Estimation of the Stand Carrying Capacity of Chinese Fir Plantations In Taiwan

臺灣杉木人工林林分承載量的估測

邱祈榮(Chyi-Rong Chiou) ； 楊勝驛(Sheng-I Yang)

《台灣林業科學》 34卷4期 (2019/12) Pp. 305-315

https://doi.org/10.7075/TJFS.201912_34(4).0006

摘要

Forest stand dynamics is the process of stand structural changes through time, which is a function of species, site quality, climate, stand age, and management treatments. Assessing competition behaviors is important to predict stand growth and yield and to prescribe appropriate silvicultural treatments. Chinese fir (Cunninghamia lanceolata Hook), an important commercial species in southern China, was imported to Taiwan in the early 20th century. Since stand productivity has considerably declined with successive short rotations, it was suggested that the length of rotations be extended. However, the potential growth and yield of older Chinese fir plantations have not been explicitly explored in the forestry literature. Therefore, in this study, we evaluated the stand dynamics of Chinese fir plantations established over 60 yrs . Data were collected from 30 Chinese fir stands in central Taiwan and from inventory records published in the past few decades, which provide a sound basis for analyzing long-term stand carrying capacity and competition behaviors. Results indicated that competition behaviors were similar between Taiwan and southern China, but tree mortality levels in Taiwan were lower than those in southern China for a given tree size. The difference may have been due to higher winter temperatures in Taiwan. At age 18 , the maximum stand basal area of 56.52 m^2 ha^(-1) estimated for Chinese fir is close to that for loblolly pine at the same age planted in the southeastern US. However, stand basal area among stands varied. In addition, we suggest that the impacts of unpredictable natural disturbances, such as typhoons, on stand dynamics and stand structure need to be assessed. Results of this study can provide insightful information about long-term stand dynamics for Chinese fir and useful guidance for forest resource managers in designing forest management practices.

關鍵字

old-growth stand ； competition ； self-thinning ； Cunninghamia lanceolata ； growth and yield

並列摘要

林分的動態改變受到物種組成、立地條件、氣候、林齡與撫育方法等不同因子的交錯影響。林木競爭的評估是預測林分生長收穫與制定育林措施的重要指標。杉木（Cunninghamia lanceolata Hook）作為中國南方重要的人工林經濟樹種，於二十世紀初葉引進臺灣栽植。現有的連續短輪伐期森林經營方式，造成林分產出量的大幅下降。有鑑於此，許多文獻建議將原有的杉木人工林輪伐期延長。然而，過去對於杉木長期生長與收穫的研究尚顯不足（大於三十年生的林分）。因此，本研究將探討杉木人工林長時間的林分動態改變。研究資料來自於中臺灣30座杉木人工林長期監測資料和過去研究文獻發表的杉木人工林資源調查資料，提供了研究杉木長期生長收穫與林分承載量的重要基礎。本研究結果顯示，杉木人工林在中國南方與臺灣的競爭表現相似，但是臺灣杉木的死亡率較中國南方低，此差異或許導因於臺灣冬季的氣溫較高。18年生的臺灣杉木林分，林分胸高斷面積承載量可達56.52 m^2 ha^(-1)和美國南方松相同林齡的林分承載量相近，但臺灣杉木林分間的差異仍大。此外，自然災害（如：風害）造成林分動態與結構的改變，為長輪伐期的杉木人工林經營須考量的影響因子。希望本研究的成果能提供長期杉木生長研究與人工林經營方法擬定的參考依據。

並列關鍵字

老齡林 ； 林木競爭 ； 自我疏伐 ； 杉木 ； 生長收穫