梅木 清

Summary Unraveling the mechanisms of home‐field advantage (HFA) is essential to gain a complete understanding of litter decomposition processes. However, knowledge of the relationships between HFA effects and microbial communities is lacking. To examine HFA effects on litter decomposition, we identified the microbial communities and conducted a reciprocal transplant experiment, including all possible combinations of soil and litter, between sites at two elevations in cool‐temperate forests. Soil origin, rather than HFA, was an important factor in controlling litter decomposition processes. Microbiome‐wide association analyses identified litter fungi and bacteria specific to the source soil, which completely differed at a low taxonomic level between litter types. The relative abundance of these microbes specific to source soil was positively correlated with litter mass loss. The results indicated that the unique relationships between plant litter and soil microbes through plant–soil linkages drive litter decomposition processes. In the short term, soil disturbances resulting from land‐use changes have the potential to disrupt the effect of soil origin and hinder the advancement of litter decomposition. These findings contribute to an understanding of HFA mechanisms and the impacts of land‐use change on decomposition processes in forest ecosystems.

Abstract Interspecific relationships between growth and survival are critical determinants of tree species diversity maintenance in forests. The trade‐offs between growth and survival in co‐occurring tree species are believed to arise along a continuum of life‐history strategies. For example, co‐occurring species range from those that grow slowly and survive well in resource‐poor environments to those that grow quickly but have low survival rates in resource‐rich environments. However, uncertainties remain regarding how growth–survival trade‐offs are related to species traits, tree sizes or environmental conditions. We examined how the relationships between species traits and growth–survival relationships shift in response to changes in stem sizes and across census periods with different climate conditions (frequency of strong winds, drought intensity) across 45 co‐occurring tree species based on 23 years of growth and survival records in a warm temperate rainforest on Yakushima Island, Japan. We developed hierarchical Bayesian models of relative growth and survival rates, including leaf traits, wood density and 95‐percentile maximum stem diameter as explanatory variables. We tested the relationships between estimated trait‐mediated growth–survival relationships and the indices of climate events during five census periods. Each trait's effects on growth–survival relationships differed across the five census periods in response to climate conditions. Interspecific growth–survival relationships affected by a single trait axis for leaves or wood tended to be negative. In contrast, those affected by the maximum stem diameter tended to be positive. Such trends increased with more frequent strong winds or more intense droughts. The single‐trait effects on growth–survival relationships were stronger for smaller sizes than for larger sizes. For all traits combined, we found a significant growth–survival trade‐off only for small‐sized stems in three of five census periods. Synthesis. Our results indicate that the effect of species traits on the growth–survival relationships depended on tree sizes, the census periods or both in response to the frequency or intensity of climate events. We argue the importance of incorporating spatial and temporal variations in environmental conditions into long‐term data from tree census to predict forest dynamics.

Habitat partitioning is a key mechanism that allows coexistence of species, but studies of sympatric mesocarnivore species’ habitat partitioning have mostly been conducted at pre-determined single spatial scales, without considering the spatial scales of habitat selections (SSHS). In this study, we applied a multi-scale occupancy modeling approach to the camera trap data of five sympatric mesocarnivore species in a cool temperate forest in eastern Japan to accurately estimate their habitat preferences and SSHS. We constructed hierarchical Bayesian models with a detection process assumed separately from the occupancy process. This was done to consider inherent detection bias in the camera trap data, due to variations of local environmental variables between camera trap deployment points. In the occupancy model, avoidance of conifer plantations and preference for sloped sites were detected for multiple species, and estimated SSHS for these significant habitat preferences showed both intraspecific and interspecific differentiation for most focal species. These results signify that a mesocarnivore species’ habitat selection occurs simultaneously at multiple spatial scales. Furthermore, they also imply that interspecific differences of habitat selection processes and the spatial scales at which they occur both contribute to the coexistence of sympatric mesocarnivores in their natural habitats. In the detection model, bias in site use was indeed detected, reinforcing the existing argument for the necessity of its consideration in habitat selection modeling of survey data.

Aim of study: To develop a statistical model framework to analyze longitudinal wind-damage records while accounting for autocorrelation, and to demonstrate the usefulness of the model in understanding the regeneration process of a natural forest.Area of study: University of Tokyo Chiba Forest (UTCBF), southern Boso peninsula, Japan.Material and methods: We used the proposed model framework with wind-damage records from UTCBF and wind metrics (speed, direction, season, and mean stand volume) from 1905–1985 to develop a model predicting wind-damage probability for the study area. Using the resultant model, we calculated past wind-damage probabilities for UTCBF. We then compared these past probabilities with the regeneration history of major species, estimated from ring records, in an old-growth fir–hemlock forest at UTCBF.Main results: Wind-damage probability was influenced by wind speed, direction, and mean stand volume. The temporal pattern in the expected number of wind-damage events was similar to that of evergreen broad-leaf regeneration in the old-growth fir–hemlock forest, indicating that these species regenerated after major wind disturbances.Research highlights: The model framework presented in this study can accommodate data with temporal interdependencies, and the resultant model can predict past and future patterns in wind disturbances. Thus, we have provided a basic model framework that allows for better understanding of past forest dynamics and appropriate future management planning.

This study investigated the composition, age-and size-structure, and tree-ring relationships for an old-growth, warm-temperate, mixed-evergreen forest at the University of Tokyo Chiba Forest, Japan. A total of 32 tree species were recorded, which was dominated by Abies firma and Quercus acuta. Tsuga sieboldii dominated the recruitment after 1850, followed by Abies firma. After 1920, many individuals of Castanopsis, Cinnamomum, Cleyera and Quercus became established. The temporal pattern of conifer recruitment did not correspond to the record of strong wind events. Basal area increment in Abies firma and Castanopsis sieboldii trees increased throughout their lives, a trend not seen in the ring width index. Mean annual temperature was below the 100-year mean between 1920 and 1940 and 1960-1980, but increased rather abruptly after 1980. Mean annual precipitation decreased after 1960. Tree-ring releases are very common at the study forest, which are indicative of frequent small to moderate-sized disturbances. At least one release was recorded in every decade from 1890 to the present day, which is likely the primary causal factor promoting tree growth and recruitment. Our results suggest that early logging activities coupled with natural disturbances had a great influence on the developmental process and current structure of the study stand and that tree growth is varying in a manner consistent with forest dynamics.

Elevational diversity gradients (EDGs) of vegetation are shaped by the evolutionary histories of plants as well as by ecological factors. However, few studies of EDGs have focused on the roles of phylogenetic constraints and the effects of complicated interactions among environmental factors. Here, we examine the direct and indirect effects of environmental factors in forming EDGs of forest understory vegetation. The study plots were selected along elevational gradients in cool-temperate and sub-alpine forests in the University of Tokyo Chichibu Forest of central Japan. Tree seedlings and herbs were identified, and environmental factors (elevation, soil temperature, soil pH, soil CN ratio, forest type, basal area, canopy openness, and slope) were measured in these plots. Structural equation modeling (SEM) including taxonomic and phylogenetic diversity was used to consider the causal relationships between environmental conditions and the diversity of understory vegetation. In addition, phylogenetic signals in habitat requirements were tested. The taxonomic and phylogenetic diversities of tree seedlings increased monotonically with elevation, and the same pattern was found for the taxonomic diversity of herbs. The SEM indicated that both the taxonomic and phylogenetic diversity of tree seedlings were most affected by soil properties, although the phylogenetic diversity of herbs was determined by light conditions. These results highlight the importance of environmental filtering by soil properties in shaping EDGs of tree seedlings. This study implies that phylogenetic constraints in the adaptation to soil properties should be considered when predicting changes in EDGs under environmental fluctuations.

© 2017 Elsevier B.V. Thermal image is important source of information in the urban climate. In this study, we proposed “structure-from-motion (SfM) thermal mosaicing” which uses only thermal images to make orthogonal land surface temperature (LST) image in the process of SfM. With this method, orthogonal LST image can be made automatically without finding many ground control points manually. For the application of the method, LST images of central Tokyo in the summer of 2007 and 2013 were made. The quality of the images was practically precise. The images were compared and it is clearly shown that the LST in 2013 became cooler than in 2007 in many areas of development. There were also hotter areas where loss of green spaces was observed. With prevailing usage of drones for obtaining airborne LST image, this automatic method to make LST image will be very useful for UHI studies and urban planning.

森林土壌の生態系機能を維持管理する上で，土壌特性と環境要因の関係を理解することは重要 である。急峻な地形を有する秩父演習林では，その土壌特性が植生のみならず，標高や傾斜度，曲率などの地形によって規定されると考えられる。そこで，本研究では，深度別の土壌特性（pH，全炭素量，全窒素量，CN 比）と，植生（樹木の種多様性，針葉樹率）および地形（標高，傾斜度および斜面方位，曲率，累積流量）の関係を報告し，土壌特性に対する各環境要因の相対的重要性を調べた。土壌pH は土壌が深くなるにつれ上昇し，標高と樹木の種多様性は有意な負の関係を示していた。土壌特性と各環境要因の関係を線形混合モデルにより解析した結果，表層土壌のpH については標高と植生が最も重要な変数であった。一方で，深度10-20 cm と20-30 cmの全窒素量においては，南側で流速が小さい場所で多くなる傾向が示され，地形が標高や植生より土壌特性に強い影響を及ぼし得ることが明らかとなった。これらの結果から，森林の土壌特性に対する局所的な地形や標高に沿った植生変化の重要性が示唆された。It is important to understand the relationship between environmental factors and soil properties in managing the ecosystem functions of forest soils. In the University of Tokyo Chichibu Forest (UTCF), located in a steep mountainous region, soil properties are prescribed by topographic factors such as elevation, slope, and curvature as well as vegetation. In this study, we investigated soil properties (pH, total carbon contents, total nitrogen contents and CN ratio) for each depth, and vegetation (tree diversity and the proportion of coniferous trees) and topography (elevation, slope, aspect, curvature and flow accumulation) in UTCF, and examined the relative importance of environmental factors to soil properties. Soil pH increased with depth and tree diversity showed a significant negative correlation with elevation. In topsoil layers (0-5 cm and 5-10 cm), elevation was the most important variable in explaining soil pH, based on analyses of linear mixed models. On the other hand, total nitrogen content in the 10-20 cm and 20-30 cm depths increased toward sites with south facing slopes and low flow rate, where these topographic variables have stronger influences than elevation and vegetation. These results suggested the importance of local topographic factors and vegetation changes to soil properties along elevational gradients.

Tree growth, especially diameter growth of tree stems, is an important issue for understanding the productivity and dynamics of forest stands. Metabolic scaling theory predicted that the 2/3 power of stem diameter at a certain time is a linear function of the 2/3 power of the initial diameter and that the diameter growth rate scales to the 1/3 power of the initial diameter. We tested these predictions of the metabolic scaling theory for 11 Japanese secondary forests at various growth stages. The predictions were not supported by the data, especially in younger stands. Alternatively, we proposed a new theoretical model for stem diameter growth on the basis of six assumptions. All these assumptions were supported by the data. The model produced a nearly linear to curvilinear relationship between the 2/3 power of stem diameters at two different times. It also fitted well to the curvilinear relationship between diameter growth rate and the initial diameter. Our model fitted better than the metabolic scaling theory, suggesting the importance of asymmetric competition among trees, which has not been incorporated in the metabolic scaling theory.

森林において土壌は植物の生育に影響を及ぼすと同時に、そこに生息する植物の活動も土壌の形成に寄与する。樹木の落葉落枝の形質の違いは分解過程や物質循環といった土壌生態系の機能に強い影響を及ぼすことが知られており、樹木の形質の多様性は土壌微生物相と関係があると考えられる。しかし、山岳地では、標高と関係して変化する気温などの環境も、土壌微生物相にとって重要な要因となる。本研究では、標高傾度に伴う劇的な環境変化の中で、土壌微生物相に対する樹木の機能的多様性の重要性を評価することを目的とした。 東京大学秩父演習林の天然林において、標高傾度（900 m～1800 m）に沿った60ヶ所の調査区を設置して、植生調査と土壌採取を行った。2014年5月下旬から6月上旬にかけて、深度ごと（0～5 cm、5～10 cm、10～20 cm、20～30 cm）に土壌を採取し、真正細菌の16S rRNA遺伝子V4領域を対象とした土壌微生物群集の多様性の解析をした。また、調査区内に出現する樹木種の機能形質については、調査地周辺で各種5個体からサンプルを採取し測定を行った。本講演では、これらのデータ用いて、樹木の形質が土壌微生物相の多様性に及ぼす影響ついて議論する。

<p>本研究では2020年の東京五輪のマラソンコースを例に，その温熱環境を把握することを目的として，MRT（平均放射温度）とWBGT（湿球黒球温度）の計算事例を示した。その結果，猛暑日である2015年8月7日の事例では，9時～18時でコース上のすべての地点でWBGTが熱中症の「厳重警戒レベル」とされる28℃以上となった。またコース上にできる影によってWBGTが低下するため， 日陰を選んでコース取りをすることにより，ランナーが体感するWBGTを低く抑えられる可能性が示唆された。</p>

<p>A method for computing photosynthesis rate of a tree using realistic plant models, AMAP, is discussed in this paper. Photosynthetic rate calculation is an important factor to estimate the growth rate of plants and landscape dynamics in green spaces. However, photosynthesis of plants is difficult to compute because of plants' complex three-dimensional structures composed of leaves, branches and trunks. Complicated structure makes it hard to quantify irradiation intensity caught by each leaf, which is a major factor to define photosynthetic rate. On another front, simulation models which recreate a plant structure inside computer make progress. This enables simulating light acquisition of leaves by ray-tracing methods. Accordingly we compute photosynthesis rate in a sunny summer day using AMAP plant models. The results show that photon weight for ray-tracing greatly influence the amount of photosynthesis rate, and should be set carefully according to target scale. And these calculations suggest that an impact of light shading by branches is slightly large. This method can be applied to a simulation of plants dynamics, for example. And such a simulation will be expected to offer new insights of the landscape managements.</p>

Perennial organ functions of trees living in seasonal environments exhibit temporal changes that can be classified as long-term interannual changes and seasonal fluctuations within single years. However, few studies have separately quantified these changes from longitudinal measurement data or analyzed the relationships between them. We developed a hierarchical Bayesian statistical model consisting of three parts: a long-term interannual change expressed by consecutive annual linear trends, seasonal fluctuations with 26 values for two-week periods in a year, and a random effect for repeated measurements. The model can extract long-term interannual changes and seasonal fluctuations from longitudinal repeated measure data. The pattern of seasonal fluctuation, the amount of seasonal fluctuation, and the net annual change are expressed by the estimated model parameters. We applied our model to foliar chlorophyll (Chl) and nitrogen (N) content measured repeatedly on more than 1-year-old leaves of saplings in four evergreen broad-leaved tree species using nondestructive optical methods. The model successfully explained large variations in the Chl and N content. In general, seasonal fluctuations corresponded to the phenology of current-year leaves; Chl and N tended to decrease from the opening to maturation of new leaves and increased during the rest period. The magnitude of the decrease in the Chl and N content in the growth period of current-year leaves (Delta gamma) did not decrease noticeably as leaves aged. For the Chl content, Delta gamma was positively correlated with the maximum value before leaf opening across species. For the N content, Delta gamma and the maximum value before leaf opening were not clearly correlated across species, but were positively correlated within some species. A model parameter for annual linear trends in Chl and N varied from positive (indicating increasing trends) to negative values (indicating decrease) depending on species and leaf age in years.

Factors influencing branch growth differed between a qualitative element (whether a branch grows) and a quantitative element (the amount of biomass accretion). We measured branch growth in saplings of four evergreen broad-leaved tree species growing in a temperate Japanese forest. A hierarchical Bayesian approach was used to model two elements of branch growth: a qualitative component [whether branches produce new annual shoots (AS(n))] and a quantitative component (total AS(n) mass). The two components were influenced by somewhat different factors. The probability that a branch would produce AS(n) was affected by the total mass of previous-year annual shoots (total AS(n-1) mass), branch age, relative branch height, canopy openness measured at the branch tip, maximum canopy openness within a single sapling, and the interaction between canopy openness and maximum canopy openness. The total AS(n) mass was influenced by the total AS(n-1) mass, relative branch height, branch inclination, and maximum canopy openness. These two components of branch growth should be considered separately when tree architecture is modeled. In addition, we detected interactive responses among branches within individual saplings. The relative importance of interactive modular response and branch autonomy may differ depending on the status of plants, such as individual age, environmental conditions, and the timing of the measurements. We found considerable similarities in the responses of branch growth to the internal and environmental factors among the species studied. We also found some among-species differences in branch growth responses to the explanatory variables measured.

We analyzed basal area (BA) growth using growth data obtained from permanent plots over 4 years for five major tree species in Anhui Province, eastern China. The studied species were dominant conifers (Pinus massoniana and Cunninghamia lanceolata) and co-dominant broad-leaved species (Castanopsis eyrei, Castanopsis sclerophylla, and Loropetalum chinense). A hierarchical Bayesian approach was used to estimate species-specific parameters and to quantify a spatially autocorrelated random effect. We selected a model that included only the following relevant predictor variables: initial size, asymmetric competition, spatially autocorrelated random effect, and random effect associated with plots. For all species analyzed, the model accounted for significant proportions of the variation (R (2) = 70-98 %) in BA growth rates. The initial slope of the relationship between BA growth rate and the initial BA tended to be steeper for P. massoniana than for C. lanceolata. The BA growth rate increased from an initial low value and then leveled off, with a lower maximum BA growth rate for C. lanceolata than for P. massoniana. The BA growth rate of P. massoniana was significantly affected by asymmetric competition with neighbors. The results of our analyses were used to predict to what extent thinning neighboring trees at different intensities would reduce competition impacts on BA growth of P. massoniana and C. lanceolata. Our results also helped to clarify the ecological characteristics of the species analyzed, as well as the spatial distribution of unknown factors influencing tree growth.

近年のレーザーリモートセンシング技術（LiDAR）の発展により，近距離レーザーを用いた森林構造の詳細なデータを迅速かつ正確に取得できるようになった。これまでは航空機レーザーによる研究が圧倒的に多かったが，地上・車載型の近距離レーザーセンサーが身近に利用可能となり，森林構造計測に利用され始めている。航空機レーザーデータから林分レベルでの平均樹高，単木の梢端，樹冠範囲，樹冠単位での単木判別，成層構造，経年的樹高成長を把握できる。一方，地上レーザーを用いることで，幹を主体とした現存量や正確な立木密度が把握できるようになった。これまで手が届かなく測定不可能であった樹冠を森林の内部から測定でき，人的測定誤差の少ない客観的なデータを取得できる。レーザーデータは森林の光・水環境の推定，森林動態の予測，森林保全などといった生態学的研究に応用されてきた。今後は，生理機能の定量化，森林動態の広域・長期モニタリング，森林保全における環境評価手法など，様々な分野での利用拡大が期待される。樹木の形状や林分の現存量を正確に計測できるだけでなく，様々な生態現象を数値的に把握できるようになることを大いに期待したい。

Models were developed to estimate nondestructively chlorophyll (Chl) content per unit of leaf area (Chl(area)) and nitrogen content per unit of leaf area (N-area) using readings of two optical meters for five warm-temperate, evergreen, broadleaved tree species (Castanopsis sieboldii, Cinnamomum tenuifolium, Eurya japonica, Machilus thunbergii, and Neolitsea sericea). It was determined whether models should be adjusted seasonally. Readings (were obtained six times during a year period and Chl(area) and N-area were determined using destructive methods. Bayesian inference was used to estimate parameters of models that related optical meter readings to Chl(area) or N-area for each species. Deviance information criterion values were used to select the best among models, including the models with seasonal adjustment. The selected models were species-specific and predicted Chl(area) accurately (R (2) = 0.93-0.96). The best model included parameters with seasonal adjustments for one out of five species. Model-based estimates of N-area were not as accurate as those for Chl(area), but they were still adequate (R (2) = 0.64-0.82). For all species studied, the best models did not include parameters with seasonal adjustments. The estimation methods used in this study were rapid and nondestructive; thus, they could be used to assess a function of many leaves and/or repeatedly on individual leaves in the field.

レーザーリモートセンシング技術の発展により、これまで不可能であった樹木構造把握が可能となってきた。本研究では地上レーザーを用いて詳細に樹木構造データを取得し、3次元点群データから樹木の幹枝を分類し、各構造を測定した。樹木構造の把握は、コンピュータグラフィックの技術を用いて、レーザー点群に対し内挿する表面を作成した。地上レーザー計測を北海道から滋賀まで様々な樹種を対象に行い、得られたデータを解析し、現地調査したデータと比較した。現地調査は伐倒やロープ登攀によって取得した。研究結果は、胸高直径はどの樹種に対しても3cm以内の誤差で測定可能であり、樹高は地上からのレーザー照射にも関わらず、50cm以内の誤差で測定できた。地上レーザーは航空機レーザーによるデータ取得と視点が異なるため、今後効率の良いサンプル手法が必要である。また枝葉構造の把握も可能であるが、レーザー照射可能距離がセンサーによって異なることから、樹木測定に有効な照射範囲を今後考慮する必要があることがわかった。

Analyzing branch growth is a key to understand survival and growth strategies of tree species because branch growth determines architecture, which, in turn, determines the amount of light captured by the foliage and carbon gain by the photosynthesis. In this study, we measured mass growth of first-order branches together with light intensity, branch initial size, and branch age to understand how branch growth is determined by these factors in four evergreen broad-leaved species growing under a forest canopy. We used hierarchical Bayesian approaches to fit a model that related branch growth and the factors considering nesting error structure. There were some quantitative differences in the parameter estimates. Therefore, patterns in branch growth differ among species.

日本の暖温帯林の広葉樹4 種（スダジイ，ヤブニッケイ，タブノキ，シロダモ）の被陰された稚樹における樹形の違いを明らかにするため，当年シュートの相対的高さ・長さ・角度を解析した。他の３種に比べ，スダジイの稚樹は，水平に近い当年シュートを樹冠の中に比較的均等に分布させていた。これらの当年シュートの特徴により，被陰下のスダジイ稚樹は強い自己被陰をさけ，受光効率を増加させることができる。これに対して，他の種の稚樹は，典型的には，長く，垂直に近い当年シュートを樹冠の上部に集中分布させていた。これらの当年シュートの特徴により，他の種の稚樹は，被陰された低い空間から日のあたる高い空間に葉群をもち上げることができる。

日光金精山亜高山針葉樹林林床にみられる蘚苔類の生育地特性を明らかにするために,生育地の土壌水分率を測定し,種間の比較を行った。調査地のわずか20mのライン上に最低の9%から最高の84%までという大きな土壌分の違いがみられた。ホソバミズゴケ(Sphagnum girgensohnii)の生育地の土壌水分率が最も高く,コケが生育していない場所でも土壌水分率は比較的高く,オオシノブゴケ(Thuidium tamariscinum)の生育地の土壌水分率は最も低かった。明らかにされた蘚苔類の分布と土壌水分率の関係から,水分状態が異なる土壌に蘚苔類が選択的に生育していると考えられた。

We examined the effect of early and intense pruning on light intensity under the canopy, individual growth, diameter-height relationships, and epicormic shoot dynamics in young hybrid larch (Larix gmelinii var. japonica x L. kaempferi) to establish a new effective management method for hybrid larch plantations. The objective is to produce high-quality wood while reducing silviculture costs using a combination of low-density planting and early and intense pruning. In a young hybrid larch plantation, we pruned branches to two different heights (2 and 4 m above ground level) using a no-pruning treatment as a control. Although the growth rates were lower in the heavy pruning treatment (4 m above the ground level) than in other treatments in the year following pruning, when measured 4 years later, growth did not differ between treatments. The number of epicormic shoots increased in the year following pruning, as did the relative photosynthetic photon flux density (rPPFD). The number of epicormic shoots was also dependent on the size of individual trees. However, survival of epicormic shoots was not sufficiently high to be problematic for high-quality timber production. If branches are pruned carefully such that the rPPFD does not rise above 20%, the emergence of epicormic shoots can also be controlled. Our results indicate that early and intense pruning is an effective component of a new management system for hybrid larch plantations.

We analyzed the probability that Betula maximowicziana Regel (monarch birch) would suffer crown dieback (crown-dieback probability) and the basal area growth rate (GB), which was found to be a predisposing stress factor making birch trees susceptible to crown dieback. First, we analyzed the relationship between the probability that birch trees would suffer from crown dieback in 1999 and GB from a period prior to the occurrence of crown dieback (1985-1987), using a data set of repeated measurements on 217 trees. Logistic regression analysis revealed that monarch birch had a larger crown-dieback probability when GB was low in the preceding period. Hence, there were predisposing stress factors that reduced GB and continued to affect trees for at least a decade. Next, we analyzed GB in the same period in relation to symmetrical and asymmetrical competition between trees and found that GB was reduced by symmetrical competition, suggesting that this was one of the predisposing factors for crown dieback. Based on these results, we used selected models for crown-dieback probability and GB to calculate crown-dieback probabilities for individuals with different initial basal areas and experiencing different intensities of symmetrical competition. The predicted crown-dieback probability decreased with decreasing symmetrical competition between trees. We discuss a possible process of crown dieback to death for monarch birch and the use of thinning as a method to reduce the risk of crown dieback.

We developed a functional-structural plant model for Fagus crenata saplings and calculated annual photosynthetic gains to determine the influences of foliar phenology and shoot inclination on the carbon economy of saplings. The model regenerated the three-dimensional shoot structure and spatial and temporal display of leaves; we calculated the hourly light interception of each leaf with a detailed light model that allowed us to estimate hourly leaf photosynthetic gain taking leaf age into account. To evaluate the importance of simultaneous foliar phenology and slanting shoots in beech saplings, we calculated the photosynthetic budgets for saplings with contrasting foliar phenologies and shoot inclinations. In our simulations, we distinguished between simultaneous and successive foliar phenologies, upright and slanting shoot inclinations, and environments with and without a vertical gradient in light intensity. Other model parameters (including photosynthesis vs. light curve, leaf size, and leaf shape) were obtained directly from live beech saplings. With no vertical gradient in light intensity, modeled saplings with simultaneous foliar phenology and slanting shoots (as in live beech) had larger annual photosynthetic gains than saplings with other combinations of traits. Hence, simultaneous foliar phenology and slanting shoots are efficient ways to display leaves in the shaded forest understory light regime where beech saplings thrive. In the presence of vertical light gradients, which can occur in canopy gaps, saplings with upright shoots had larger annual photosynthetic gains than counterparts with slanting shoots. Although mean daily photosynthetic gains of saplings with successive foliar phenology were elevated by exposing leaves to strong light when young and productive, the annual photosynthetic budget of these saplings was reduced (compared to saplings with simultaneous foliar phenology) by their relatively short leaf lifespan. Overall, our results suggest that slanting shoots with simultaneous foliar phenology are particularly successful in shaded environments, where beech often dominates, because they appear to maximize the annual carbon budget by avoiding self-shading and extending leaf lifespans. (C) 2009 Elsevier B.V. All rights reserved.

中国華東地方の針葉樹二次林の優占種二種バビショウ（Pinus massoniana Lamb）とコウヨウザン(Cunninghamia lanceolata (Lamb) Hook) のサイズ分布・空間分布・直径－樹高関係を検討し，両種の生態学的特徴を明らかにした。バビショウは林冠木のみの一山型サイズ分布を持っていた。コウヨウザンは稚樹から亜高木層まで連続したサイズ分布を持っていた。バビショウは小さな空間スケールで一様な空間分布をしていた。コウヨウザンは集中分布をしていた。弱齢林のバビショウ小個体は，コウヨウザンと比べて，直径より樹高成長を優先させる傾向があった。バビショウはオープンサイトにおける成長速度が速い低耐陰性種，コウヨウザンは被陰下での死亡率が低い中耐陰性種であると考えられた。

While leaves typically emerge near shoot apices around the outer surface of a plant canopy, their relative position "moves" deeper into the canopy as additional leaves emerge. The photosynthetic capacity (A (max)) of a given leaf can be expected to decline over time as its relative position (P (r)) in the canopy becomes progressively deeper; this can be observed as a spatial gradient with the A (max) of leaves declining distally from the shoot apex. As a consequence, we propose that the photosynthetic capacity averaged over a single leaf&apos;s lifespan is equivalent to the average photosynthetic capacity of the entire plant canopy at a given time; in other words, there is an ergodic time to space averaging in the organization and development of plant canopies. We tested this "canopy ergodic hypothesis" in two woody (Alnus sieboldiana and Mallotus japonica) and two herbaceous (Polygonum sachalinensis and Helianthus tuberosus) species by following the photosynthetic capacity in 100 individual leaves from the time of their emergence until their death. We compared the average photosynthetic capacity of individual leaves through time (time-average) to the average photosynthetic capacity of all the leaves along a shoot at the time of emergence of the focal leaf (space-average). We found that A (max) and P (r) were positively correlated and that the time-averages of three plant species (Alnus, Mallotus, and Helianthus) were not significantly different from the corresponding space-averages, although the averages differed among individual plants. Polygonum, however, did show significant differences between time and space averages. Ergodicity appears to apply to the leaf-canopy relationship, at least approximately-the average photosynthetic capacity of a single leaf through time (time-average) can represent the average photosynthetic capacity of the entire canopy.

Since the late 1990s, decline of B. maximowicziana Regel has been observed in mature secondary forests in various parts of Hokkaido, northern Japan. To develop a method of thinning for large-timber production of B. maximowicziana, we measured basal area growth and the mortality of 217 trees during a four-year period (1999-2003) in a 90-year-old secondary forest with serious tree damage. We analyzed growth and mortality in relation to the degree of crown dieback (DC), symmetric and asymmetric competition from neighbors, and initial tree size. Individual basal area growth decreased with increasing DC, with increasing symmetric (two-sided) competition, and with decreasing initial tree size. During the four-year period, 4.1% of the observed trees died. Logistic regression analysis revealed that mortality rate increased with increasing DC and with increasing symmetric competition. These results suggest that both growth and mortality rates were affected by the same factors (i.e., DC and symmetric competition). We concluded that the resource for which individuals were competing at the study site was underground, most likely water. Modeled growth and mortality rates can be used to improve the management of damaged forests. A management plan for the damaged study site is proposed.

Three-dimensional landscape information can be easily transferred through the Internet with Google Earth. In this study, we developped a landscape visualization system that enables simulation of planned landscape on Google Earth and the applicability of the system to the landscape design was shown. The visualization system generates KML (Keyhole Markup Language) and KML file is visualized on Google Earth. To make the data small, a tree was expressed by using textured planes instead of thousands of polygons. Trees were placed automatically on a terrain based on the measured data by the system developed in this study. With the system, we made models of real gardens based on measured data and walk-through simulations were tested. The system showed good performance and it also indicated the potential of the systems. © 2010 IEEE.

An increase in size of sika deer populations has caused severe damage to forest vegetation in many regions of Japan. In a Natural World Heritage area on the western part of Yakushima Island, existing high densities of deer are thought to be increasing, but the impact of deer on forest vegetation has not been estimated. Roadside censuses of deer between 1988 and 2006 showed that encounter rates are continuing to increase. Long-term monitoring of individual tree saplings in a 0.13 ha area of the forest between 1992 and 2005 showed that many saplings still remain despite increases in sika deer density. However, differences in growth and mortality rates of preferred, neutral (neither preferred nor avoided) and avoided sika deer food species varied over time. As a group, preferred species continuously had a low growth rate, while their mortality rate increased through time. The growth rates of the neutral and avoided groups decreased especially in the second half of our study period at the same time that their mortality rates increased. These data suggest that in spite of food species preference, direct feeding pressures as well as indirect physical effects by increasing sika deer density are affecting growth and mortality of tree saplings. Clearly, it is difficult to predict how plant communities will respond to possible continued sika deer population growth, and it is therefore important to continue monitoring these forest communities in the interest of preserving the unique ecosystems on Yakushima Island. (c) 2008 Elsevier B.V. All rights reserved.

To clarify mortality patterns of current-year shoots within the crown of Betula maximowicziana Regel after severe insect herbivory in central Hokkaido, northern Japan, we investigated the degree of defoliation, pattern of shoot development, shoot mortality, and leaf tissue-water relations. One hundred current-year long shoots growing in a B. maximowicziana plantation were observed for defoliation and mortality in June 2002. An outbreak of herbivorous insects (Caligula japonica and Lymantria dispar praeterea) occurred in the stand in mid-to-late June, and the monitored shoots were defoliated to various degrees. Within 1 month of defoliation, some of the severely defoliated shoots had produced new leaves on short shoots that had emerged from axillary buds. Stepwise logistic regression revealed that the probability that current-year long shoots would put out axillary short shoots with leaves is closely related to the degree of defoliation. To evaluate the water relations of the leaves, we determined pressure-volume curves for the leaves that survived the herbivorous insect outbreak and the new leaves that emerged after defoliation. The water potential at turgor loss (Psi(l,tlp)) and the osmotic potential at full turgidity (Psi(pi,sat)) were higher for the new leaves than for the surviving leaves, indicating a lower ability to maintain leaf cell turgor against leaf dehydration in the new leaves. Of the 100 shoots, 13 died after the emergence of new leaves. Stepwise logistic regression revealed that the probability that the long shoots would die generally increased with the emergence of new leaves, with increasing shoot height. This result suggests that the combined effect of the vulnerability of newly emerged leaves and low water availability, associated with higher shoot positions within the crown, caused shoot mortality. Based on our results, some possible mechanisms for mortality in severely defoliated B. maximowicziana are discussed.

The "foliage cluster (FC) model" shows that the size (the amount of leaves, number of yearly shoots and total twig length), turnover time, and branching (i.e., forking) structure of a twig becomes stable in the top of the crown in an oak species by forming a "stable FC" [1]. A stable FC can be treated as a basic component of the crown structure and as an alternative to individual leaf or current-year shoot. The FC model is composed of several equations approximating the branching structure of twigs. Differences in size and branching morphology among twigs are represented by differences in values of the parameters of the equations. We described details of our analyses of data taken from real twigs and applied to the equations implemented in the FC model. © 2007 IEEE.