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Landscape characteristics of disturbed shrubsteppe habitats in southwestern Idaho (USA)

Landscape Ecology

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Abstract

We compared 5 zones in shrubsteppe habitats of southwestern Idaho to determine the effect of differing disturbance combinations on landscapes that once shared historically similar disturbance regimes. The primary consequence of agriculture, wildfires, and extensive fires ignited by the military during training activities was loss of native shrubs from the landscape. Agriculture created large square blocks on the landscape, and the landscape contained fewer small patches and more large shrub patches than non-agricultural areas. In contrast, fires left a more fragmented landscape. Repeated fires did not change the distribution of patch sizes, but decreased the total area of remaining shrublands and increased the distance between remaining shrub patches that provide seed sources. Military training with tracked vehicles was associated with a landscape characterized by small, closely spaced, shrub patches. Our results support the general model hypothesized for conversion of shrublands to annual grasslands by disturbance. Larger shrub patches in our region, historically resistant to fire spread and large-scale fires because of a perennial bunchgrass understory, were more fragmented than small patches. Presence of cheatgrass (Bromus tectorum), an exotic annual, was positively related to landscape patchiness and negatively related to number of shrub cells. Thus, cheatgrass dominance can contribute to further fragmentation and loss of the shrub patch by facilitating spread of subsequent fires, carried by continuous fuels, through the patch. The synergistic processes of fragmentation of shrub patches by disturbance, invasion and subsequent dominance by exotic annuals, and fire are converting shrubsteppe in southwestern Idaho to a new state dominated by exotic annual grasslands and high fire frequencies.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Landscape characteristics of disturbed shrubsteppe habitats in southwestern Idaho (USA)
Series title:
Landscape Ecology
Volume
12
Issue:
5
Year Published:
1997
Language:
English
Contributing office(s):
Forest and Rangeland Ecosystem Science Center
Description:
p. 287-297
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Landscape Ecology
First page:
287
Last page:
297
Number of Pages:
11