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USDA Forest Service Res. Note RMRS-RN-8. 2000 Abstract—We estimate number of tree species in National Forest populations, using the nonparametric estimator, CM f c fc c s 2 2 1 2 2 = + ( ) / , where cs is the number of species observed, c1 and c2 are the numbers of species occurring once and twice, respectively, in the sample plots, and f is the finite population correction for sampling. Data from the Current Vegetation Survey (CVS) of Region 6 of the USDA Forest Service were used to estimate the number of tree species with a plot close in size to the Forest Inventory and Analysis (FIA) plot and the actual CVS plot for the 5.5 km FIA grid and the 2.7 km CVS grid. Ignoring seedlings, FIA missed seven out of 55 species estimated by the CVS plot on the 2.7 km grid, five with the 5.5 km grid. For observed tree species, FIA missed three species observed on the CVS plot. For the 2.7 km grid including seedlings, FIA missed six out of 53 species, four tallied on the CVS plot were not tallied on the FIA plot. For the 5.5 km grid, FIA missed six estimated to be there with CVS, CVS observed five species not observed by FIA. Ignoring seedlings, the estimate indicates that five species were not observed on the CVS plots, with seedlings two species were not observed, but number of species estimated was less than if seedlings were not considered in estimation. Similar results were obtained by zones and forests except that the results were sometimes erratic because of the small sample sizes involved. Even for the large sample of over 10,000 plots over the whole region, the number of species estimated if seedlings were included was two less (53 versus 55) than if they were ignored in estimation. One more species was actually observed when seedlings were included than when they were ignored (51 versus 50). There is a definite dilemma. Clearly a first step in protecting rare and endangered species is to determine if they are there. For this purpose the CVS plot and grid intensity are a must at a minimum but still not adequate. To ensure all species are observed requires an even more intensive grid. The problem may be more acute though in Oregon and Washington with the large number of tree species occurring there than in other areas that are more homogeneous in tree species such as the Intermountain West.

hathi trust digital library (the hathitrust research center)

Estimating the number of tree species in forest populations using current vegetation survey and forest inventory and analysis approximation plots and grid intensities