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Temporal variability in taxonomic completeness of streammacroinvertebrate assemblages

机译：大型无脊椎动物组合分类完整度的时间变化

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Natural temporal variation in biological assemblages is generally acknowledged, but rarely controlled for in existing bioassessment approaches. Many bioassessment methods ignore the variation of assemblage structure through time and, thus, lack a process to evaluate the effects of natural temporal variation on their outcomes. We used an 11-y data set from 24 near-pristine reference streams (validation sites) and a 5-y data set from 10 streams exposed to human disturbance (test sites) in northern Finland to examine: 1) the amount of interannual variation in macroinvertebrate communities in both types of streams measured as variation in taxonomic completeness (i.e., ratio of observed/expected taxa; 0/E ratio), and 2) how temporal variability affects bioassessment outcomes. Most of the variation in 0/E values was explained by stream type (validation or test). Interannual variation in 0/E was low at both validation and test sites, a result supporting the assumption of high constancy of biological assemblages through time. Temporal variation in 0/E at validation sites was related to climatic factors (regional precipitation) and to some local environmental variables, e.g., substratum heterogeneity. Communities in validation and test sites responded differentially to climatic variation. The low interannual variation in 0/E suggests that 1-y data from reference sites can be extrapolated across years relatively safely, but climatically extreme years may be problematic. Temporal variability in 0/E was low at both types of sites, but it was still high enough to result in variable ecological status assessments across years, mainly at test sites with lower 0/E ratios. Thus, at test sites, use of only 1-y data may cause erroneous management decisions, and accurate assessment of the biological quality of test sites might require repeated sampling over several years.
机译：人们普遍认识到生物集合体的自然时间变化，但是在现有的生物评估方法中很少受到控制。许多生物评估方法会忽略装配结构随时间的变化，因此缺乏评估自然时间变化对其结果影响的过程。我们使用了来自24个近原始参考流（验证点）的11年数据集和来自10条暴露于芬兰北部人为干扰的流（测试点）的5年数据集，以检查：1）年际变化量在两种类型的河流中，无脊椎动物群落中生物分类完整性的变化（即观测/预期分类单位的比率; 0 / E比率），以及2）时间变异性如何影响生物评估结果。 0 / E值的大部分变化是由流类型（验证或测试）解释的。在验证和测试位置，0 / E的年际变化都较低，这一结果支持了随着时间的推移生物集合具有高恒定性的假设。验证地点0 / E的时间变化与气候因素（区域降水）以及某些局部环境变量（例如，地下异质性）有关。验证和测试站点中的社区对气候变化的反应不同。 0 / E的低年际变化表明，可以相对安全地推断出参考站点的1-y数据跨年，但气候极端年份可能会出现问题。两种地点的0 / E的时间变异性都较低，但仍高到足以导致多年间生态状况评估的变化，主要是在0 / E比率较低的试验地点。因此，在测试地点，仅使用1-y数据可能会导致错误的管理决策，并且准确评估测试地点的生物学质量可能需要在数年内进行重复采样。

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