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，它们的成功是以牺牲当地物种多样性和树木再生为代价的。入侵灌木可能对当地生态系统造成如此大的影响的原因之一是，与当地木本植物相比，它们有更长的叶期，也被称为扩展叶物候(ELP)。物候学是与气候条件相对应的生物现象发生的时间。春季较早的落叶和/或秋季较晚的落叶在一年中的独特时间创造了阴凉。到目前为止，比较入侵灌木和本地灌木的ELP的研究都是在单一地点进行的。然而，我们知道，影响叶片物候的因素，例如温度，在不同地区和不同年份之间差异很大。那么，当我们比较美国东部的地区时，我们会发现本土灌木和入侵灌木在叶物候上的差异吗？有没有因为入侵灌木的ELP较大而需要集中管理的地区？随着温度的变化，叶片的物候会发生怎样的变化？为了解决这些问题，研究人员开展了一项名为“Shady Invaders”的公民科学活动，以收集美国东部地区的树叶物候观测结果。通过参与者培训、电子通讯和网络研讨会更新，公众和科学研究都从这一合作中受益。在没有众多观察者的情况下，不可能在整个区域范围内同时收集特定物种的叶片物候数据。幸运的是，数据收集是直截了当的，允许公民科学家越来越多的努力应用到这个问题上。对原生和入侵灌木的区域公民科学物候观测将提供对入侵灌木在美国东部的新叶物候的空间范围和一致性的洞察，并将有助于我们理解在这一主题上的本地规模研究的更广泛的适用性。这种景观尺度的多年方法可以通过开发物候预测模型来预测气候变化对叶片物候的潜在影响。通过与中国的研究人员合作，正在纳入入侵美国东部森林的灌木物种原生范围的物候数据，以了解新的物候是作为原生范围(适应前)的进化压力的产物出现的，还是最近在引入范围(快速适应并扩大范围)的范围内出现的。这将有助于提出紧迫的研究问题，并告知叶片物候是否是预测和防止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.