Toshiaki Owari

The University of Tokyo | Todai · Faculty and Graduate School of Agriculture and Life Sceince

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 inf...

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...

Uneven-aged mixed forests have been recognized as important contributors to biodiversity conservation, ecological stability, carbon sequestration, the provisioning of ecosystem services, and sustainable timber production. Recently, numerous studies have demonstrated the applicability of integrating remote sensing datasets with machine learning for...

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 (...

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 eff...

Canopy gaps and their associated processes play an important role in shaping forest structure and dynamics. Understanding the information about canopy gaps allows forest managers to assess the potential for regeneration and plan interventions to enhance regeneration success. Traditional field surveys for canopy gaps are time consuming and often ina...

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 com...

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 ma...

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 p...

The frequency and intensity of typhoons are expected to increase over time due to climate change. These changes may expose forests to more windthrow in the future, and increasing the resilience of hemiboreal forests through forest management after windthrow is important. Here, we quantified forest structure recovery using aerial photos and light de...

Future climate conditions will alter the frequency and intensity of typhoons. Thus, post-windthrow management, which can enhance tree recovery in wind-disturbed forests with dense understory species, is essential for sustainable forest management to adapt to climate change. This study explores management options that can recover the above-ground bi...

Context Forest landscape management practices that conserve species composition and maximize carbon sequestration despite changes in climate and disturbance regimes are required to achieve social and environmental targets. Although post-windthrow management, such as salvage logging, can reduce carbon dioxide (CO2) emissions within ecosystems by rem...

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 bi...

Quantifying individual tree growth of economically high-value timber species is important for the simulation and development of forest management options. Long-term permanent plot data provides crucial information of forest stand dynamics that can be used to predict individual tree growth. In this study, we developed individual tree basal area grow...

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 relat...

It is important to predict the growth of Sugi forest plantations in old age. When predictions about the growth of Sugi forest plantations are made and there is a lack of growth data from older trees, it is possible that the accuracy of these predictions becomes worse. For example, it is known that the growth of Sugi does not get slower at older age...

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...

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 neces...

This study aims to comprehend the association between visual stem indicators in natural forest management under the selection system by employing Bayesian network analysis. A tree-marking exercise was conducted at a research plot comprising 184 trees with natural forest management at the University of Tokyo Hokkaido forest, located in northern Japa...

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 dem...

Many reports on the effects of conventional salvage logging—the removal of fallen and damaged trees after a catastrophic windthrow—on subsequent forest restoration have focused on short-term results occurring over less than 20 years; however, this time scale is inadequate, especially for boreal forests, because of the time required for tree growth....

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 aeria...

This study aims at achieving the automatic extraction of attributes for influencing tree-marking decisions and decision rules, and constructing classification models for marked trees by employing machine-learning algorithms. A tree-marking exercise was conducted at a research plot comprising 184 trees with natural forest management at the Universit...

Remote sensing (RS) data are often used as a complementary data source to acquire accurate quantitative es-timations of merchantable volume (V) and carbon stock in living biomass (CST), which are critical for thesustainable use of forest resources. In this study, we investigated the utility of unmanned aerial vehicles (UAVs)and the structure from m...

Tree marking for harvesting is one of the crucial techniques for natural forest management under the selection system. In this study, we examined the visual stem indicators that affect tree-marking decisions, and the effects of tree markers experiences on stem assessment and decisions about tree marking. A tree-marking exercise was conducted with 1...

Determining forest structural complexity, i.e., a measure of the number of different attributes of a forest and the relative abundance of each attribute, is important for forest management and conservation. In this study, we examined the structural complexity of mixed conifer–broadleaf forests by integrating multiple forest structural attributes de...

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 pr...

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 paper presents the single-tree management system for high-value timber species as practised for 50 years at the University of Tokyo...

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, coul...

Global navigation satellite system (GNSS) is a worldwide system that enables pinpointing geographic locations anywhere by receiving satellite signals. In this study, field tests with two mapping-grade GNSS receivers (Trimble Pro series 6H) and a consumer-grade GNSS receiver (Garmin GPSMAP 62 SCJ), both of which were the latest models as of April 20...

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 (...

Recently, containerized seedlings attract attention due to their planting efficiency and rooting success compared to bare-rooted seedlings. However, the survival rate and growth of containerized seedlings in Hokkaido might show different tendency since naturally-distributed conifers grow slowly at the early stage in Hokkaido and the forest floor is...

Quantifying the growth and survival of underplanted Korean pine (Pinus koraiensis Sieb. et Zucc.) in existing plantations provides a critical step toward developing an uneven-aged management system in northeast China. We conducted neighborhood analysis to quantify the effect of individual-level competition on the growth and survival of underplanted...

We investigated the survival and growth of eleven tree species in 2008, after the elapse of more than 45 years from their planting at four different altitudinal zones in the University of Tokyo Hokkaido Forest. Japanese larch and Todo fir exhibited good performance at low- to mid-altitudes but they suffered from severe damage at high-altitudes. We...

The University of Tokyo Hokkaido Forest (UTHF) owns and manages approximately 20 thousand hectare of forestland in central Hokkaido, northern Japan, and has been implementing the management experiment called ‘Rinbun Segyo Ho’ (the stand-based silvicultural system) since 1958. This paper synthesized type and contents of forest dynamics and managemen...

Quantifying tree damage and mortality caused by single-tree selection harvesting is critical to under-standing postharvest forest dynamics and management. In this study, we quantified the effects of tree size and species and the distance from residual trees to felled trees and skid trails on damage to residual trees and mortality in mixed coniferou...

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 fore...

This case study analysis examines how overstory and topographic conditions impact regeneration of Abies sachalinensis (Abies) in a selection forest at the University of Tokyo Hokkaido Forest in Northern Japan. The analysis includes 1,382 inventory plots that were regularly surveyed between 1995 and 2004. The density of Abies juveniles and basal are...

Competition among individual trees is a fundamental structuring feature of uneven-aged mixed-species stands. We developed a Bayesian model for neighborhood competition in uneven-aged mixed-species stands, in which the interspecic variability in competitive impact is explicitly represented. We used data from 16 permanent plots in the University of T...

Long-term air temperature data have been collected at Shirasaka at the Ecohydrology Research Institute, Yamabe in the University of Tokyo Hokkaido Forest and Tochimoto in the University of Tokyo Chichibu Forest. During the long-term monitoring, various instruments and measurement protocols have been used at each site. To produce long-term data sets...

Spatially explicit classification is an essential planning technique in managing natural forests having structural heterogeneity on a landscape scale. Operationally, forest planners demarcate classification boundaries on-site, based on their empirical knowledge. This study examined factors affecting spatially explicit classification decisions by ex...

We calibrated a spatially-explicit individual-based forest dynamics model SORTIE-ND to conifer-broadleaved mixed stands in the University of Tokyo Hokkaido Forest, and evaluated its accuracy of reconstructing past stand structure development under a single-tree selection system. We also modified the model so that it would be applicable under variou...

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 ince...

The purpose of this study was to evaluate the sustainability in selection cutting stands at the UT Hokkaido Forest. Data from the long-term research plots with measurement records and management history was used. As a preliminary assessment, this study adopted four indicators of sustainability: tree density, growing stock, volume increment, and har...

Hurricanes cause abrupt carbon reduction in forests, but silviculture treatment can be an effective means of quickly regenerating and restoring hurricane-damaged sites. This study assessed how silviculture treatments affect carbon balance after hurricane damage in central Hokkaido, Japan. We examined carbon storage in trees and underground vegetati...

A single-tree selection system has been widely employed to manage natural forests in Hokkaido, Northern Japan. Tree marking is an essential component of this system; the procedure involves careful selection of trees for harvest according to forest management objectives. Practically speaking, forest managers make tree marking decisions based on thei...

Selection forest is a forest managed with the uneven-aged silvicultural system, in which trees are removed individually from a large area periodically. Selection system has been used to manage natural forests in Hokkaido, northern Japan. This study demonstrated the characteristics of natural selection forests in central Hokkaido. A case analysis wa...