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ForestERA Metadata - Northern Goshawk Nesting Habitat

Abstract

This is a 90m resolution raster dataset describing predicted Northern Goshawk (Accipiter gentilis) nesting habitat across the western Mogollon Plateau in Arizona. It was created as part of the Forest Ecosystem Restoration Analysis (ForestERA) project to support landscape-scale forest restoration planning efforts by a broad group of stakeholders including federal and state agencies, academic institutions, and non-governmental entities.

Purpose

This layer was developed by the ForestERA project for use in landscape-level planning and prioritization of forest management on the western Mogollon Plateau. It was designed for multiple purposes, including prioritization of management actions and assessment of management effects on goshawk populations.

Supplementary Information

We chose two modeling approaches to optimize the use of available information on Northern Goshawk. First, because previous studies documented characteristics of nesting habitat for these species, we used rules developed from the literature to identify the extent of potential nesting habitat on the landscape. This involved a search of the literature to identify a set of variables related to nesting habitat and a range of possible threshold values that might be used to identify areas most likely to support nesting pairs of these raptors. Second, we employed the Mahalanobis distance statistic (hereafter M-distance) to generate a dataset that could be used as a surrogate for habitat "suitability" or "preference". Georeferenced locations of 123 nest sites for Northern Goshawk were obtained from the Arizona Game and Fish Department and studies at Northern Arizona University for use in the modeling effort.

To identify potential nesting habitat, we used publications that described habitat characteristics around Northern Goshawk nest sites, and current management guidelines to choose a range of threshold values. We classified areas with both canopy cover > 40% and basal area > 18 m²/ha as potential nesting habitat for goshawks. We then eliminated patches of habitat smaller than 10ha because these patches would likely be too small to be suitable for nesting. The final extent of potential nesting habitat covered 350,000 ha (43% of the study area).

After delineation of potential nesting habitat, we used M-distance and habitat characteristics at Northern Goshawk Nest sites to develop an index of habitat suitability within potential nesting habitat. M-distance has been used frequently in mathematics and physics to compare the similarity of datasets, but is rarely used in ecology. M-distance is a multivariate statistic that provides a measure of dissimilarity between two multivariate datasets. In this effort, one dataset is the mean vector of habitat characteristics at known Northern Goshawk nest sites while the other dataset is the range of conditions across the entire landscape. The "distance" for any location on the landscape represents the dissimilarity between conditions at that location and the mean habitat conditions at the known nest sites. This value is scaled in multivariate space using the covariance between the measured habitat conditions at the locations used by the species.

We used dominant overstory vegetation, canopy cover, basal area, tree density, slope, and the sine and cosine derivatives of aspect as predictor variables for our M-distance modeling effort. We determined values for each of these variables at Northern Goshawk nest sites by extracting the values from the GIS raster layers using the "zonal statistics" function in ArcGIS Spatial Analyst. We overlaid the nest locations with the raster layers of the predictive variables and determined the value of each raster layer in the pixel corresponding to the nest location. Analysis of characteristics of the 90m (0.81ha) pixel in which each nest fell was deemed appropriate since other studies have shown significant patterns between nest site selection by large raptors and habitat characteristics at scales of approximately 0.5 - 1ha. For purposes of developing the M-distance model we used 2/3 (82) of the nest sites as training data and the remaining 1/3 (42) of the nest sites were withheld for accuracy assessment.

The final habitat layer represents a combination of our two modeling efforts. We classified this layer into 5 categories for purposes of display, analysis, and dissemination. The zero category represents areas not predicted to be suitable for nesting habitat using our simple rules. The remaining 4 categories represent areas of increasing similarity to the mean habitat characteristics at Northern Goshawk nest sites based on M-distance. Fifty percent of nest sites would be expected to fall into category 4, an additional 25% into category 3, an additional 15% into category 2, and the final 10% into category 1.

To test the effectiveness of using threshold values within predictor variables as a means of identifying potential habitat, we used Chi-squared goodness of fit tests to determine whether the potential habitat models did significantly better at predicting locations of Northern Goshawk nests than chance alone. For this analysis we used the entire set of nest sites (n = 123). This analysis suggested that significantly more (101 or 82%) nest sites fell within the predicted extent of potential nesting habitat than would be expected by chance alone (v = 2, X² = 41.6, P < 0.0001).

To test whether the M-distance statistic was effective at identifying the locations of nest sites, we used Chi-squared goodness of fit tests to determine whether the M-distance statistic accurately predicted the number of nests within the test datasets that fell within the portion of the predicted habitat in each of the four categories identified above. For these analyses we used the 1/3 of the nests (n = 41) that were not used as training data for the M-distance model. This analysis showed that the distribution of nests within each habitat category fit the expected distributions (v = 3, X² = 0.24, P = 0.97). This suggests that the simple rules did a good job at defining potential habitat, and that M-distance was effective at predicting the area within potential habitat where a given percentage of nests would be expected to occur.

Status of the data

Complete
Data update frequency: None planned

Time period for which the data is relevant

Date and time: 2000
Description:
publication date

Publication Information

Who created the data: Forest Ecosystem Restoration Analysis Project
Date and time: February 1, 2005.

Data storage and access information

File name: nogohab90m
Type of data: raster digital data
Location of the data:
\\ENVSCI41\Shared\metadata_layers\grids\tesdens90m
\\ENVSCI41\Shared\metadata_layers\grids\tesrecruit90m
Data processing environment: Microsoft Windows 2000 Version 5.0 (Build 2195)
Service Pack 4; ESRI ArcCatalog 8.1.2.671

Accessing the data

Size of the data: 11.172 MB
Data transfer size: 11.172 MB

Constraints on accessing and using the data

Access constraints: This layer may be accessed by any interested party. It is
provided by the Forest Ecosystem Restoration Analysis project, the Ecological
Restoration Institute (ERI), and Northern Arizona University (NAU).
Use constraints: This layer is provided for public use by the ForestERA project, ERI, and NAU. Reports, presentations, and publications in which this layer is presented or
used for analytical purposes should acknowledge the ForestERA project.

Details about this document

Contents last updated: 20040421 at time 14425800

Who completed this document

Forest Ecosystem Restoration Analysis Project
Center For Environmental Sciences and Education:
Northern Arizona University
Flagstaff, Arizona 86011-5694
United States
928-523-0068 (voice)
928-523-7423 (fax)

Contact Instructions

Contact Dr. Thomas D. Sisk or the Forest Ecosystem Restoraton Analysis Project.

Standards used to create this document

Standard name: FGDC Content Standards for Digital Geospatial Metadata
Standard version: FGDC-STD-001-1998
Time convention used in this document: local time
Metadata profiles defining additonal information
ESRI Metadata Profile: http://www.esri.com/metadata/esriprof80.html

Horizontal coordinate system

Projected coordinate system name: NAD_1983_UTM_Zone_12N
Geographic coordinate system name: GCS_North_American_1983
Details
Grid Coordinate System Name: Universal Transverse Mercator
UTM Zone Number: 12
Transverse Mercator Projection
Scale Factor at Central Meridian: 0.999600
Longitude of Central Meridian: -111.000000
Latitude of Projection Origin: 0.000000
False Easting: 500000.000000
False Northing: 0.000000

Planar Coordinate Information

Planar Distance Units: meters
Coordinate Encoding Method: row and column
Coordinate Representation
Abscissa Resolution: 90.000000
Ordinate Resolution: 90.000000

Geodetic Model

Horizontal Datum Name: North American Datum of 1983
Ellipsoid Name: Geodetic Reference System 80
Semi-major Axis: 6378137.000000
Denominator of Flattening Ratio: 298.257222

Bounding coordinates

Horizontal
In decimal degrees
West: -113.044931
East: -109.878536
North: 35.587479
South: 34.107751
In projected or local coordinates
Left: 314687.387285
Right: 601607.387285
Top: 3938195.572581
Bottom: 3775925.572581

Spatial data description

Raster dataset information
Raster format: ESRI GRID
SDTS raster type: Grid Cell
Number of raster bands: 1
Raster properties
Origin location: Upper Left
Has pyramids: FALSE
Has colormap: FALSE
Data compression type: Default
Display type: matrix values
Cell information
Number of cells on x-axis: 3188
Number of cells on y-axis: 1803
Number of cells on z-axis: 1
Number of bits per cell: 32
Cell Size
X distance: 90.000000
Y distance: 90.000000
No detailed attribute information is available.

Last updated March 4, 2005