title: Feature extraction techniques for measuring piñon and juniper tree cover and density, and comparison with field-based management surveys.
abstract: Western North America is experiencing a dramatic expansion of piñon (Pinus spp.) and juniper (Juniperus spp.) (P-J) trees into shrub-steppe communities. Feature extracted data acquired from remotely sensed imagery can help managers rapidly and accurately assess this land cover change in order to manage rangeland ecosystems at a landscape-scale. The objectives of this study were to: (1) develop an effective and efficient method for accurately quantifying P-J tree canopy cover and density directly from high resolution photographs and (2) compare feature-extracted data to typical in-situ datasets used by land managers. Tree cover was extracted from aerial-photography using Feature Analyst®. Tree density was calculated as the sum of the total number of individual polygons (trees) within the tree cover output file after isolation using a negative buffer post-processing technique. Feature-extracted data were compared to ground reference measurements from Utah's Division of Wildlife Resources Range Trend Project (DWR-RTP). We found that the proposed feature-extraction techniques used for measuring cover and density were highly correlated to ground reference and DWR-RTP datasets. Feature-extracted measurements of cover generally showed a near 1:1 relationship to these data, while tree density was underestimated; however, after calibration for juvenile trees, a near 1:1 relationship was realized. Feature-extraction techniques used in this study provide an efficient method for assessing important rangeland indicators, including: density, cover, and extent of P-J tree encroachment. Correlations found between field and feature-extracted data provide evidence to support extrapolation between the two approaches when assessing woodland encroachment.
authors.affiliation: USDA - Agricultural Research Service, Eastern Oregon Agricultural Research Center, Burns, OR, USA. matthew.madsen@oregonstate.edu
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Madsen
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Zvirzdin
authors.forename: Bracken D
authors.initials: BD
authors.lastname: Davis
authors.forename: Steven L
authors.initials: SL
authors.lastname: Petersen
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Roundy
mesh_terms: D003247:Conservation of Natural Resources / Q000379:methods*; D003625:Data Collection; D018653:Juniperus; D028223:Pinus