DISSERTATION RESEARCH: Phenological shifts in seed-dispersal networks of the Sierra Nevada, California

许多娱乐和文化活动是根据自然事件的季节性时间安排的。例如，游客们涌向新英格兰欣赏秋天的树叶颜色，观鸟者在五月聚集在一起欢迎候鸟。季节性时间对植物和动物也很重要。为了补充秋季迁徙的能量，鸟类依靠富含卡路里的野果。同样地，生产这些水果的植物依赖于候鸟将它们的种子带到它们可以长成新植物的地方。这种互惠互利的互动之所以有效，是因为野果生产的时间与鸟类迁徙的时间相匹配。然而，在许多地方，鸟类迁徙和水果生产的季节性时间已经错位。由于没有足够的水果来为它们的迁徙飞行提供燃料，鸟类在迁徙过程中可能会受到影响。而且，没有鸟类传播种子，一些植物可能无法产生下一代。这项研究将测量水果产量和鸟类迁徙有多少不一致。调查人员将研究秋季迁移和水果生产的环境线索，以及控制野生植物生产多少水果的因素。公众将通过观察鸟类与水果的相互作用来参与，并将通过调查人员带领的实地考察来了解科学研究。 鸟类和植物的环境线索和秋季季节性事件之间的关系在很大程度上仍未被探索。该项目将使用多年、多物种、公开可用的数据集来估计鸟类秋季迁徙时间和肉质果实灌木结果实时间的年度差异。将采用两种方法来确定关系。首先，研究人员将使用贝叶斯生存模型分别从国家物候网络和eBird中回归关于每年迁移和结果时间的数据，以及环境驱动因素的数据。 其次，将建立一个五属灌木的普通花园实验，以首次机械地确定温度升高、干旱以及温度和干旱之间的相互作用如何影响果实的时间和丰度。研究结果将有助于预测鸟类迁徙和果树传播种子的能力。

Many recreational and cultural events are based on the seasonal timing of natural events. For example, visitors flock to New England to enjoy fall leaf colors and birdwatchers congregate in May to welcome migrating birds. Seasonal timing also matters to plants and animals. To fuel their fall migrations, birds rely on calorie-rich wild fruits. Likewise, the plants that make those fruits rely on migrating birds to carry their seeds to places where they can grow into new plants. This mutually beneficial interaction works because the timing of wild fruit production matches the timing of bird migration. In many places, however, the seasonal timing of bird migration and fruit production has become misaligned. With not enough fruit to fuel their migratory flights, birds may suffer during migration. And, without birds to disperse their seeds, some plants could fail to produce the next generation. This research will measure how much fruit production and bird migration are misaligned. Investigators will study the environmental cues for fall migration and fruit production as well as the factors that control how many fruits are produced by wild plants. Members of the public will participate by providing observations on bird-fruit interactions and will learn about scientific research through field trips led by the investigators. The relationships between environmental cues and fall seasonal events in birds and plants remain largely unexplored. This project will use multi-year, multi-species, publicly available datasets to estimate year-to-year differences in the timing of fall migration in birds and fruiting in fleshy-fruited shrubs. Two methods will be employed to determine relationships. First, researchers will use Bayesian survival models to regress data on yearly timing of migration and fruiting from the National Phenology Network and eBird, respectively, with data on environmental drivers. Second, a common garden experiment with five genera of shrubs will be set up to mechanistically determine for the first time how increased temperature, drought, and the interaction between the temperature and drought affect the timing and abundance of fruits. Results will be useful in predicting the ability of birds to migrate and fruiting-plants to disperse their seeds.