ABSTRACT
We employ a multi-scale approach to examine the evolving spatial
patterns of avian diversity following rewatering (1991-1999) of the Owens
River Gorge in eastern California. We
based our analysis on three independent data sets representing 18 canyon
locations (4 reference and 14 rewatered) consisting of bird counts, measures of
landscape variation (canyon dimensions), and vegetation structure and
composition (foliage height diversity, total vegetation volume, and
plant species diversity). We analyzed
our data by grouping sites according to bird diversity and environmental
factors using Sørenson's similarity index and cluster analysis, and by
employing correlation (Spearman rank) and regression (multiple and backward
stepwise) procedures to determine the relative importance of environmental
factors on avian diversity at different spatial scales. Our results reveal: 1) valley bottom width
determines the extent of riparian vegetation (rs =
.73, p < .01) and indirectly, bird species diversity (rs = .52, p < .05) at the
landscape scale and 2) avian diversity at the habitat scale is most strongly correlated
with plant species diversity (rs
= .57, p < .05). These results indicate avian diversity is
responding to habit restoration resulting from the rewatering of the Owens
River Gorge but is spatially constrained by canyon dimensions that limit the
area of riparian habitat and indirectly, plant species diversity. We suggest future evaluations of stream
restoration and its role on animal communities consider the merits of a
multi-scale analysis.