Point sampling for leaf area index in sagebrush steppe communities

Although point sampling has been used for more than 30 years to quantify le af 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 inclinatio ns 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 nea r 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 degrees from the horizontal, used alone or in combinati on with pins of 52 degrees and/or 90 degrees inclinations, performed poorly for estimating LAI in the Wyoming big sagebrush and low sagebrush communit ies. Estimating total LAI with either the combination of 52 degrees and 90 degrees angle pins or with 52 degrees or 90 degrees pins alone explained at least 96% of the variability in LAI standard values from the Wyoming big s agebrush and mountain big sagebrush communities. Using 52 degrees angle pin s alone produced model fits similar to those obtained when the combination of 52 degrees and 90 degrees angle pins were used to estimate shrub, gramin oid, and forb LAI across all 3 communities (P > 0.1). Collecting point data using 52 degrees angle pins often provided better or similar model fits wi th LAI standards compared to other pin angles but using 90 degrees angle pi ns offers a better compromise between practicality, efficiency, and accurac y.