| NSF Org: |
DEB Division Of Environmental Biology |
| Recipient: |
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| Initial Amendment Date: | February 25, 2021 |
| Latest Amendment Date: | May 21, 2021 |
| Award Number: | 2118125 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Steven Dudgeon
sdudgeon@nsf.gov (703)292-2279 DEB Division Of Environmental Biology BIO Directorate for Biological Sciences |
| Start Date: | March 1, 2021 |
| End Date: | February 29, 2024 (Estimated) |
| Total Intended Award Amount: | $199,998.00 |
| Total Awarded Amount to Date: | $199,998.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
921 S 8TH AVE POCATELLO ID US 83201-5377 (208)282-2592 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
921 South 8th Avenue, Stop 8046 Pocatello ID US 83209-0002 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | Population & Community Ecology |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.074 |
ABSTRACT
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.
PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Across the world, wildfires are becoming more frequent due to invasion by highly-flammable grasses. These introduced species often replace native plants following wildfire, and land managers are increasingly challenged to take actions to prevent such unwanted ecosystem transitions. Applying seeds of native plants is a primary management action intended to suppress invasive plants and encourage ecosystem recovery after fire, but the mechanisms for this are still unclear. In addition, prior human activities have caused landscape changes that have lasting effects on ecosystems today, but little is understood about how these ‘ecological memories’ affect post-fire recovery. In this study, we made use of a unique opportunity due to a wildfire in a sagebrush steppe ecosystem at Idaho State University’s Barton Ecological Research Area in Pocatello, Idaho. In August 2020, a wildfire burned most of this research site, including a former experiment on the ecological effects of shrub removal (a rangeland management practice) and nitrogen pollution that was conducted from 1997 to 2010. Building on that experiment, we investigated whether a history of prior shrub removal and nitrogen pollution affects plants and soils recovering from wildfire, and if these ecological memories influence the success of native seed additions. In April 2021, we created three different native seed mixes that we expected would suppress introduced plants, and dividing each of the original experimental plots into four subplots, we added each seed mix type to a subplot (keeping one subplot as a control). During the ensuing summer, we assessed responses by measuring vegetation ground cover, height, aboveground dry mass, and leaf chemistry, and soil nutrients (ammonium, nitrate, phosphate) and other properties.
We found that a history of shrub removal strongly influenced plants and soils recovering from wildfire. Soils in shrub removal plots had higher phosphate, and different nitrate and ammonium (depending on time of year), levels than soils in control plots. Shrub removal plots were also dominated by introduced plant species, particularly cheatgrass (Bromus tectorum), whereas control plots were mostly composed of native plants. Similarly, we found that a history of nitrogen pollution affected plants and soils. Plots with a high rate of nitrogen pollution had higher soil nitrate content than control plots or plots with a history of low-level nitrogen pollution, and high nitrogen plots tended to have lower vegetation ground cover as well. Furthermore, though it had only been three months since seeding, we found that vegetation ground cover was greatest in subplots that received a mixture of native grass and forb seeds. We are continuing to monitor plant responses to evaluate the establishment of the native seed additions and their ability to suppress invasive plants. These data will help to inform post-fire vegetation management, highlighting management challenges that may arise due to ecological memories of prior human activities.
This award supported two early-career professors in initiating their research programs, while fostering collaboration among new and established faculty at Idaho State University. This collaboration resulted in a data collection effort that included paid research experiences for fourteen undergraduate students, three graduate students, and a post-graduate project manager. Three of the students participated as NSF-supported Research Experiences for Undergraduates (REU) students, one of whom became a graduate student co-mentored by this project’s two early-career principal investigators. The REU and graduate students worked on independent projects related to the primary research agenda, which resulted in additional datasets and insights. In particular, these studies showed that soil-conditioning by shrubs and nest-building by ants create ecological memories that affect post-fire plants and soils at a microhabitat scale and can be considered in combination with the landscape-level factors above (shrub removal, nitrogen pollution, native seed addition). Altogether, these research efforts resulted in seven student-led presentations at local/regional conferences, three presentations at national/international conferences, one completed Master of Science thesis, a published dataset, and multiple manuscripts that are in preparation for submission to peer-reviewed journals for publication. Trainees gained marketable skills in experimental design, data collection, data analysis, plant ecology, and soil ecology, while also generating new knowledge about the dominant ecosystem in which they live. The majority of the trainees used this research experience to advance in their careers during the COVID-19 pandemic, and most are currently in related academic, government, or industry positions.
Last Modified: 06/27/2024
Modified by: Joshua Grinath
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