In large-area mapping projects, existing reference data, often collected for a different purpose, are increasingly being used for map accuracy assessment. Multiattribute digital vegetation maps have been developed for all National Forest lands in California (8.1 million ha). We developed decision rules that could be applied to quantitative Forest Inventory and Analysis (FIA) plot data in order to score the fuzzy membership of plot locations in all possible map classes. We compare the accuracy of the vegetation map attributes estimated using this method to accuracy estimated from fuzzy class membership scores assigned by experts (inventory crews) during field work. Accuracy of the vegetation life form attribute was estimated to be higher when expert label assignments were used as reference data (76±87%), instead of FIA plot data (62±79%). This suggests that automated decision rules applied to detailed data from FIA plots, which have smaller area Transactions in GIS, 2001, 5(4): 285±304 ß 2001 Blackwell Publishers, than map polygons, may systematically underestimate map accuracy. However, assignment of the actual map labels to FIA plot locations by inventory crews appears to be a robust method for using the FIA data for accuracy assessment.

This report summarizes an inventory of chaparral-dominated lands in southern California conducted during the mid-1990s and provides a review of contemporary literature on the ecological dynamics of chaparral vegetation with emphases on stand development, species composition, and the role of fire. Detailed tables provide estimates of chaparral area by owner, type, size, and cover, and, for lands outside national forests, area by fire-hazard class and 10-year change in chaparral area.In the mid-1990s, chaparral in California's south and central coast regions was estimated to occupy 4.6 million acres, 14 percent of total land area. About 2.1 million acres of the chaparral were privately owned, and 1.6 million acres were in national forests. The Bureau of Land Management, military reservations, and miscellaneous federal, state, and local agencies accounted for the rest. These estimates were among the results of a field-plotbased vegetation inventory with emphasis on woody species. Chaparral area decreased by 108,000 acres outside national forests between 1984 and 1994 owing to conversions to urban and agricultural use. At 42 percent of the total chaparral area, the chamise and red shank type was the most common type of chaparral, followed by mixed and montane (31 percent), scrub oak (12 percent) and coastal transition (15 percent). Adenostoma fasciculatum (chamise) was the most common shrub species, occurring on 71 percent of the area sampled, followed by Quercus dumosa/john-tuckeri (California scrub and Tucker oaks) at 39 percent, and Heteromeles arbutifolia (toyon) at 19 percent. Emergent trees, important to wildlife and scenery values, and thought by some to have been more prevalent in chaparral before Europeans settled here, were found on 11 percent of the area.Outside national forests, 16 percent of the chaparral burned between 1984 and 1994; within national forests, 27 percent of the chaparral burned over that period. Remeasured plots that had burned between visits (all within 10 years) showed significantly less shrub and significantly more grass and forb cover. Notable was the loss of Ceanothus spp., obligate seeders that fix nitrogen in the soil. During this period, unburned chaparral outside national forests showed little evidence of degradation or loss of biodiversity. Shrub cover held steady or increased on 70 percent of the plots, and many shrub species increased in occurrence while very few decreased.Outside national forests, application of a chaparral hazard class rating system based on ocular estimates of percentage of dead material in live shrubs and total shrub cover placed 38 percent of the chaparral area in the highest hazard class (greater than 25 percent cover of shrubs and greater than 25 percent dead material in more than half of those shrubs), and 42 percent in the moderate hazard class (greater than 25 percent cover of shrubs and some dead material in at least half of those shrubs). It appears that nearly all chaparral older than 10 years (i.e., since the last disturbance by fire) has moved o...

The data for unreserved land in the study area (85 percent of the forested landscape) for the Current came from the most current National Forest inventories conducted by the Forest Inven Assessment tory and Analysis (FIA) program (USDA Forest Service 1994) and the recent PNW Research Station inventory of private and public unreserved lands outside National Unreserved Lands Forests (Waddell and Bassett 1997a,1997b,1997c). The National Forest inventories-Forest inventories of the Eldorado,

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Beardsley, Debby; Warbington, Ralph. 1996. Old growth in northwestern California National Forests. Res. Pap. PNW-RP-491. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 47 p. This report estimates old-growth forest area and summarizes stand characteristics of old growth in northwestern California National Forests by forest type. Old-growth definitions for each forest type are used.