Estimated Percent Cover of Bromus tectorum (cheatgrass)

Metadata:

• Identification_Information
• Data_Quality_Information
• Spatial_Data_Organization_Information
• Spatial_Reference_Information
• Entity_and_Attribute_Information
• Distribution_Information
• Metadata_Reference_Information

Identification_Information:

Citation:

Citation_Information:

Originator: Nevada Natural Heritage Program: Eric B. Peterson

Publication_Date: December 2003

Title: Estimated Percent Cover of Bromus tectorum (cheatgrass)

Geospatial_Data_Presentation_Form: raster digital data

Other_Citation_Details:

Peterson, E. B. 2003. Mapping Percent-Cover of the Invasive Species Bromus tectorum (Cheatgrass) over a Large Portion of Nevada from Satellite Imagery. Report for the U.S. Fish and Wildlife Service, Nevada State Office, Reno, by the Nevada Natural Heritage Program, Carson City.

Online_Linkage: <http://www.heritage.nv.gov/gis/gis.htm>

Description:

Abstract:

SUMMARY FROM ASSOCIATED REPORT: Bromus tectorum (cheatgrass) is an annual grass from Eurasia that has invaded western rangelands. It frequently invades landscapes after wildfire, forming dense stands with fine fuels that shorten typical fire intervals. Thus B. tectorum and wildfire form a positive feedback mechanism that threatens native ecosystems and often impact the rare and endangered species those ecosystems host. It is not an understatement to say that B. tectorum is among the greatest threats to conservation in the intermountain west. Elimination of B. tectorum from the landscape is unrealistic with current technology. Instead, we must learn to manage rangelands so as to minimize the dispersal and establishment of B. tectorum, and to promote the reestablishment of native vegetation after disturbances such as wildfire. Key to such management is a strong understanding of where B. tectorum has invaded the landscape and how dense it has become. With this need in mind, the Nevada Natural Heritage Program set out to map B. tectorum over a large portion of the state of Nevada. A portion of this area was used to test how well the mapping method could be extended to areas beyond the training area. The mapping method involved developing a statistical model for the estimation of B. tectorum cover at training plots with variables derived from satellite imagery and matching topographic data. The model was then applied to each 28.5 X 28.5 meter pixel in the satellite images. Map accuracy was then determined as Root-Mean-Square Error (RMSE) at additional accuracy assessment plots. Sample plots involved an ocular estimation of percent ground-cover of B. tectorum over a circular area of 0.1 hectares. Training data included 262 sampled plots scattered throughout an original (northern 2/3) mapping area. These plots were located arbitrarily to include a broad variety of landscape conditions. For accuracy assessment, an additional 75 plots were sampled. These assessment plots were located throughout the entire mapping area with a constrained-random distribution: random within public lands and within 1 kilometer of a significant road. Landsat 7 ETM+ satellite data were obtained for two time periods in order to use the unusual early phenology (green-up and senescence) of B. tectorum as the primary component of the mapping method. The Normalized Differential Vegetation Index (NDVI) was calculated for each time period and the difference in NDVI between the time periods was then used as the measure of phenology across the landscape. This measure of phenology corresponded well to the cover of B. tectorum at the training plots and formed the most important factor in the mapping model. Additional factors that were found statistically significant and decreased error were elevation and the green spectrum band of the satellite image from the senescence-period. Additionally the average pixel brightness was used to bound maximum estimations, reducing error for particularly bright areas of the imagery such as playas and dark areas such as lakes. Post-modeling edits included cultivated fields, urban areas, clouds and their shadows, and a few shallow water bodies where the estimated cover was greater than zero. The resulting map covers of 32.8 million acres within Nevada, or 46.4 % of the state, plus an additional 2.5 million adjacent acres in neighboring states for potential edge-matching with future mapping projects. The 75 accuracy assessment plots indicate a map-wide RMSE of 9.14 %. To examine how well the model extended to the area beyond the area sampled for training data, accuracy assessment plots were split into two groups: those from the trained portion of the map and those from the untrained portion. Accuracy assessment plots from the trained portion indicate an RMSE of 12.0 %, while plots from the untrained portion indicate an RMSE of 2.8 %. These results are surprising, however the untrained portion of the map includes a great deal of land without B. tectorum, so these results are largely indicating that there is greater accuracy in the prediction of absence or low cover of B. tectorum, than in the prediction of the precise cover amount where it is abundant. These results at least do not indicate any problem with extending the model to areas within 100 km of the training area, where B. tectorum invasion is low.

Purpose:

These data are intended to guide conservation and land management, though no actions should be taken based on these data without on-the-ground verification in the project area.

Supplemental_Information:

Recommended Citation: Peterson, E. B. 2003. Mapping Percent-Cover of the Invasive Species Bromus tectorum (Cheatgrass) over a Large Portion of Nevada from Satellite Imagery. Report for the U.S. Fish and Wildlife Service, Nevada State Office, Reno, by the Nevada Natural Heritage Program, Carson City.

Time_Period_of_Content:

Time_Period_Information:

Multiple_Dates/Times:

Single_Date/Time:

Calendar_Date: Publication: December 2003

Single_Date/Time:

Calendar_Date: Effective map: Spring 2001

Currentness_Reference:

Source imagery from 2001, training and assessment data from 2002-2003. Map is effectively for cheatgrass cover in 2001.

Status:

Progress: Complete

Maintenance_and_Update_Frequency: As further data becomes available.

Spatial_Domain:

Bounding_Coordinates:

West_Bounding_Coordinate: -119.998290

East_Bounding_Coordinate: -114.905975

North_Bounding_Coordinate: 42.244567

South_Bounding_Coordinate: 37.952151

Keywords:

Theme:

Theme_Keyword: Bromus tectorum

Theme_Keyword: cheatgrass

Theme_Keyword: percent cover

Theme_Keyword: Tobit Regression

Theme_Keyword: Phenology

Place:

Place_Keyword: Nevada

Temporal:

Temporal_Keyword: 2001

Temporal_Keyword: 2002

Temporal_Keyword: 2003

Access_Constraints: Data are for public access; appropriate citation is required.

Use_Constraints: Acknowledgement of error level (RMSE = 9.14 % )

Point_of_Contact:

Contact_Information:

Contact_Person_Primary:

Contact_Person: Eric B. Peterson

Contact_Organization: Nevada Natural Heritage Program

Contact_Position: Vegetation Ecologist

Contact_Address:

Address_Type: mailing and physical address

Address: 901 S Stewart St #5002

City: Carson City

State_or_Province: NV

Postal_Code: 89701-5245

Country: USA

Contact_Voice_Telephone: 775-684-2906

Contact_Facsimile_Telephone: (775) 684-2909

Contact_Electronic_Mail_Address: peterson@heritage.nv.gov

Data_Set_Credit:

Peterson, E. B. 2003. Mapping Percent-Cover of the Invasive Species Bromus tectorum (Cheatgrass) over a Large Portion of Nevada from Satellite Imagery. Report for the U.S. Fish and Wildlife Service, Nevada State Office, Reno, by the Nevada Natural Heritage Program, Carson City.

Native_Data_Set_Environment:

Microsoft Windows 2000 Version 5.1 (Build 2600) Service Pack 1; ESRI ArcCatalog 8.2.0.700

Cross_Reference:

Citation_Information:

Title:

Peterson, E. B. 2003. Mapping Percent-Cover of the Invasive Species Bromus tectorum (Cheatgrass) over a Large Portion of Nevada from Satellite Imagery. Report for the U.S. Fish and Wildlife Service, Nevada State Office, Reno, by the Nevada Natural Heritage Program, Carson City.

Data_Quality_Information:

Attribute_Accuracy:

Attribute_Accuracy_Report:

From 75 near-random accuracy assessment plots, RMSE = 9.14 percent, and estimated vs measured cover R-squarred = 0.51.

Positional_Accuracy:

Horizontal_Positional_Accuracy:

Horizontal_Positional_Accuracy_Report:

Imagery georeferenced to UTM zone 11, NAD 27 projection of Southwest Regional GAP summer images with positional RMSE < 1 pixel (30 m) over 50+ reference points.

Lineage:

Process_Step:

Process_Description:

See report: Peterson, E. B. 2003. Mapping Percent-Cover of the Invasive Species Bromus tectorum (Cheatgrass) over a Large Portion of Nevada from Satellite Imagery. Report for the U.S. Fish and Wildlife Service, Nevada State Office, Reno, by the Nevada Natural Heritage Program, Carson City.

Process_Date: December 2003

Process_Step:

Process_Description: Dataset copied.

Source_Used_Citation_Abbreviation: W:\Share\final\lm5a-smwc-au

Process_Step:

Process_Description: Dataset moved.

Source_Used_Citation_Abbreviation: W:\BRTE-Report\brte

Cloud_Cover: 2 %

Spatial_Data_Organization_Information:

Direct_Spatial_Reference_Method: Raster

Raster_Object_Information:

Raster_Object_Type: Grid Cell

Row_Count: 16585

Column_Count: 14749

Vertical_Count: 1

Spatial_Reference_Information:

Horizontal_Coordinate_System_Definition:

Planar:

Grid_Coordinate_System:

Grid_Coordinate_System_Name: Universal Transverse Mercator

Universal_Transverse_Mercator:

UTM_Zone_Number: 11

Transverse_Mercator:

Scale_Factor_at_Central_Meridian: 0.999600

Longitude_of_Central_Meridian: -117.000000

Latitude_of_Projection_Origin: 0.000000

False_Easting: 500000.000000

False_Northing: 0.000000

Planar_Coordinate_Information:

Planar_Coordinate_Encoding_Method: row and column

Coordinate_Representation:

Abscissa_Resolution: 28.500000

Ordinate_Resolution: 28.500000

Planar_Distance_Units: meters

Geodetic_Model:

Horizontal_Datum_Name: North American Datum of 1927

Ellipsoid_Name: Clarke 1866

Semi-major_Axis: 6378206.400000

Denominator_of_Flattening_Ratio: 294.978698

Entity_and_Attribute_Information:

Detailed_Description:

Entity_Type:

Entity_Type_Label: brte

Attribute:

Attribute_Label: ObjectID

Attribute_Definition: Internal feature number.

Attribute_Definition_Source: ESRI

Attribute_Domain_Values:

Unrepresentable_Domain:

Sequential unique whole numbers that are automatically generated.

Attribute:

Attribute_Label: Value

Attribute_Definition: Estimated Percent Cover (101 = cultivation, 102 = urban)

Attribute_Definition_Source:

Peterson, E. B. 2003. Mapping Percent-Cover of the Invasive Species Bromus tectorum (Cheatgrass) over a Large Portion of Nevada from Satellite Imagery. Report for the U.S. Fish and Wildlife Service, Nevada State Office, Reno, by the Nevada Natural Heritage Program, Carson City.

Attribute_Value_Accuracy_Information:

Attribute_Value_Accuracy: RMSE = 9.14 percent

Attribute:

Attribute_Label: Count

Overview_Description:

Distribution_Information:

Resource_Description: Downloadable Data

Standard_Order_Process:

Digital_Form:

Digital_Transfer_Information:

Transfer_Size: 103.024

Metadata_Reference_Information:

Metadata_Date: 20040105

Metadata_Contact:

Contact_Information:

Contact_Organization_Primary:

Contact_Organization:

REQUIRED: The organization responsible for the metadata information.

Contact_Person: REQUIRED: The person responsible for the metadata information.

Contact_Address:

Address_Type:

REQUIRED: The mailing and/or physical address for the organization or individual.

City: REQUIRED: The city of the address.

State_or_Province: REQUIRED: The state or province of the address.

Postal_Code: REQUIRED: The ZIP or other postal code of the address.

Contact_Voice_Telephone:

REQUIRED: The telephone number by which individuals can speak to the organization or individual.

Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata

Metadata_Standard_Version: FGDC-STD-001-1998

Metadata_Time_Convention: local time

Metadata_Extensions:

Online_Linkage: <http://www.esri.com/metadata/esriprof80.html>

Profile_Name: ESRI Metadata Profile