Japanese Forest Research Articles

Different patterns of fine-root exudation rates along soil depth of Pinus densiflora, Chamaecyparis obtusa, and Cryptomeria japonica in coniferous forests

Tree fine-root exudation and organic carbon compounds in the soil affect physiological functions through degradation by microorganisms around the roots and the enhancement of allelopathic effects on invasion attempts by other plant species. However, the underlying mechanism of fine-root action in vertically heterogeneous resource-distribution patterns along the soil profile is little known. Here, we quantified root exudation and its morphological and chemical traits in the soil layers down to 100-cm depth for three conifer species, Pinus densiflora (ectomycorrhiza), Chamaecyparis obtusa, and Cryptomeria japonica (arbuscular mycorrhiza), in a cool temperate Japanese forest. By using glass filter-trap method, root exudation rates in all three species varied with soil depth in a species dependent pattern. Specifically, the root exudation rate of P. densiflora was significantly higher in the middle soil layer, and lower in the topsoil layer, whereas the exudation rates significantly decreased in C. japonica and did not vary in C. obtusa along soil depth. Exudation strongly correlated with variation in root traits in C. obtusa and C. japonica but not in P. densiflora. These findings suggest that differences in exudation patterns among tree species are likely compensated for by structural modifications in fine roots in response to soil depth. In addition, the traits with mycorrhizal types might be related to adequate root exudation and enhanced soil-nutrient acquisition. Distinct differences among species in exudation, associated with vertical root distribution, will increase our understanding of root survival strategies for nutrient acquisition and carbon sequestration in forest tree species.

Quantitative importance of subsoil nitrogen cycling processes in Andosols and Cambisols under temperate forests

Nitrogen availability often limits plant growth in forest ecosystems. Plants, including trees, utilize soil inorganic nitrogen transformed via nitrogen cycling processes, including mineralization and nitrification. While most plant fine roots are distributed in surface soil layers, plants take up nitrogen even from subsurface soil layers in addition to the surface soil layers, especially under high nutrient competition. However, there is still limited knowledge about nitrogen cycles within deeper soil layers. In this study, we investigated the vertical profiles (0–60 cm) of the net nitrogen mineralization and nitrification rates at four Japanese forest sites with two different soil types (Andosols and Cambisols). The partial least square path modeling (PLS-PM) was used to determine factors affecting nitrogen cycling processes. The net nitrogen mineralization and nitrification rates per unit soil weight were considerably higher in the surface soil layer than in the deeper soil layers in Andosols but not in Cambisols. PLS-PM analysis showed that microbial biomass and soil organic matter quantities were the important factors influencing the net nitrogen mineralization and nitrification rates, indicating that a similar mechanism, which drives the spatial variations of nitrogen cycling processes in the surface soil layer, predominantly regulates the vertical variations of the processes. Moreover, it was estimated that the net nitrogen mineralization rate could be comparable at all soil types and depths when the rate was expressed per unit soil volume. Therefore, subsoil layers could be a quantitatively important source of plant-available nitrogen in Andosols and Cambisols.

Accuracy assessment of GEDI terrain elevation, canopy height, and aboveground biomass density estimates in Japanese artificial forests

Global forests face severe challenges owing to climate change, making dynamic and accurate monitoring of forest conditions critically important. Forests in Japan, covering approximately 70% of the country's land area, play a vital role yet often overlooked in global forestry. Japanese forests are unique, with approximately 50% comprising artificial forests, predominantly coniferous forests. Despite the Japanese government's extensive use of airborne Light Detecting and Ranging (LiDAR) to assess forest conditions, these data need more availability and frequency. The Global Ecosystem Dynamics Investigation (GEDI), the first Spaceborne LiDAR data explicitly designed for vegetation monitoring, is expected to provide significant value for high-frequency and high-accuracy forest monitoring. To assess the accuracy of GEDI data in Japanese artificial coniferous forests, the reference data were gathered from 53,967,770 artificial coniferous trees via airborne LiDAR data in Aichi Prefecture, Japan. This data was then compared to the corresponding GEDI-derived terrain elevations, canopy heights (GEDI RH98), and aboveground biomass density (AGBD) estimates to assess the accuracy of GEDI data. This research also explored how different factors influence the accuracy of GEDI terrain elevation estimates, including the type of beam, time of acquisition (day or night), beam sensitivity, and terrain slope. Additionally, the effects of various forest structural parameters, such as the height-to-diameter ratio, crown length ratio, and the number of trees on the accuracy of the GEDI canopy height and AGBD, were investigated. The results showed that GEDI terrain elevation demonstrated high accuracy across various slope conditions, with rRMSE ranging from 2.28% to 3.25% and RMSE ranging from 11.68 m to 16.54 m. After geolocation adjustment, the comparison of canopy height estimates derived from GEDI to airborne LiDAR-derived canopy height also showed high accuracy, exhibiting a rRMSE of 22.04%. In contrast, the GEDI AGBD product showed moderate accuracy, with a rRMSE of 52.79%. The findings also indicated that the accuracy of GEDI RH98 was influenced by terrain slope and crown length ratio, whereas the accuracy of GEDI AGBD was mainly impacted by the number of trees and crown length ratio. This study provided the first baseline accuracy assessment of GEDI terrain elevation, RH98, and AGBD estimates in Japanese artificial forests. Furthermore, this study provided valuable insights into the accuracy of GEDI metrics by examining potential factors.

Effects of distance from the sea and bedrock on foliar mineral contents in Japanese forests: Implications for mineral acquisition by folivores

AbstractMinerals are among the important nutritional components that are indispensable for animals. In particular, the acquisition of sodium is important for plant‐feeding animals because sodium may be deficient for these animals as plants do not need sodium. This study compiled data on the mineral contents of leaves in 28 forests in Japan, with special emphasis on the effect of distance from the sea and bedrock type. The aim of this study was to provide basic data on mineral availability for forest‐dwelling folivores, which provide important baseline data for understanding the mineral acquisition strategy of plant‐feeding animals. Sodium and phosphorus contents of live leaves were lower than the levels required for folivores (captive non‐human primates and ungulates). The effect of the distance from the sea was evident only for magnesium and sodium. The sodium content of live leaves was high enough to satisfy folivores' requirements at only a few hundred meters from the sea. The live leaves in forests growing on sedimentary bedrocks contained more minerals than those on granite/rhyolite. Seasonality was also evident based on repeated sampling at three study sites. The mineral contents of dead leaves at the three study sites showed similar inter‐site and inter‐season variations to those of live leaves. Phosphorus and potassium contents in dead leaves were consistently lower and iron content was consistently higher than in live leaves.

Carbon stock projection for four major forest plantation species in Japan

Carbon sequestration via afforestation and forest growth is effective for mitigating global warming. Accurate and robust information on forest growth characteristics by tree species, region, and large-scale land-use change is vital and future prediction of forest carbon stocks based on this information is of great significance. These predictions allow exploring forestry practices that maximize carbon sequestration by forests, including wood production. Forest inventories based on field measurements are considered the most accurate method for estimating forest carbon stocks. Japan's national forest inventories (NFIs) provide stand volumes for all Japanese forests, and estimates from direct field observations (m-NFIs) are the most reliable. Therefore, using the m-NFI from 2009 to 2013, we selected four major forest plantation species in Japan: Cryptomeria japonica, Chamaecyparis obtusa, Pinus spp., and Larix kaempferi and presented their forest age–carbon density function. We then estimated changes in forest carbon stocks from the past to the present using the functions. Next, we investigated the differences in the carbon sequestration potential of forests, including wood production, between five forestry practice scenarios with varying harvesting and afforestation rates, until 2061. Our results indicate that, for all four forest types, the estimates of growth rates and past forest carbon stocks in this study were higher than those considered until now. The predicted carbon sequestration from 2011 to 2061, assuming that 100 % of harvested carbon is retained for a long time, twice the rate of harvesting compared to the current rate, and a 100 % afforestation rate in harvested area, was three to four times higher than that in a scenario with no harvesting or replanting. Our results suggest that planted Japanese forests can exhibit a high carbon sequestration potential under the premise of active management, harvesting, afforestation, and prolonging the residence time of stored carbon in wood products with technology development.

Forest monitoring data of 45 plots across the Japanese archipelago during 1980–2021

AbstractLong‐term monitoring of forest tree communities is a basis for elucidating forest structure and dynamics and for evaluating ecosystem functions such as primary production. Because global climate change is changing forest ecosystems from the local to the global scale, it is essential to document long‐term monitoring data of forests to examine the temporal and geographical trends of forest changes. We report monitoring data of 45 forest plots (average area 0.69 ha; range 0.0325–6.25 ha) at 27 sites in Japan. These plots are situated within 32.38° N to 43.36° N and at elevations ranging from 8 to 2453 m above sea level. The forest plots include both old‐growth and secondary forests, and cover various forest biomes, such as warm‐temperate evergreen forests, temperate deciduous broadleaved forests, and boreal or sub‐alpine coniferous forests. In each plot, all living trees and lianas larger than a certain minimum size (typically 15 cm stem girth at breast height) were repeatedly measured and survival and recruitment of stems were recorded over 5–40 years (average 17.3 years). The data are presented in the format used by the Monitoring Sites 1000 Project in Japan (Ishihara et al. 2011, Ecological Research, 26, 1007–1008) and in the sample‐based Darwin Core format. This dataset expands existing open monitoring data for Japanese forests and thereby facilitates further meta‐analysis of forest community structures and changes in relation to climate change and other drivers. The complete data set for this abstract is available in electronic format in MetaCat in JaLTER at http://db.cger.nies.go.jp/JaLTER/metacat/metacat/ERDP-2024-03.1/jalter-en.

Contrasting fungal functional groups influence nutrient cycling across four Japanese cool-temperate forest soils

Understanding soil dynamics and nutrient cycling is crucial for the sustainable management of Japanese forests covering 70 % of the national land area. These forests are dominated by tree species with contrasting traits, influencing soil dynamics differently. We investigated how changes in soil characteristics across different forest stands shift in composition and functioning of fungal communities. Four different forest stands dominated by two different mycorrhizal types were selected: Fagus crenata and Larix kaempferi, representing ectomycorrhizal (ECM) types, and Cryptomeria japonica and Robinia pseudoacacia, representing arbuscular mycorrhizal (AM) types. In total, 62 composite topsoil samples from two depths were analyzed for their physicochemical properties and fungal communities were profiled by DNA sequencing. Ectomycorrhizal fungi dominated soils of Fagus crenata and Larix kaempferi forests, while fungal saprotrophs were more abundant in Cryptomeria japonica and Robinia pseudoacacia forests. Forest stand type rather than soil depth determined the composition and structure of soil fungal communities. Soil pH was positively correlated with abundances of saprotrophic fungi (P < 0.05) and negatively with ECM fungi. Soil C:N ratio was positively correlated, and nitrate was negatively correlated with relative abundances of root-associated fungi, primarily ECM fungi. No links between C nor N stocks with fungal guilds were found across the dataset. Observed links between soil C:N ratio and relative abundances of root-associated fungi and saprotrophs stress the importance of these guilds for influencing nutrient cycling economy across contrasting forest types. The lack of correlation between fungal communities and soil C and N stocks suggests distinct mechanisms driving stocks in these soils.

Plant–mycorrhizal associations may explain the latitudinal gradient of plant community assembly

Biogeographical variation in community assembly processes forms the basis of the latitudinal gradient of biodiversity by driving β‐diversity. Classical studies on community assembly predict environmental filtering affecting β‐diversity more strongly at higher latitudes, where productivity is lower and abiotic stress is stronger. Contrary to this prediction, recent evidence indicates that plant community composition at higher latitudes exhibits more spatially clustered distributions independently of background environments, suggesting the importance of spatial processes, such as priority effects. In this study, we propose a hypothesis that resolves this paradox by considering plant–soil feedback and biogeographic variations in the dominant mycorrhizal type: we predict that the increasing prevalence of ectomycorrhizal (EcM) trees with latitude contributes to the spatially clustered distribution of plants, as EcM trees tend to exhibit positive plant–soil feedback. We analyzed a large‐scale standardized dataset of Japanese forests covering a latitudinal gradient of &gt;10° and found that 1) the proportion of EcM trees was higher at higher latitudes, and 2) EcM tree‐rich communities exhibited more spatially clustered distributions likely due to positive plant–soil feedback. Consequently, 3) tree species composition at higher latitudes was better explained by spatial variables suggesting the importance of priority effects. Consistent with the predictions of the plant–soil feedback theory, these patterns were more pronounced in understory than in canopy communities. Taken together, our results lend support to our hypothesis that biogeographic variation in tree community assembly patterns is defined by mycorrhizal types and plant–soil feedback, thereby resolving a paradox in the latitudinal gradient of plant community assembly. Our work highlights that plant mycorrhizal type underlies the determinants of β‐diversity which is a critical component of the latitudinal gradient of diversity.

Analysis of forest environment transfer tax and prefectural policies: typology of prefectural support to municipalities in the initial phase from 2019 to 2021 in Japan

ABSTRACT The Forest Environment Transfer Tax (FETT), a scheme similar to Payment for Ecosystem Services (PES), was introduced for Japanese forests at the national level in 2019 to address the challenges of climate change and promote management mainly in privately owned forests under the New Forest Management System (NFMS). Given insufficient human and financial resources, support by prefectures for municipalities is a key step forward, and we examined the policies of 47 prefectures. The study period is from 2019 to 2021. We conducted the following analysis: (1) categorization of prefectures by cluster analysis based on questionnaire surveys, and (2) quantitative analysis of the relationship between policy choices and characteristics of prefectures. Based on the analyses, we identified two typologies of prefectures based on policy selections and changes; (i) prefectures focused on specific policy items and (ii) those distributed the FETT budget relatively uniformly for each policy item, and further trends of changes based on temporal sequences in the early years of the scheme. The results suggest two further implications: geographical proximity among prefectures and the ratio of forestry production outputs among the overall outputs of agriculture, forestry, and fisheries may affect policy choices by prefectures, especially those of the former type of prefectures. The findings of this study can contribute to an understanding of the factors influencing policy choices in the context of PES-related schemes for forest management.

Nitrate leaching and its susceptibility in response to elevated nitrogen deposition in Japanese forests

ABSTRACT Understanding the variability in nitrogen (N) leaching from forested ecosystems and its susceptibility to elevated atmospheric N deposition is essential for assessing the impact of atmospheric N deposition on forested ecosystems. This study explored the site variability in nitrate (NO3 −) leaching from forested areas and its susceptibility to elevated atmospheric N deposition from five sites in broadleaved forests grown on Andosols and Cambisols from northern to southern Japan. Site variability of NO3 − leaching and its possible contributing factors, including soil parent material and net nitrification rate, were evaluated using a generalized linear model with Akaike’s Information Criterion used for model selection. Three-year experimental N fertilization (50 kg N ha−1 yr−1 as ammonium nitrate) experiments were conducted at each site to evaluate the susceptibility of NO3 − leaching to elevated atmospheric N deposition. Soil solution NO3 − concentration below the rooting zone (50 cm below the ground surface) was variable among the five sites and was the highest in Shibecha, one of the Andosols sites in northern Japan where soil net nitrification tended to be higher than elsewhere. In model selection for NO3 − leaching, the soil parent material was not selected but soil net nitrification was selected, indicating that soil net nitrification could explain the variability of NO3 − leaching. A significant increase in NO3 – leaching after the 3-year N fertilization experiment was observed at the site with the highest levels of NO3 – leaching (Shibecha), indicating that the susceptibility of NO3 – leaching is high in locations where N leaching was originally high.

Energy Expenditure Estimation for Forestry Workers Moving on Flat and Inclined Ground

Forestry workers endure highly physical workloads. Japanese forestry workers experience additional up-and-down movements due to geographical features. Fatigue is a common cause of injury. This pilot study aimed to determine an appropriate method for estimating energy expenditure while moving across inclined ground to simulate a Japanese forest. Six participants wore a portable indirect calorimeter (V˙O2), heart rate (HR) monitor (17 g), accelerometer (20 g; vector magnitude; VM), and a global navigation satellite system (GNSS) device. They walked shouldering 20 kg of weight on flat, 15°- and 30°-slopes. The time course of HR was similar to that of V˙O2, but that of VM and the vertical movement varied from that of V˙O2. GNSS cannot correctly detect vertical movements. The HR index (HRI), indicating the ratio of activity HR to resting HR, was significantly correlated with the metabolic equivalent of the task (MET) calculated from V˙O2 (r = 0.932, p &lt; 0.0001), which fit the previously proposed formula for METs (METs = HRI × 6 − 5). However, VM was not correlated with VM (r = 0.354, p = 0.150). We can use HRI to measure the workload of Japanese forestry workers with a small burden in the field.

Summary of the Symposium (“Current Status and Problems of Renewable Energy Promotion and Social Acceptance” The Symposium hosted by The Japanese Forest Economic Society and Japanese Association for Environmental Sociology)

Summary of the Symposium (“Current Status and Problems of Renewable Energy Promotion and Social Acceptance” The Symposium hosted by The Japanese Forest Economic Society and Japanese Association for Environmental Sociology)

2. Current Status and Issues of Biomass Energy Utilization in Japan (“Current Status and Problems of Renewable Energy Promotion and Social Acceptance” The Symposium hosted by The Japanese Forest Economic Society and Japanese Association for Environmental Sociology)

2. Current Status and Issues of Biomass Energy Utilization in Japan (“Current Status and Problems of Renewable Energy Promotion and Social Acceptance” The Symposium hosted by The Japanese Forest Economic Society and Japanese Association for Environmental Sociology)

Closing Address (“Current Status and Problems of Renewable Energy Promotion and Social Acceptance” The Symposium hosted by The Japanese Forest Economic Society and Japanese Association for Environmental Sociology)

Closing Address (“Current Status and Problems of Renewable Energy Promotion and Social Acceptance” The Symposium hosted by The Japanese Forest Economic Society and Japanese Association for Environmental Sociology)

Comment: Forest Sectorʼs Challenges Posed by Renewable Energy Development (“Current Status and Problems of Renewable Energy Promotion and Social Acceptance” The Symposium hosted by The Japanese Forest Economic Society and Japanese Association for Environmental Sociology)

Comment: Forest Sectorʼs Challenges Posed by Renewable Energy Development (“Current Status and Problems of Renewable Energy Promotion and Social Acceptance” The Symposium hosted by The Japanese Forest Economic Society and Japanese Association for Environmental Sociology)

Possibilities and Tasks of the Forest-related Service Industry (2022 Symposium of Eastern Japanese Forest Economic Research Society)

Possibilities and Tasks of the Forest-related Service Industry (2022 Symposium of Eastern Japanese Forest Economic Research Society)

1. Diffusion of Renewable Energy Usage and Its Social Acceptance (“Current Status and Problems of Renewable Energy Promotion and Social Acceptance” The Symposium hosted by The Japanese Forest Economic Society and Japanese Association for Environmental Sociology)

1. Diffusion of Renewable Energy Usage and Its Social Acceptance (“Current Status and Problems of Renewable Energy Promotion and Social Acceptance” The Symposium hosted by The Japanese Forest Economic Society and Japanese Association for Environmental Sociology)

Panel Discussion (“Current Status and Problems of Renewable Energy Promotion and Social Acceptance” The Symposium hosted by The Japanese Forest Economic Society and Japanese Association for Environmental Sociology)

Panel Discussion (“Current Status and Problems of Renewable Energy Promotion and Social Acceptance” The Symposium hosted by The Japanese Forest Economic Society and Japanese Association for Environmental Sociology)

3. Current Status and Problems of Photovoltaic Power Generation with Deforestation (“Current Status and Problems of Renewable Energy Promotion and Social Acceptance” The Symposium hosted by The Japanese Forest Economic Society and Japanese Association for Environmental Sociology)

3. Current Status and Problems of Photovoltaic Power Generation with Deforestation (“Current Status and Problems of Renewable Energy Promotion and Social Acceptance” The Symposium hosted by The Japanese Forest Economic Society and Japanese Association for Environmental Sociology)

The effects of forest therapy on public mental health and circular economy: A policy support model in Japan.

Forest therapy has gained popularity in Japan and even other nations/regions due to its health benefits. In addition, forest therapy has contributed to the development of circular economy and industrial upgrading. Japanese successful practice can serve as a model for other countries in the Asia-Pacific region. To this end, the aim of this study was to determine whether forest therapy can improve the whole well-being of the participants and has a positive effect on the development of circular economy in the region. Both empirical and inductive research methods were used; empirical approach was conducted to perform comparative analysis of regional data that was retrieved from the research project of Japanese Forestry Agency in 2015. Specifically, the efficacy of forest therapy on physical (blood glucose, blood pressure, body weight) and mental (sleep quality e.g.,) health outcomes among 815 participants was investigated. Regional data are from the statistics of Iiyama City from 1990 to 2005. After the concept of forest therapy became popular in the late 1990s, this element had a great positive impact on the economic benefits of Ishiyama City and other major forest scenic areas. We summarize and analyze a series of policies made by relevant departments of the Japanese government in the years from 2019 to 2021 to promote forest therapy and related circular industry development. Significant (pre-to-post participation) changes in physical measure was observed. Firstly, mean weight of those overweight participants decreased across three different time points (pre-test/enrollment = 79.7 kg, 3-month participation = 77.2, and 6-month participation = 76.8 kg), while overall mean weight of the participants decreased to 61, 60.5, and 60.4 kg, respectively. Secondly, Participant with normal weight showed a decrease on mean HbA1C (from 6.09 to 6.06) at Week 24, while overweight participants demonstrated a slight change 6.03-6.01 after 6 months the average HOMA-IR for overweight participants decreased from 3.5 to 2.5 at Week 24, while participants with normal weight demonstrated a decrease from 2.2 to 1.7 at Week 24. Forest Therapy has emerged in Japan since Mid-1990s and has attracted a large number of tourists all over the world due to its unique health benefits. Forest therapy in Japan has positive effects on whole well-being of Japanese residents and it has helped public mental health promotion and economic growth. Under the guidance and support of government policies, it can promote the development of circular economy and industrial transformation and set a model of Japanese forest therapy development for other countries in the Asia-Pacific region.