烏來地區次生林、柳杉林、桂竹林三種林分枯落物量之動態變化

Abstract

枯落物量是為瞭解森林冠層之營養回歸土壤的重重慢程之一，因此，本研究以臺灣北部烏來地區三種不同之林分----次生林、柳杉林、桂竹林為對象，調查其枯落物量之動態變化，自2002年2月至2003年1月一年之監測，獲悉年枯落物量次生林為7.13 t/ha/yr、桂竹林為3.67 t/ha/yr、柳杉林為5.23 t/ha/yr，顯示次枯落物量為次生林＞桂竹林＞柳杉林。三種林分之各組成成份枯落物量中，落葉所佔的比例最大，次生林的葉佔62.2%、柳杉林的葉佔76%，桂竹林的葉佔55.1%，幾乎構成三個林分枯落物之主體。另外，次生林中的次要的組成份是蟲屎，佔總枯落物量的15.8%；而在桂竹林中，枝條也佔據相當大的比例，為41.6%，將近一半的枯落物量；在柳杉林中，次要的組成份為繁殖部，佔總枯落量的9.6%。 三個林分在7月皆出現一致的高峰期，主要是因為颱風干擾所造成大量的枯落物。次生林及桂竹林則在3月樹木生長季節出現另一高峰期，因為此時大量的老葉被新葉所取代而掉落；柳杉林則因為於11月中旬進行疏伐作業而在當月出現另一高峰期。本研究顯示三種林分冠層養分回歸土壤的通量是受到林木物候及颱風干擾的影響，而人為擾動亦可能增加枯落物量。

In order to understand the organization of flux from the canopy to soil in 3 forests, this study monitored litterfall dynamics of secondary forest, Japanese cedar plantation, and bamboo plantation in the Wulai area of northern Taiwan from February 2002 to January 2003. Litterfall was collected once a month for 12months (from February, 2002 to January, 2003). Results showed that annual litterfall was 7.13 t/ha/yr, 5.23 t/ha/yr, and 3.67 t/ha/yr for secondary forest, Japanese cedar plantation, and bamboo plantation, respectively, showing these three stands, leaf, which made up 62.2%, 76%, and 55.1% of annual litterfall, was the dominant component of litterfall. In all three stands, there was a litterfall peak flux occurred in July, 2002, resulting from typhoon disturbance, causing massive amount litterfall. In addition, another litterfall peak of secondary forest and bamboo plantation occurred in the growing season in March, 2002, because a large number of old leaves were replaced by new leaves. Furthermore, in Japanese cedar plantation, its secondary peak of littterfall was caused by the thinning treatment in November, 2002. This study clearly showed that litterfall for 3 stands in Wulai area were affected by the phenology of dominant trees, as well as typhoon and human disturbance.