Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 1/19/2004
Publication Date: 1/24/2004
Citation: ROSE, J., VERMEIRE, L.T., WESTER, D.B. ESTIMATING STANDING CROP WITH VISUAL OBSTRUCTION IN THE NORTHERN PLAINS. SOCIETY FOR RANGE MANAGEMENT MEETING ABSTRACTS. NO. 309. 2004. Interpretive Summary:
Technical Abstract: Visual obstruction (VO) has been used successfully as a non-destructive, herbage standing crop estimation method in southern tallgrass, mixed prairie, and shortgrass plains. This method has not proven as successful in the Northern Great Plains. Forty-six VO trials were conducted to determine the effectiveness of VO and assess observer differences in northern mixed prairie. Data were collected throughout the growing season on upland, lowland and hillside sites near Miles City, Mont. Experienced observers explained the concept independently to novice observers with no attempt at standardizing readings. A single observer read VO from one direction and recorded readings in 2-cm increments within 15 or 20, 0.10-m2 quadrats per trial. Herbage was clipped to ground-level to determine standing crop. Standing crop was regressed on VO using trial means. Model coefficients differed among observers, but an r2 of 0.91 was maintained after pooling data from 3 of 4 observers. The fourth model differed from the combined model only in intercept. We believe this difference was caused by one observer defining obstruction more strictly. Similarity in slopes indicates the relationship between VO and standing crop is consistent. However, training should be provided to ensure readings are uniform among observers and a single model can be used. Standing crop SD across observers was 329 kg ha-1 and residual SD was 109 kg ha-1. Models differed from those developed in the Southern Plains, but r2 values were similar. More trials are required to determine the effectiveness of VO across seasons and years in northern mixed prairie.