RAPID: Ecological memories and theory-guided recovery of post-fire steppe

RAPID：火灾后草原的生态记忆和理论指导恢复

• 批准号: 2118125
• 负责人: Joshua Grinath
• 金额: $ 20万
• 依托单位: Idaho State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-03-01 至 2024-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2118125&HistoricalAwards=false
• 关键词: RAPID; Ecological; memories; theory; guided

Wildfires are becoming more common as environmental change progresses, destroying entire landscapes and costing the American public billions of dollars annually. Wildfire frequency in many regions is intensified by the invasion of exotic grasses that are highly flammable, and which often replace native plants as burned landscapes regrow. To prevent invasive species from taking over burned landscapes, land managers are increasingly applying seeds of native plants to encourage ecosystem recovery and keep invasive plants at bay. However, there is still much to learn about the factors that determine the success of seed additions in terms of the ability of seeded species to establish, and to suppress flammable invaders. It is also unclear how previous human-caused landscape changes, such as nitrogen pollution or the removal of water-hogging shrubs (a practice common in western USA rangelands), will affect the success of native seed additions and plant recovery from fire. Moreover, it is unclear how different seed mixes repel exotic plants from invading disturbed areas. This research project addresses these issues by building on a long-term experiment investigating the effects of past nitrogen pollution and shrub removal (originally intended to improve rangeland forage) in a highly invaded sagebrush steppe ecosystem. The experimental site was entirely burned in a recent wildfire, providing a unique opportunity to evaluate how a history of nitrogen pollution and shrub removal will influence plant recovery from wildfire. The research team will develop criteria for creating seed mixes that suppress invasive plants, particularly flammable annual grasses, and will determine their effectiveness within the different long term experimental environments present across the study site. The results from this study will aid land managers in choosing native seed mixes that will help to prevent the spread of invasive plants and decrease the risks and costs of future wildfires.This project investigates how ecological memories of nutrient enrichment and dominant plant removal impact plant re-assembly following wildfire and addresses a critical need to test the applicability of current models for creating post-fire communities that will be resistant to invasion by transformative invasive species. The research will evaluate a promising, but under-studied, trait-based model (the Community Assembly by Trait Selection model) for establishing native plant assemblages that are resistant to invasive grasses and forbs. This model will be applied in a novel experimental design to discern whether seed additions result in biotic resistance via limiting similarity, fitness hierarchies and/or trait complementarity. While much focus has been given to limiting similarity as a mechanism of resistance to invasion, experimental support has been mixed because this mechanism has been difficult to distinguish from fitness hierarchies and because ecosystems are frequently invaded by more than one exotic species simultaneously. This project will overcome these issues by using two separate seed mixes designed to convey resistance to invasive grasses and forbs, plus a high-diversity seed mix that combines these. With this experimental setup, evidence for biotic resistance within functional groups will support limiting similarity, resistance across different groups will support fitness hierarchies, and relatively greater resistance in the high diversity mix will support trait complementarity. The seed mix treatments will be nested within plots of long-term nitrogen enrichment and shrub removal, which at a microhabitat scale are characterized by environmental variation due to ecosystem engineering by shrubs and ants. This hierarchical design will enable the researchers to assess how ecological memories of landscape and microhabitat-level factors affect the success of seed additions for conveying biotic resistance to invasive plants. It also allows evaluation of how nutrient availability influences mechanism conferring resistance to invasion.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.

随着环境变化的进展，野火正变得越来越常见，摧毁了整个景观，每年给美国公众造成数十亿美元的损失。外来草本植物的入侵加剧了许多地区的野火频率，这些外来草本植物高度易燃，随着被烧毁的景观重新生长，它们往往会取代本土植物。为了防止入侵物种侵占被烧毁的景观，土地管理者越来越多地使用本土植物的种子，以鼓励生态系统恢复，并遏制入侵植物。然而，在种子物种建立和抑制易燃入侵者的能力方面，决定种子添加成功的因素仍然有很多需要了解。目前也不清楚以前人为造成的景观变化，如氮污染或移除吸水灌木(这是美国西部牧场的常见做法)，将如何影响本地种子添加和植物火灾恢复的成功。此外，目前还不清楚不同的种子混合物如何击退入侵干扰地区的外来植物。这项研究项目通过一个长期实验来解决这些问题，该实验调查了在高度入侵的山艾树草原生态系统中，过去的氮污染和灌木移除(最初旨在改善牧场牧草)的影响。实验场在最近的一场野火中被完全烧毁，这为评估氮污染和灌木移除的历史将如何影响植物从野火中恢复提供了一个独特的机会。研究小组将制定标准来创造种子混合物，以抑制入侵植物，特别是易燃的一年生草本植物，并将确定它们在整个研究地点存在的不同长期实验环境中的有效性。这项研究的结果将帮助土地管理者选择本土种子混合物，这将有助于防止入侵植物的传播，并降低未来野火的风险和成本。该项目调查了营养丰富和优势植物移除的生态记忆如何影响野火后植物的重组，并解决了测试当前模型的适用性的迫切需要，以创建火灾后群落，以抵御变革性入侵物种的入侵。这项研究将评估一种有前途但研究不足的基于特征的模型(通过特征选择的群落组装模型)，以建立抵抗入侵草本植物和杂草的本地植物组合。这一模型将被应用于一种新的实验设计，以区分种子添加是否通过限制相似性、适应度等级和/或性状互补来导致生物抗性。虽然人们把重点放在限制相似性作为抵抗入侵的一种机制上，但由于这种机制很难与适应度等级区分开来，而且生态系统经常同时受到不止一个外来物种的入侵，因此对实验的支持褒贬不一。该项目将通过使用两种单独的种子混合物来克服这些问题，这些种子混合物旨在传达对入侵牧草和杂草的抗性，以及一种结合了这些的高度多样性的种子混合物。在这种实验设置下，功能组内生物抗性的证据将支持有限的相似性，不同组之间的抗性将支持适应度等级，而高多样性混合中相对较大的抗性将支持性状互补性。种子混合处理将嵌套在长期氮素积累和灌木去除的地块中，这些地块在微生境尺度上的特点是由于灌木和蚂蚁的生态系统工程而产生的环境变化。这种分层设计将使研究人员能够评估景观的生态记忆和微生境水平的因素如何影响种子添加的成功，以传递对入侵植物的生物抗性。它还允许评估营养供应如何影响赋予入侵抵抗的机制。该奖项反映了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。