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ARS Home » Pacific West Area » Burns, Oregon » Range and Meadow Forage Management Research » Research » Publications at this Location » Publication #292473
Title: Utilizing national agriculture imagery program data to estimate tree cover and biomass of pinyon and juniper woodlands

Author
item Hulet, April
item ROUNDY, BRUCE - Brigham Young University
item PETERSEN, STEVEN - Brigham Young University
item BUNTING, STEPHEN - University Of Idaho
item JENSEN, RYAN - Brigham Young University
item ROUNDY, DARRELL - Brigham Young University

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/11/2014
Publication Date: 9/1/2014
Publication URL: http://handle.nal.usda.gov/10113/60842
Citation: Hulet, A., Roundy, B.A., Petersen, S.L., Bunting, S.C., Jensen, R.R., Roundy, D.B. 2014. Utilizing national agriculture imagery program data to estimate tree cover and biomass of pinyon and juniper woodlands. Rangeland Ecology and Management. 67:563-572. DOI: 10.2111/REM-D-13-00044.1.

Interpretive Summary: With the encroachment of pinyon and juniper (P-J) woodlands into sagebrush steppe communities, there is an increasing interest in rapid, accurate, and inexpensive quantification methods to estimate tree canopy cover and aboveground biomass over large landscapes. We: 1) evaluated the relationship and agreement between P-J canopy cover extracted using object-based image analysis (OBIA) techniques and National Agriculture Imagery Program (NAIP) imagery with ground-measurements, and 2) investigated the relationship between predicted aboveground biomass using remotely-sensed tree canopy cover and ground-measured aboveground biomass. Remotely-sensed tree canopy cover did not consistently over- or under-estimate P-J tree canopy cover across all sites, and were highly correlated to ground-measurements of tree canopy cover (r = 0.92). Predicted aboveground biomass using remotely-sensed tree canopy cover were also highly correlated with ground-measured aboveground biomass (r = 0.89). While some accuracy and precision may be lost when utilizing aerial imagery to identify P-J canopy cover and aboveground biomass, it is still a good alternative to both time-consuming and expensive ground monitoring and inventory practices.

Technical Abstract: With the encroachment of pinyon (Pinus ssp.) and juniper (Juniperus ssp.) (P-J) woodlands into sagebrush steppe communities, there is an increasing interest in rapid, accurate, and inexpensive quantification methods to estimate tree canopy cover and aboveground biomass over large landscapes. The objectives of this study were to: 1) evaluate the relationship and agreement of P-J canopy cover estimates using object-based image analysis (OBIA) techniques and National Agriculture Imagery Program (NAIP) imagery with ground-measurements; and 2) investigate the relationship between remotely-sensed P-J canopy cover and ground-measured aboveground biomass. For the OBIA, we used eCognition Developer software to extract tree canopy cover from NAIP imagery across 12 P-J woodlands within the Sagebrush Steppe Treatment Evaluation Project (SageSTEP) network. Following tree canopy cover extractions, relationships were assessed between remotely-sensed P-J canopy cover and ground-measured aboveground biomass for each site. Our OBIA classification methods did not consistently over- or under-estimate P-J canopy cover across all sites, and were highly correlated to ground measurements (averaged across all sites r = 0.92). Ground measurements and remotely-sensed measurements were statistically different for western and Utah juniper sites (P < 0.05); differences between methods were more prominent for subplots where tree canopy cover was > 40%. Correlation coefficients were relatively strong between predicted aboveground biomass estimates using remotely-sensed tree canopy cover and ground-measured aboveground biomass (averaged across all sites r = 0.89). Our results suggest that OBIA techniques combined with NAIP imagery can provide land managers with quantitative data that can be used to rapidly evaluate P-J woodlands cover and aboveground biomass on a landscape scale. While some accuracy and precision may be lost when utilizing aerial imagery to identify P-J canopy cover and aboveground biomass, it is still a good alternative to both time-consuming and expensive ground monitoring and inventory practices.