. Annual inventory report for Pennsylvania's forests [electronic resource] : results from the first three years. Forest surveys Pennsylvania Statistics; Forests and forestry Pennsylvania Statistics. $ 4000 < 3000 ° 2000 | 1000 3 Q n ? 1978 ? 1989 2002 5% Figure 4.—Area of forest land by inventory region, Pennsylvania, 1978, 1989, and 2002 (error bars reflect 67-percent confidence interval; not available for 1978). Forest-Type Group and Stand-Size Class The forest types and groupings used by FIA are useful for tracking changes through time. In fact, FIA has used the same forest-type naming a
. Annual inventory report for Pennsylvania's forests [electronic resource] : results from the first three years. Forest surveys Pennsylvania Statistics; Forests and forestry Pennsylvania Statistics. $ 4000 < 3000 ° 2000 | 1000 3 Q n ? 1978 ? 1989 2002 5% Figure 4.—Area of forest land by inventory region, Pennsylvania, 1978, 1989, and 2002 (error bars reflect 67-percent confidence interval; not available for 1978). Forest-Type Group and Stand-Size Class The forest types and groupings used by FIA are useful for tracking changes through time. In fact, FIA has used the same forest-type naming and grouping system over the years to ensure the best trend information possible. Although the goal has been to track forest types over decades, there are inherent difficulties. For example, because the data are not in digital form, we cannot use the new classification algorithms to reconfigure past inventory data to current standards. As a result, information on forest-type group is shown for only the 1989 and 2002 inventories (Fig. 5). It is clear that the distribution of forest land by forest-type group has been stable over the past decade, but this is likely because </) 0) o < o V) T3 C CO <fl 3 O 10000 8000 6000 4000 2000 0 ? 1989. '/fa Forest-Type Group Figure 5.—Distribution of forest land by forest-type group, Pennsylvania, 1989 and 2002 (error bars reflect 67-percent confidence interval). Pennsylvania's forests have been maturing gradually. At this level of data use, FIA inventories generally monitor only major disturbance events or other shifts in composition. Thus, no sweeping changes would be anticipated. The oak-hickory group decreased by 3 percent since 1989, but this change is relatively minor. Also, the current acreage of oak-hickory probably is greater than in the 1978 inventory even though a precise estimate for that inventory is not reliable due to computational differences. The distribution of the specific oak types also seems relatively stable.
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