殘留木與周遭地景對復育造林地食果鳥類的影響

Abstract

人類大幅開發加速了全球森林的流失與劣化，因此常需要進行森林復育加速其重建。然而人為種植小苗的復育成效有其限制，故森林復育應與天然更新相輔相成，方可達到較佳功效。食果鳥為森林生態系中重要的種子傳播者，若有大量且多樣的食果鳥進入復育地，應可促進天然更新，促進森林復育。本實驗於南投台大實驗林進行，對30個復育地樣區進行鳥類調查，分析食果鳥類與復育地內殘留木形質及周遭地景結構的關係。結果顯示復育地內的食果鳥種豐富度與樹種豐富度成顯著正相關(p<0.01)，食果鳥造訪頻率則與樹種多樣性及枝葉量成顯著正相關(p<0.01)，而與周遭地景內的人工針葉林比例成顯著負相關(p=0.03)。食果鳥與復育地殘留木的關係在不同地景結構內會有差異。在以人工針葉林為主的地景中，食果鳥種豐富度不受復育地內植群形質影響，這樣的差異應該來自於鳥類對不同地景結構的反應。不同食果鳥類對環境因子的反應亦有分別，白耳畫眉及紅嘴黑鵯最為普及，容易出現於各樣復育地。食果鳥進入復育地的比例會隨季節及鳥種而不同，灌叢鳥較不易進入，樹棲鳥除了五色鳥外大多容易進入，而且在非繁殖季時進入的比例會大幅提高。研究結果表示多樣及多量的殘留木可以吸引食果鳥類進入復育地，但是在周遭環境以人工針葉林為主的復育地裡，這樣的效果會較不顯著，食果鳥種較為單調，可能影響復育地種子雨的種類多樣性，因此需要投入更多的人為復育，補充天然更新之不足。白耳畫眉及紅嘴黑鵯為復育地重要的種子傳播者，且許多食果鳥類會在非繁殖季時會大量進入復育地，可能帶來豐富的種子雨。

Human exploitation is the major threat to forests worldwide, which resulted in severe forest loss and degradation and compelling need of forest restoration. Due to the limitation of planting seedlings, effective forest restoration strategy should combine both human planting and accelerating natural recovery. The visitation of avian frugivores to a site is thought to be positively correlated with seed rain. Therefore, more visits of avian frugivore to restored site should increase input of seed rain, which promotes forest restoration. In this study, I monitored avian frugivore visitation in 30 forest restored sites within Experimental Forest of National Taiwan University in Nantou. As my results, avian frugivore species richness was positively related with tree species diversity. Avian frugivore visitation rate was positively related with tree species diversity and foliage volume of remnant trees, and negatively related with conifer plantation coverage in surrounding landscape. However, the effect of remnant trees differed as landscape structure changed. In area dominated by conifer plantations, the effect of remnant tree was limited, and few frugivore species appeared in the restored sites. Some Frugivore species showed different habitat associations in restored sites. Black Bulbul (Hypsipetes leucocephalus) and White-eared Sibia (Heterophasia auricularis) were relatively general in different restored sites. Entering ratio of avian frugivore differed among species and seasons. Shrub-dwelling frugivore species rarely entered restored sites. However, tree frugivore species entered restored sites more often except Taiwan barbet (Megalaima nuchali), and their entering ratios increased dramatically during the non-breeding season. My results suggest more diverse and dense structure of remnant tree is more effective on attracting avian frugivores to restored sites. However, for restored sites within conifer plantations, remnant trees would become less effective and more human efforts are needed to promote forest recovery. Black bulbul and White-eared Sibia are important seed dispersers in restored sites, and some frugivore specie would enter more frequently during non-breeding season, which may result in higher abundance of seed rain.