碩士 / 國立臺灣大學 / 森林學研究所 / 84 / Selective logging and sylviculture practices in the timber improvement program modify forest structure. In order to understand the influence of such disturbance on bird community, and the relationship between forest structure and bird community, investigation was carried out in mid-elevation area in northern Taiwan. I compared the forest structure, bird community, and the microhabitat utilization of birds in the site 9 years after selective logging for Cypress plantation, with those in undisturbed forest. Breeding bird density was censused in 23 sample stations by variable circular method. In microhabitat investigation, each bird was recorded with respect to the plant lifeform, forest stratum, and perch position in the tree crown where it is observed in active state. Vegetation and habitat structure were censused with 20 5m×5m quadrates in each sample station. Birds were divided into 8 guilds by their diet, foraging maneuver, and activity strata according to the information of previous studies and data from my microhabitat investigation.
A total of 110 tree species was recorded during the study period. The treatment of timber improvement significantly reduced tree density of small to medium size and the coverage of shrub to subcanopy layer. The coverage and height of groundlayer , and the vertical heterogeneity increased. Tree species diversity, total coverage, foliage height diversity, and the horizontal heterogeneity of understory were also reduced .
35 breeding bird species were recorded in undisturbed forest, 27 of them were abundant enough for estimating density. Such species richness was slightly higher than those recorded in treated forest, where 32 species were found, and 25 of them with estimated density. However, the difference of species composition was small. The total bird density in undisturbed site was higher than in treated site, but the dominance was more concentrated in the former, thus rendering the species diversity index lower than the latter. The number of species which became more abundant in the undisturbed site was equal to that increased in treated one, but the treatment effect differed among guilds significantly. Ground gleaning omnivores, upperstory gleaning insectivores, and upperstory hovering insectivores suffer more impacts from timber improvement treatment. On the other hand, understory gleaning insectivores, upperstory trunk probing insectivores, and upperstory gleaning omnivores were more abundant in treated site. The diverse response among guild were attributed to the difference of the food resource and foraging microhabitat.
In treated site, microhabitat utilization of birds was significantly concentrated on dominant tree canopy and groundlayer. The utilizing range in vertical strata were reduced.
The perch position of upperstory birds tended to shift towards the outside of crowns. The trend of microhabitat breadth followed that of density of each guild, but the average microhabitat overlap among species showed reverse pattern. The microhabitat breadth wasn''t related to the density difference between the two site, neither was the microhabitat shift.
Detrended correspondence analyze was used to analysis bird species assemblages.
The most important factor corresponding to the bird community variation was the habitat structure difference resulted from timber improvement treating. The second was altitude. Bird community variation among sample stations was highly correlated with vegetation variation and habitat structure variation. Most of the species distributed towards higher altitude were more abundant in undisturbed site. The diversity index along altitudinal gradient was higher there. Tree species diversity index, foliage height diversity, total coverage, horizontal heterogeneity index were related to the major variation gradient of bird community, but all of them had low correlation with bird species diversity, number of species, and total density.
| Identifer | oai:union.ndltd.org:TW/084NTU03360002 |
| Date | January 1996 |
| Creators | Fang, Yun-Ju, 方韻如 |
| Contributors | Su, Horng-Jye, Lucia Liu, 蘇鴻傑, 劉小如 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 70 |
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