Evidence that oak is decreasing in abundance

Oak (Quercus spp.) is widely believed to be decreasing in abundance in eastern North America, but most evidence is anecdotal or localized.  In this paper we present analyses of FIA datasets designed to formally quantify changes in abundance of oaks in the eastern U.S. during the period of 1980 to 2005.  The results indicate that oak species in the aggregate became less important.  In the first measurement period, oak importance value (IV) had a range between 1.8 and 60.2 percent, and an average of 21.2 percent.  In the second measurement period, oak IV had a range between 2.2 and 47.9 percent, and an average of 19.2 percent.  Oak IV decreased between inventories in 22 states (11 were significant at p < 0.05) and increased in only eight [five states (Vermont, Florida, Texas, Georgia, and Louisiana) were significant at p < 0.05].  The overall trend is that oak abundance is decreasing in the northern states, while increasing in the southern coastal states.