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Collaborative Research: LTREB: Experimental determination of trophic dynamics and energy flows in a semiarid habitat in Chile.

合作研究：LTREB：智利半干旱栖息地营养动态和能量流的实验测定。

基本信息

批准号：
2025816
负责人：
Douglas Kelt
金额：
$ 35.64万
依托单位：
University of California-Davis
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2020
资助国家：
美国
起止时间：
2020-09-15 至 2025-08-31
项目状态：
未结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2025816&HistoricalAwards=false
关键词：
Collaborative Research LTREB Experimental determination

项目摘要

Long-term environmental research provides context that shorter-term efforts lack. Data collected over extended periods allows researchers to quantify the influence of fleeting or episodic factors that simply elude short-term efforts. This project started in 1989 as an experimental investigation of the importance of biotic interactions in a semiarid thorn scrub community in Bosque Fray Jorge National Park, Chile. While a role of predation was documented in early years, the overwhelming role of episodic rainfall (especially El Niño-associated rains) became clear in the first decade of work. Through the second and third decades the study focused on the relative role of biotic vs. abiotic influences, the role of invasive plans and rabbits, and the impact of extended drought conditions. Now the longest-running experimental field research program of its kind, this project has documented significant but limited effects of small mammal herbivory, and significant effects of invasive species and rainfall (and its absence) on populations of both plants and small mammals. The current research adds novel and sophisticated assessment of energy flow (from plants through consumers to predators) as a function of rainfall and hydrologic conditions, and advanced modeling of long-term population dynamics to identify mechanisms underlying changes in community stability observed in this highly variable system. Data collected at this site will be used to improve outreach efforts on the natural history and ecology of the National Park and the surrounding region, and will also be included in IsoCamp (isocamp.org), a two-week short course on stable isotope biogeochemistry and ecology for graduate students and postdoctoral researchers.This project is centered on 20 experimental grids (75x75 m) in which the following activities occur: (1) small mammals are sampled monthly (4 days/month); (2) cover by shrubs is measured every three months, and that of ephemeral plants monthly during the growing season; (3) soil samples are taken every 4 months to estimate seed density; and (4) fox scat and owl pellets are collected monthly from the site and nearby roosts to characterize their diets. Whereas exclusions of one small mammal herbivore (the degu) had limited effects, installation of all‐small mammal exclusions in 2002 demonstrated strong effects on several plant species. Superimposed on these effects were dramatic responses of plants, small mammals, and predators to increased precipitation during 8 El Niño/high rainfall events. North-central Chile has experienced severe drought conditions for over a decade, but forecasters predict more frequent and intense El Niño events, suggesting extreme temporal variation in abiotic conditions. This project will continue to track the interactive roles of environmental change and invasive species, but adds novel integration of stable isotopes, fecal DNA metabarcoding, and empirical dynamic modeling to better characterize how trophic structure is influenced by temporally varying energy flows. Key foci over the next 5 years include: (1) How are plants and small mammals influenced by the presence and abundance of invasive lagomorphs?; (2) How does variation in the availability of fast-growing ephemeral herbs and slow-growing perennial shrubs influence dietary breadth and niche partitioning among small mammals?; (3) Does omnivory facilitate individual- and population-level niche partitioning during boom-bust population cycles?; (4) How does multichannel energy flow and temporal variation in trophic structure affect small mammal community stability? These goals are being pursued through extensive collaboration with multiple investigators at multiple institutions in Chile and the United States.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.

长期的环境研究提供了短期努力所缺乏的背景。长时间收集的数据使研究人员能够量化短暂或偶发因素的影响，这些因素只是逃避短期的努力。该项目始于1989年，作为一个实验性的调查生物相互作用的重要性，在半干旱的荆棘灌木丛社区在博斯克弗雷豪尔赫国家公园，智利。虽然在早期记录了捕食的作用，但在工作的第一个十年中，间歇性降雨（特别是与厄尔尼诺有关的降雨）的压倒性作用变得明显。在第二和第三个十年，研究重点是生物与非生物影响的相对作用，入侵计划和兔子的作用，以及长期干旱条件的影响。目前，该项目是同类项目中运行时间最长的实验性实地研究项目，该项目记录了小型哺乳动物食草性的显著但有限的影响，以及入侵物种和降雨（及其缺乏）对植物和小型哺乳动物种群的显著影响。目前的研究增加了对能量流（从植物到消费者到捕食者）的新颖和复杂的评估，作为降雨和水文条件的函数，并对长期种群动态进行了高级建模，以确定在这个高度可变的系统中观察到的社区稳定性变化的机制。在该网站收集的数据将用于改善国家公园及其周边地区的自然历史和生态的外联工作，并将纳入IsoCamp（isocamp.org），为研究生和博士后研究人员举办的为期两周的稳定同位素地球化学和生态学短期课程。该项目以20个实验网格（75 x75米）为中心，其中进行以下活动：（1）每月对小型哺乳动物进行采样（4天/月）;（2）每三个月测量灌木的覆盖率，在生长季节每月测量短命植物的覆盖率;（3）每四个月采集土壤样本，以估计种子密度;（4）每月从现场和附近的栖息地收集狐狸粪便和猫头鹰粪便，以确定其饮食特征。虽然排除一种小型哺乳动物食草动物（德古）的影响有限，但2002年实施的所有小型哺乳动物排除对几种植物物种产生了强烈影响。叠加在这些影响是戏剧性的反应，植物，小型哺乳动物和捕食者在8厄尔尼诺/高降雨事件降水量增加。智利中北部十多年来一直经历着严重的干旱状况，但预报员预测厄尔尼诺事件会更加频繁和强烈，这表明非生物条件的极端时间变化。该项目将继续跟踪环境变化和入侵物种的相互作用，但增加了稳定同位素，粪便DNA metabarcoding和经验动态建模的新整合，以更好地表征营养结构如何受到随时间变化的能量流的影响。未来5年的重点包括：（1）植物和小型哺乳动物如何受到入侵兔形目动物的存在和丰度的影响？(2)快速生长的短命草本植物和缓慢生长的多年生灌木的可利用性的变化如何影响小型哺乳动物的食物宽度和生态位划分？(3)在繁荣-萧条的种群周期中杂食动物促进个体和种群水平的生态位划分吗？(4)多通道能量流和营养结构的时间变化如何影响小型哺乳动物群落的稳定性？通过与智利和美国多个机构的多名研究人员的广泛合作，正在实现这些目标。该奖项反映了NSF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。