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TWO-STAGE SAMPLING FOR RARE RESOURCES: SAMPLING WETLANDS IN THE JUNIATA WATERSHED OF PENNSYLVANIA
Citation:
Stevens, D. L., D. Waldrup, M E. Kentula, AND R. Brooks. TWO-STAGE SAMPLING FOR RARE RESOURCES: SAMPLING WETLANDS IN THE JUNIATA WATERSHED OF PENNSYLVANIA. Presented at Annual meeting of the International Environmetrics Society, Portland, OR, August 13-17, 2001.
Description:
The National Wetland Inventory (NWI) is the most complete catalog of wetland location, type, and extent that is presently available. As such, it is the default frame for developing a survey to assess wetland condition. However, experience suggests that the NWI may miss a substantial portion of smaller wetlands in forested watersheds, possibly resulting in significant undercoverage.
To address this potential deficiency, a two-stage sample design was utilized. Landscape features where wetland occurrence was likely were identified, and a first-stage point sample was selected from these features. An area around each sample point was examined for wetlands, and a second-stage sample was selected from the identified wetland area. A second sample was selected using only NWI-identified wetlands. Condition measurements were made on both samples.In this paper, we develop estimators using the two-stage sample and the NWI sample. We also develop a combined estimator using multiple-frame techniques.