木質資源動態予測モデルの構築ならびに資源活用可能性に関する評価

Abstract

Around the betwixt mountainous areas in Japan, regional decline due to depopulation and aging has become serious. So, the regional redesign and economical promotion are required to maintain the quality of life and area. The fact that the economic value of wood resources has declined and employment has been lost in the 1970s is closely related to depopulation and aging in the betwixt mountainous areas. Therefore, in this research, we evaluate the CO2 emission reduction and the economic revitalization effect of low carbonization countermeasures by means of regional redesign and reestablishment of forestry for rural areas. In the previous paper, we designed a model household to estimate energy consumption and demand for building materials with the aim of evaluating various CO2 emission reduction effects by low carbonization countermeasures. Subsequently, in this paper, the amount of wood resources that can be used continuously for the future is evaluated by constructing “the dynamic prediction model for the regional wood resources” based on forest GIS data. By the prediction model, not only the amount of wood resources that can be sustainably utilized for the future, we can also evaluate forestry production activities to respond to the demand of wood resources. From these results, we can analyze the relationship between the demand for wood resources and the amount of resources available in the case of rebuilding from traditional farmhouses to urban houses and changing heating sources from kerosene to firewood. This study was targeted at Inami Town, Wakayama Prefecture. In Inami Town, the total population is about 8,700 and the number of households is about 3,300, and this town is the underpopulated area prescribed in the Act on Special Measures for Promotion for Independence for Underpopulated Areas. The resulting findings are as follows. 1) In the target area, significant aging of wood resources has been proceeding, so the rapid maintenance is desired not only from the absorption of CO2 but also from the aspect of maintaining the value of materials. 2) The current amount of transport wood from the mountain was estimated about 12% of the annual growth. Due to the further aging of resources, the amount of growth sharply will decrease in the near future. 3) As a sustainable and maximally utilizable condition of wood resources, the appropriate rate of the harvesting was evaluated for this area by the prediction model. 4) The average (for 100 years) amount of wood resources available for building materials was estimated 6,249 m3 and for energy was 16,553 m3, the total was equivalent to about 20 times the amount of transport wood from the mountain in the current status. 5) The dynamic prediction model made it possible to evaluate the transportation amount from the logging of wood resources to the sawmill plant, the area of new afforestation after cutting and the labor volume required for those work. 6) While the total transported material volume increases by about 50% after 100 years due to poplar conversion, labor volumes required for transportation in the forest only increased by 8% on average in 100 years, this indicate that efficient wood resources production will be possible by poplar conversion. 7) When the maximum sustainable production conditions are assumed, demand for building materials in the town will be satisfied in 6 years, it will become possible to use outside Inami Town. Even if all heating is assumed for firewood as a heat source, it is possible to use around 10,000 m3 per year outside Inami Town.