The Effects of Prescribed Fire on Grasslands of the Southern Great Plains
The Effects of Prescribed Fire on Grasslands of the Southern Great Plains

Author: Whitney L. Behr

Publisher:

Published: 2023

Total Pages: 0

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Grasslands can support high levels of biodiversity and provide numerous ecosystem services, but they have been widely degraded, often via loss of natural disturbance regimes. North American grasslands were once created and maintained by fire. In some cases, fire has been more important than climate in determining the distribution and extent of grasslands. Conservation of the biodiversity harbored by grasslands relies, in part, on ecological restoration of these habitats and the fire regimes that historically maintained them. In this dissertation, I examined the effects of prescribed fire on grassland plant species and plant communities of the southern Great Plains in the short-term (up to two years after fire) and longer-term (twelve years after fire). Cool-season prescribed burns (those conducted in January – March) were not sufficient to shift overall plant community composition (e.g., increase richness of native plant species or reduce cover of the invasive grass Bothriochloa ischaemum) in 10 sites distributed from central Texas to southern Oklahoma (Chapter 2). However, these fires did have measurable effects on eight individual forb species in the same sites (Chapter 3). In general, the eight forb species studied individually responded to the winter fire individualistically, but all three annual species increased their floral displays (flowers/m2) in the burned plots in the short term. Forb species that increased their floral display in burned areas did so via increased plant biomass (grams of dry aboveground biomass) or plant density (plants/m2). We found little evidence that these forb species shifted their resource allocation towards reproduction. In a separate study (Chapter 4), a prescribed fire conducted in July was sufficient to shift plant community composition in the short term, mostly by reducing the cover of the invasive grass B. ischaemum and increasing native species richness; the latter effect was likely the result of reducing B. ischaemum. In the same study, only the increases in native grass cover and richness were still detectable twelve years after the fire. Perhaps due to two additional cool-season fires across the entire site, B. ischaemum cover remained low twelve years after the fire in burned plots but unexpectedly had also decreased in unburned plots. The results from all three chapters supported our expectation that summer fires would be more effective than cool-season fires in changing the plant community composition, including controlling the invasive grass B. ischaemum. Interestingly, forb species were highly individualistic, from differences in their abundances among sites in the multi-site study (Chapter 3) to differences in their responses to fire (Chapter 4). These findings support conducting prescribed fires in summer months to control invasive grasses and to increase native plant species richness, and consequently conserve the biodiversity supported by grasslands in this region

Seed Bank Response to Prescribed Fire in the Central Appalachians
Seed Bank Response to Prescribed Fire in the Central Appalachians

Author:

Publisher:

Published: 2010

Total Pages: 16

ISBN-13:

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Pre- and post-treatment seed-bank characteristics of woody species were compared after two prescribed fires in a mesic mixed-oak forest in the central Appalachians. Nineteen woody species were identified from soil samples. Mean species richness declined but evenness did not after prescribed burning. The seed bank was dominated by black birch, yellow-poplar, blackberry, grapevine and Hercules club before burning. Following burning, the median density of seed bank propagules declined by 45 percent. Black birch, yellow-poplar, and grapevine declined by 69, 56, and 40 percent, respectively. The results illustrate the importance of the seed bank as a robust source of non-oak regeneration in mixed-oak forests and of the potential effect of fire altering it.

Prescribed Fire Effects on Vegetation and Arthropod Dynamics, and Sampling Techniques in a Wyoming Big Sagebrush Community
Prescribed Fire Effects on Vegetation and Arthropod Dynamics, and Sampling Techniques in a Wyoming Big Sagebrush Community

Author: Edward C. Rhodes

Publisher:

Published: 2006

Total Pages: 258

ISBN-13:

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In the western United States, sagebrush (Artemisia spp L.) dominated rangelands are extensive, accounting for approximately 63 million ha. The Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle & Young) alliance is found in more xeric environments, occupying the largest area of the big sagebrush complex in areas within a 200-300mm precipitation zone at elevations ranging from 610-2130m. Wyoming big sagebrush communities provide habitat for nearly 100 bird and 70 mammal species throughout its range. A species that is of particular concern is the sage grouse (Centrocercus urophasianus Bonaparte), which depends on big sagebrush associations for food, nesting and cover. Much of its historical range has Redacted for privacy Redacted for privacy dwindled, prompting increasing scrutiny on land use and management throughout the big sagebrush association. Destruction of remaining habitat and the danger of invasion by annual grasses such as cheatgrass (Bromus tectorum L.), has necessitated the assessment of the effects of disturbance such as fire on these communities. This study was designed to: (A) determine the effects of prescribed fire on vegetation characteristics, (B) analyze the specific response of forbs and arthropods that are important in the diet of sage grouse to fire, and (C) compare the Modified- Whittaker and Daubenmire methods of estimating species richness and vegetation cover in a Wyoming big sagebrush community. In the first project, prescribed fire had little effect on herbaceous density, cover, or species richness, but did increase perennial grass and total herbaceous standing crop the second and third year post burn, and annual forb standing crop the first and second year. Big sagebrush and total shrub cover and density were greatly reduced in burned treatments. Green rabbitbrush cover was greater in unburned treatments, but no change in density was noted. Burning did not affect soil water availability. The second project showed little overall benefit to perennial forbs preferred by sage grouse, however there was a short-lived increase in Microsteris/Collinsia parviflora (Lindl.) cover in the second post burn year. Prescribed fire may be detrimental to Hymenoptera abundance. Orthoptera may benefit from prescribed fire, but further exploration is needed in that area. Annual exotic species richness was not shown to increase in either sampling method or treatment in the third project. This is important, as it shows that sites which are dominated by a large proportion of native species from various functional groups can resist invasion. There was no clear-cut delineation between the Modified-Whittaker and Daubenmire methods. While there were some similarities in the data between the two, the Modified-Whittaker method had substantially different percent cover estimations for perennial grass and total herbaceous components in 2005. The Modified-Whittaker method also did not detect treatment effects for biotic crust, bare ground/rock, and litter cover measurements that were seen with the Daubenmire method. Shrub cover measurements were similar in both methods. Further investigation is warranted to test the applicability of the Modified- Whittaker design.