Experimental, latitudinal, and historical approaches have been used to explore and/or predict the effects of global change on biota, and each approach has its own advantages and disadvantages. The weaknesses of these individual approaches can, potentially, be avoided by applying them simultaneously, but this is rarely done in global change research. Here, we explored the temporal and spatial variations in the leaf size and fluctuating asymmetry (FA) of mountain birch (Betula pubescens var. pumila) in the Murmansk region of Russia, with the aim of verifying the predictions derived from the responses of these traits to experimental manipulations of abiotic drivers of global change. The examination of herbarium specimens revealed that leaf length increased during the 20th century, whereas the FA in the number of leaf teeth decreased, presumably reflecting an increase in the carbon and nitrogen availability to plants in that century. Along a northward latitudinal gradient, leaf length decreased whereas FA increased, presumably due to the poleward decreases in air temperature. The study site, collection year, and latitude explained a larger part of the leaf length variation in mountain birch relative to the variation in FA. Leaf length is likely a better indicator than FA in studies addressing global environmental change impacts on plant performance.

中文翻译：

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山桦（Betula pubescens var. pumila）叶片大小的变化和时空波动的不对称性：对全球变化研究的影响

实验、纬度和历史方法已被用于探索和/或预测全球变化对生物群的影响，每种方法都有其自身的优点和缺点。这些单独方法的弱点可以通过同时应用它们来潜在地避免，但这在全球变化研究中很少这样做。在这里，我们探索了俄罗斯摩尔曼斯克地区山桦（Betula pubescens var. pumila）叶片大小和波动不对称性（FA）的时空变化，目的是验证从这些性状的反应中得出的预测对全球变化的非生物驱动因素进行实验操作。植物标本的检查显示，20 世纪叶长度增加，而叶齿数量的 FA 减少，大概反映了该世纪植物的碳和氮可用性增加。沿着向北的纬度梯度，叶长减少而 FA 增加，大概是由于气温向极地降低。研究地点、采集年份和纬度解释了山桦叶片长度变化相对于 FA 变化的较大部分。在解决全球环境变化对植物性能影响的研究中，叶长可能是比 FA 更好的指标。相对于 FA 的变化，纬度解释了山桦叶片长度变化的很大一部分。在解决全球环境变化对植物性能影响的研究中，叶长可能是比 FA 更好的指标。相对于 FA 的变化，纬度解释了山桦叶片长度变化的很大一部分。在解决全球环境变化对植物性能影响的研究中，叶长可能是比 FA 更好的指标。