烏來地區次生闊葉林、桂竹人工林、柳杉人工林之枯落物動態

Litterfall Dynamics of a Secondary Hardwood Forest, Plantations of Japanese Fir and Makino Bamboo in Wulai Area

蕭怡茹(Yi-Ju Hsiao) ； 王立志(Lih-Jih Wang)

《國立臺灣大學生物資源暨農學院實驗林研究報告》 19卷3期 (2005/09) Pp. 217-230

https://doi.org/10.6542/EFNTU.200509_19(3).0004

摘要

有機物凋落為森林冠層養分回歸土壤以使養分不斷循環的重要生態過程。本研究自2002年2月至2003年l月一年期間，於臺灣北部烏來地區次生闊葉林、桂竹人工林及柳杉人工林內架設枯落物收集網，每月收集一次，區分組成並秤其乾種，以了解三種林分枯落物量之動態。結果顯示：次生闊葉林年枯落物量為7126.7kd/ha/yr，組成包括：落葉62.2%、枝條9.6%、繁殖部11.0%、蟲屎15.8%及其他1.4%。桂竹人工林年枯落物量為5229.9kg/ha/yr，組成包括：落葉55.1%、枝條41.6%、無繁殖部份、蟲屎1.9%及其他1.5%。而柳杉人工林年枯落物量為3665.4 kg/ha/yr，組成包括：落葉76.0%、枝條9.1%、繁殖部9.6%、蟲屎4.7%及其他0.6%。此結果顯示烏來地區三種林分枯落物量以次生闊葉林較高，桂竹人工林略低，而柳杉人工林則最低。三種林分枯落物組成皆以落葉為主。此外，次生闊葉林枯落物組成中蟲屎比例較高於桂竹林及柳杉林，極為特殊。進一步對照三林分枯落物月變化及各組成月變化趨勢顯示：三種林分皆於7月出現明顯高峰，主要為颱風干擾所致，致使三林分各組成量明顯增加，尤以桂竹人工林之枝條及柳杉人工林之落葉量增加最為顯著。而次生闊葉林及桂竹人工林則在3、4月春季出現另一高峰，主要為原生樹種春季抽芽換葉所致。至於次生闊葉林於2002年初夏6月時蟲屎部份突增（近668kg/ha/mp），而落葉量顯著減少，可能為昆蟲大發生幹擾所致。除此之外，柳杉人工林則因2002年11月因未預期之疏伐經營作業影響，致使月枯落物量突增。透過此三種林分枯落物監測顯示，烏來地區森林冠層經此有機物凋落回歸土壤養分的過程主要受森林組成、植物物候，颱風幹擾、昆蟲干擾影響及經營活動影響。

關鍵字

枯落物 ； 次生闊葉林 ； 桂竹人工林 ； 柳杉人工林 ； 干擾

並列摘要

From February 2002 to January 2003, litterfall dynamics of a secondary forest, plantations of Japanese fir (Cryptomeria japonica), and Makino bamboo (Phllostachys makinoi) were monitored in the Wulai area, NE Taiwan. Results showed that annual litterfall in the secondary forest was 7126.7 kg/ha/yr (including leaf, 62.2%; branch, 9.6%; reproductive parts, 11.0%; insect feces, 15.8% and miscellaneous, 1.4%). Annual litterfall was 5229.9 kg/ha/yr in the Makino bamboo plantation (including leaf, 55.1%; branch, 41.6%; reproductive parts, 0.0%; insect feces, 1.9% and miscellaneous, 1.5%). While the annual litterfall was 3665.4 kg/ha/yr in the Japanese fir plantations (including leaf, 76.0%; branch, 9.1%; reproductive parts, 9.6%; insect feces, 4.7% and miscellaneous, 0.6%). Results clearly showed that litterfall production were in the order: the secondary hardwood forest＞ Makino bamboo plantation＞ Japanese fir plantation, and leaf-fall made up the major component of litterfall in these 3 stands. As to the monthly variation, all 3 stands showed peaked litterfall resulting from typhoon disturbances in July 2002. On the other hands, higher amount of litterfall occurred from March to May both in the secondary forest and the Makinoii bamboo plantation, possible due to the shedding of senescent leaves after new leaf budding, while in contrast, no similar pattern was observed in the Japanese fir plantation. Nevertheless, unusual amount of insect feces (~668 kg/ha/mo) was collected, and dense population of foliar caterpillars was also observed in June, 2002 only in the secondary hardwood forest, possible indicating other disturbance from insect outbreak to this hardwood forest. Furthermore, the un-natural increase in litterfall of November, 2002 in the Japanese fir plantation was caused by the unexpected management activities from local forestry Bureau. This study clearly showed that litterfall dynamics could be influenced by the phenology of canopy trees, typhoon disturbances, insect outbreak and human activities in these subtropical forests.

並列關鍵字

litterfall ； secondary hardwood forest ； Makino bamboo plantation ； Japanese fir plantation ； disturbances