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Changes in avian and plant communities of aspen woodlands over 12 years after livestock removal in the northwestern Great Basin

Conservation Biology

By:
, , and
DOI: 10.1111/j.1523-1739.2012.01903.x

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Abstract

Riparian and quaking aspen (Populus tremuloides) woodlands are centers of avian abundance and diversity in the western United States, but they have been affected adversely by land use practices, particularly livestock grazing. In 1990, cattle were removed from a 112,500-ha national wildlife refuge in southeastern Oregon. Thereafter, we monitored changes in vegetation and bird abundance in years 1–3 (phase 1) and 10–12 (phase 2) in 17 riparian and 9 snow-pocket aspen plots. On each 1.5-ha plot, we sampled vegetation in 6 transects. Three times during each breeding season, observers recorded all birds 50 m to each side of the plot's 150-m centerline for 25 minutes. We analyzed data with multivariate analysis of variance and paired t tests with p values adjusted for multiple comparisons. In both periods, riparian and snow-pocket aspen produced extensive regeneration of new shoots (x̄ = 2646 stems/ha and 7079 stems/ha, respectively). By phase 2, a 64% increase in medium-diameter trees in riparian stands indicated successful recruitment into the overstory, but this pattern was not seen in snow-pocket stands, where the density of trees was over 2 times greater. By phase 2 in riparian and snow-pocket stands, native forb cover had increased by 68% and 57%, respectively, mesic shrub cover had increased by 29% and 58%, and sagebrush cover had decreased by 24% and 31%. Total avian abundance increased by 33% and 39% in riparian and snow-pocket aspen, respectively, ground or understory nesters increased by 133% and 67% and overstory nesters increased by 34% and 33%. Similarly, ground or understory foragers increased by 25% and 32%, aerial foragers by 55% and 57%, and overstory foragers by 66% and 43%. We interpreted the substantial regeneration of aspen shoots, increased densities of riparian forbs and shrubs, and increased avian abundances as a multitrophic-level response to the total removal of livestock and as substantial movement toward recovery of biological integrity.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Changes in avian and plant communities of aspen woodlands over 12 years after livestock removal in the northwestern Great Basin
Series title:
Conservation Biology
DOI:
10.1111/j.1523-1739.2012.01903.x
Volume
26
Issue:
5
Year Published:
2012
Language:
English
Publisher:
Society for Conservation Biology
Publisher location:
Washington, D.C.
Contributing office(s):
Forest and Rangeland Ecosystem Science Center
Description:
11 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Conservation Biology
First page:
862
Last page:
872
Country:
United States
Other Geospatial:
Aspen Woodlands;Great Basin