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

热带森林具有全球重要性，因为它们具有高度的生物多样性和对碳储存的巨大贡献。这个项目研究热带森林植物繁殖的时机和成功。热带物种可能会利用季节变化的迹象(例如，降雨量或光照条件)来确定繁殖开始的时间，或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生殖的每个阶段--开花、果实成熟、种子传播和幼苗生长。由于季节性的原因，繁殖的有利条件在一年内可能会有所不同，而由于厄尔尼诺这样的气候周期，也可能会在几年之间发生变化。该项目专注于长期数据，以便捕捉各种类型植物条件更好或更差的时期。这项研究在多个热带森林研究地点进行，以区分当地天气变化的影响和大型区域气候模式。通过测量热带植物用于开始繁殖的线索，并检查哪些环境条件影响幼苗的生长和存活，该项目的长期数据将加强我们预测热带森林的未来以及这些森林为社会带来的好处的能力。这些长期的研究将对以下假设进行测试：(1)什么是诱导开花的环境线索；(2)热带森林中的繁殖如何受到风暴、干旱等干扰以及自然气候周期(如厄尔尼诺南方涛动、北大西洋涛动和大西洋十年振荡)的影响，这些周期在十年到十年的时间尺度上变化；(3)具有不同特征的物种(例如，小种子与大种子、软木材与密木材)如何应对环境变化；以及(4)间歇性繁殖如何影响到成年种群的结构。这种研究方法将有效地缩小早期繁殖研究与幼树和成年树种群动态之间的人口统计学差距。在每个田间地点，每年都会使用种子诱捕器多次记录特定物种的花卉、果实和种子雨。此外，所有木本幼苗都被记录在每年一次的普查中，普查对象是每个地点种子捕捉器附近数百块1平方米的地块。诱捕器和样地普查在大型绘制的森林动态地块内进行，所有直径1厘米的树木都被识别并定期测量。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.