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Although the causes of and impacts against forest road failure differ according to the type of damage that occurs, the statistical understanding of the trends in the type of failure is insufficient. In this study, we collected data on 526 forest road failures due to heavy rainfall during 2006–2010 in the mountainous regions of Japan and statistically analyzed the characteristics. The forest roads covered in this study include those used primarily for timber extraction as well as those used for public purposes. Forest road segments were classified into four categories: streamside, stream crossings, zero-order basin, and others, and comparisons were made regarding the length of damage, the relative probability of occurrence, repair costs, and induced rainfall intensity in each category. Streamside segments accounted for only 15% of the total length of routes analyzed but 42% of all damaged segments. Furthermore, the relative risk of the streamside segments was about 6.0 times higher than that of the other categories of segments, indicating that they were the most likely to be damaged in this analysis. It is clear that the most important issue in the target area is to prevent damage to streamside segments. [ABSTRACT FROM AUTHOR]

• Acceleration of solving a forest stand selection problem using neural networks. • Iterative identification of optimal harvesting schedules has large computing cost. • Direct method reduces computing cost by relaxing the curse of dimensionality. • Indirect method tries further acceleration by root-finding using neural networks. • Direct method was viable in an application and expected to accerelate 8.7 times. A method of forest stand selection for subsidization requires iterative identification of optimal harvesting schedules for each stand. The time required for the iterative calculation and the existence of numerous stands in the focused regions prevent the application of the stand selection method in practice. In this study, we developed two methods to reduce the calculation cost of stand selection using neural networks. One method approximates the necessary indices for stand selection using neural networks, thereby reducing the calculation cost. The other method reduces the calculation cost during the iterative optimization processes and indirectly predicts the necessary indices. Acceptable predictions of the necessary indices were made by the first method even with imbalanced training data. Although neural networks with reasonable accuracy were generated using the second method, the predicted indices had unignorable errors owing to indirect predictions. The first method generated neural networks with reasonable accuracy using 20,000 tuning and validation data, which reduced the computation time from 61.09 h to 7.62 h when applied in Nagano Prefecture, Japan. [ABSTRACT FROM AUTHOR]

To utilize timber and forest biomass resources for bioenergy, technically feasible and economically viable timber and forest biomass resources should be estimated accurately considering their long-term availability. This study focuses on five prefectures, namely, Aomori, Iwate, Miyagi, Akita, and Yamagata, and considers trade between these prefectures. The annual availability of timber and forest biomass resources, such as small-diameter or defect stem logs, rather than logging residues in Japan was estimated as supply potential from profitable forests where expected revenues surpassed all costs, from planting to final harvest. As a result, the supply potential and annual availability of timber were estimated at 11,388,960 m3/year and 1,631,624 m3/year, whereas those of forest biomass resources were estimated at 2,277,792 m3/year and 326,325 m3/year, respectively. Therefore, the rate of annual availability to supply potential was 14.3%. Since timber production and wood chip usage from thinned woods and logging residues in 2018 were 4,667,000 m3/year and 889,600 m3/year, the rates of annual availability for timber and forest biomass resources to those values were 35.0% and 36.7%, respectively. Furthermore, the demand was estimated at 951,740 m3/year from 100,000 m3/year with a generation capacity of 5 MW. The rate of forest biomass resource availability to demand was 34.2%. A thinning subsidy was provided for operational site areas larger than 5 ha in Japan. The rates from subcompartments and aggregated forests with a thinning subsidy increased to 91.4% and 190.3%, respectively. Thus, the estimated availability from aggregated forests with a thinning subsidy met the demand sufficiently in this region. [ABSTRACT FROM AUTHOR]

• Timber and forest biomass resource availability estimated with inter-prefectural trade. • Appropriate harvesting system determined based on topography. • CTL has highest productivity and lowest cost; annual availability is highest under CTL. • Thinning and additional regeneration subsidies enhance availability. • Subsidy plays an important role in the supply of timber and forest biomass resources. This study estimates the supply potential and annual availability of timber and forest biomass resources under profitable forest management in Japan. It focuses on four prefectures, namely, Fukushima, Ibaraki, Tochigi, and Gunma, and considers the trade between these prefectures. Production forests were extracted as subcompartments where the expected revenues surpassed all costs, from planting to final harvest. To estimate harvesting costs, appropriate harvesting systems were determined according to each prefecture's topographical features. The log markets and woody biomass power generation plants were assumed to be the destinations for timber and forest biomass resources. Annual availability from the Cut-To-Length (CTL) system, consisting of the use of harvesters and forwarders, accounted for 58 % of the total availability, even though the supply potential from CTL was only 15 %; this is because CTL is the most productive and least expensive harvesting system. Then, the effects of subsidies on availability are examined. Availability under an additional regeneration subsidy meets almost the entire current demand in this region. Furthermore, availability with a thinning subsidy can meet the forecasted future demand in this region, while availability with both thinning and additional regeneration subsidies can meet future demand in all prefectures analyzed in the present study. Thus, subsidies play an important role in the profitability of forestry operations as well as the supply of timber and forest biomass resources in Japan. [ABSTRACT FROM AUTHOR]