塔塔加地區不同植群演替階段之鳥類群聚研究

Abstract

本研究調查台灣中部塔塔加地區植群演替序列各階段之鳥類群聚組成及群聚介量，同時記錄鳥類在不同演替階段對食物資源的利用方式，以進一步探討植群演替對鳥類群聚的影響。自2004年3月至7月間於箭竹草原、二葉松疏林、二葉松密林、鐵杉林及雲杉林等不同演替階段的植群類型中設置22個調查點，以定點計數法進行鳥類密度調查，後續進行的鳥類食物資源利用調查則藉以區分生態同功群。此外，並於每一調查點設置20×20 m樣區以調查各植群類型的棲地因子。 研究期間共記錄到49種鳥類，依其覓食位置、覓食方式及食性區分為10個生態同功群。不同演替階段植群類型間的鳥種組成、同功群結構及棲地因子測量值都有顯著的差異。密度、豐富度、歧異度及生物量等鳥類群聚介量大致隨著植群演替呈現遞增的趨勢，並在雲杉林中達到最高。各植群類型間的鳥類群聚相似性分析顯示，鳥類群聚相似性隨植群演替階段相隔愈大而遞減。 群聚的梯度分析以降趨對應分析進行，排序結果再與各棲地因子進行相關分析。結果顯示，在五個不同演替階段的植群類型中，鳥類群聚變異梯度一、二軸與多數的植群形相結構(physiognomy)及植群組成(floristics)因子有很大的相關性。大多數鳥種皆沿著排序軸第一軸呈水平分佈，對照各鳥種之生態同功群分類及調查點在變異梯度軸上的分佈位置，地棲性及活動於灌層的鳥種偏好演替早期的非森林型態植群，樹棲性的鳥種則在演替中後期的植群類型中有較高的族群密度。而由生態同功群之組成及所佔比例來看，植群結構與枝葉量在各層次分佈的差異會影響不同演替階段鳥類對食物資源的利用。

I investigated avian assemblages in five seral stages of vegetation succession which were conducted in Tataka area of the central Taiwan during March to July, 2004. The study included (1) the effects of vegetation succession on bird community structures and (2) the differences of food resources utilization among birds in different stages of succession. Twenty- two sampling plots were selected to represent the five different seral stages: Yushan Cane (Yushania niitakayamensis) steppe (YCS), Taiwan Red Pine (Pinus taiwanesis) savanna (TRPS), Taiwan Red Pine woodland (TRPW), Taiwan Hemlock (Tsuga chinensis) forest (THF) and Taiwan Spruce (Picea morrisonicola) forest (TSF). I examined breeding bird density by point count method and discriminated different guilds from foraging behaviors. Besides, twenty habitat factors were measured in a 20 × 20 m grid cell of each station in the study site. 49 species were recorded during the study period. All species were grouped into 10 guilds based on its diets, foraging tactics and foraging locations. The results showed that bird species compositions, guild structures and habitat factors revealed significant differences in different seral stages. Moreover, avian community parameters such as population density, richness, species diversity and biomass increased with the succession gradient and reached the highest value at TSF. In avian community similarity analysis, the Bray-Curtis index decreased with the increasing intervals of succession seral stages. Most of the physiognomic and floristic factors showed strong correlations with the variation of avian assemblages in vegetation succession. Ground and shrub-foraging species favored non-forest vegetation in the early succession stages. However, tree-foraging bird species showed the higher population density in the middle-late succession stages. According to the composition of guilds in seral stages, the differences in vegetation structures and distribution of foliage volumes among stratums might influence the utilization of food resources in birds.