Data from: The scale of effect of landscape context varies with the species’ response variable measured

ABSTRACT FROM THE ASSOCIATED PAPER IN LANDSCAPE ECOLOGY: Context: To detect an effect of landscape context on a species’ response, the landscape variables need to be measured within the appropriate distance from the species’ response, i.e. at the scale of effect. However, it is not clear what factors determine the scale of effect. Objective: Our objective was to test the prediction that the scale of effect should be smallest when the species’ response is fecundity, larger for abundance, and larger still for occurrence. Methods: We compared the scale of effect of two landscape variables (road density, forest proportion) on the three responses (fecundity, abundance, occurrence) for the wood frog (Lithobates sylvaticus) in eastern Ontario, Canada. We used egg mass surveys of 34 ponds to estimate fecundity (mean eggs/mass), abundance (number of masses), and occurrence (presence/absence of egg masses). We then empirically estimated the scale of effect of each landscape variable on each response. Results: The scale of effect differed among responses, from 0.2 to 3.0 km radii; however, it did not vary in the predicted order. Furthermore, the order was not consistent between the two landscape variables. Conclusions: Our results show that the scale of effect of a landscape variable on a given species can differ for different response variables. However, they also suggest that these differences in the scale of effect are not predictable. Thus, the most reliable way to ensure a landscape context study is conducted at the correct spatial extent is to estimate the scale of effect empirically, rather than ‘guesstimating’ the extent a priori.刊载于《景观生态学》的相关论文摘要 研究背景：为探究景观背景对物种种群响应的影响，需在与该物种响应相匹配的距离范围内，即效应尺度（scale of effect），对景观变量进行测定。然而目前尚不明确哪些因素决定该效应尺度。 研究目的：验证如下假说：当物种种群响应为繁殖力（fecundity）时，效应尺度最小；响应为丰度（abundance）时尺度更大；响应为出现率（occurrence）时尺度最大。 研究方法：以加拿大安大略省东部的林蛙（Lithobates sylvaticus）为研究对象，选取道路密度（road density）与森林占比（forest proportion）两类景观变量，比较其对林蛙三项响应指标的效应尺度。通过对34处池塘的卵块调查，分别估算林蛙的繁殖力（每卵块平均卵数）、丰度（卵块总数）与出现率（卵块存在/缺失情况），随后通过实证方法估算每一类景观变量对各响应指标的效应尺度。 研究结果：不同响应指标对应的效应尺度存在差异，范围为0.2至3.0千米半径；但该差异并未遵循预设的变化顺序。此外，两类景观变量的效应尺度变化顺序也并不一致。 研究结论：本研究结果表明，针对某一物种的景观变量，其效应尺度会因响应指标的不同而存在差异。但同时也说明，效应尺度的这类差异无法通过预先推测得出。因此，若要确保景观背景研究采用正确的空间范围，最可靠的方法是通过实证方式估算效应尺度，而非先验地凭猜测确定研究范围。