EAGER: Quantifying the relative importance of reproduction in forest dynamics under historical and future climate change

环境变化将改变森林动态和物种组成。树木的繁殖和补充是树木种群的关键过程，并最终决定未来森林的物种组成。尽管树木繁殖对气候敏感，但这一过程对森林动态的相对重要性尚不清楚，特别是与预期的气候变化对树木生长和死亡的影响相比。种子产量和幼苗存活率也受个体和林分水平性状的影响。例如，幼苗的存活受到光供应的影响。气候变化导致的死亡率上升将改变照射到森林地面的光照量，并影响幼苗的存活。种子产量也受大小的影响（即，较大的个体往往产生更多的种子）。如果树木的生长对气候变化有积极的反应，这可能间接导致种子产量的增加。因此，为了捕捉所有这些直接和间接的影响，该项目将更新一个动态植被模型（DVM），以明确地模拟气候和林分结构对生殖的影响。将树木更新动态纳入基于过程的植被模型是一个重大的研究空白，也是准确预测森林对气候变化响应的关键步骤。该项目更广泛的影响包括(1)对学生进行计算机编程、数据库管理、数据分析和通信科学方面的培训，以及(2)扩大妇女参与计算机科学的外展活动。以太平洋西北地区（PNW）的森林为例，该项目将量化PNW常见树种的种子产量（作为天气和大小的函数）和幼苗存活率（作为天气和林分结构的函数）之间的关系。这些关系将被纳入一个森林模型，该模型已经包括了对生长、竞争和死亡作为环境函数的特定物种的模拟。更新后的模型将用于模拟历史气候和各种气候变化情景下位于PNW的林分。通过比较模型版本，该研究将能够量化繁殖对森林动态和物种更替的相对作用，并确定易受气候变化影响的物种。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。

Environmental change will alter forest dynamics and species composition. Tree reproduction and recruitment are critical processes for tree populations and ultimately, determine the future species composition of forests. Even though tree reproduction is sensitive to climate, the relative importance of this process for forest dynamics is unclear, especially compared to anticipated climate-change effects on tree growth and mortality. Seed production and seedling survival are also determined by individual and stand level properties. For example, seedling survival is affected by light availability. Increasing mortality due to climate change will alter the amount of light hitting the forest floor, and affect seedling survival. Seed production is also affected by size (i.e., larger individuals tend to produce more seed). If tree growth responds positively to climate change, this could indirectly cause an increase in seed production. Thus, to capture all these direct and indirect effects, the project will update a dynamic vegetation model (DVM) to explicitly simulate reproduction as a function of weather and stand structure. Including tree regeneration dynamics in process-based vegetation models is a major research gap and a critical step for accurately projecting forest responses to climate change. The project broader impacts include (1) training for students in computer programming, database management, data analysis, and communicating science, and (2) outreach activities to broaden participation of women in computer science.Using forests located in the Pacific Northwest (PNW) as a case study, the project will quantify the relationships for seed production (as a function of weather and size) and seedling survival (as a function of weather and stand structure), for common tree species in the PNW. These relationships will be incorporated into a forest model, that already includes species-specific simulations of growth, competition and mortality as a function of the environment. The updated model will be used to simulate forest stands located in the PNW under historical climate and various climate change scenarios. By comparing model versions, the research will be able to quantify the relative role of reproduction on forest dynamics and species turnover and identify species vulnerable to climate change.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.