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Contemporary Land Cover Change in the North Central Appalachians Ecoregion
By Kristi L. Sayler 1
Ecoregion Description
| The North Central Appalachians ecoregion (fig. 1) is a forested, sedimentary upland that is punctuated by high hills and low mountains (Woods and others, 1996). The ecoregion covers approximately 30,500 km2 (11,700 mi2) and is divided into two separate portions. The unglaciated western portion lies along the headwaters of the Allegheny and Susquehanna Rivers in north central Pennsylvania with a sliver in southern New York. This forested landscape supports the major economic activities of forestry and recreation. This part of the ecoregion is also at the northern fringe of the Appalachian coal belt and includes substantial portions of Pennsylvania's oil and gas production (Woods and others, 1996). The eastern portion comprises the Pocono Mountains of Pennsylvania and portions of the Catskill Mountains of New York and New Jersey, which range from low mountains to rolling hills with a dissected plateau at the eastern edge of the Allegheny Front (Ackroyd-Kelly, 1987). This area has historically provided an accessible, rural recreation oasis for generations of residents of nearby New York and Philadelphia. The climate of the North Central Appalachians ecoregion can be characterized as continental, with cool summers and cold winters. The average annual precipitation ranges from 825 to 1,250 mm (33 to 50 in). |
Figure 1. North Central Appalachians and surrounding ecoregions. The 10 randomly selected 400-km˛ sample blocks are shown along with land use/land cover from the 1992 National Land Cover Dataset. Click on image to enlarge
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Contemporary Land Cover Change (1973 to 2000)
The overall spatial change from 1973 to 2000 for the North Central Appalachians was 6.2 percent (table 1), a fairly low amount of change compared to other Eastern U.S. ecoregions (fig. 2). Of the 6.2 percent estimated area of change, nearly half of the land changed multiple times. The change per time period ranged between 1.5 percent and 2.9 percent with margins of error ranging from 0.7 to 1.4 percent (table 2). The average annual rates of change (fig. 3) showed that the 1980 to 1986 period had the greatest amount of change with an average rate of 0.4 percent per year (table 2). This number would have been substantially lower had there not been an outbreak of around 42 tornadoes on May 31, 1985 (Monfredo, 1999), which deforested a significant portion of the ecoregion. The tornado damage and its subsequent return to pre-storm land cover made up about 8.1 percent of the total change between 1980 and 2000 in the ecoregion.
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Table 1: Amount of overall spatial change detected in ecoregion and proportion of ecoregion that experienced change during one or multiple time periods 
Table 2: Raw estimates of percent change in ecoregion computed for each of four time periods and associated margin of error at 85-percent confidence level. 
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Figure 2: The overall spatial change in all Eastern U.S. ecoregions. Each bar chart shows the proportion of the ecoregion that experienced change on 1, 2, 3, or 4 dates. Click to enlarge image
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Figure 3: The estimates of land cover change per time interval normalized to an annual rate of change. North Central Appalachian ecoregion is highlighted in black.Click image to enlarge
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Forest made up 87.4 percent of the land cover in 1973, and it decreased only 0.8 percent during the study period to 86.7 percent in 2000 (table 3). This decrease is mostly attributed to forest clear-cutting in the ecoregion and forest loss caused by tornado activity in 1985. These clear-cuts primarily represent the harvesting of hardwood trees for lumber and other wood products and are shown as conversions from forest to the mechanically disturbed land cover class. The area is known for its exceptionally high quality of black cherry, with other hardwoods commonly harvested, including yellow poplar, white ash, red maple, and sugar maple (Napton and others, 2003).
Both mining and developed lands had very small increases in all time periods. Surface coal mining, quarries, gravel pits, and natural gas field developments all contributed to the 0.3 percent increase in mining. Developed lands increased slightly (0.4 percent), primarily in the eastern portion of the ecoregion where the proximity to the Poconos and Catskills regions makes it possible for individuals to have second homes and still live and work near New York City.
Table 3: Proportion of ecoregion covered by each land cover class during each of five mapped dates.
The leading land cover conversions were all related to the vast forests of the North Central Appalachians ecoregion. Forest to mechanically disturbed and mechanically disturbed to forest were the top two land cover conversions during all time periods (table 4). These two conversions were related to the forest harvest and regrowth cycles of the timber industry of the ecoregion. The other main land cover change agent was the tornado activity, shown as a forest to non-mechanically disturbed conversion in 1980 to 1986 and the subsequent conversion of non-mechanically disturbed to forest as the affected forest areas regenerated (table 4). Overall, these conversions accounted for 82.4 percent of the area changed in the ecoregion.
Table 4: Leading land cover conversions during each of four time periods
1 Kristi L. Sayler – U.S. Geological Survey, Center for Earth Resources Observation and Science, Sioux Falls, SD 57198
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References
Ackroyd-Kelly, I.H., 1987, The near country-the historical geography of Pocono resorts: The Pennsylvania Geographer, v. 25, no. 1, p. 18-23.
Monfredo, W., 1999, Significant tornado activity in southwestern Pennsylvania: The Pennsylvania Geographer, v. 37, no. 2, p. 43-63.
Napton, D., Sohl, T.L., Auch, R.F., and Loveland, T.R., 2003, Land use and land cover change in the North Central Appalachians ecoregion: The Pennsylvania Geographer, v. 41, no.2, p. 46-66.
Woods, A.J., Omernik, J.M., Brown, D.D., and Kiilsgaard, C.W., 1996, Level III and IV ecoregions of Pennsylvania and the Blue Ridge Mountains, the Ridge and Valley, and Central Appalachians of Virginia, West Virginia, and Maryland: EPA/600/R-96/077, U.S. Environmental Protection Agency, National Health and Environmental Effects Research Laboratory, Corvallis, Oreg., 50 p.
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U.S. Department of the Interior |
U.S. Geological Survey
