A tale of two studies: Detection and attribution of the impacts of invasive plants in observational surveys
A tale of two studies: Detection and attribution of the impacts of invasive plants in observational surveys
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两项研究的故事：观测调查中入侵植物影响的检测和归因
DOI：
10.1111/1365-2664.13075
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发表时间：
2018
影响因子：
5.7
通讯作者：
Peter B. Reich
中科院分区：
文献类型：
--
作者：
Kevin E. Mueller;Alexandra G. Lodge;Alexander M. Roth;Timothy J. S. Whitfeld;S. Hobbie;Peter B. Reich
1.短期实验无法表征长寿的入侵灌木如何影响变化缓慢的生态特性，包括本土多样性和土壤肥力。因此，观察性研究是必要的，但常常遇到方法论问题。
2.为了强调改进评估入侵植物影响的观察性研究的设计和解释的方法，我们比较了两项关于养分循环和蚯蚓沿着入侵灌木丰度的两个不同梯度的研究。通过考虑这两项研究不同的采样策略和统计分析，并在其他研究的背景下解释它们相互矛盾的结果，我们还旨在更好地描述焦点入侵者鼠李的影响。
3.在对明尼苏达州一个地点的一项新研究中，我们观察到沙棘丰度与土壤 pH 值、土壤养分库、落叶层养分通量、蚯蚓丰度和根生物量之间呈正相关。多元回归模型显示，在考虑了土壤质地和树种组成的变化后，这些关系仍然存在。在伊利诺伊州进行的另一项更广泛的研究中，其他作者报告说，沙棘丰度与 10 种土壤特性（包括蚯蚓丰度、pH 值和养分浓度）之间几乎没有相关性。然而，与许多其他研究一样，他们的回归模型仅评估与入侵者丰度相关的预测因子。对于我们在明尼苏达州的研究，生态系统属性模型的 R2 值范围为 0-0.79（调整后的 R2）；对于伊利诺伊州先前的研究，R2 值范围为 <0.05-0.16（未调整）。
4. 两项研究之间抽样误差和预测变量使用的差异可能解释了对比结果。
5.合成与应用。为了减少入侵植物观测研究结论的不确定性，未来的研究必须确保在采样策略和统计分析（例如协方差分析、多元回归）中充分考虑土壤和植被的异质性。应特别关注可能早于入侵者的生态系统特性（例如地球物理特征和树木群落组成）。在我们的研究中，沙棘对生态系统特性的影响不仅对于包含潜在混淆的预测因素是稳健的，而且与基于生态化学计量和元素流质量平衡的预期一致。
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1.Short-term experiments cannot characterize how long-lived, invasive shrubs influence ecological properties that can be slow to change, including native diversity and soil fertility. Observational studies are thus necessary, but often suffer from methodological issues.
2.To highlight ways of improving the design and interpretation of observational studies that assess the impacts of invasive plants, we compare two studies of nutrient cycling and earthworms along two separate gradients of invasive shrub abundance. By considering the divergent sampling strategies and statistical analyses of these two studies, and interpreting their contradictory results in the context of other studies, we also aim to better describe the impacts of the focal invader, Rhamnus cathartica.
3.In a new study of a single site in Minnesota, we observed positive correlations between buckthorn abundance and soil pH, soil nutrient pools, nutrient fluxes through leaf litterfall, earthworm abundance, and root biomass. Multiple regression models showed these relationships persisted after accounting for variability in soil texture and tree species composition. For a separate, more expansive study in Illinois, other authors reported little to no correlation between buckthorn abundance and 10 soil properties, including earthworm abundance, pH, and nutrient concentrations. However, like many other studies, their regression models only assessed predictors related to invader abundance. R2 values for models of ecosystem properties ranged from 0-0.79 (adjusted-R2) for our study in Minnesota and from <0.05-0.16 (unadjusted) for the prior study in Illinois.
4.Differences in sampling error and use of predictor variables between the two studies likely explain the contrasting results.
5.Synthesis and applications. To reduce the uncertainty of conclusions from observational studies of invasive plants, future studies must ensure that heterogeneity of soils and vegetation is adequately accounted for in the sampling strategy and statistical analyses (e.g., analysis of covariance, multiple regression). Particular attention should be given to ecosystem properties with variability that likely predates the invader (e.g., geophysical features and tree community composition). In our study, effects of buckthorn on ecosystem properties were not only robust to the inclusion of potentially confounding predictors, but also consistent with expectations based on ecological stoichiometry and mass balance of element flow.
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