Summary: The Institute for Natural Resources (INR) and The Nature Conservancy produced a 30-meter resolution tree canopy cover raster dataset for the area defined by distribution of Greater Sage-Grouse in Oregon.
Purpose: Trees, particularly Western Juniper (Juniperus occidentalis) can have a profound negative impact on Sage-Grouse. Juniper, while a native species to Oregon, has been expanding its range 600% in the last 150 years by some estimates. When junipers expand and begin to dominate they cause drastic changes in habitat, shifting species composition and structure with corresponding changes in available food and shelter for species like the Sage-Grouse. In addition Sage-Grouse demonstrate an avoidance of trees and other tall vertical structures, perhaps due to use by avian predators as perches, resulting in up to 90% reduction in nesting activity. The Nature Conservancy has partnered with the Sage-Grouse Initiative to document these impacts and to inform effective ways to address this problem. In order to better understand this issue and support efficient targeting of restoration efforts in Oregon we have partnered with INR to accurately map trees across SE OR.
Methodology: Nested Texture Metrics (NTM) was developed at the INR (Nielsen and Noone 2014). This methodology uses 1-meter aerial imagery from the National Agricultural Imagery Program (NAIP) and 30-meter Landsat imagery to create texture and spectral information at multiple spatial scales to distinguish crowns and cover of trees of seven feet and greater height from the surrounding land. Canopy cover was treated as a categorical variable using six cover classes: absent, present at less than 4%, 4 – 10%, 10 – 20%, 20 – 50%, and > 50%. The imagery used to create this product is from the years 2011 and 2012.
Accuracy & Scope: An accuracy comparison was completed in three areas in SE Oregon to compare the NTM tree cover class results with those of six other methods and independent datasets. The NTM method had significantly higher accuracies (exact class accuracy 57.8%, fuzzy class accuracy 92.8%) than all other methods (Nielsen, Poznanovic and Popper 2014). Because it uses sources that are regularly available (NAIP and Landsat), NTM is repeatable.
This dataset represents cover of all vegetation over 7 feet high for the 29 million acre area in SE Oregon. Within known sage-grouse habitat, it is likely that nearly all the trees represented are western juniper (Juniperus occidentalis).
For more information: Please contact the Institute for Natural Resources or The Nature Conservancy in Oregon with questions about the data and info on development of NTM methods for additional areas or vegetation types. The most recent version of this dataset, as well as many others can be found on the
Oregon Explorer SageCon website.
