effect of the landscape structure of the AD-model was greater than that of the A-model. These results suggested that the distance to natural forests is an important landscape factor for evaluating pollination services by native honey bees.

We examined the effect of watering and shading treatments on eugenol productivity of clove seedlings in order to provide the information of the suitable site conditions for eugenol production. After a six-month experiment growing clove seedlings under twelve treatments (3 shading treatments (0%, 60% and 80%) x 4 watering treatments (1.0, 0.75, 0.5 and 0.25 l/m2/day), the total leaf mass per tree (LM), the eugenol content per unit leaf mass (EL) and the eugenol yield per tree (EY) were measured and compared between treatments. As the results, the low watering rates reduced LM slightly; however, this effect was counteracted by the drastically increased EL under the same conditions, resulting in the highest EY in the least watered treatment (0.25 l/m2/day). Heavy shading consistently reduced LM and EL, resulting in the lowest LY under the 80% shading treatment. The relatively dryer site condition where moderate water stress is likely to occur is more suitable for planting clove trees from the aspect of the for long-term high productivity of eugenol, and that the high tree density which may cause a severe competition and a heavy mutual shading among clove trees should be avoided to maintain long term high productivity.

The growth responses of clove seedling to light and soil water regimes were studied by a field experiment with shading and irrigation treatments to clarify their growth traits at the early stage of plantation establishment. Eighteen-month-old clove seedlings were subjected to twelve treatments, that is, 3 shading treatments (0%, 60% and 80% shading) × 4 watering treatments (1.0, 0.75, 0.5 and 0.25 l/m2 /day), for ca. 6 months. Increment ratio of seedling height (IH), number of newly created buds (NB) during the experimental period and dry mass per plant at the end of the experiment (leaves: LM, stem and branch: SM, root: RM and total plant: TM) were compared among the treatment. The growth of clove seedlings (height < 150 cm) was generally more susceptible to water stress than to low light availability. The growth retardation by water shortage was observed in all the examined parameters except for SM. The effect of the shading treatment appeared to be limited; however, LM and NB showed significantly lower values under the heavy shade (80% shading). We concluded that dense planting of clove seedling with other competitive crops should be avoided to ensure the fast growth of clove seedlings at the establishment stage.

暖温帯における小扇状地渓畔林の7年間の動態から，雑木林・夏緑樹林構成種群および常緑広葉樹主要樹種の枯死要因および空間的な分布を被圧状態に着目して解析し，同一地形内での共存機構の一端を明らかにした。生残率を目的変数としたGLMの結果，ホソバタブを除く常緑広葉樹主要樹種および雑木林・夏緑樹林構成種群では，上層木密度が有意な変数して検出された。最も生残率の低かった雑木林・夏緑樹林構成種群は，常緑広葉樹主要樹種に比べて耐陰性が著しく低いと考えられた。また，常緑広葉樹主要樹種内では，イチイガシの耐陰性が比較的低いと考えられた。空間分布からは，雑木林・夏緑樹林構成種群は流路沿いに分布する傾向がみられた。イチイガシは，大規模ギャップ跡への出現割合が有意に高かった。以上の結果から，雑木林・夏緑樹林構成種群が常緑広葉樹と共存するには，高頻度で発生する弱度の攪乱が常緑広葉樹の成立を制限することで，恒常的に良好な光環境が提供されることが重要であると考えられた。常緑広葉樹主要樹種内では，イチイガシが大規模ギャップに一部依存することで他の常緑広葉樹主要樹種と共存していると考えられた。

We investigated stand dynamics of an abandoned evergreen coppice (c.a. 100 years old) over the course of 21 years in south Kyushu, Japan. The study stand showed a change in species composition from being dominated by Castanopsis cuspidata to Distylium racemosum, that is, from a typical coppice species to a typical climax species of the region. However, the relative dominance of Castanopsis spp. appeared to remain very high in the study stand compared to that in the Aya Research Site, a typical old-growth forest in the region, due to abundant C. cuspidata canopy trees of coppice origin. This suggests that the species composition of the study stand remained distinct from that of climax forests in the region. On the other hand, D. racemosum did not show a significant change in diameter at breast height (DBH) class frequency distribution from 1996 to 2017, probably due to the slow growth of this species. However, generalized linear models (GLMs) were used to identify the factors affecting better DBH growth of this species in the gap, indicating the potential for further development of the population structure when small trees are released from suppression of canopy trees. This suggests, inversely, that the development of the D. racemosum population was heavily suppressed by abundant C. cuspidata canopy trees of coppice origin that survived to the age of nearly 100 years. Further, large typhoons are suggested to cause severe canopy disturbances that remove canopy trees of C. cuspidata, which might be important for promoting further forest succession, even for a nearly 100-year-old evergreen old coppice.

Stand structure develops with stand age. Old-growth forests with well-developed stand structure support many species. However, development rates of stand structure likely vary with climate and topography. We modeled structural development of 4 key stand variables and a composite old-growth index as functions of climatic and topographic covariates. We used a hierarchical Bayesian method for analysis of extensive snap-shot National Forest Inventory (NFI) data in Japan (n = 9244) to account for differences in stand age. Development rates of structural variables and the old-growth index exhibited curvilinear responses to environmental covariates. Flat sites were characterized by high rates of structural development. Approximately 150 years were generally required to attain high values (approximately 0.8) of the old-growth index. However, the predicted age to achieve specific values varied depending on environmental conditions. Spatial predictions highlighted regional variation in potential structural development rates. For example, sometimes there were differences of >100 years among sites, even in the same catchment, in attainment of a medium index value (0.5) after timber harvesting. The NFI data suggested that natural forests, especially old natural forests (>150 years), remain generally on unproductive ridges, steep slopes, or areas with low temperature and deep snow, where many structural variables show slow development rates. We suggest that maintenance and restoration of old natural forests on flat sites should be prioritized for conservation due to the likely rapid development of stand structure, although remaining natural forests on low-productivity sites are still important and should be protected.

Plantations are expanding globally and dominate landscapes in many parts of the world. Biodiversity conservation within plantations is becoming an important issue and developing indicators of conservation values is valuable. Although plantations support less biodiversity than natural forests, older plantations can provide habitat for some native trees and associated biota. The amount (basal area) of native trees can be a simple indicator of conservation value of plantations. Various factors are likely to affect rates of increase in native trees in plantations with stand age. We developed an empirical model to predict the amount of broad-leaved trees as an indicator of conservation value of conifer plantations. We quantified relationships between rates of increase in the amount of broad-leaved trees and plantation tree species, density of planted trees, climate, topography and landscape cover. We used a hierarchical modeling framework based on extensive snapshot plot data (n = 3265 plots) from the national forest inventory in Japan. Our results showed that plantation tree species had the largest effect on the rate of increase in broad-leaved trees. Japanese cedar Cryptomeria japonica and hinoki cypress Chamaecyparis obtuse, which are two primary plantation species in Japan (both from the cypress family), had low rates of increase. In plantations of other species (red pine, larch, fir and spruce from the pine family), broad-leaved trees started to increase in amount after 20 years. We found that 50-year-old plantations of the pine family supported 10-20% of the amount of broad-leaved trees typically found in old-growth natural forests. Planted tree density also had important, but nonlinear relationships with the rate of increase in broad-leaved trees. Stands with fewer planted trees had higher rates of increase in broad-leaved trees. Rates of increase also were associated with snow depth, temperature, slope angle and the amount of natural forest in the surroundings. Our results suggest that management practices related to stand age, selection of plantation species and the density of planted trees can contribute to the conservation value of plantations. As our model is based on broadly available covariates and accommodates stand age, it may be applicable to other regions under different management regimes.

We examined a new method to detect the biodiversity hotspots in terms of complex patch mosaics at a regional scale in East Java, Indonesia, in order to develop the safeguard against further expansion of monocultures by REDD+. A land-cover map consisting of five major land-cover types (forest, agricultural land, bare land, water, and residential) was generated with a 30 m x 30 m resolution by the unsupervised classification of a Landsat8-OLI image. Shannon’s diversity index (H’) was calculated for each of 10.98 ha (11 x 11 pixels) landscape throughout the study area based on the dominance of the land-cover types by five calculation methods with different combinations of land-cover types. Then, the landscapes of upper 5 % in H’ was selected as the potential hotspots in terms of highly complex patch mosaics. Among the five potential hotspots, the calculation of H’ with four land-cover types (forest, agriculture, water, and bare land) was thought to be most suitable to set conservation targets at a regional scale, because the potential hotspots by this method showed aggregated distribution patterns, and was less sensitive to the small residential patches. While, no clear distribution trend was observed along the environmental gradients.

We examined differences in the responses of deciduous and evergreen broadleaved trees to fluvial disturbance and light environment near a river-facing forest edge in order to identify the factors limiting the distribution of deciduous trees, which are important components of warm-temperate mountainous riparian forests. Deciduous trees tended to be distributed on lower terraces of less than 2-m relative elevation from the water level, which corresponded with sites suffering from strong bank erosion due to high flood frequency. On the other hand, evergreen trees showed an opposite trend of distribution, indicating that high flood frequency associated with strong erosion-dominated soil disturbances might be a constraint for their establishment and/or survival. Furthermore, crowns of deciduous trees tended to be in the canopy layer at the forest edge, with fewer individuals observed beneath the canopy of evergreen trees, even at the forest edge. In contrast, evergreen trees were concentrated in the understory of the forest interior. These observations suggested that the light environment is the predominant factor affecting the establishment and survival of deciduous trees in warm-temperate mountainous riparian forests; however, the river-facing forest edge beneath the evergreen canopy is not a suitable habitat for deciduous trees. We concluded that erosion-dominated soil disturbance on lower terraces provides suitable habitats for deciduous trees by facilitating their reaching the canopy layer by limiting the establishment and/or survival of evergreen trees.

ABSTRACT We studied the effect of preweeding size of undesirable plants competing against planted hinoki (Chamaecyparis obtusa) trees on their resprouting ability subsequent to weeding in a warm-temperate region. Further, we investigated the period of heterotrophic-dominative growth by estimating the contribution toward growth in height of the preweeding tree size in terms of total basal area (TBA) and stem height at the initial stage of resprouting. No positive correlation was found between size of the sprouts (in terms of height and D2H, product of DBH2 and height) and the preweeding tree size (in terms of TBA). These results may be related to the contribution of the parental stumps on the growth of sprouts having diminished at an early stage of growth, indicating that the period of heterotrophic-dominative growth of sprouts was limited to the very early stage subsequent to weeding. On the other hand, an increase of preweeding tree TBA had a positive effect on the number of the sprouts, which can increase the time required for the practice of weeding.

This study aimed to evaluate the effect of climate change on the potential site productivity of sugi (Cryptomeria japonica)-planted forests in Kyushu Island. In this study, potential site productivity was defined as the simulated 10-year average of net primary production by using the carbon balance-based stand growth model. The spatial unit was a 1-km grid, which had the same as resolution as the climate data, and 15-year-old sugi-planted forests were virtually established in each 1-km grid in the Kyushu Island. Maps of site productivity estimated using current and future climatic data were obtained and compared to generate a map of sugi site productivity change. The average difference between the estimated current and future potential site productivity was −2.61, and the potential site productivity in 87% of the land area of Kyushu Island and of sugi-planted forests was estimated to decrease with future climatic changes. The increase of respiration rate with an increase in temperature was the main factor for the decrease in the potential site productivity of sugi-planted forests.

We investigated forest development processes for a period of 30years (during 87-116-year-old) in an evergreen coppice stand in southern Japan that was highly dominated by Castanopsis sieboldii. Stand age changing developmental stages were verified and compared with the results of a previous case study of evergreen coppices mainly dominated by C. cuspidata, C. sieboldii and Quercus salicina in the same region. A survey plot was established in 1985, and tree height and diameter at breast height of all living stems were recorded. Stems of single-stem individuals and multi-stem individuals were distinguished based on observations of stem bases for each of the overstory and understory. Changes in stem density and species diversity were then evaluated. In the overstory, stem density declined between 92- and 116-year-old. On the other hand, stem density in the understory exhibited a distinct increase during the study period; however, it was primarily single-stem and multi-stem evergreen shrubs, such as Aucuba japonica, and multi-stem evergreen trees, such as C. sieboldii that contributed to this increase. The species diversity index (H') also indicated the same trends. Therefore, it was concluded that the stand examined in the present study exhibited characteristics of the understory re-initiation stage after 92-year-old, and that stand development was delayed compared to development of stands examined in a previous study. These results indicated that the progress of stand development may differ depending on dominant species or forest environment even within evergreen coppices in the same region.

日向備長炭の持続的生産を支援するアラカシ林抽出技術の開発に向けて，Landsatデータによる分光反射特性の時系列解析を行った。宮崎県美郷町のアラカシ純林とその他広葉樹林，宮崎県綾町のアラカシ優占度が高い林分と低い林分において，アラカシの開葉期を含む時系列LandsatデータからBand2，Band3およびBand4の地表面反射率合計に対するそれぞれの地表面反射率の割合（B比，G比およびR比）およびNDVI を算出し，比較した。ドローンを用いた時系列写真では開葉直後のアラカシ純林においてB比の著しい減少，G比の著しい上昇がみられたが，時系列Landsatデータを用いた解析ではそのような変化はみられず，アラカシ純林とその他広葉樹林の間に指標変化傾向の違いもみられなかったため，アラカシ林抽出に必要な情報を得ることはできなかった。