Patterns of post-fire invasion of semiarid shrub-steppe reveals a diversity of invasion niches within an exotic annual grass community

2021 ◽  
Author(s):  
Cara Applestein ◽  
Matthew J. Germino
Keyword(s):  
Annual Grass ◽  
Shrub Steppe ◽  
Exotic Annual Grass

Restoration of Exotic Annual Grass-Invaded Rangelands: Importance of Seed Mix Composition

2014 ◽  
Vol 7 (2) ◽  
pp. 247-256 ◽  
Author(s):  
Kirk W. Davies ◽  
Dustin D. Johnson ◽  
Aleta M. Nafus
Keyword(s):  
Species Richness ◽  
Life Forms ◽  
Perennial Grasses ◽  
Annual Grass ◽  
Herbaceous Vegetation ◽  
Plant Life ◽  
Annual Grasses ◽  
Exotic Annual Grass ◽  
Resistance To Invasion ◽  
Plant Life Form

AbstractRestoration of exotic annual grass-invaded rangelands is needed to improve ecosystem function and services. Increasing plant species richness is generally believed to increase resistance to invasion and increase desired vegetation. However, the effects of species richness and individual plant life forms in seed mixes used to restore rangelands invaded by exotic annual grasses have not been investigated. We evaluated the effects of seeding different life forms and increasing species richness in seed mixes seeded after exotic annual grass control to restore desirable vegetation (perennial herbaceous vegetation) and limit exotic annual grasses at two sites in southeastern Oregon. We also investigated the effects of seeding two commonly used perennial grasses individually and together on plant community characteristics. Large perennial grasses, the dominant herbaceous plant life form, were the most important group to seed for increasing perennial herbaceous vegetation cover and density. We did not find evidence that greater seed mix species richness increased perennial herbaceous vegetation or decreased exotic annual grass dominance more than seeding only the dominant species. None of the seed mixes had a significant effect on exotic annual grass cover or density, but the lack of a measured effect may have been caused by low annual grass propagule pressure in the first couple of years after annual grass control and an unusually wet-cool spring in the third year post-seeding. Although our results suggest that seeding only the dominant plant life form will likely maximize plant community productivity and resistance to invasion in exotic annual grass-invaded northern Great Basin arid rangelands, seeding a species rich seed mix may have benefits to higher tropic levels and community stability. Clearly the dominant species are the most prudent to include in seed mixes to restore exotic annual grass-invaded plant communities, especially with finite resources and an increasingly large area in need of restoration.

scholarly journals Characterizing Land Surface Phenology and Exotic Annual Grasses in Dryland Ecosystems Using Landsat and Sentinel-2 Data in Harmony

2020 ◽  
Vol 12 (4) ◽  
pp. 725 ◽  
Author(s):  
Neal J. Pastick ◽  
Devendra Dahal ◽  
Bruce K. Wylie ◽  
Sujan Parajuli ◽  
Stephen P. Boyte ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Data Mining ◽  
Land Surface ◽  
Western United States ◽  
Grass Cover ◽  
Annual Grass ◽  
Annual Grasses ◽  
Dryland Ecosystems ◽  
Exotic Annual Grass ◽  
Sentinel 2

Invasive annual grasses, such as cheatgrass (Bromus tectorum L.), have proliferated in dryland ecosystems of the western United States, promoting increased fire activity and reduced biodiversity that can be detrimental to socio-environmental systems. Monitoring exotic annual grass cover and dynamics over large areas requires the use of remote sensing that can support early detection and rapid response initiatives. However, few studies have leveraged remote sensing technologies and computing frameworks capable of providing rangeland managers with maps of exotic annual grass cover at relatively high spatiotemporal resolutions and near real-time latencies. Here, we developed a system for automated mapping of invasive annual grass (%) cover using in situ observations, harmonized Landsat and Sentinel-2 (HLS) data, maps of biophysical variables, and machine learning techniques. A robust and automated cloud, cloud shadow, water, and snow/ice masking procedure (mean overall accuracy >81%) was implemented using time-series outlier detection and data mining techniques prior to spatiotemporal interpolation of HLS data via regression tree models (r = 0.94; mean absolute error (MAE) = 0.02). Weekly, cloud-free normalized difference vegetation index (NDVI) image composites (2016–2018) were used to construct a suite of spectral and phenological metrics (e.g., start and end of season dates), consistent with information derived from Moderate Resolution Image Spectroradiometer (MODIS) data. These metrics were incorporated into a data mining framework that accurately (r = 0.83; MAE = 11) modeled and mapped exotic annual grass (%) cover throughout dryland ecosystems in the western United States at a native, 30-m spatial resolution. Our results show that inclusion of weekly HLS time-series data and derived indicators improves our ability to map exotic annual grass cover, as compared to distribution models that use MODIS products or monthly, seasonal, or annual HLS composites as primary inputs. This research fills a critical gap in our ability to effectively assess, manage, and monitor drylands by providing a framework that allows for an accurate and timely depiction of land surface phenology and exotic annual grass cover at spatial and temporal resolutions that are meaningful to local resource managers.

Exotic annual grass invasion alters fuel amounts, continuity and moisture content

2013 ◽  
Vol 22 (3) ◽  
pp. 353 ◽  
Author(s):  
Kirk W. Davies ◽  
Aleta M. Nafus
Keyword(s):  
Moisture Content ◽  
Plant Communities ◽  
Large Scale ◽  
Cumulative Effect ◽  
Fuel Moisture ◽  
Annual Grass ◽  
Fire Cycle ◽  
Exotic Annual Grass ◽  
Fuel Characteristics ◽  
Fuel Moisture Content

Many exotic annual grasses are believed to increase wildfire frequency to the detriment of native vegetation by increasing fine fuels and thus, creating a grass-fire cycle. However, information on differences in fuel characteristics between invaded and non-invaded plant communities is lacking, or is based mainly on speculation and anecdotal evidence. We compared fuel biomass, cover, continuity and moisture content in plant communities invaded and not invaded by cheatgrass (Bromus tectorum L.), an exotic annual grass, in 2010 and 2011 in south-eastern Oregon, USA. Annual grass-invaded communities had higher fine fuel amounts, greater fuel continuity, smaller fuel gaps and lower fuel moisture content than did non-invaded plant communities. These conditions would increase the probability that ignition sources would contact combustible fuels and that fires would propagate. Fuel characteristics in the annual grass-invaded communities in our study may also support faster spreading fires. Fuel moisture content was low enough to burn readily more than a month earlier in annual grass-invaded communities than in non-invaded communities, thereby expanding the wildfire season. The cumulative effect of these differences in fuel characteristics between exotic annual grass-invaded and non-invaded plant communities is an increased potential for frequent, large-scale, fast-spreading wildfires. We suggest that research is needed to develop methods to mediate and reverse these changes in fuel characteristics associated with B. tectorum invasion.

Susceptibility of Exotic Annual Grass Seeds to Fire

2008 ◽  
Vol 1 (2) ◽  
pp. 158-167 ◽  
Author(s):  
Sara B. Sweet ◽  
Guy B. Kyser ◽  
Joseph M. DiTomaso
Keyword(s):  
Annual Grass ◽  
Exotic Annual Grass

Community Structure Affects Annual Grass Weed Invasion During Restoration of a Shrub–Steppe Ecosystem

2014 ◽  
Vol 7 (1) ◽  
pp. 1-13 ◽  
Author(s):  
Phil S. Allen ◽  
Susan E. Meyer
Keyword(s):  
Community Structure ◽  
Native Species ◽  
Propagule Pressure ◽  
Alternative Hypothesis ◽  
Perennial Grasses ◽  
Invasion Success ◽  
Sagebrush Steppe ◽  
Annual Grass ◽  
Shrub Steppe ◽  
Steppe Communities

AbstractEcological restoration of shrub–steppe communities in the western United States is often hampered by invasion of exotic annual grasses during the process. An important question is how to create restored communities that can better resist reinvasion by these weeds. One hypothesis is that communities comprised of species that are functionally similar to the invader will best resist invasion, while an alternative hypothesis is that structurally more complex and diverse communities will result in more effective competitive exclusion. In this field experiment, we examined the effects of restored community structure on the invasion success of three annual grass weeds (downy brome, jointed goatgrass, and cereal rye). We created replicated community plots that varied in species composition, structural complexity and density, then seeded in annual grass weeds and measured their biomass and seed production the following year, and their cover after 1 and 3 yr. Annual grass weeds were not strongly suppressed by any of the restored communities, indicating that it was difficult for native species to completely capture available resources and exclude annual grass weeds in the first years after planting. Perennial grass monocultures, particularly of the early seral grass bottlebrush squirreltail, were the most highly invaded communities, while structurally complex and diverse mixtures of shrubs (big sagebrush, rubber rabbitbrush), perennial grasses (bluebunch wheatgrass and bottlebrush squirreltail) and forbs (Lewis flax, Utah sweetvetch, hairy golden aster, gooseberryleaf globemallow) were more resistant to invasion. These results suggest that restoration of sagebrush steppe communities resistant to annual grass invasion benefits from higher species diversity; significant reduction of weed propagule pressure prior to restoration may be required.

scholarly journals The elevational ascent and spread of exotic annual grass dominance in the Great Basin, USA

2021 ◽  
Author(s):  
Joseph T. Smith ◽  
Brady W. Allred ◽  
Chad S. Boyd ◽  
Kirk W. Davies ◽  
Matthew O. Jones ◽  
...  
Keyword(s):  
Great Basin ◽  
Annual Grass ◽  
Exotic Annual Grass

Dormant-Season Moderate Grazing Prefire Maintains Diversity and Reduces Exotic Annual Grass Response Postfire in Imperiled Artemisia Steppe

2021 ◽  
Vol 79 ◽  
pp. 91-99
Author(s):  
Kirk W. Davies ◽  
Jon D. Bates ◽  
Chad S. Boyd ◽  
Rory O'Connor ◽  
Stella Copeland
Keyword(s):  
Annual Grass ◽  
Dormant Season ◽  
Exotic Annual Grass
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