Vegetation Response to Prescribed Fire in Mountain Big Sagebrush Ecosystems at Lava Beds National Monument, California

Vegetation Response to Prescribed Fire in Mountain Big Sagebrush Ecosystems at Lava Beds National Monument, California
Author: Lisa M. Ellsworth
Publisher:
Total Pages: 224
Release: 2006
Genre: Big sagebrush
ISBN:

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Anthropogenic land use alterations such as livestock grazing and fire suppression have greatly altered sagebrush grasslands of the Great Basin, facilitating invasion of exotic annuals, increases in woody species, and losses of native species. Much of the current research surrounding wildland and prescribed fire in sagebrush dominated ecosystems has focused on a persistent belief that fire in sagebrush systems results in a loss of native flora and a trend toward dominance by exotic annuals. Fire was historically the dominant disturbance throughout the sagebrush steppe and the plant species that comprised these communities possess a variety of adaptations facilitating survival to the fire regime. In order to restore ecosystems, land managers will need to reintroduce natural ecosystem processes, including natural disturbance processes. To describe the response of these plant communities to fire, I examined the plant community response, seedbank response, and reproductive and density responses of three native bunchgrasses (Pseudoroegneria spicata, Achnatherum therberianum, and Elymus elymoides) as well as one native forb (Calochortus macrocarpus) following spring and fall prescribed fires at Lava Beds National Monument. Fires were applied to three Artemisia tridentata ssp. vaseyana (Mountain Big Sagebrush) plant communities with different land use and fire histories. These communities were different in composition ranging from a dominance of exotic annuals to dominance by native grasses, shrubs, and trees. Little is known about how prescribed fire affects the soil seed bank in sagebrush-dominated ecosystems. To address this, we quantified the emergence of Bromus tectorum (cheatgrass) seedlings as well as emergence of seedlings of functional groups (native forbs, bunchgrasses, and shrubs) in a seedbank germination study. At the invasive dominated site (Gillems Camp), we found 91% fewer B. tectorum seedlings germinated in spring burned sites than in controls immediately following spring prescribed burns. However, soils collected one-year following fire had 40% more B. tectorum germinants (8017 germinants/m [superscript 2]) than unburned controls (5132 germinants/m [superscript 2]). Following fall burns at this site there was a similar response, with a 56% immediate reduction in B. tectorum (as compared to unburned control) and a 59% increase in B. tectorum and 58% increase in exotic forb germinants one year following fires. There was an increase in native forb germination following spring burns (94%) and fall burns (45%) at a site dominated by native plants (Fleener Chimneys). Native bunchgrass seed germination declined following spring fire in sites dominated by sagebrush and native understory vegetation (79%), and in sites where Juniperus occidentalis (western juniper) and other woody species dominated (Merrill Caves) (71%). In invasive-dominated sites (Gillems Camp), there was a decrease in B. tectorum cover following both spring (81% decrease) and fall fires (82% decrease), and little native vegetation composition change. Shrub cover, made up predominantly of Chrysothamnus nauseosus, decreased following spring (95% decrease) and fall (93% decrease) fires. At the sagebrush, native understory site (Fleener Chimneys), there was a reduction in native bunchgrass cover (64% decrease), and an increase in native forbs (168% increase) following spring burns, with no changes following fall fires. At the juniper- woody dominated site (Merrill Caves), fire treatments resulted in a decrease in woody plant cover, with no immediate postfire differences seen in the herbaceous plant community. Density of bunchgrass species (Pseudoroegneria spicata, Achnatherum therberianum, Elymus elymoides) did not change following either spring or fall prescribed fire treatments. Fire enhanced flowering was not seen in C. macrocarpus following spring or fall burns at the native or juniper dominated sites. There was increased reproductive effort in native bunchgrass species following fires in all communities studied. Following spring fires at invasive dominated sites, there was a 245% increase in reproductive culms of P. spicata. Following fall fires in native dominated sites, we saw a 974% increase in reproductive culms of P. spicata and a 184% increase in reproductive culms of A. therberianum. Following fall fires at juniper-dominated sites, we saw in an increase in reproductive culms of P. spicata (678% increase), A. thurberianum (356% increase), and Elymus elymoides (209% increase). These results suggest that implementing prescribed fire in order to restore the natural disturbance regime in these fire-adapted ecosystems is beneficial to restoration and preservation of the native biota.

Guidelines for Prescribed Burning Sagebrush-grass Rangelands in the Northern Great Basin

Guidelines for Prescribed Burning Sagebrush-grass Rangelands in the Northern Great Basin
Author: Stephen C. Bunting
Publisher:
Total Pages: 46
Release: 1987
Genre: Forests and forestry
ISBN:

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Summarizes recent literature on the effects of fire on sagebrush-grass vegetation. Also outlines procedures and considerations for planning and conducting prescribed fires and monitoring effects. Includes a comprehensive annotated bibliography of the fire-sagebrush-grass literature published since 1980.

Associations Between Crested Wheatgrass and Native Vegetation in Southeastern Oregon

Associations Between Crested Wheatgrass and Native Vegetation in Southeastern Oregon
Author: Aleta M. Nafus
Publisher:
Total Pages: 105
Release: 2015
Genre: Crested wheatgrass
ISBN:

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Crested wheatgrass (Agropyron cristatum [L] Gaertm), an introduced bunchgrass, has been seeded on over 5 million hectares of degraded rangeland in western North America because it establishes more readily than native bunchgrasses. Because crested wheatgrass stands are associated with native species displacement and low biological diversity, there is substantial interest in re-establishing native species within seeded stands. However, efforts to reintroduce native grasses into crested wheatgrass stands have been largely unsuccessful, and little is known about the long-term dynamics of crested wheatgrass/native species mixes. This project was composed of two studies evaluating interactions between crested wheatgrass and associated native vegetation. In the first study, I examined the abundance of crested wheatgrass and seven native sagebrush steppe bunchgrasses which had been planted concurrently 13 years prior at equal densities. Thirteen years after planting, crested wheatgrass was the dominant bunchgrass with a ten-fold increase from its original planted density. Of the seven native bunchgrasses, four species: Idaho fescue (Festuca idahoensis Elmer); Thurber's needlegrass (Achnatherum thurberianum (Piper) Barkworth); basin wildrye (Leymus cinereus (Scribn. & Merr.) A. Löve) and Sandberg bluegrass (Poa secunda J. Presl) maintained their low planting density while three species: bluebunch wheatgrass (Pseudoroegneria spicata (Pursh) A. Löve), needle-and-thread (Hesperostipa comata (Trin. & Rupr.) Barkworth), and squirreltail (Elymus elymoides (Raf.) Swezey), declined in density over the 13-year period. Results suggested that densities of native bunchgrasses planted concurrently with crested wheatgrass were unlikely to increase and that some species only persisted at low levels. However, the continued persistence of native bunchgrasses, even at low densities, suggests that co-planting of some native bunchgrasses may be a viable way of avoiding crested wheatgrass monocultures when this species is necessary for rehabilitation or restoration. In the second study, I sought to identify environmental, historic and livestock management factors associated with native vegetation occasionally found in seeded crested wheatgrass stands. Basal cover, density, species richness and diversity were measured in 2012 and 2013 on 121 sites previously seeded to crested wheatgrass in southeastern Oregon. Plant community composition of crested wheatgrass stands was variable; some of the seedings were monocultures of crested wheatgrass while others contained diverse native species. Functional group variability explained by environmental factors ranged from 0% of annual grass density to 56% of large native perennial bunchgrass density. Soil texture was significant and appeared to be an important environmental characteristic explaining functional group cover and density 10-50 years post seeding. Native vegetation was, for all functional groups, positively correlated with soils lower in sand content. Precipitation in the year following seeding of crested wheatgrass has long-term effects on plant community dynamics, especially for Wyoming big sagebrush. Higher precipitation in the year following crested wheatgrass seeding was associated with decreased shrubs, likely because crested wheatgrass seedlings were more successful and therefore sagebrush seedlings experience greater competition. Moderate grazing was associated with reduced crested wheatgrass monoculture characteristics relative to ungrazed sites. However, within spring grazed and spring-summer grazed sites, there was a negative relationship between increased stocking rate and native species cover and abundance. I speculate that was largely the effect of higher stocking rates being allotted to more productive crested wheatgrass seedings. Overall, my research suggested that pre-seeding treatment/disturbance on a site appears to have long-term implications for plant community dynamics. However, functional groups varied in response to different pre-seeding treatments. Results support the notion that crested wheatgrass is very competitive with native bunchgrasses in particular; and that introducing natives into crested wheatgrass stands may require high levels of disturbance and may be most successful in more finely-textured soils. The results of this study also suggest that management actions, both at the time of seeding and after seeding, can influence plant community characteristics.

The Great Basin Naturalist

The Great Basin Naturalist
Author:
Publisher:
Total Pages: 426
Release: 1992
Genre: Natural history
ISBN:

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