The Interior Plateau ecoregion is a series of grassland plateaus and forested uplands that are generally lower in elevation than the Appalachian Mountains to the east but higher than the plains to the south. The ecoregion has a total area of approximately 127,810 km² (49,348 mi²) and covers large areas of western Kentucky and central Tennessee, as well as parts of Indiana, Alabama, and Ohio (fig. 1). The Ohio River, which runs along the northern border of Kentucky, drains most of the northern part of the ecoregion.

The relatively flat and fertile lowlands, which include the Bluegrass area of central Kentucky and the Nashville Basin in central Tennessee, attracted early settlement and farming. Today, those areas are highly populated, including the cities of Louisville, Kentucky, and Nashville, Tennessee. The Pennyroyal Plateau in south-central Kentucky and northern Tennessee is a dense agricultural area that also contains a distinctive “flatwood” ecosystem. The area is characterized by oak forests and wet conditions that are caused by an underlying hard, dense fragipan soil (Chester and others, 1995).

Rapid subsurface drainage occurs in sinkhole areas such as south-central Kentucky where extensive cave systems wind through the karst limestone landscape. Water quality of the associated aquifers and streams is a special concern in watersheds where agriculture and coal mining are prevalent.

Ecoregion-wide, climate conditions are humid temperate and average about 1,200 mm (47.2 in) of annual precipitation. Oak-hickory stands are the most common forest type, although mixed stands of red cedar and hardwoods grow on many of the rockier sites and limestone glades. Blue-stem prairie is the most common grassland. Historically, fire was an important natural process for maintaining open-canopied, savannah-like conditions on the plateaus (Chester and others, 1995; Hudson, 2002).

Population has increased steadily, by approximately 40 percent between 1970 and 2000, from 4.4 million to 6.2 million people. Automobile manufacturing has expanded into the area, and tourism and service industries are also important in several locations. Major agricultural products include soybeans, corn, tobacco, and dairy. The Bluegrass area has unique land uses, including a tradition of race horse breeding and training farms and the production of high-value burley tobacco.

Figure 1. Interior Plateau and surrounding ecoregions. The 40 randomly selected 100-km˛ sample blocks are shown along with land use/land cover from the 1992 National Land Cover Dataset. Click on image to enlarge

The Interior Plateau had a relatively low rate of overall land cover change when compared to other Eastern ecoregions (fig. 2). Between 1973 and 2000, 4.3 percent of the ecoregion underwent change, and 95.7 percent of the total area was stable. An estimated 3.6 percent of the ecoregion changed once. The percentage of area that underwent multiple changes was relatively low. An estimated 0.6 percent of the area changed twice, and 0.1 percent changed three times (table 1).

The highest total change occurred between 1980 and 1986 (1.7 percent), with an annual rate of 0.28 percent (table 2 and fig. 3). The lowest rate of change occurred during the period between 1973 and 1980, when total change was less than 1 percent (0.8 percent) and the annual rate was 0.12 percent.

Table 1. Estimated overall spatial land cover change between 1973 and 2000

Table 2. Total and annual rates of land cover change for each time interval

Figure 2. Overall spatial change from 1973 to 2000 for all Eastern U.S. ecoregions. The entire bar shows the overall spatial change, while the gradients indicate the percent of ecoregion area that changed during one or multiple periods. Click on image to enlarge

Figure 3. Estimates of land cover change per time interval normalized to annual rates of change. Click on image to enlarge

Table 3. Land cover area, including net change

Figure 4. Land cover changes are shown for the four time intervals of the study. Click on image to enlarge