PhD

Forest Management

03years00months

A: Sustainable forest management of conifer plantations in Japan.
Keywords: strip selection, group selection, clearcutting, productivity, biodiversity
B: Sustainable forest management of tropical forests in Southeast Asia
Keywords: selective logging, rubber plantation, community forestry
C: Quality assurance and data utilization of forest monitoring
Keywords; National Forest Inventory, Forest health monitoring, Control survey, Image analysis,

Research Interests

• Multiple assessments of silviculture and management systems of conifer plantations
  keyword : selective logging, clear cutting, productivety, biodiversity
  2001.04.
• Sustainable Forest Management in Southeast Asia
  keyword : Selevtive logging, plantation forestry, communitry forestry
  1994.04.
• Quality assurance and effective utilization of forest monitoring data
  keyword : QA/QC, precesion, accuracy, data quality, measurement errors, image analysis
  2000.04.

Current and Past Project

• Transformation of silvicultural systems of conifer plantations in Japan; from clearcutting to strip/group selection systems
  In Japan, about 40% of the forested area (ca. 10 million hectares) is covered with plantation forests, mainly even-aged conifer stands, and forest management policy for these simple conifer plantations has shifted away from large-scale clearcutting towards uneven-aged methods (Nyland 1996). Recently, the group selection system has received considerable attention as an alternative for uneven-aged stand management, as a compromise between the environmental effects of clearcuts and the productivity penalties associated with single-tree selection (York et al. 2004). However, there are few examples of where the group selection system has been used in conifer plantations in Japan. Therefore there is a lack of basic information on the growth of planted trees in group selection openings as well as on an appropriate opening size. The objective of this study is to propose an optimal opening size of group selection system, composed of Cryptomeria japonica and Chamaecyparis obtusa, which are the most widely used species in plantations.
  One possible approach to get answers on an appropriate opening size is to compare the growth of trees planted under different size of openings; Indeed York et al. (2003) and Coates (2000) examined the growth of 3 and 5 year old tress regenerated in opening of size from 0.1 to 1.0ha and from 0.03 to 0.1 ha, respectively. However, there have been no such an experimental site in Japan, so we applied a simulation approach based on an empirical growth model.
  Data for developing the growth model were collected from 6-year- old and 18- and 19-year-old Cryptomeria japonica and/or Chamaecyparis obtusa planted group selection openings with size of 0.06 to 0.4 ha. We used the between-cohort competition index (BCI) for predicting tree size within openings, and BCI is calculated from information on tree position and tree height of residual trees.
  We found that simple regression equations were well used to predict tree size of planted trees from BCI. Then we simulated average tree height and diameter within openings under different opening size. It was found that there was largely decreasing in the average size of planted trees below a certain size of openings, with these trends being consistent with the experimental results by York et al. (2003) and Coates (2000). We conclude that at least 0.2 and 0.1 ha for Cryptomeria japonica and/or Chamaecyparis obtusa, respectively, could be need as opening size to avoid large reduction in growth of trees planted in group selection openings.
  
• Multiple functions of rubber plantations as forest and wood resources;
  The objective of this research is to evaluate new functions of rubber plantations as forest and wood resources, not only as cash crop and its by-product. We first clarified importance of rubberwood in wood markets in Malaysia, Thailand and Cambodia. And we evaluated wood production and carbon uptake functions, through developing biomass and stem volume equations and investigating wood quality. Finally, we examined interactions between wood and latex production, and climate factor, finding clear trade-off of wood and latex production in rainy season.
  
• Interdisciplinary and transnational networking for education and research on adaptive management in Asian tropical countries.
  
  Recently, “adaptive management” is becoming an important concept for any ecosystem management. Adaptive management is to ensure the circle of “Plan-Do-Check-Action” for continuous improvements of management methods. In tropical forestry, there have been so many “Plan-Do” activities of selective logging, community forestry and plantation forestry, but there have been little “Check-Action”, which are monitoring and assessment of multiple impacts of forestry, by which the management methods and policy are continuously improved.
  
  In this situation, our objective of this P&P is to make strategies and prototypes of adaptive management in Asian tropical forests, based on strengthening and stimulating interdisciplinary and transnational networking and discussion on multiple impacts of tropical forestry. To achieve this objective, there are two main approaches:
  (1) to carry out monitoring and assessments of multiple impacts of forestry in Asian countries and core research sites in Cambodia.
  (2) to hold “Asia Forest Workshop” for strengthening and stimulating interdisciplinary and transnational discussion on multiple impacts of forestry and for finding a solution to implement adaptive management of Asian tropical forest.
  
• Quality assurance and effective utilization of forest resource monitoring data
  National Forest Inventories (NFIs) have been carried out in many countries , and historically, NFIs were very much oriented toward describing state and change of forests with regard to timber production . Over recent decades, there is an increased demand for information on non-productive functions of forests due to the requests of policy makers and the public’s perception of forests . Quality Assurance (QA) is essential in long-term and large-scale environmental monitoring programs to ensure a documentation of quality of the field data and allow a data quality evaluation. However, there has been very limited information of current level of NFI data quality over the world.
  We evaluated data quality of Japanese National Forest Inventory, which had started in 1999 and had not carried out quality assurance program. Forty eight plots in four prefectures were remeasured by a control team, making careful and unhurried measurements. The paired data between field teams of each prefecture and the control team were evaluated, including two tree-level valuables (DBH and total height) and seven plot-level valuables (tree count, tree species richness, understory vegetation species richness and 4 of topographic condition). As compared to the control team, all field teams of each prefecture tended to significantly underestimate all of the continuous valuables. Most variables had larger variability as compared to the published literature, without achieving measurement quality objectives adopted in other monitoring programs. The findings of consistent bias and large variation of the field team measurements call for urgent implementation of quality assurance (QA) program (extensive field training and regular remeasurement) to improve data quality in Japan as well as countries without QA program. This study also suggested to promote international comparisons of data quality data to standardize the quality level at global scale.
  

Academic Activities