Grace James B, Keough Janet, Guntenspergen Glenn R
Department of Botany, Louisiana State University, 70803, Baton Rouge, LA, USA.
U.S. Fish and Wildlife Service, National Wetlands Research Center, 1010 Gause Blvd., 70458, Slidell, LA, USA.
Oecologia. 1992 Jun;90(3):429-434. doi: 10.1007/BF00317702.
The objective of this study was to examine the claim that traditional measures of competitive performance in substitutive experiments are biased towards larger plants. Results from a three-year diallele experiment of 6 marsh plant species were analyzed using both Relative Yields (a traditional analysis) and the Relative Efficiency Index (a recently proposed analysis presumed to be size-independent). In adddition, a mechanistic model of competition was used to explore the behavior of both methods of estimating competitive performance.Results from the three-year experiment showed that Relative Yields (RYs) were correlated with the initial sizes of plants for the first two years but not the third. By the third year, RYs were highly correlated with Relative Efficiency Index values (REIs) suggesting that the effects of initial size were eventually overcome. Model results showed that RYs are inherently biased in favor of larger plants during the early phases of competition while REIs are not. Further, model analysis confirmed that the size bias associated with RYs declines with increasing duration of the experiment. It is concluded that current generalizations about the relationship between plant size and competitive ability may be biased by the procedures used to analyze competition experiments.
替代实验中传统的竞争性能衡量指标偏向于较大的植株。使用相对产量（一种传统分析方法）和相对效率指数（一种最近提出的据推测与大小无关的分析方法）对6种沼泽植物进行的为期三年的双列杂交实验结果进行了分析。此外，还使用了一个竞争机制模型来探究这两种估计竞争性能方法的行为。为期三年的实验结果表明，前两年相对产量（RYs）与植株的初始大小相关，而第三年则不相关。到第三年时，相对产量与相对效率指数值（REIs）高度相关，这表明初始大小的影响最终被克服。模型结果表明，在竞争早期，相对产量本质上偏向于较大的植株，而相对效率指数则不然。此外，模型分析证实，与相对产量相关的大小偏差会随着实验持续时间的增加而减小。得出的结论是，目前关于植株大小与竞争能力之间关系的概括可能受到用于分析竞争实验的程序的影响。
