Application of aerial images and GIS techniques in forest resources estimation動態清查公私有林木、竹材資源之技術研發

Bamboo, a widely distributed plant species and has been utilized for a long history in Asia, is one of the most plentiful forest resources of Taiwan. The first report was published in 1956 to reveal the statics of six economical bamboo species with a total area of 113,900 ha. Taiwan Forestry Bureau has kept on updating the distribution of forest resource via several censuses during recent decades, it demonstrated that the exact area of bamboo forest in Taiwan ranges from 113,900-183,330 ha. However, few of studies focused on the distribution of single economical bamboo species so that led to a scarcity of information for bamboo forest resource management and utilization.
In this study, we established a workflow to integrate land cover maps from the 4th forest resources inventory and slopeland utilization inventory project. Based on the latest aerial images, we also implemented field work and set up forest plots to reidentify distributions and stocks of bamboo species in several administrative districts which were regarded as bamboo-dominant regions of Taiwan. Finally, a GIS database of land use and distribution of bamboo species was constructed which covered six districts including New Taipei, Taoyuan, Hsinchu, Miaoli, Nantou and Tainan. The result demonstrated that Hsinchu and Miaoli have the most abundant bamboo forest resources with an area up to 17,000 ha, which was dominantly consisted by Makino Bamboo (Phyllostachys makinoi). New Taipei and Taoyuan were also rich in bamboo resource with an area of 12,000 ha but dominant by two species (Phyllostachys makinoi and Bambusa oldhamii) in different localities. The cost of bamboo harvesting was influenced by several factors such as topography, harvest methods and traffic accessibility. We used a GIS tool called Cost-Distance analysis to incorporate these parameters to evaluate the relative cost of bamboo production among districts. It demonstrated that New Taipei, Taoyuan and Tainan could be ideal and accessible regions for large-scale management and bamboo timber production.
竹林是生長快速、利用歷史悠久且加工技術成熟的森林資源。臺灣第一次對全臺竹林資源的完整調查，始於1956年中國農村復興聯合委員會特刊發表之「台灣之森林資源」調查報告，記錄台灣全島竹林面積113,900 ha。後經歷年森林資源調查更新，概可瞭解全臺灣竹林面積約介於113,900至183,330 ha間。然而，除1956年「台灣之森林資源」報告以外，對於全臺各經濟竹種的面積與分布資料始終缺如，無法提供準確數據做為經營管理參據。
本研究針對國有林事業區外土地，包含山坡地及部分平地為範圍，建立整合林務局第四次全國森林資源調查及水土保持局山坡地利用調查及山坡地可利用限度查定成果圖資之流程，再經現地調查與航攝影像補充判釋，針對竹林資源充沛之縣市（新北市、桃園市、新竹縣、苗栗縣、南投縣、台南縣），建立全區木竹資源分布及土地利用現況圖。此外，特別針對竹林進行竹種組成判釋，瞭解竹林與竹種分布現況，並透過樣區調查，瞭解各縣市竹材資源之蓄積情形。研究結果顯示，以面積而言，竹苗地區竹林面積最廣，達17,000公頃；其次則為桃園及新北地區，面積達12,000公頃。主要地點為苗栗獅潭、泰安、大湖、新竹尖石、桃園復興及新北八里等行政區，組成竹種以桂竹為主，八里地區則以綠竹為大宗。然而，經調查竹林伐採現場之地形與交通參數，進一步於地理資訊系統進行套疊分析，顯示台南地區與桃園新北地區竹林分布環境之地勢緩平，交通可及性較高，從資源利用角度而言，其伐採利用成本較低。本所已完成前述研究成果之地理資訊系統資料庫建置，可提供各界後續使用。