人工林鳥類組成及多樣性的時間變化

本研究分別於造林後6～7、9～10、15～16年在花蓮縣大農大富平地造林區的相同樣區內進行4季鳥類群聚調查。本文依鳥類與森林的相依性將其區分為專一森林型、廣適森林型、森林訪客型及其他型等4類；前兩者合稱森林鳥類，後兩者合稱非森林鳥類。結果顯示所有鳥類中以專一森林型鳥類的物種數、隻次數及Shannon-Wiener多樣性指數隨造林年份有極為明顯的增加，即專一森林型鳥類之物種數等3項數值，在15～16年林齡的造林地皆顯著高於9～10年林齡的造林地，以及9～10年林齡造林地皆顯著高於6～7年林齡的造林地。專一森林型及廣適森林型鳥類的Shannon-Wiener多樣性指數，皆隨造林木生長上升，推測造林木成長對鳥類尤其是森林鳥類的多樣性產生明顯影響。除了鳥類多樣性逐漸增加之外，3個造林年份的鳥類群聚組成亦各不相同。群聚的代表性鳥種在6～7年林齡的造林地以非森林鳥類為主，例如經常在開墾地及農林邊際活動的棕背伯勞（Lanius schach）及環頸雉（Phasianus colchicus）；9～10年林齡造林地的鳥類群聚已轉變為以森林鳥類為主；與森林關聯性低的鳥種在15～16年林齡的造林地僅有大卷尾（Dicrurus macrocercus）1種對群聚組成有較大影響力，故物種置換成森林性物種的趨勢已很明確。但15～16年林齡的造林與鄰近次生林純然以森林鳥類為主的群聚結構仍有相當差異，推測造林地單一層次的樹冠以及經常性的林下除草作業，導致造林下層植被包括草本、灌木及原生樹種難以更新及成長，致使人工林不易朝次生林演替，可能是造成人工林與次生林鳥類群聚不同的主要原因之一。從維護生物多樣性的角度而言，促進人工林往次生林演替的林地經營方式，將能庇護更多鳥類多樣性。從本研究的監測結果來看，平地造林的鳥類多樣性呈現上升趨勢，鳥類群聚組成未來可能隨林分結構、物種組成的變化而持續變動；建議未來可從時間序列及空間分布來探討平地造林的鳥類變動。

關鍵字

鳥類群聚；生物多樣性；再植林；森林鳥類

並列摘要

In this study, 4 seasons of bird communities were surveyed in Danongdafu plantations, Hualien County when the plantations were 6~7, 9~10, and 15~16 yr old. Birds were classified according to their forest dependency as forest specialists, forest generalists, forest visitors, or other non-forest users. Birds in the former 2 and the latter 2 types were respectively categorized as forest and non-forest species. Results showed that averages of the number of species, the number of individuals, and the Shannon-Wiener diversity indices of the forest specialists significantly increased as the plantations grew older. In other words, averages of the number of species, the number of individuals, and Shannon-Wiener diversity indices of the forest specialists in 15~16-yr-old plantations were significantly higher than those of 9~10-yr-old plantations, and averages of the number of species, the number of individuals, and the Shannon-Wiener diversity indices of forest specialists in 9~10-yr-old plantations were significantly higher than those in 6~7-yr-old plantations. The Shannon- Wiener diversity indices of forest specialists and forest generalists increased with the growth of the tree biomass. It was speculated that the growth of tree biomass has a significant effect on the diversity of birds, especially forest birds. In addition to the increasing diversity of birds, the compositions of birds in the 3 time periods also differed. Based on contributions of representative bird species to the similarity of communities, the bird community in 6~7-yr-old plantations was dominated by non-forest birds, such as Lanius schach and Phasianus colchicus, which often appear on open land and in the ecotone between farmlands and forests. In 9~10-yr-old plantations, the major group of the bird community had transformed into forest birds. In 15~16-yr-old plantations, only 1 non-forest user, Dicrurus macrocercus, had a greater influence on the community composition, so the trend of forest species replacing non-forest species was clear. However, the bird community structure of 15~16-yr-old plantations still greatly differed from that of an adjacent secondary forest, the avian community of which was dominated by forest birds. It was speculated that canopy closure and frequent understory weeding might lead to less herbaceous, shrub, and native tree species. Thus, it might be difficult for the plantation to succeed toward a secondary forest. Hence, the plantation had a different bird community from the secondary forest. From the perspective of promoting biodiversity, the succession of a plantation toward a secondary forest should be able to harbor greater bird diversity. In summary, the variation in bird diversity in plantations showed an upward trend. The composition of bird communities may continue to change with changes in the forest structure and species composition. It is suggested that in the future, time series and spatial analysis be used to explore bird changes in plantations.

並列關鍵字

bird community ； biodiversity ； reforestation ； forest bird

國際替代計量

人工林鳥類組成及多樣性的時間變化

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