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Forest structural parameters are crucial for assessing ecological functions and forest quality. To improve the accuracy of estimating these parameters, various approaches based on remote sensing platforms have been employed. Although remote sensing yields high prediction accuracy in uniform, even-aged, simply structured forests, it struggles in complex structures, where accurately predicting forest structural parameters remains a significant challenge. Recent advancements in unmanned aerial vehicle (UAV) photogrammetry have opened new avenues for the accurate estimation of forest structural parameters. However, many studies have relied on a limited set of remote sensing metrics, despite the fact that selecting appropriate metrics as powerful explanatory variables and applying diverse models are essential for achieving high estimation accuracy. In this study, high-resolution RGB imagery from DJI Matrice 300 real-time kinematics was utilized to estimate forest structural parameters in a mixed conifer–broadleaf forest at the University of Tokyo Hokkaido Forest (Hokkaido, Japan). Structural and textual metrics were extracted from canopy height models, and spectral metrics were extracted from orthomosaics. Using random forest and multiple linear regression models, we achieved relatively high estimation accuracy for dominant tree height, mean tree diameter at breast height, basal area, mean stand volume, stem density, and broadleaf ratio. Including a large number of explanatory variables proved advantageous in this complex forest, as its structure is influenced by numerous factors. Our results will aid foresters in predicting forest structural parameters using UAV photogrammetry, thereby contributing to sustainable forest management. [ABSTRACT FROM AUTHOR]

High-value timber species with economic and ecological importance are usually distributed at very low densities, such that accurate knowledge of the location of these trees within a forest is critical for forest management practices. Recent technological developments integrating unmanned aerial vehicle (UAV) imagery and deep learning provide an efficient method for mapping forest attributes. In this study, we explored the applicability of high-resolution UAV imagery and a deep learning algorithm to predict the distribution of high-value deciduous broadleaf tree crowns of Japanese oak (Quercus crispula) in an uneven-aged mixed forest in Hokkaido, northern Japan. UAV images were collected in September and October 2022 before and after the color change of the leaves of Japanese oak to identify the optimal timing of UAV image collection. RGB information extracted from the UAV images was analyzed using a ResU-Net model (U-Net model with a Residual Network 101 (ResNet101), pre-trained on large ImageNet datasets, as backbone). Our results, confirmed using validation data, showed that reliable F1 scores (>0.80) could be obtained with both UAV datasets. According to the overlay analyses of the segmentation results and all the annotated ground truth data, the best performance was that of the model with the October UAV dataset (F1 score of 0.95). Our case study highlights a potential methodology to offer a transferable approach to the management of high-value timber species in other regions. [ABSTRACT FROM AUTHOR]

Old plantations are iconic sites, and estimating stand parameters is crucial for valuation and management. This study aimed to estimate stand parameters of a 115-year-old Japanese larch (Larix kaempferi (Lamb.) Carrière) plantation at the University of Tokyo Hokkaido Forest (UTHF) in central Hokkaido, northern Japan, using unmanned aerial vehicle (UAV) photogrammetry. High-resolution RGB imagery was collected using a DJI Matrice 300 real-time kinematic (RTK) at altitudes of 80 and 120 m. Structure from motion (SfM) technology was applied to generate 3D point clouds and orthomosaics. We used different filtering methods, search radii, and window sizes for individual tree detection (ITD), and tree height (TH) and crown area (CA) were estimated from a canopy height model (CHM). Additionally, a freely available shiny R package (SRP) and manually digitalized CA were used. A multiple linear regression (MLR) model was used to estimate the diameter at breast height (DBH), stem volume (V), and carbon stock (CST). Higher accuracy was obtained for ITD (F-score: 0.8–0.87) and TH (R2: 0.76–0.77; RMSE: 1.45–1.55 m) than for other stand parameters. Overall, the flying altitude of the UAV and selected filtering methods influenced the success of stand parameter estimation in old-aged plantations, with the UAV at 80 m generating more accurate results for ITD, CA, and DBH, while the UAV at 120 m produced higher accuracy for TH, V, and CST with Gaussian and mean filtering. [ABSTRACT FROM AUTHOR]

Context: Forest management practices that conserve biodiversity and maximize carbon sequestration under climate change are needed. Although post-windthrow salvage logging and scarification can reduce carbon dioxide (CO2) emissions within ecosystems by removing downed logs, they can greatly affect species composition. Additionally, salvage logging may increase CO2 emissions based on a cradle-to-grave analysis of salvaged wood. Objectives: We aimed to assess the effects of changes in climate, windthrow regimes and post-windthrow management on aboveground biomass, species composition, and carbon balance in the forest sector by combining forest landscape simulations and life cycle assessment (LCA). Methods: The study landscape is a 12,169 ha hemiboreal forest located in northern Japan. We simulated 115 years (2015–2130) of forest dynamics in 36 scenarios based on features of the climate, windthrow regime, and management using the LANDIS-II forest landscape model. CO2 emissions related to management and salvaged wood were estimated by LCA. Results: Increases in the windthrow area, which was more vulnerable to climate warming, caused a shift to temperate broadleaved forests and a decrease in aboveground biomass. These were accelerated by the removal of advanced seedlings and dead wood, which greatly reduced the recruitment of Picea species. The 115-year cumulative net CO2 absorption of the forest sector, including carbon balance within ecosystems and CO2 emissions estimated by LCA, greatly decreased due to salvage logging (maximum 81%) and scarification (maximum 114%). Conclusions: Leaving downed logs and advanced seedlings is recommended to conserve boreal conifers and carbon sinks and maximize net CO2 absorption under climate change. [ABSTRACT FROM AUTHOR]

The accurate estimation of carbon stocks in natural and plantation forests is a prerequisite for the realization of carbon peaking and neutrality. In this study, the potential of optical Sentinel-2A data and a digital elevation model (DEM) to estimate the spatial variation of carbon stocks was investigated in a mountainous warm temperate region in central Japan. Four types of image preprocessing techniques and datasets were used: spectral reflectance, DEM-based topography indices, vegetation indices, and spectral band-based textures. A random forest model combined with 103 field plots as well as remote sensing image parameters was applied to predict and map the 2160 ha University of Tokyo Chiba Forest. Structural equation modeling was used to evaluate the factors driving the spatial distribution of forest carbon stocks. Our study shows that the Sentinel-2A data in combination with topography indices, vegetation indices, and shortwave-infrared (SWIR)-band-based textures resulted in the highest estimation accuracy. The spatial distribution of carbon stocks was successfully mapped, and stand-age- and forest-type-level variations were identified. The SWIR-2-band and topography indices were the most important variables for modeling, while the forest stand age and curvature were the most important determinants of the spatial distribution of carbon stock density. These findings will contribute to more accurate mapping of carbon stocks and improved quantification in different forest types and stand ages. [ABSTRACT FROM AUTHOR]

The accurate classification of forest types is critical for sustainable forest management. In this study, a novel multiscale global graph convolutional neural network (MSG-GCN) was compared with random forest (RF), U-Net, and U-Net++ models in terms of the classification of natural mixed forest (NMX), natural broadleaved forest (NBL), and conifer plantation (CP) using very high-resolution aerial photographs from the University of Tokyo Chiba Forest in central Japan. Our MSG-GCN architecture is novel in the following respects: The convolutional kernel scale of the encoder is unlike those of other models; local attention replaces the conventional U-Net++ skip connection; a multiscale graph convolutional neural block is embedded into the end layer of the encoder module; and various decoding layers are spliced to preserve high- and low-level feature information and to improve the decision capacity for boundary cells. The MSG-GCN achieved higher classification accuracy than other state-of-the-art (SOTA) methods. The classification accuracy in terms of NMX was lower compared with NBL and CP. The RF method produced severe salt-and-pepper noise. The U-Net and U-Net++ methods frequently produced error patches and the edges between different forest types were rough and blurred. In contrast, the MSG-GCN method had fewer misclassification patches and showed clear edges between different forest types. Most areas misclassified by MSG-GCN were on edges, while misclassification patches were randomly distributed in internal areas for U-Net and U-Net++. We made full use of artificial intelligence and very high-resolution remote sensing data to create accurate maps to aid forest management and facilitate efficient and accurate forest resource inventory taking in Japan. [ABSTRACT FROM AUTHOR]

Quantifying how understory vegetation responds to individual neighboring trees is critical to understanding forest dynamics. To do so, we used a spatial neighborhood approach to quantify the competitive effect of individual trees on the density and height of dwarf bamboo (Sasa senanensis (Franch. et Savat.) Rehder) in a mixed conifer-broadleaf forest on the island of Hokkaido, northern Japan. Using hierarchical Bayesian models, we analyzed how the effect of neighboring trees varies with stem size, distance to the dwarf bamboo, and tree species. The effect of neighbors peaked when the tree reached a medium size (33.0-45.0 cm in diameter at breast height) and decreased for larger trees. The effect of neighbors decreased with increasing distance to the dwarf bamboo. The slope of the decrease was gentler for larger trees. Conifers exerted an average of 7.2 times the effect of broadleaved trees. Species with higher shade tolerance exerted larger effects. Species with late leaf flush and early defoliation tended to exert smaller effects. Our results provide evidence that neighborhood analysis is an effective approach for quantifying the effects of individual trees on understory vegetation and represents a critical step toward understanding how fine-scale interactions between understory vegetation and trees influence overall forest dynamics. Resume: Il est essentiel de quantifier la reaction de la vegetation du sous-etage a chacun des arbres avoisinants pour comprendre la dynamique forestiere. A cette fin, nous avons utilise une approche spatiale de voisinage pour quantifier l'effet de competition d'arbres individuels sur la densite et la hauteur du bambou nain (Sasa senanensis (Franch. & Savat.) Rehder) dans une foret mixte sur l'ile d'Hokkaido, dans le nord du Japon. A l'aide de modeles bayesiens hierarchiques, nous avons analyse la facon dont l'effet des arbres voisins varie selon le diametre de la tige, la distance du bambou nain et l'espece d'arbre. L'effet des voisins culmine lorsqu'un arbre atteint une taille moyenne (33 a 45 cm de diametre a hauteur de poitrine) et diminue lorsque les arbres sont plus gros. L'effet des voisins diminue avec l'augmentation de la distance du bambou nain. La pente de la diminution etait plus faible pour les arbres plus gros. L'effet produit par les coniferes etait en moyenne 7,2 fois plus grand que celui des feuillus. Les especes les plus tolerantes a l'ombre avaient plus d'effet. Les especes qui debourraient tardivement et perdaient leur feuilles tot avaient tendance a avoir moins d'effet. Nos resultats montrent que l'analyse de voisinage constitue une approche efficace pour quantifier les effets d'arbres individuels sur la vegetation du sous-etage et represente une etape essentielle pour comprendre comment les interactions a petite echelle entre la vegetation du sous-etage et les arbres influencent la dynamique forestiere globale. [Traduit par la Redaction], Introduction In many of the world's forest ecosystems, understory vegetation plays a crucial role in forest dynamics (Nakashizuka 1988; Abe et al. 2002; Royo and Carson 2006, 2008). The attributes [...]

Forest canopy structure is an important parameter in multipurpose forest management. An understanding of forest structure plays a particularly important role in the management of uneven-aged forests. The identification of vertical and horizontal variations in forest canopy structure using a ground-based survey is resource intensive, hence often demands for alternative data sources. In this study, one of the advanced remote sensing (RS) techniques, i.e. digital aerial photogrammetry was used to characterize forest canopy structure in a mixed conifer–broadleaf forest. We used aerial imagery acquired with a fixed-wing unmanned aerial vehicle (UAV) platform to produce RS metrics that could be used to classify and map forest structure types at landscape scale. Our results demonstrated that few structural and spectral metrics derived from UAV photogrammetric data, e.g. mean height, standard deviation of height, canopy cover, and percentage broadleaf vegetation cover, could characterize the forest structure across landscapes, particularly at the forest management compartment level, in a limited amount of time. We used cluster analysis for classification of forest structure types and identified five forest structure classes with varying levels of forest canopy structural complexity: (1) short, open-canopy, conifer-dominated structure; (2) short, dense-canopy, broadleaf-dominated structure; (3) tall, closed-canopy, broadleaf-dominated structure; (4) very tall, closed-canopy, conifer-dominated structure with a relatively high degree of variation in canopy height; and (5) very tall, closed-canopy, conifer-dominated structure with a relatively low degree of variation in canopy height. These classes showed relationships with forest management activities (e.g. selection harvesting) and natural disturbances (e.g. typhoon damage). Spatial distribution of forest canopy structural complexity that was revealed in this study is capable of providing important information for forest management planning and habitat modelling. Further, the simple, and flexible data-driven method used in this study to characterize forest structure has the potential to be applied with necessary changes over larger landscapes and different forest types for characterizing and mapping forest structural complexity. [ABSTRACT FROM AUTHOR]

Unmanned aerial vehicles (UAVs) and digital photogrammetric techniques are two recent advances in remote sensing (RS) technology that are emerging as alternatives to high-cost airborne laser scanning (ALS) data sources. Despite the potential of UAVs in forestry applications, very few studies have included detailed analyses of UAV photogrammetric products at larger scales or over a range of forest types, including mixed conifer-broadleaf forests. In this study, we assessed the performance of fixed-wing UAV photogrammetric products of a mixed conifer-broadleaf forest with varying levels of canopy structural complexity. We demonstrate that fixed-wing UAVs are capable of efficiently collecting image data at local scales and that UAV imagery can be effectively utilized with digital photogrammetric techniques to provide detailed automated reconstruction of the three-dimensional (3D) canopy surface of mixed conifer-broadleaf forests. When combined with an accurate digital terrain model (DTM), UAV photogrammetric products are promising for producing reliable structural measurements of the forest canopy. However, the performance of UAV photogrammetric products is likely to be influenced by the structural complexity of the forest canopy. Furthermore, we highlight the potential of fixed-wing UAVs in operational forest management at the forest management compartment level, for acquiring high-resolution imagery at low cost. A future direction of this research would be to address the issue of how well the photogrammetric products can predict the actual structure of mixed conifer-broadleaf forests. [ABSTRACT FROM AUTHOR]

High-value hardwood species such as monarch birch (Betula maximowicziana) and castor aralia (Kalopanax septemlobus) are important economic and ecological elements of cool-temperate mixed forests in northern Japan. This article presents the single-tree management system for high-value timber species as practised for 50 years at the University of Tokyo Hokkaido Forest. Nearly 2000 valuable broad-leaved trees meeting the size and quality criteria have been registered as ‘superior trees’, and their status is periodically monitored for timing of harvest. A case study was conducted using 2105 inventory plots to characterize the stand types in which superior trees occur. A total of 57 superior trees of 11 broad-leaved species was found in 2.2% of the inventory plots. The results indicated that superior trees generally grew in mature species-rich stands. Superior trees of some species may have promoted their abundance by dispersing relatively more seeds to the surroundings. Single-tree management facilitates the sustainable use of high-value timber species by explicitly monitoring the numbers, attributes and locations of superior trees, and contributes to conserving stand structural diversity through protection of these large-sized canopy trees, which promotes ecological values such as biomass and carbon storage, species diversity, seed abundance and bird habitat. The production of fancy wood from superior trees earns significant income through extremely high log prices (maximum > 20,000 USD m–3). EDITED BY Nicholas Brokaw [ABSTRACT FROM PUBLISHER]

Quantifying the strength of competition and understanding how it translates into consequences at the community level are among the key aims of plant ecology. Neighborhood analysis based on the neighborhood competition index has been widely used to estimate species‐specific competition coefficients in tree communities. These estimates, however, could not be estimated for rare species with small sample sizes using the conventional species‐by‐species approach. Here, we develop a new modeling framework for neighborhood analysis in which the competition coefficient is assumed to have a hierarchical parameter structure. Using actual tree census data consisting of 38 species, we demonstrate that the hierarchical model enables us to estimate competition coefficients for all species, including rare ones, within a community. The hierarchical models were selected over the models based on the species‐by‐species approach as a result of model selection, in either cases where we assumed the competitive strength is determined by niche difference or competitive ability difference. Our results suggest that the hierarchical approaches can serve as a useful alternative to species‐by‐species approach for estimating competition coefficients in tree communities. [ABSTRACT FROM AUTHOR]

To develop two-storied forest management of larch plantations in Northeast China, this study examined the height growth of Korean pine (Pinus koraiensis Sieb. et Zucc.) seedlings planted under strip-cut larch canopies. We measured the height growth of the underplanted seedlings 4 years after planting. The larch canopies were of varying stand age (12, 17, and 37 years) and strip-cut width (4.5, 6.0, and 7.5 m). We measured the seedling height growth in an open site (i.e., a site with no canopy). Underplanted seedlings had a smaller height growth (12.1–20.1 cm year−1) than the seedlings planted in the open site (23.7 cm year−1). The seedlings underplanted in the wider strip-cuts tended to have greater height growth than the seedlings underplanted in the narrowest strip-cuts. A generalized linear mixed model analysis predicted the greatest seedling height growth in the open site. A 36–47% reduction in annual height growth was predicted for the narrowest strip-cuts (4.5 m) versus the open site, while a 13–36% reduction in annual height growth was predicted for the wider strip-cuts (6.0–7.5 m) versus the open site. To maintain adequate height growth, forest managers are recommended to create wider strip-cuts (i.e., ≥6.0 m) for the purpose of underplanting Korean pine seedlings in larch plantations. [ABSTRACT FROM AUTHOR]

Highlights: [•] The growth of underplanted Korean pine depends on competition from neighbors. [•] The survival of Korean pine depends solely on tree size. [•] Neighbors located southwest of the target tree produce stronger competition. [•] Creating wider strip openings increases the growth of underplanted trees. [•] The position of underplanting within strip openings affects tree growth. [ABSTRACT FROM AUTHOR]

Damage to the Fukushima Nuclear Power Plant by the recent earthquake and tsunami that hit northern Japan should stimulate consideration of alternative sources of energy. In particular, if managed appropriately, the 25.1 million ha of Japanese forests could be an important source of wood biomass for bioenergy production. Here, we discuss policy incentives for substituting wood bioenergy for nuclear power, thereby creating a safer society while better managing the forest resources in Japan. [ABSTRACT FROM AUTHOR]

Damage to Japanese cedars caused by the sugi bark borer in plots with low, medium and high planting density (1,700, 3,200, and 7,300 trees/ha, respectively) was examined in a 20-year-old sugi plantation. Radial growth and annual ring-width at breast height of three trees sampled per plot were measured by stem analysis. Stand age when each pupal chamber formed on the sample trees by the borer was also investigated by sawing the trees. There was less damage in the high density plot than in the low density plot. Radial growth at breast height increased rapidly from the 7th year after planting in all plots. The width of the annual ring reached a maximum in the 9th or 10th year, and decreased gradually thereafter. Radial growth in the low density plot was larger than that in the high density plot. Pupal chambers were first observed in the 7th year. The number of pupal chambers increased yearly, reaching a maximum in the 12th or 13th year, and decreased rapidly thereafter. These results indicate that restriction of radial growth of trees in the juvenile period by high density planting can prevent infestation of the sugi bark borer. In this study, we measured the positioning accuracy of the Global Positioning System (GPS) while walking in forested areas and analyzed the GPS data to find factors that affected the positioning accuracy. In the field tests, we repeated GPS measurements with different types of GPS receivers, types of forests and modes of GPS positioning. The GPS data were analyzed using ANOVA. As a result, the type of GPS receivers, type of forests and modes of GPS positioning were found to be a significant factor (P < 0.001) to determine positioning accuracy while any interactions between these factors were not. The result also showed that the GPS receiver with multipath rejection technology produced higher positioning accuracy than without it. Therefore, multipath errors, which are caused by the reflection of GPS signals due to nearby stems, can be a critical cause to adversely affect GPS positioning accuracy. It was also suggested that GPS positioning accuracy while walking in forested areas was affected not by basal area but by stand density. That was because temporal signal blocking occurred more often with increasing stand density while walking forested areas. As a result of multiple regression analysis, the observed Position Dilution of Precision (PDOP) was not a significant factor (P = 0.590) to determine positioning accuracy. Deciduous oak (Quercus serrata) forest is a major vegetation type of temperate broad-leaved forests in the north Kanto Region, Japan. The objective of this study is to examine the past and present human-use of the forests and to foresee the future prospects. The shiitake mushroom (Lentinus edodes) producing districts in Saitama and Tochigi were selected as the study areas. Until the 1960s more than 70% of local broad-leaved forests were used as fuelwood in the areas studied. After the revolutionary change in the forms of energy used in the 1960s, oak forests turned to being used mainly for shiitake cultivation in many rural areas. Most oak logs for shiitake have been provided within the shiitake-producing area, but in recent years the number of logs brought from other areas is increasing in fresh shiitake cultivation. Because of the rapid expansion of shiitake imports, aging of the domestic cultivators and labor shortage, domestic shiitake cultivation has declined conspicuously for the last 15 years. In addition, many forest owners and cultivators have already stopped managing the forests as they used to. As a result, if the shiitake cultivation continues to shrink, it is estimated that around 90% of the local broad-leaved forests will be abandoned by the year of 2,015 even in shiitake-producing areas. This paper describes our comparative study on forest policies in Japan, the United States, and Sweden (EU) to assess the policies of Japan for preventing global warming. The forest policies in these three countries were compared in terms of the process of policy-making, overview of policy execution, forest management, forest conservation and protection, conserved and reserve forests, urban forests, biomass utilization, forest studies and indirect slash tools, and policies for attaining the goal of the first period. The forest policies of Japan are characterized by the use of non-physical methods of CO2 absorption, such as cultivating sound forests, managing reserve forests, promoting the use of biomass, and educating people. The United States has substantial policies for physical methods for actively absorbing CO2, such as planting trees. However, the US has not been able to acquire sufficient funds for the policies, and the target absorption has not been attained. Sweden has tended to use non-physical methods and has substantial policies for promoting the certification system, assigning conservation areas, and promoting the use of biomass energy. Hydrological control of streamwater NO3- concentrations was investigated in a weathered granitic headwater forest catchment. The catchment was divided into three parts: the stream channel area, the soil sedimentation area, and the hillslope area connected to the soil sedimentation area. The discharge rate of saturated throughflow within the hillslope and catchment and the groundwater levels in the soil sedimentation area were measured in tandem with the hydrochemical observations. At the points observed, the streamwater had the lowest NO3- concentrations. The concentrations were low during baseflow conditions and increased with the discharge rate. Considering the water budget in the hillslope, about half of the total rainfall infiltrated into the bedrock. This bedrock groundwater was the dominant component of the baseflow, with low NO3- concentrations, while groundwater in the soil sediment area with relatively high concentrations flowed into the stream during rainstorms. The dynamics of the streamwater NO3- concentrations were strongly affected by the hydrological processes in the forest catchment. Especially, the baseflow NO3- concentrations were kept low by the groundwater flow passing through the bedrock. The objective of this study is establishment of vegetative propagation of Japanese black pine (Pinus thunbergii). We examined the effect of defoliation, disbudding and shape of basal cut on the rooting ability of cuttings, and we tried to find an optimal method of propagation. Cuttings were made from terminal shoots of 1-year-old seedlings. As a result, 1) When 0–46% of the needles of cuttings were removed, those rooting percentages were steady between 54 and 62%. However, when needles were removed excessively, rooting ability decreased notably. Moreover, 46% needle removal cuttings had the longest root systems. 2) In the case of cuttings with a part or all their buds removed, the rooting percentage was greater than that of control cuttings. 3) On the examination of treatments of the cut end, rooting ability was better for diagonal shape than for horizontal shapes, but difference in the effect was insignificant. So the optimal method is to remove half of the needles or buds from cuttings and to cut end in a diagonal shape. However, as growth of cuttings from which buds had been removed was bad, a careful needs to be paid to disbudding for commercial production. Chlorophyll fluorescence methods have been used to evaluate the effects of environmental stresses on photosynthetic properties. Chlorophyll fluorescence can provide detailed information of photosystem II (PSII) photochemistry, which is vulnerable to environmental stresses such as strong light, low temperature, heat and drought. I reviewed photoinhibition of photosynthesis and discussed the mechanism to prevent photoinhibition in drought-acclimated leaves. As drought stress is often accompanied by strong light, a decline in photosynthesis caused by stomatal closure increases the risk of photoinhibition. Energy dissipation via electron flow would be an effective way to prevent photodamage as well as thermal energy dissipation in PSII antennae. When plants are illuminated by excess light, inhibition of photosynthesis occurs by harmful molecules generated by excess excitation energy. Photochemical efficiency is also decreased during the dissipation of excitation energy by protective mechanism. Inhibition of photosynthesis by low temperature results in a considerable excess of excitation energy leading to photodamage. Although evergreen woody plants are considered to be subjected to photoinhibition, they develop many photoprotective mechanisms against photoinhibition. In this review, I summarized the molecular aspects of photoinhibition and role of photoprotective mechanisms, and discus the ecophysiological meanings of photoprotections, especially xanthophyll cycle, water-water cycle, and photodynamic screen provided by the accumulation of pigments such as rhodoxanthin and anthocyanine observed in over-wintering woody plants. Acid fog is considered to have a large influence on tree physiology because it has a high concentration of air pollutants and is persistent in the atmosphere. Long-range transported pollutants contribute to acidification of fog in mountainous areas and therefore trees grown in these areas are thought to be affected by acid fog. The effects of acid fog using tree seedlings are well documented. From the results of these experimental studies, acid fog is known to induce visible injury, reduce the dry weight and photosynthesis systems, disintegrate the epicuticular wax, alter the nutrient status, and increase the sensitivity to other stresses, such as frost, wind and ozone. In addition, the extent of these effects is dependent on the pH and the components of acid fog and tree species. In this review, we summarize these reports and discuss further developments in research. Degraded lands abandoned after failures of agricultural development are widely distributed over tropical areas. – Environmental reforestation – in degraded lands is needed for the rehabilitation of regional environments. In this paper, I review properties of problem soils in tropical Asia and stress responses of tropical trees, and discuss the development of methods of environmental reforestation. Food shortage and environmental deterioration due to rapid growth of the global population are the most serious problems that face us human beings. Improvement of tolerance of plants to abiotic stresses such as drought, high salinity, low temperature, and heat is one of the promising approaches for the future of agriculture and environmental conservation. It is essential to know at first how plants respond to environmental stresses and which molecules are involved in stress tolerance. According to recent development in genomics in Arabidopsis, it has been shown that hundreds of genes are involved in stress response and/or stress tolerance. More recently, functional genomics in woody plants has been promoted mainly in the occident. A US group, in particular, is determining the nucleotide sequence of whole poplar genome, and this information will have been released by the end of the year 2003. We are convinced that the poplar will be more important as a model forest tree in the post-genome era. We here introduce the world-wide situation of genomics in the poplar and discuss a direction of study on stress physiology in woody plants. Genetic engineering has the potential to allow the selective improvement of individual traits in woody plants without the loss of any of the desired trait of the parental line. Using such techniques, we can overcome the difficulties associated with the breeding of long-lived perennials, which need to long time to produce progeny. In this paper, we introduce recent advances in the application of genetic engineering to forest trees to solve environmental problems. And, we also discuss the necessity of flowering control of transgenic woody plants. [ABSTRACT FROM AUTHOR]

• We incorporated regeneration on downed logs into LANDIS-II forest landscape model. • We revealed the long-term effects of post windthrow management on forest recovery. • Birch-dominated forests regenerated and persisted over 100 years at scarified sites. • Salvaging after a first windthrow delayed biomass recovery after a second one. • CWD-dependent species hardly recover after multiple windthrows in case of salvaging. Post-windthrow management delays forest biomass recovery by altering the situation of disturbance legacies and can change the species composition. Although the short-term effects of post-windthrow management have been well studied, we do not have enough knowledge about the long-term effects of post-windthrow management on species composition and biomass recovery. Those effects associated with an increase in the windthrow frequency are also unknown. Although forest landscape models can effectively evaluate these effects, conventional models do not represent the regeneration process on downed logs, which is essential for simulating forest succession. We focused on hemiboreal forests in northern Japan and aimed to (1) incorporate the regeneration process on downed logs into LANDIS-II, which is one of the most used forest landscape models; (2) evaluate the long-term effects of post-windthrow management on tree species composition and aboveground biomass recovery; and (3) evaluate the associated long-term effects of interactions between post-windthrow management and increased windthrow frequency. We incorporated the regeneration process on downed logs into LANDIS-II by regulating the probability of the establishment of species that depend on dead wood, such as spruce, according to the availability of well-decayed dead wood. The incorporation of this process resulted in simulations of trends in species composition and aboveground biomass recovery after post-windthrow management that were more accurate than those produced by the original model. In the modified LANDIS-II simulation, reductions in dead wood and advanced seedlings due to salvage logging had little effect on the tree species composition or aboveground biomass recovery; however, the complete destruction of advanced seedlings by scarification induced a delay in aboveground biomass recovery and a shift to birch-dominated forests that continued for 100 years. In addition, the reduction in dead wood due to salvage logging decreased the number of seedlings, especially of dead wood-dependent species, that established after windthrow. When the windthrow frequency doubled, this decrease in seedlings induced a delay in aboveground biomass recovery, and a substantial decrease in dead wood-dependent species biomass occurred after a subsequent windthrow event. However, after the second windthrow event and following scarification, the forest recovered in the same way as after the first windthrow because the destruction of advanced seedlings and understory plants, namely, dwarf bamboo (Sasa spp.), by scarification reset the site conditions. To conserve the species composition and aboveground biomass of hemiboreal forests under climate change, which is expected to increase windthrow frequency, salvage logging and scarification should be avoided. [ABSTRACT FROM AUTHOR]

High-value timber species play an important economic role in forest management. The individual tree information for such species is necessary for practical forest management and for conservation purposes. Digital aerial photogrammetry derived from an unmanned aerial vehicle (UAV-DAP) can provide fine spatial and spectral information, as well as information on the three-dimensional (3D) structure of a forest canopy. Light detection and ranging (LiDAR) data enable area-wide 3D tree mapping and provide accurate forest floor terrain information. In this study, we evaluated the potential use of UAV-DAP and LiDAR data for the estimation of individual tree location and diameter at breast height (DBH) values of large-size high-value timber species in northern Japanese mixed-wood forests. We performed multiresolution segmentation of UAV-DAP orthophotographs to derive individual tree crown. We used object-based image analysis and random forest algorithm to classify the forest canopy into five categories: three high-value timber species, other broadleaf species, and conifer species. The UAV-DAP technique produced overall accuracy values of 73% and 63% for classification of the forest canopy in two forest management sub-compartments. In addition, we estimated individual tree DBH Values of high-value timber species through field survey, LiDAR, and UAV-DAP data. The results indicated that UAV-DAP can predict individual tree DBH Values, with comparable accuracy to DBH prediction using field and LiDAR data. The results of this study are useful for forest managers when searching for high-value timber trees and estimating tree size in large mixed-wood forests and can be applied in single-tree management systems for high-value timber species. [ABSTRACT FROM AUTHOR]

• We revealed long-term effects of salvaging after windthrows on total carbon stocks. • The total carbon stock almost recovered 64 years after the windthrow and salvaging. • Broadleaves and CWD generated after the windthrow have offset CWD lost by salvaging. • Well-decayed CWD and the organic layer carbon stock were low in salvaged forests. To mitigate the negative effects of climate change, it is necessary to conserve carbon stocks in forests. Typhoons fell many standing trees and generate a substantial amount of coarse woody debris (CWD). In boreal forests, CWD contributes to maintaining carbon stocks for a long time after a disturbance because the decomposition rate of CWD is relatively low. We know that salvage logging after a disturbance tremendously decreases the forest carbon stock over the short term after logging but know little about its long-term effects. We targeted a catastrophic windthrow caused by a super typhoon in 1954 in boreal forests in northern Japan and estimated the long-term effects of salvage logging after the windthrow on the above- and belowground carbon stocks by comparing old-growth forests with low damage from the super typhoon in 1954 or any subsequent typhoons (OG), forests damaged by the typhoon with remaining CWD (i.e., windthrow, WT), and forests damaged by the typhoon followed by salvage logging (WT + SL). The CWD carbon stock of decay class 5 (i.e., the most decayed CWD) in WT was significantly larger than that in OG and WT + SL, suggesting that the CWD in decay class 5 in WT had been generated by the typhoon 64 years ago, and the negative effect of salvage logging on the carbon stock still remains apparent in the CWD carbon stock of decay class 5. The carbon stock of the organic (O) layer in WT was larger than that in WT + SL, probably because of three factors: (1) the slower decomposition rate of fallen leaves and twigs of conifers than broadleaves, as conifer litter is abundant in WT; (2) greater carbon transition from the CWD to the O layer in WT; and (3) the occurrence of a lower decomposition rate in the O layer in WT. However, the total carbon stock in WT + SL has almost recovered to the level of that in WT within the last 64 years. The carbon stocks of broadleaves that grew rapidly after the disturbance and the newly accumulated dead trees generated throughout the stand developmental process might contribute to the recovery of carbon stock in WT + SL. These results indicate that salvage logging affects the allocation of carbon in the forest even after 64 years after a catastrophic windthrow, although there was no large difference in total carbon stock. [ABSTRACT FROM AUTHOR]

Understanding the sustainability of high-value timber species in managed forests provides useful information for the management of these species in the long-run. Using nearly 50 years of census data in long-term permanent plots, we investigated the sustainability of three high-value timber species—monarch birch (Betula maximowicziana Regel), castor aralia (Kalopanax septemlobus (Thunb.) Koidz), and Japanese oak (Quercus crispula Blume)—in cool-temperate mixed forest under a selection system in northern Japan. We used stocking, demographic parameters, and species proportions of these species as measures of sustainability. Results showed that the tree density and basal area of the three high-value timber species increased during the study period. Moreover, the basal area increment of these species showed an increasing trend across census periods. However, while no significant differences in the tree mortality of these species were observed, the numbers of in-growth fluctuated across census periods. Increasing trends in species proportions of monarch birch and Japanese oak were observed. Even though there were some fluctuations across census periods, especially in smaller diameter classes, diameter distribution curves of high-value timber species followed a reversed J-shaped pattern. The results revealed that the sustainability measures of high-value timber species can be achieved in forest stands managed under single-tree selection system. In addition, the results also indicated the changing structure and composition of the forest stand. The stocking and basal area increment of conifers decreased while those of broadleaves increased. The proportion of conifers decreased to 33.01% in 2008–2016 from 48.35% in 1968–1978. The results of this study would be useful for adapting silvicultural practices and harvesting practices as well as for simulating various silvicultural and management options for high-value timber species. [ABSTRACT FROM AUTHOR]

High-value timber species such as monarch birch (Betula maximowicziana Regel), castor aralia (Kalopanax septemlobus (Thunb.) Koidz), and Japanese oak (Quercus crispula Blume) play important ecological and economic roles in forest management in the cool temperate mixed forests in northern Japan. The accurate measurement of their tree height is necessary for both practical management and scientific reasons such as estimation of biomass and site index. In this study, we investigated the similarity of individual tree heights derived from conventional field survey, digital aerial photographs derived from unmanned aerial vehicle (UAV-DAP) data and light detection and ranging (LiDAR) data. We aimed to assess the applicability of UAV-DAP in obtaining individual tree height information for large-sized high-value broadleaf species. The spatial position, tree height, and diameter at breast height (DBH) were measured in the field for 178 trees of high-value broadleaf species. In addition, we manually derived individual tree height information from UAV-DAP and LiDAR data with the aid of spatial position data and high resolution orthophotographs. Tree heights from three different sources were cross-compared statistically through paired sample t-test, correlation coefficient, and height-diameter model. We found that UAV-DAP derived tree heights were highly correlated with LiDAR tree height and field measured tree height. The performance of individual tree height measurement using traditional field survey is likely to be influenced by individual species. Overall mean height difference between LiDAR and UAV-DAP derived tree height indicates that UAV-DAP could underestimate individual tree height for target high-value timber species. The height-diameter models revealed that tree height derived from LiDAR and UAV-DAP could be better explained by DBH with lower prediction errors than field measured tree height. We confirmed the applicability of UAV-DAP data for obtaining the individual tree height of large-size high-value broadleaf species with comparable accuracy to LiDAR and field survey. The result of this study will be useful for the species-specific forest management of economically high-value timber species. [ABSTRACT FROM AUTHOR]

Scientifically robust yet economical and efficient methods are required to gather information about larger areas of uneven-aged forest resources, particularly at the landscape level, to reduce deforestation and forest degradation and to support the sustainable management of forest resources. In this study, we examined the potential of digital aerial photogrammetry (DAP) for assessing uneven-aged forest resources. Specifically, we tested the performance of biomass estimation by varying the conditions of several factors, e.g., image downscaling, vegetation metric extraction (point cloud- and canopy height model (CHM)-derived), modeling method ((simple linear regression (SLR), multiple linear regression (MLR), and random forest (RF)), and season (leaf-on and leaf-off). We built dense point clouds and CHMs using high-resolution aerial imagery collected in leaf-on and leaf-off conditions of an uneven-aged mixed conifer–broadleaf forest. DAP-derived vegetation metrics were then used to predict the dominant height and living biomass (total, conifer, and broadleaf) at the plot level. Our results demonstrated that image downscaling had a negative impact on the accuracy of the dominant height and biomass estimation in leaf-on conditions. In comparison to CHM-derived vegetation metrics, point cloud-derived metrics performed better in dominant height and biomass (total and conifer) estimations. Although the SLR (%RMSE = 21.1) and MLR (%RMSE = 18.1) modeling methods produced acceptable results for total biomass estimations, RF modeling significantly improved the plot-level total biomass estimation accuracy (%RMSE of 12.0 for leaf-on data). Overall, leaf-on DAP performed better in total biomass estimation compared to leaf-off DAP (%RMSE of 15.0 using RF modeling). Nevertheless, conifer biomass estimation accuracy improved when leaf-off data were used (from a %RMSE of 32.1 leaf-on to 23.8 leaf-off using RF modeling). Leaf-off DAP had a negative impact on the broadleaf biomass estimation (%RMSE > 35% for SLR, MLR, and RF modeling). Our results demonstrated that the performance of forest biomass estimation for uneven-aged forests varied with statistical representations as well as data sources. Thus, it would be appropriate to explore different statistical approaches (e.g., parametric and nonparametric) and data sources (e.g., different image resolutions, vegetation metrics, and leaf-on and leaf-off data) to inform the interpretation of remotely sensed data for biomass estimation for uneven-aged forest resources. [ABSTRACT FROM AUTHOR]