DISSERTATION RESEARCH: Exploring novel leaf phenology of invading shrubs

入侵灌木是美国东部森林的一个主要问题，它们的成功是以本地物种多样性和树木再生为代价的。入侵灌木对本地生态系统影响如此之大的原因之一是，与本地木本物种相比，它们的叶片生长期更长，也被称为延长叶物候（ELP）。物候学是与气候条件相对应的生物现象的时间。春天的早出晚落和/或秋天的晚落在一年中独特的时间里创造了树荫。到目前为止，比较入侵灌木和原生灌木的ELP的研究都是在单一地点进行的。然而，我们知道驱动叶片物候的线索，例如温度，在不同地区和每年都有很大差异。那么，当我们比较美国东部地区时，我们会发现本土和入侵灌木在叶片物候上的差异吗？是否有一些地区由于入侵灌木的ELP更大而需要集中管理？叶片物候如何随温度变化而变化？为了解决这些问题，研究人员开展了一项名为“阴暗入侵者”的公民科学运动，以收集美国东部的树叶物候观测结果。通过参与者培训、电子新闻通讯和网络研讨会更新，公众和科学研究都从这次合作中得到了丰富。在没有众多观测者的情况下，不可能在区域范围内同时收集到特定物种的叶片物候数据。幸运的是，数据收集很简单，这使得越来越多的公民科学家的努力可以应用到这个问题上。本地和入侵灌木的区域公民科学物候观测将提供对美国东部入侵灌木新型叶片物候的空间范围和一致性的洞察，并将有助于我们对这一主题的地方尺度研究的更广泛适用性的理解。景观尺度的多年期方法可以通过建立物候预测模型来预测气候变化对叶片物候的潜在影响。通过与来自中国的研究人员的合作，我们正在整合来自美国东部入侵森林的灌木物种的本地范围的物候数据，以了解新的物候是作为本地范围（预适应）的进化压力的产物出现的，还是最近在引进范围（随着范围扩大的快速适应）出现的。这将有助于解决紧迫的研究问题，并告知叶片物候学是否是预测和预防未来入侵的有用工具。

Invasive shrubs are a major concern in eastern U.S. forests where their success is at the cost of native species diversity and tree regeneration. One of the reasons invasive shrubs may impact native ecosystems so greatly is that they have an extended period with leaves, as compared to native woody species, also called extended leaf phenology (ELP). Phenology is the timing of biological phenomena that correspond to climatic conditions. This earlier leaf emergence in the spring and/or later leaf fall in the autumn creates shade at unique times of the year. So far, studies comparing ELP of invasive compared to native shrubs have been done at single locations. However, we know that cues that drive leaf phenology, for example temperature, vary greatly from region to region and from year to year. So, when we compare regions across the eastern U.S., will we find differences in leaf phenology between native and invasive shrubs? Are there regions where it is important to focus management efforts because ELP of invading shrubs is greater? How will leaf phenology change with temperature changes? To address these questions, researchers have developed a citizen science campaign called "Shady Invaders" to collect leaf phenology observations across the eastern U.S. Through participant training and eNewsletter and webinar updates, both the public and scientific research are enriched from this collaboration. Species-specific leaf phenology data are impossible to collect simultaneously across a regional scale without numerous observers. Fortunately, data collection is straightforward, allowing the growing efforts of citizen scientists to be applied to this problem. Regional citizen science phenology observations for native and invasive shrubs will provide insight into the spatial extent and consistency of the novel leaf phenology of invasive shrubs across eastern U.S. and will contribute to our understanding of the broader applicability of local-scale research on this topic. The landscape-scale, multi-year approach can be used to predict the potential implications of climate change for leaf phenology by developing a predictive model for phenology. Through collaboration with researchers from China, phenology data are being incorporated from the native range of the shrub species invading forests of eastern U.S. to understand whether novel phenology arose as a product of evolutionary pressures in the native range (pre-adaptation), or more recently in the introduced range (rapid adaptation with range expansion). This will contribute to pressing research questions as well as informing whether leaf phenology is a useful tool for predicting and preventing future invasions.