| Patrick E. Clark and Mark S. Seyfried |
| Authors are range scientist and soil scientist, USDA Agricultural Research Service, 800 Park Blvd., Plaza IV, Suite 105, Boise, Ida. 83712. |
Abstract |
| Although point sampling has been used for more than 30 years to quantify leaf area index (LAI), this field technique has not been rigorously evaluated in sagebrush steppe plant communities. Leaf area index estimates obtained using different sampling pin inclinations or combinations of pin inclinations were evaluated in Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle and Young), low sagebrush (Artemisia arbuscula Nutt.), and mountain big sagebrush (Artemisia tridentata Nutt. ssp. vaseyana [Rydb.] Beetle) communities within the Reynolds Creek Experimental Watershed near Boise, Ida. Leaf area index values determined by clipping and processing green foliage through a leaf area meter were used as evaluation standards. Pins inclined at 13° from the horizontal, used alone or in combination with pins of 52° and/or 90° inclinations, performed poorly for estimating LAI in the Wyoming big sagebrush and low sagebrush communities. Estimating total LAI with either the combination of 52° and 90° angle pins or with 52° or 90° pins alone explained at least 96% of the variability in LAI standard values from the Wyoming big sagebrush and mountain big sagebrush communities. Using 52° angle pins alone produced model fits similar to those obtained when the combination of 52o and 90° angle pins were used to estimate shrub, graminoid, and forb LAI across all 3 communities (P > 0.1). Collecting point data using 52° angle pins often provided better or similar model fits with LAI standards compared to other pin angles but using 90°angle pins offers a better compromise between practicality, efficiency, and accuracy. |
| Key Words: Artemisia arbuscula, Artemisia tridentata ssp. vaseyana, Artemisia tridentata ssp. wyomingensis, LAI, low sagebrush, mountain big sagebrush, Wyoming big sagebrush |