- 期刊
A New Method to Establish Scoring Criteria of the Index of Biotic Integrity
一種建立生物整合指標評分標準之新方法
摘要
生物整合指標（Index of Biotic Integrity, IBI）是綜合魚種歧異度、食性群與健康等12個魚類群聚特徵，以評估溪流環境之生物評估系統。本研究之目的在改進計算IBI給分標準之程序，並以改良之IBI使用於愛荷華州中北部流域，以測試其評估溪流環境品質之功能。我們在Boone River選擇21個採集點，於1988和1989年七月，以電魚法採集魚類樣本，作為建立IBI計分標準的基本資料。另於受到城市廢水和農業影響的Lizard Creek流域選擇8個採樣點，於1988和1989年六月、八月和十月以電魚法進行魚類採集，以探討IBI之環境評估功能。IBI的計分標準，由原來以目測法決定Maximum-Species-Richness Line（MSRL）再三分其下限區域之方法，改為如果群聚變數與流域面積間有統計上顯著的直線關係存在時，則MSRL由Y軸截距的95%上限和原有斜率決定，再三分其下區域，以建立高於平均值（5分）、類似於平均值（3分），與低於平均值（1分）的區域以為IBI的計分標準，若無直線迴歸關係存在，則先移除上下5%的採集點建立界限，再將剩餘區域均衡三分。根據我們的改良計分法，一組資料間將只會產生一條MSRL，這可解決目測法因研究人員目視差異而有同組資料產生多條MSRL之缺點，這個新的計分法也可能促進IBI評估溪流環境之能力，因為與環境因子之測量結果此對，利用改良方法計算的IBI（1）可分辨Lizard Creek中採集點間的環境品質差異，（2）對枯水期造成的溪流環境變化可迅速反應，（3）同時季節變動時，分辨空間環境差異的敏感度仍維持穩定，且優於Shannon-Weiner Diversity index。在本研究中，IBI分數之變化主要受到和魚種歧異度有關的群聚變數影響。
並列摘要
Karr's Index of Biotic Integrity (IBI) was applied in north central Iowa streams to examine the technique's utility for measuring environmental quality in agriculturally-influenced streams and to develop methodological improvement. During 1988 and 1989, fish were collected in the Boone River and Lizard Creek systems, and physical and chemical measurements of stream environmental conditions were taken. A modified two-step procedure was proposed for establishing the scoring standard of the 12 IBI metrics. First, a simple linear regression relationship of the metric variable on log drainage area was calculated (p = 0.1). If a significant correlation was found, a Maximum-Species-Richness Line (MSRL) was determined by calculating the 95% V-intercept as its intercept, and then plotted by the original regression slope. If a nonsignificant relationship was obtained, the upper and lower 5% data points were deleted to define the upper and lower boundaries of the remaining points with horizontal lines. Finally, the area below the calculated 95% MSRL and the area between the two horizontal lines were equally trisected into above average (5 point), average (3 point), and below average (1 point) categories. After the scoring criteria were established, the IBI value of each sampling site in Boone River and Lizard Creek systems was calculated.The new scoring procedure resolved the problem of the commonly adopted ”eye-fit” method through generating only a single MSRL for a given data set. In Lizard Creek, IBI results were generally consistent with evaluations of physical and chemical environmental quality. During the drought period, variations of IBI scores reflected the dynamics of environmental conditions in the sampling sites. Additionally, the IBI showed greater temporal consistency than another commonly used analytical tool, the Shannon-Weiner Diversity Index. Thus, the new scoring procedure seems to advance the effectiveness of IBI in assessing the environment quality of lotic waters. Numerical species metrics associated with species diversity were more important than proportional ones in contributing to the IBI. Drought conditions throughout the study period influenced some of the data and analytical results.