How Much Sagebrush Is too Much: An Economic Threshold Analysis

Bastian, Christopher T.; Jacobs, James J.; Smith, Michael A.

doi:10.2307/4002508

Cited by 10 publications

(12 citation statements)

References 20 publications

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“…Managers have used various techniques -herbicides, mechanical manipulations, fire-to reduce the abundance of sagebrush (Bastian et al 1995). People are skeptical of herbicidal remedies and mechanical manipulations often are not justifiable economically.…”

Section: Discussionmentioning

confidence: 99%

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Supplemental barley and charcoal increase intake of sagebrush by lambs

Banner¹,

Rogosic²,

Burritt³

2000

REM

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We evaluated the influence of supplemental barley and activated charcoal on the intake of sagebrush by lambs in individual pens. In 3 experiments, lambs were fed sagebrush (harvested and chopped to 2-3 cm) during the morning; they were fed a basal diet of alfalfa pellets in the afternoon. In the first experiment, lambs supplemented with activated charcoal + barley ate more A. tridentata ssp. vaseyana than lambs supplemented with barley (304 vs. 248 g; P = .071). A second set of experiments, which consisted of 3 trials, determined the effects of activated charcoal, barley, and subspecies of sagebrush on intake of sagebrush. Lambs supplemented with activated charcoal + barley ate more A. tridentata ssp. vaseyana (Trial 1; 292 vs. 225 g; P = .086), and more A. tridentata ssp. tridentata (Trial 2; 371 vs. 255 g; P = .031) than lambs supplemented with barley. In Trial 3, lambs supplemented with barley ate more sagebrush than lambs that were not supplemented (480 vs. 318 g; P = .0002). A third set of experiments compared activated charcoal + barley, barley, and no supplement in 2 trials. In Trial 1, lambs supplemented with activated charcoal + barley or barley generally ate more A. tridentata ssp. v a s e y a n a than lambs not supplemented (P = .017). In Trial 2, lambs supplemented with activated charcoal + barley ate slightly more A. t r i d e n t a t a ssp. v a s e y a n a than lambs supplemented with barley, and they ate substantially more than lambs not supplemented (P = .032). Collectively, the results suggest that energy from supplemental barley increased intake of sagebrush by lambs fed a basal ration of alfalfa pellets which are high in protein, and that activated charcoal played a minor role in further increasing intake of sagebrush.

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Section: Discussionmentioning

confidence: 99%

“…Sagebrush (Artemisia tridentata Nutt.) refers to a diverse array of subspecies and ecotypes of shrubs that occur on approximately 39 million hectares of land in the western United States (Bastian et al 1995). While accounts vary, there is evidence that sagebrush has increased in abundance in many areas due to grazing preferences of herbivores and lack of fire.…”

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confidence: 99%

Supplemental barley and charcoal increase intake of sagebrush by lambs

Banner¹,

Rogosic²,

Burritt³

2000

REM

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“…Prescribed burning has become a commonly applied management tool over the last 30 years in these ecosystems to reduce the shrub cover and stimulate forb and grass production (Sapsis and Kauffman 1991;Bastian et al 1995;Wambolt et al 2001). Burning may be done in the spring or autumn when temperatures are low.…”

Section: Field Site Descriptionsmentioning

confidence: 99%

Spatial patterns in leaf area and plant functional type cover across chronosequences of sagebrush ecosystems

Ewers

Pendall

2007

Plant Ecol

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Since most studies of ecosystem dynamics after disturbance require longer durations of study than the life span of most research careers, many studies rely on chronosequence approaches to substitute space for time. We tested the chronosequence approach for assessing the change in plant functional type cover and leaf area index (L) using three replicated mountain big sagebrush (Artemesia tridentata var. vaseyana (Rydb.) Boivin) dominated ecosystems in southern Wyoming. We further tested our broader inferences of mountain big sagebrush ecosystem chronosequences by assessing whether dynamics in spatial patterning of plant functional type cover and leaf area index would compromise the chronosequence approach. We hypothesized that (1) L and total cover increase with age at similar rates across replicated chronosequences, (2) spatial autocorrelation is greatest with shrub cover, and (3) spatial autocorrelation increases with age. We failed to reject all three hypotheses. Our analyses showed that mean shrub cover, total cover, and L all increased linearly with time since disturbance across all three replicated chronosequences. While neither graminoid nor forb cover was correlated with time since disturbance, graminoid cover did show an inverse relationship with shrub cover and L. Semivariogram analysis showed that spatial patterning increased with shrub cover and time since disturbance. Thus, while we cannot yet provide a process to fit the spatial patterns, the chronosequence approach for sagebrush ecosystems recovering from disturbance has survived a rigorous test because the mean changes in shrub cover, total cover, and L were replicable across three different sites.

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“…These changes in vegetation are of considerable socioeconomic concern, as they often contribute to reductions in livestock carrying capacity and thus impact commercial enterprises, pastoral Manuscript received 11 January 1996;revised 18 June 1996;accepted 20 June 1996. 1 societies, and subsistence cultures in arid and semiarid environments (Heady 1975, Scifres 1980, Schofield and Bü cher 1986, Skarpe 1991, MacLeod 1993, Walker 1993, Young and Solbrig 1993, Bastian et al 1995. Woody plant encroachment into grasslands and savannas also has potentially important ramifications for desertification, biodiversity, wildlife habitat conservation, nutrient cycling, and soil erosion (Grover and Musick 1990, Schlesinger et al 1990, Hibbard 1995.…”

Section: Introductionmentioning

confidence: 99%

Small-Mammal Regulation of Vegetation Structure in a Temperate Savanna

Archer¹,

Heitschmidt²

1997

Ecology

107

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Explanations for documented increases in woody plant dominance in grasslands and savannas of North America include atmospheric CO 2 enrichment and changes in climate, livestock grazing, and fire regimes. However, tree/shrub encroachment has also coincided with the eradication of a once widespread native herbivore, the black-tailed prairie dog (Cynomys ludovicianus). We used field experiments and repeat aerial photography to demonstrate that prairie dogs, and the herbivores and granivores associated with their colonies, probably maintained grassland and savanna by preventing woody species such as Prosopis glandulosa (honey mesquite) from establishing or attaining dominance.Prosopis seed and pod disappearance was 3-99 times greater within prairie dog colonies. Ants were the primary agent of seed removal, whereas prairie dogs and associated vertebrates were the primary agents of pod removal. Survival of Prosopis seedlings protected from vertebrate herbivory was similar on and off prairie dog colonies (ഠ60%), whereas survival of unprotected seedlings was 3 times greater off-than on-colony. On-colony, prairie dogs and associated herbivores girdled and destroyed all Prosopis saplings within 2 d of planting; survival of 1-yr-old seedlings was reduced by 50% after 3 mo of exposure to on-colony herbivores. Despite high levels of woody plant seed disappearance and seedling herbivory, on-colony ''seedling'' reserves were substantial (950 plants/ha). Thus, prairie dogs and the fauna that occur on their colonies suppressed rather than eliminated Prosopis from the colony site. Removal of prairie dogs led to rapid development of Prosopis stands. Repeat aerial photography showed that Prosopis canopy cover on a colony eradicated in 1950 (27%) increased to a level (61%) comparable to that of off-colony Prosopis stands (65%) within 23 yr.These data illustrate how transitions from grassland to woodland vegetation can be mediated by a rodent herbivore. They further demonstrate how purposeful or inadvertent removal of native herbivores can have unforeseen effects on plant species composition and landscape physiognomy. Investigations of environmental constraints on vegetation distribution and abundance should take into account the historical role of herbivores in shaping the present system. Inconsistencies among historic accounts of woody plant distribution and abundance in semiarid western North America may be resolved by considering population dynamics of prairie dogs. Widespread eradication of this formerly abundant rodent has eliminated a significant constraint to woody plant establishment on many semiarid grassland and savanna landscapes and has thereby facilitated transitions to shrubland and woodland states. Past land management designed to remove one perceived impediment to livestock production appears to have contributed significantly to development of another management problem that is now a major detriment to sustainable livestock production.

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How Much Sagebrush Is too Much: An Economic Threshold Analysis

Cited by 10 publications

References 20 publications

Supplemental barley and charcoal increase intake of sagebrush by lambs

Supplemental barley and charcoal increase intake of sagebrush by lambs

Spatial patterns in leaf area and plant functional type cover across chronosequences of sagebrush ecosystems

Small-Mammal Regulation of Vegetation Structure in a Temperate Savanna

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