Project Overview

Reports

Commodities

Target Pests

Practices

Cheatgrass (Bromus tectorum) has invaded over 50 million acres of rangelands in the western United States reducing cattle forage availability, increasing wildfire frequency, and limiting wildlife habitat. Cheatgrass is highly competitive, tolerant of cold germination temperatures, and grows rapidly – all contributing to its successful invasion. In addition, cheatgrass has been found to modify the soil microbial community, resulting in reduced soil microbial diversity and inhospitable conditions for native species. Millions of dollars have been put towards restoring cheatgrass-invaded areas, but often these efforts do not meet management goals. Further, extreme weather events (e.g. drought and heatwaves) are projected to become more frequent and intense in the future. This will add additional challenges to any restoration projects, potentially resulting in reduced restoration success and increased costs of restoration. There is a need for novel restoration practices that can be cost-efficient in restoring cheatgrass invaded areas and resilient to extreme and variable weather. 

In this proposal, we will trial a novel seed technology (inoculated soil seed coatings) as a more efficient method to restore cheatgrass-invaded areas addressing three Western IPM priorities: Invasive Species, IPM in Changing Landscape, and New Technologies to Manage Pests. First, we will quantify the variability of soil microbial community composition in plant communities with native species and cheatgrass presence at six sites across five states (Oregon, Idaho, Washington, Wyoming, and Nevada). We will next determine how the soil microbial composition from the different sites impacts germination and seedling growth rates of two native species commonly used in restoration and of important forage value: Sandberg bluegrass (Poa secunda) and bottlebrush squirreltail (Elymus elymoides). To do this, we will use a two-way thermogradient table that allows us to vary day and night temperatures in a full factorial design. We will then implement a proof-of-concept study to examine how inoculated seed coatings affect seedling emergence and growth. Seeds of the two native species will be coated with native-inoculated soil (i.e., with soil collected from native species areas at all sites) and planted into pots with cheatgrass-inoculated soil. In addition, we will implement an experimental drought, heatwave, and drought + heatwave combination treatment on the pots to examine how inoculated soil seed coatings may ameliorate plant stress under such extreme weather conditions.  

This project will quantify the impact of soil microbial composition on plant germination, growth, and survival in experimental settings – key for future field trials of this novel soil seed coating technology. Outcomes of this work will be disseminated through presentations at the Society of Range Management Annual Meeting and in a Master Gardener program hosted by OSU Extension. In addition, we will write at least two peer-reviewed research papers and respective one-page outreach flyers that will be disseminated by OSU Extension and other partners to broad audiences. If successful, this project initiation proposal will provide foundational information for further development of this inoculated soil seed coating technology into a scalable application on rangelands across the US West.  

Through this proposed project initiation study, we aim to test the potential of inoculated soil seed coatings to improve plant establishment and ameliorate extreme weather stress for two commonly used restoration species, Sandberg bluegrass (Poa secunda) and bottlebrush squirreltail (Elymus elymoides). We selected these two native species because of their restoration and forage importance and broad range in the US West. Project sites will be at six locations across five states (Oregon, Washington, Idaho, Wyoming, and Nevada) and span a wide range of climatic conditions (Figure 1).  

Our overall objective is to improve understanding of soil microbial variation, the role of soil microbes in plant establishment and growth, and the potential usage of inoculated soil seed coatings. We have identified four objectives that logically build upon one another to systematically explore this. Specifically, our objectives are: 

Objective 1. To understand how soil microbial composition varies across sites, we will quantify the variability in soil microbial composition (both bacterial and fungal) associated with native grass species (specifically the two species noted above) and cheatgrass. Soil will be collected from and compared across sites in multiple states.  

Objective 2. To test how soil microbial composition affects plant germination and growth, we will add inoculated soil (both cheatgrass- and native-inoculated) to seeds in agar on a two-way thermogradient table. We will determine the impact of differing soil microbial compositions on: 

(a) germination rates for two restoration species under variable day and night temperatures (range from 5-40C) on the two-way thermogradient table. 

(b) seedling root and shoot growth rates under those same variable day and night temperatures. 

Objective 3. To trial the usage of inoculated soil seed coatings, we will use a greenhouse study and two restoration species. In this study, we will examine the effectiveness of native-inoculated soil seed coatings on seeds when planted into cheatgrass-inoculated soil pots. Specifically, we will measure the impact on: 

(a) emergence rates within a 3-week emergence window. 

(b) seedling growth rates, survival, and final biomass over a 12-week study period. 

Objective 4. To test the potential ability of inoculated soil seed coatings to ameliorate stress under extreme weather conditions (drought, heatwave, and drought + heatwave combination conditions), we will also perform a greenhouse study. We are focused on measuring the potential of the following for two restoration species: 

(a) improvement in seedling survival. 

(b) increase in seedling biomass. 

Our procedures, below, are designed to address each objective. Through successfully addressing our objectives, we will provide baseline, proof-of-concept information that could support the scalable usage of inoculated soil seed coatings in restoration. We will track dissemination of our project outcomes via citation number, further funding acquired, number of attendees in presentations, and outreach material distribution.