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

许多娱乐和文化活动都是基于自然事件的季节性时间。例如，游客蜂拥到新英格兰欣赏秋叶的颜色，观鸟者在五月聚集在一起欢迎候鸟。季节对植物和动物也很重要。为了给秋季的迁徙提供能量，鸟类依靠富含卡路里的野果。同样，结出果实的植物也依靠候鸟将种子带到可以长成新植物的地方。这种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时间已经变得不一致。由于没有足够的水果为它们的迁徙飞行提供燃料，鸟类在迁徙过程中可能会遭受痛苦。而且，如果没有鸟类来传播它们的种子，一些植物可能无法产生下一代。这项研究将测量有多少水果生产和鸟类迁徙不一致。调查人员将研究秋季迁徙和果实生产的环境线索，以及控制野生植物产生多少果实的因素。市民将参与观察鸟与水果的相互作用，并通过调查人员带领的实地考察了解科学研究。环境因素与鸟类和植物的秋季季节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、可公开获取的数据集来估计鸟类秋季迁徙时间和肉果灌木果实时间的逐年差异。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将来自国家物候网络和eBird的每年迁徙时间和结果的数据与环境驱动因素的数据进行回归。其次，对五属灌木进行普通的园艺试验，首次从机械上确定温度升高、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。结果将有助于预测鸟类的迁徙能力和果树的种子传播能力。

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.