RUI: LTREB: Collaborative Research: Cyclic vs. anthropogenic causes of long-term variation in the regeneration of tropical forests with contrasting latitude and diversity

热带森林因其高度生物多样性和对碳储存的巨大贡献而在全球具有重要意义。本项目研究热带森林植物的繁殖时间和繁殖成功率。热带物种可能会利用季节变化的线索（例如，降雨或光照的可用性）来确定繁殖开始的时间，也许是为了确保它们的种子在有利于幼苗生长和存活的条件下传播。降雨、光照、温度和其他环境条件影响着繁殖的每个阶段——开花、果实成熟、种子传播和幼苗生长。由于季节性的原因，有利于繁殖的条件可能在一年内发生变化，而在几年之间，由于厄尔尼诺等气候周期的影响，有利的繁殖条件可能会发生变化。该项目侧重于长期数据，以便捕捉各种类型植物条件较好或较差的时期。这项研究在多个热带森林研究地点进行，以将当地天气变化的影响与大区域气候模式分开。通过测量热带植物开始繁殖的线索，并检查影响幼苗生长和存活的环境条件，该项目的长期数据将加强我们预测热带森林未来以及这些森林给社会带来的利益的能力。多名本科生的培训将由每一所合作大学在这些地点进行。这些长期研究将使以下假设得以验证：(1)什么是诱导开花的环境线索；(2)热带森林的繁殖如何受到风暴、干旱等干扰以及厄尔尼诺-南方涛动、北大西洋涛动和大西洋多年代际涛动等自然气候周期的影响，这些周期在年代际至年代际时间尺度上变化；(3)具有不同性状（如种子小与大、木材软与密）的树种如何应对环境变化；(4)偶发繁殖如何影响成年种群的结构。这种研究方法将有效地缩小早期生殖研究与树苗和成树种群动态之间的人口统计学差距。在每个田间地点，使用种子陷阱每年多次记录特定物种的花、水果和种子雨。此外，所有的木本幼苗都被记录在每年的普查中，在每个地点靠近种子陷阱的数百个1平方米的地块上。捕集器和样地普查是在大型森林动态地图样地内进行的，在这些样地中，所有直径为1厘米的树木都被确定并定期测量。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。

Tropical forests are globally important because of their high biodiversity and large contributions to carbon storage. This project studies the timing and success of reproduction in tropical forest plants. Tropical species may use cues of seasonal shifts (for example, in rainfall or light availability) to time the start of reproduction, perhaps to ensure their seeds are dispersed during conditions that will be favorable for the growth and survival of young seedlings. Rainfall, light availability, temperature, and other environmental conditions influence each stage of reproduction- flowering, fruit maturation, seed dispersal, and seedling growth. Beneficial conditions for reproduction can vary within a year, due to seasonality, and among years, due to climate cycles like El Nino. This project focuses on long term data in order to capture periods when conditions are better or worse for various types of plants. The research takes place at multiple tropical forest study sites to separate the effects of local weather variability from large regional climate patterns. By measuring the cues tropical plants use to start reproduction and examining which environmental conditions affect seedling growth and survival, the long-term data from this project will strengthen our ability to predict the future of tropical forests and the benefits these forests confer to society. Training of multiple undergraduate students will occur at the sites, by each of the collaborating universities.These long-term studies will enable tests of hypotheses concerning: (1) what are the environmental cues that induce flowering; (2) how is reproduction in tropical forests affected by disturbances such as wind storms, droughts, and by natural climate cycles such as the El Nino Southern Oscillation, the North Atlantic Oscillation, and the Atlantic Multidecadal Oscillation, which vary at subdecadal to multidecadal time scales; (3) how do species with different traits (e.g., small vs. large seeds, soft vs. dense wood) respond to environmental variation; and (4) how does episodic reproduction ramify through to the structure of adult populations. This research approach will effectively close the demographic gap between studies of early reproduction and the dynamics of sapling and adult tree populations. At each of the field sites, species-specific flower, fruit and seed rain is recorded multiple times each year using seed traps. Additionally, all woody seedlings are recorded in an annual census of hundreds of 1-m2 plots adjacent to seed traps, at each site. The trap and plot censuses take place within large mapped forest dynamics plots where all trees 1 cm in diameter are identified and regularly measured.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.