森林因自然干擾及人為干擾因素致使林木死亡(或受損)使林冠疏開,造成林間孔隙,且足以營造出不同於原森林生態系之生育環境,稱之為森林孔隙(Forest gap),簡稱為孔隙,孔隙會因更新的過程及時間的變化由其他樹木更替,此種森林演替(Forest succession)過程稱之為孔隙動態(Gap dynamics)。孔隙動態變化為天然林演替之自然現象,其對於天然林生態系之樹種組成,林分結構及更新扮演重要角色。本研究使用2007年及2009年兩期高解析度航空影像為材料,在南仁山自然保護區設立338.56 ha大面積樣區,以人工判釋樣區孔隙的分布,並分為強風坡型、背風坡型、向風緩坡型、溪谷型四類孔隙類型,以溪谷型孔隙面積率為最高,強風坡型最低,孔隙面積大小集中於40 m2以下,孔隙平均大小為47.55±1.43 m2,孔隙形成率為0.41% year-1、孔隙閉合率為0.36% yaer-1,冠層轉換率為241年,各項數據的趨勢與世界熱帶地區森林動態相符,結果顯示孔隙形成的位置及面積大小會受到地形不同而有所影響,受東北季風影響的強風坡及向風緩坡區,其孔隙平均面積及個數都較小,地形確實會影響孔隙的大小、個數、孔隙形成原因、孔隙的形成率及閉合率及冠層轉換率,南仁山地區影響孔隙的形成與鬱閉的因素,為東北季風、地形、颱風及人為干擾。
When one or a few canopy trees die (or are injured) in a forest mainly because of natural disturbance or human disturbance, small openings, which were called ‘gaps’, that formed in the forest canopy and then filled with other trees. This phenomenon was termed ‘gap dynamics’. The gap dynamics was a natural phenomenon of forest successions. It was an important role in the species composition, stand structure and regeneration of forest ecosystems. In our study, we used high quality aerial photographs at 2007 and 2009 in the Nanjenshan area. We used the artificial interpretation to map the forest gap distribution and divided into windward I, windward II, Leeward, and Creek. The creek of the percentage gap area is the highest and windward I the minimum and most gap size less than 40 m2. The result indicated average gap size of 47.55±1.43m2, gap formation rate of 0.41% year-1, turnover rate of 241.05 (year) in compared with tropical forest dynamics consistent with the world. The Windward I type and Windward II type of gap area and average number of gap both lesser, because the receiving the northeast monsoon. Result of terrain effected Nanjenshan area gap formation of the location and size. Results of the analysis suggested Nanjenshan area affected gap dynamic factors, apart from the death of canopy trees of self-reliant, the northeast monsoon, topography, typhoons and other natural external interference and jamming, but also as an important factor.