ARS | Publication request: A PHOTO-BASED TECHNIQUE FOR MONITORING WILLOW ABUNDANCE AND UTILIZATION

Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: December 20, 2003
Publication Date: January 15, 2004
Citation: BOYD, C.S., SVEJCAR, A.J. A PHOTO-BASED TECHNIQUE FOR MONITORING WILLOW ABUNDANCE AND UTILIZATION. SOCIETY FOR RANGE MANAGEMENT MEETING ABSTRACTS. 2004.

Technical Abstract: Quantifying willow abundance has often proven difficult in the field for reasons that include irregular morphology of willow plants, between observer variability, and lack of standardized techniques. One potential solution to these challenges is the use of ground-based photographic technology. Our objective was to develop a photo-based technique could be used to: 1) monitor changes in willow abundance over time and 2) estimate within season utilization by herbivores. We focused on young willows (< 2m in height) because this size class represents a critical life history stage for establishment of willow clumps. In August of 2000 and 2001 we cut 25 willow (Salix boothii) clumps at ground level and clamped them in front of a 150 x 200cm fluorescent orange photo-board. Clumps were defoliated of current years growth (CYG - twig tip and leaves) by hand in 5 to 7 increments and photographed before and after each removal. Images were scanned to digital format and the number of visible photoboard pixels was determined using Adobe Photoshop 4.0 software. Regression analysis indicated that visible pixels were a good predictor of both total clump CYG weight (R2 = 0.89, p < 0.01) as well as CYG weight remaining following sequential defoliations (R2= 0.91, p < 0.01). These results suggest the monitoring technique provides a reliable index of both willow abundance and utilization within the size class of willow tested. Results may differ using larger willows with increased woody biomass. Research is needed to determine inter-species variability in the relationships described above.