landscape dynamics of bird and small mammal communities in sagebrush- dominated mountain meadows...
TRANSCRIPT
Landscape dynamics of bird and small mammal communities in sagebrush-
dominated mountain meadows
Tammy L. WilsonMS candidateUSGS Utah Cooperative Fish and Wildlife Research UnitDepartment of Forest, Range, and Wildlife SciencesUtah State University
Committee:John A. BissonetteThomas C. Edwards Jr.James A. MacMahon
Overview
• Status of sagebrush-steppe ecosystems• Species that use sagebrush habitats• Project goals and organization• Methodology• L+1 level analysis
– Pattern and process– What is a landscape?– Thinking outside of the box– Choosing the right scale– Vector analysis
• Brief summary
Knick et al. 2003. Teetering on the edge or too late? Conservation and research issues for avifauna of sagebrush habitats. The Condor. 105:611-634
Status of Sagebrush-steppe ecosystems in the Western United States
excluding Arizona and New Mexico
Sagebrush Obligates of Management Concern (SO)
– Sage Sparrow– Brewer’s Sparrow*– Sage Thrasher– Greater Sage-grouse– Pygmy Rabbit– Sagebrush Vole *– Least Chipmunk*
* Species Observed Greater Sage-grouseUSFWS- Mountain and Prairie Region http://mountain-prairie.fws.gov/species/birds/sagegrouse/
• Species that require sagebrush for some portion of their life history
• Species that commonly use sagebrush but do not require it– 33 species of birds– 19 species of small mammals
Sagebrush Near-Obligates (SNO)
Project Goal• Determine the contribution of high elevation sagebrush
steppe to bird and small mammal species diversity patterns
• Determine whether or not high elevation sagebrush provides a refuge for sagebrush obligate species
Tammy Wilson Jason Robinson, and Joel Ulmer cleaning mammal traps
Beth Johnson, Ruth Kikkert, and Ron Daigle trapping small mammals
Hierarchy TheoryTwo Masters Thesis projects will be divided using a conceptual hierarchy based on the triadic approach
The conceptual hierarchy
– L Project focal level is the animal community within a sagebrush meadow
– L+1 Tammy Wilson is focusing on the influence of meadow arrangement on bird and small mammal diversity and density
– L-1 Beth Johnson is examining the relationship between meadow characteristics and bird and small mammal diversity and density
Objectives
• Assess the influence of meadow arrangement on bird and small mammal diversity and density of selected species (supplementation and complementation processes)
Tammy Wilson collecting Vegetation data
Study Area
Wasatch-Cache National Forest in Northern Utah
Methods
First Tier Randomization
• Designed to reduce pseudoreplication at both levels of observation
• 50 Random points generated within the study area using a dispersion interval of 2500m
Methods• Meadows in an area around the points were digitized
using DOQQs• The meadow closest to the randomly selected point was
chosen as the focal meadow of interest
Methods• Meadows were sampled if they met the following
criteria– on public land– contain at least some sagebrush– within 5km for birds or 1km for mammals of a road– contained within a forested matrix (evaluated using a
6 km2 buffer)– mostly less than 50% slope
• 36 Meadows were sampled for birds and 11 for mammals in the summers of 2003 and 2004
• Each meadow was sampled only once
MethodsSecond Tier Randomization• 2-10 sub-sample points were placed in each
focal meadow– 100 or so Sub-sample points were randomly placed
within the meadow– Points were evaluated in order until no more points fit
in the meadow or 10 points were selected• 250m apart • occur on a slope less than 50%• not in water• not in a group of trees• excess points were deleted
Methods
• Birds and Vegetation were measured at each sub-sample point
• Mammals and soil characteristics were measured at the first 2 sub-sample points in selected meadows
• The bird and mammal data became the response variable for both L+1 and L-1 level analyses
Mammals
• Mammals were trapped using a 50m radius trap web with 8 arms
• Sherman live traps and Victor snap traps were placed at the center, 5m, 10m, 20m, 30m, 40m, and 50m points along each arm of the web
Mammals Trapped1128 Total observations16 Species observed1 SO observed4 SNOs observed
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22
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11
722
178
5553
commonDeer MouseLeast ChipmunkUinta ChipmunkGreat Basin pocket mouseRed-Backed VoleMontane VoleLong-Tailed VoleSnowshoe HareUnknown VoleGolden-Mantled Ground SquirrelUinta Ground SquirrelWestern Jumping MouseUnknown MouseUnknownNorthern Pocket GopherShort-Tailed WeaselUnknown Pocket GopherNorthern Flying SquirrelRock SquirrelLong-tailed Weasel
Birds
• Fixed-radius point counts conducted for 8 minutes at each sub-sample point
• The double observer method was used for each point count
• All birds seen or heard were recorded
• Distance and bearing was measured to each bird
Birds Observed3615 Total observations82 Species Observed1 SO observed14 SNOs observed
10 M
ost c
omm
on s
peci
esLe
ss c
omm
on S
NO
sCommon Name
Green-tailed Towhee Unknown BirdAmerican RobinBrewer's Sparrow Chipping SparrowRuby-crowned KingletDark-eyed Junco Mountain ChickadeeHermit ThrushDusky FlycatcherWhite-crowned Sparrow Vesper Sparrow MacGillivray's WarblerYellow WarblerOrange-crowned WarblerBrewer's BlackbirdWestern MeadowlarkSong SparrowWilson's WarblerSwainson's ThrushGrasshopper SparrowGray Flycatcher
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98
441
419
324245
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Objectives
• Assess the influence of meadow arrangement on bird and small mammal diversity and density of selected species
Tammy Wilson collecting bird data
• Our study area contains sagebrush patches within a forested matrix
• Habitat obligates can exist in patchy landscapes through complementation and/or supplementation of resources (Dunning et al. 1992)
Dunning, J. B., B. J. Danielson, and H. R. Pulliam. 1992. Ecological processes that affect populations in complex landscapes. Oikos. 65:169-175
Linking Pattern and Process
• Complementation– If non-substitutable resources
are located in different patches, “the presence of resources in one patch is complemented by the close proximity of the resources in a second patch.”
• Supplementation– If habitat patches are too small
to support a population or individual, then necessary resources can be supplemented by using adjacent patches.
A
B
A
B
Figures adapted from Dunning et al. 1992
Elements of complementation and supplementation
• Proximity of adjacent meadows– Supplementary or complementary resources
will have to be near enough for use by the individual or population
• Size of focal meadow and adjacent meadows– The amount of resources contained within
adjacent patches will be a function of their size
What is a Landscape?
• Landscape metrics are typically calculated on a classified satellite imagery with a fixed grain, using an arbitrary extent
• Organisms scale allometrically to their surroundings, so choice of right scale resolution and extent is important
• We intend do detect many organisms, making it difficult to use any one species life history to define scale parameters
• Without modification, these problems may limit our ability to detect important ecological phenomena
Effects of decreasing landscape extent• Large patches are
truncated and edge effects are magnified
• Rare classes are reduced or lost
• Landscape metrics will change making them difficult to interpret
Thinking outside of the box
• By eliminating the ‘landscape’ with a fixed grain and extent, we tend to eliminate the problems associated with the box and the image simultaneously– We already have a vector coverage of our digitized
meadows– Patch size and distance to nearest, next, 3rd, 4th, 5th…
nearest meadows can be measured directly with a vector analysis
– Results are much easier to interpret, because scale-related problems are reduced
Vector analysis• Create centroids in each
adjacent polygon• Measure distance to the
adjacent polygons of interest
• Create logistic regression relating presence/absence of selected SO or SNO species to distance and size of adjacent meadows
• Extract amazing story about patch arrangement and ecological processes of supplementation and/or complementation
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Thinking outside of the boxPart 2
• But we don’t get to ignore scale effects altogether because we still need to know how close a meadow needs to be in order to affect ecological process– J. Bowman related territory size and dispersal
distance of birds and small mammals– Others, including C. S. Holling, related body size and
territory size– C. S. Holling also noticed that body sizes tended to be
clumped– Maybe there is a way to use this to get at the proper
scale (extent) to use for our analysis
Choosing the right scale
• Published data on our most commonly observed species can be analyzed using Bowman’s equations
• The accuracy of these equations can be checked where we have both home range and dispersal data
• The robustness of these equations can be tested by adding our species and re-running Bowman’s analysis
• These relationships can be used to guide scale extent choices if there is a reasonable amount of overlap amongst species.
Summary• Preliminary observations
– Only 2 or maybe 3 of 7 SOs and 18 of 52 SNOs were observed
– Preliminary results suggest that small mammal diversity is lower (16 observed vs. 22 SO/SNO), and bird diversity higher (82 observed vs. 37 SO/SNO) in montane sagebrush patches than in contiguous low-elevation sagebrush
• Future analyses– Linking patch arrangement to species diversity and
habitat-specialist presence/absence– Analysis of published body mass, home range, and
dispersal data to determine the scale important to detected species
Acknowledgements
• Beth Johnson• Committee
– John Bissonette– Tom Edwards– Jim MacMahon
• Technicians– Ron Daigle – Ruth Kikkert – Jason Robinson– Joel Ulmer– Mark Johnson– Dave Johnson– Robert lloyd Morris
• Funding– United States Forest
Service– USGS Utah Cooperative
Fish and Wildlife Research Unit
Questions…