Collaborative Research: Scale-dependent processes as the drivers for understanding range- and niche-expansion in a widespread native species

东部红雪松（Juniperus virginia）原产于美国东部，这种迷人的树一直是景观美化的热门选择。但在大平原上，红雪松被称为“绿色冰川”，因为这种生长缓慢的物种正在占领曾经多产的草原。牧场主在将红雪松从牧场移除时面临着巨大的经济成本，而且红雪松与本地物种的竞争减少了草地的生物多样性。但是如何阻止“绿色冰川”呢？人口的增长可能是因为环境的变化改变了霜冻和干旱的状况，或者是因为人类实施了诸如灭火之类的草原管理措施，甚至是因为传播种子的鸟类的迁徙模式发生了变化。然而，更有可能的是，有许多因素在起作用。例如，环境变化可能允许植物迁移到一个新的地区，但鸟类的种子传播可能促进一个地区内的人口扩张。这项研究将确定几个因果因素的相对重要性，而不是集中在一个因素上。来自实验的数据将用于一个模型，该模型可以预测红杉范围可能扩张的速度和地点。研究结果将在霍尔顿植物园科学家系列讲座上向公众展示，并纳入霍尔顿植物园的“与自然合作”K-12营地和“树木公司”成人劳动力发展计划。揭示控制植物范围和生态位扩展的尺度依赖机制是生物多样性研究的关键问题。这项工作整合了跨尺度的生理和生态过程，以确定进一步扩大范围的潜力。该研究的核心假设是，在大的空间尺度上，草原管理的变化比生理气候耐受性更重要，而在较小的空间尺度上，鸟类的扩散、竞争和促进等生物因素更重要。利用微卫星确定历史种群、入侵种群和生态位扩张种群的空间变化尺度。火灾的影响将使用康扎草原NSF-LTER的长期数据进行检查，而操作和现场实验将确定霜冻和干旱的相互作用如何影响红杉树的性能。鸟类的种子传播和鸟类迁徙随时间的变化将被检查，以确定鸟类传播红杉的距离和地点。根据结构方程模型在所有三个空间尺度上的输入，经验数据将被纳入空间明确的人口水平年龄/阶段矩阵模型，空间分辨率由微卫星研究的结果确定。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Eastern Red Cedar (Juniperus virginiana) is native to the eastern United States, where this attractive tree has been a popular choice for landscaping. But out in the Great Plains, Red Cedar is known as the "green glacier", because this slow-growing species is taking over once-productive grasslands. Ranchers face substantial economic costs in removing Red Cedar from grazing lands, and it reduces grassland biodiversity through competition with native species. But how do you stop a "green glacier"? Populations might be expanding because environmental variability has altered frost and drought regimes, or because humans have implemented prairie management practices such as fire suppression, or even because of changes in the migration patterns of seed-dispersing birds. It is more likely, however, that many factors are at work. For example, environmental variability might allow plants to move into a new region, but seed dispersal by birds could promote population expansion within a region. Rather than focus on one factor, this study will determine the relative importance of several causal factors. Data from experiments will be used in a model that predicts the rate and locations where Red Cedar range expansion is likely to occur. Findings will be presented to the public at the Holden Arboretum Scientist Lecture Series and incorporated into Holden Arboretum's "Working with Nature" K-12 Camp and "Tree Corp" adult workforce development program. Uncovering scale-dependent mechanisms controlling range and niche expansion of plants is a key issue in biodiversity research. This work integrates physiological and ecological processes across scales to determine the potential for further range expansion. The central hypothesis is that, at a large spatial scale, changes in prairie management are more important than physiological climate tolerance for promoting range expansion, while at smaller scales, biotic factors such as avian dispersal, competition and facilitation are more important. The spatial scale of variation will be determined using microsatellites in historical, encroaching and niche expanding populations. The effects of fire will be examined using long-term data from the Konza Prairie NSF-LTER, while manipulative and field experiments will determine how the interaction of frost and drought impact Red Cedar performance. Seed dispersal by birds and changes in bird migration over time will be examined to determine how far, and where, birds disseminate Red Cedar. Empirical data will be integrated into a spatially explicit population-level age/stage matrix model, based on inputs from structural equation modeling at all three spatial scales, with spatial resolution determined by the results of microsatellite studies.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.