The Site Index – Biogeoclimatic Ecosystem Classification (SIBEC) model is an effective model that links site index to the ecological site series classification of the land base. Widespread application of SIBEC is limited by the expense of terrestrial ecosystem mapping (TEM) or Predictive Ecosystem Mapping (PEM) to obtain accurate site series data. OASIS presents a technique for obtaining area-based ecological information at a level of detail adequate for supporting site index estimates and yield curve generation for analysis units in a timber supply analysis.

The OASIS program utilizes site series data collected in the field to obtain a proportional breakdown of site series, and then applies SIBEC site index estimates to the site series for yield table generation. During the field data collection phase, additional SIBEC plots can be established to supplement the SIBEC database for site series with inadequate site index sample sizes. OASIS utilizes ecosystem data collected from random sampling and does not require site series mapping in terms of delineation of site series boundaries within a TFL or TSA. It is designed as a medium-term solution for obtaining good estimates of site index until reliable site series mapping becomes more widely available to supplement SIBEC. It is anticipated that the results of the OASIS project will be primarily used in timber supply forecasting.

In current timber supply analyses, productivity information is obtained from the height, age, and leading species of polygons from the forest cover inventory. The timber harvesting land base is grouped into analysis units based on species composition and productivity information. Under OASIS, the timber supply analyses proceeds as before, but once an area from an analysis unit is harvested, it is apportioned into site series in the same percentages as identified by the OASIS inventory for that specific biogeoclimatic variant. The apportioned site series are used to form the new analysis units, a yield curve based on a SIBEC-derived site index is assigned, and the timber harvest forecast model proceeds with the new analysis units.

The objective of the OASIS pilot program was to test and refine a method to improve site index estimates for timber supply forecasting. To achieve this objective, a four-step process was identified:

1. Develop an unbiased sampling design to determine the proportional area of site series within a TSA or TFL.
2. Produce quantitative estimates of the site index of the site series identified in the field through SIBEC data.
3. Develop procedures to incorporate SIBEC-based site indices into the timber supply analysis process.
4. Collect data to supplement the SIBEC database.

This manual will present a complete description of the OASIS program. It will describe in detail the methods as they apply to future implementations of OASIS. References and appendices, including pertinent data and supporting information are cited throughout the document.

Continue to Chapter 3.
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