Observer and relocation errors matter in resurveys of historical vegetation plots
Observer and relocation errors matter in resurveys of historical vegetation plots
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观察者和重新定位误差在历史植被地块的重新调查中很重要
DOI：
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发表时间：
2018
影响因子：
2.8
通讯作者：
L. Baeten
中科院分区：
文献类型：
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作者：
K. Verheyen;Martin Bažány;Ewa Chećko;Markéta Chudomelová;D. Closset‐Kopp;Patryk Czortek;G. Decocq;P. De Frenne;Luc De Keersmaeker;Cecilia Enríquez García;M. Fabšičová;J. Grytnes;Lucia Hederová;R. Hédl;T. Heinken;F. H. Schei;Soma Horváth;B. Jaroszewicz;E. Jermakowicz;Tereza Klinerová;J. Kolk;M. Kopecký;Iwona Kuras;J. Lenoir;M. Macek;F. Máliš;Tone C. Martinessen;T. Naaf;L. Papp;Ágnes Papp‐Szakály;P. Pech;P. Petřík;J. Prach;Kamila Reczyńska;Magne Sætersdal;F. Spicher;T. Standovár;Krzysztof Świerkosz;E. Szczęśniak;Z. Tóth;K. Ujházy;Mariana Ujházyová;P. Vangansbeke;Ondřej Vild;D. Wołkowycki;M. Wulf;L. Baeten
目标：对几十年前首次调查的非永久性、可重新定位的地块进行重新考察，为观察植被变化提供了一种直接的方法，并为全球变化研究形成了独特且日益使用的信息来源。尽管通过重新调查这些准永久性植被地块可以获得重要的见解，但它们的使用很容易出现观察者和重新定位错误。研究这两种误差类型的综合影响非常重要，因为它们在实践中会一起发挥作用，而且尚不清楚观测到的植被变化在多大程度上受到这些误差的影响。
方法：我们设计了一项模仿再调查研究中所有步骤的研究，并且允许仅确定观察者误差与联合观察者和重新定位误差的大小。选择生长在温带森林林下的维管束植物群落作为研究系统。为了探索不同背景下的共性，研究人员覆盖了欧洲的 10 个地区，共有 50 名观察员参与其中，他们在制作植被记录方面的经验故意有所不同。
结果：观察者+重定位误差数据集中样地之间的平均地理距离为24m。观察者误差和观察者+重定位数据集的物种丰富度平均相对差异分别为 15% 和 21%。对于观察者误差和观察者+重新定位误差数据集，准永久样地位置的五个记录之间的平均伪周转率平均分别为 0.21 和 0.35。对成分变化的更详细分析表明，在观察者数据集中，嵌套和周转成分同等重要，而在观察者+重定位数据集中，周转比嵌套重要得多。有趣的是，当观察时间变化时，观察者和观察者+重定位数据集之间的差异很大程度上消失了：在这些数据集中，物种丰富度和物种组成随时间的变化非常相似。
结论：我们的结果表明，在重新勘察准永久地块时，观察者和重新定位误差是不可忽略的。有必要对再调查研究的结果进行仔细解释，特别是当基于少量图评估变化时。最后，我们列出了应采取的措施，以最大程度地提高植被重新调查得出的推论的精度和强度。
Aim: Revisits of non-permanent, relocatable plots first surveyed several decades ago offer a direct way to observe vegetation change and form a unique and increasingly used source of information for global change research. Despite the important insights that can be obtained from resurveying these quasi-permanent vegetation plots, their use is prone to both observer and relocation errors. Studying the combined effects of both error types is important since they will play out together in practice and it is yet unknown to what extent observed vegetation changes are influenced by these errors.
Methods: We designed a study that mimicked all steps in a resurvey study and that allowed determination of the magnitude of observer errors only vs the joint observer and relocation errors. Communities of vascular plants growing in the understorey of temperate forests were selected as study system. Ten regions in Europe were covered to explore generality across contexts and 50 observers were involved, which deliberately differed in their experience in making vegetation records.
Results: The mean geographic distance between plots in the observer+relocation error data set was 24m. The mean relative difference in species richness in the observer error and the observer+relocation data set was 15% and 21%, respectively. The mean pseudo-turnover between the five records at a quasi-permanent plot location was on average 0.21 and 0.35 for the observer error and observer+relocation error data sets, respectively. More detailed analyses of the compositional variation showed that the nestedness and turnover components were of equal importance in the observer data set, whereas turnover was much more important than nestedness in the observer+relocation data set. Interestingly, the differences between the observer and the observer+relocation data sets largely disappeared when looking at temporal change: both the changes in species richness and species composition over time were very similar in these data sets.
Conclusions: Our results demonstrate that observer and relocation errors are non-negligible when resurveying quasi-permanent plots. A careful interpretation of the results of resurvey studies is warranted, especially when changes are assessed based on a low number of plots. We conclude by listing measures that should be taken to maximally increase the precision and the strength of the inferences drawn from vegetation resurveys.
影响因子：
2.8
作者：
C. Stevens;Tobias Ceulemans;J. Hodgson;S. Jarvis;J. P. Grime;S. Smart
通讯作者：
C. Stevens;Tobias Ceulemans;J. Hodgson;S. Jarvis;J. P. Grime;S. Smart