Human Impact

        Human impact has dramatically altered the biological distinctiveness of Southeastern Mixed Forests. About 99 percent of this habitat has been converted to agriculture and has become highly degraded due to European settlement (10). The effects of domestication were inescapable; it led to the clearing of land and allowed open range livestock (i.e. hogs, cattle) to feed on longleaf pine seedlings (2). The one process that took decades to become effective in the South was the passing of fence laws that required farmers to fence off their land in order to prevent livestock from running off and eating all the natural forage (2). However, this is not full proof and not all farmers abided to this law. The Southeastern Mixed Forests is "the most heavily settled ecoregion along the east coast of the U.S., and much of the land has been used for growing tobacco and peanuts" (10). After World War II many farm fields were left abandoned and there was a dramatic shift in land use from plantations to croplands (2). This shift made it easier for pines to out compete hardwoods for sun and nutrients and they better able to survive in the extreme environmental conditions of the abandoned fields (10). Due to repeated harvesting of pine stands in the mid-1960s, hardwoods began to dominate the understory of Southeastern Mixed Forests (10). 
        Conversion to agriculture is one of the main factors that led to deforestation of this ecosystem. For example, a remnant tall grass prairie known as the Black Belt was completely converted to agriculture (10). Because of the heavy rate of conversion, there is little left to conserve. The suppression of fire and the poor management of farmlands has "altered the plant communities and threatens the long-term persistence of many fire-dependent species" (10). Furthermore, high fragmentation has led to species loss, such as the black bear. In addition, large carnivores have been largely eliminated through deliberate efforts of humans (i.e. hunting, destruction of habitats). 400 years of land use for agriculture, livestock; logging; production of turpentine, and elimination of naturally-occurring wildfires have left less than 3% of the canopy's upper layer of natural vegetation (2).

Gills Creek- South Carolina

http://www.flickr.com/photos/alan_cressler/4750721274/

Black Belt Prairie 

 http://mississippientomologicalmuseum.org.msstate.edu/images/prairie.photos/prairie.erosion.jpg

McTier Creek- South Carolina

 http://www.flickr.com/photos/alan_cressler/4749965575/

Decreasing gymnosperms of southern mixed forests: (a) shortleaf pine, (b) longleaf pine, (c) swamp tupelo, and (d) pond cypress.
http://www.sciencedirect.com/science/article/pii/S0378112713004088

Table 1. (3)

Species (trees ≥ 12.7 cm diameter) that increased or decreased in percent composition ≥ 5% for ≥ 2 million ha between oldest and newest USDA FIA surveys in the eastern United States. The first p-values, from paired t-tests, were for all ecological subsections, weighted by area, where the species was present with > 100 stems. The second p-values, also from paired t-tests for all ecological subsections, compared small trees (<12.7 cm in diameter) in old surveys to large trees in new surveys.

Species	Scientific name	Net change ha	Change % composition	Mean year old surveys	Mean year new surveys	p-value	p-value small trees
Loblolly pine	Pinus taeda	72704702	17.6	1974	2007	<.0001	<.0001
Red maple	Acer rubrum	29479009	7.4	1984	2006	<.0001	<.0001
Eastern redcedar	Juniperus virginiana	11049718	7.8	1982	2007	<.0001	0.1533
Slash pine	Pinus elliotti	10310840	11.8	1972	2006	0.064	0.0069
Green ash	Fraxinus pennsylvanica	7789190	8.7	1980	2007	0.2169	N/A
Boxelder	Acer negundo	5609990	11.4	1982	2007	0.0743	N/A
Red pine	Pinus resinosa	5128902	8.9	1983	2006	<.0001	N/A
Black spruce	Picea mariana	3128760	8.7	1980	2006	<.0001	0.0037
Northern white-cedar	Thuja occidentalis	2603295	10.1	1984	2006	0.0363	<.0001
Sugar maple	Acer saccharum	2132676	7.0	1987	2006	0.0011	0.1717
Tamarack	Larix laricina	2092218	10.3	1980	2006	0.0037	0.1632
Jack pine	Pinus banksiana	−2066916	−8.3	1979	2006	0.009	0.3393
Paper birch	Betula papyrifera	−2594284	−7.0	1982	2006	<.0001	0.1072
Eastern white pine	Pinus strobus	−3040918	−7.4	1986	2006	0.3578	0.3924
Virginia pine	Pinus virginiana	−5335089	−7.0	1979	2006	0.0004	0.4223
Pond pine	Pinus serotina	−5571550	−5.7	1972	2006	0.0005	N/A
Pond cypress	Taxodium ascendens	−5824112	−9.2	1970	2005	0.0015	N/A
American basswood	Tilia americana	−6116642	−7.0	1983	2006	0.0066	0.7936
Longleaf pine	Pinus palustris	−9881192	−8.0	1972	2007	<.0001	0.2804
Quaking aspen	Populus tremuloides	−12491657	−10.1	1979	2006	<.0001	<.0001
Black oak	Quercus velutina	−12661395	−8.3	1984	2007	<.0001	0.0002
Northern red oak	Quercus rubra	−14178855	−9.3	1984	2006	<.0001	0.0843
Swamp tupelo	Nyssa biflora	−14404729	−6.8	1972	2006	<.0001	0.0561
White oak	Quercus alba	−23820115	−7.6	1982	2006	<.0001	0.0325
Shortleaf pine	Pinus echinata	−38282915	−12.1	1975	2007	<.0001	0.1218

Table 2.  (3)
Percent composition (trees ≥ 12.7 cm diameter) of eastern forests by pines, other gymnosperms, oaks, other angiosperms, and most frequent species for oldest (mean year = 1981) and newest (mean year = 2006) USDA FIA tree surveys, as well as the percent composition of groups for smaller trees (<12.7 cm diameter) in newest surveys. The first p-values, from paired t-tests, were for all ecological subsections, weighted by area, where the group contained ≥100 stems. See Table 1 for scientific names of increasing and decreasing species.

Forest type	Group	Old surveys		New surveys			p-value
		%	Most frequent	%	Most frequent	% Small trees
Eastern broadleaf	Pines	7.4	Eastern white pine	8.0	Eastern white pine	4.3	0.0233
Eastern broadleaf	Other gymnosperms	3.1	Eastern hemlock, Tsuga canadensis	5.6	Eastern redcedar	5.5	<.0001
Eastern broadleaf	Oaks	38.2	White oak	26.6	White oak	9.5	<.0001
Eastern broadleaf	Other angiosperms	51.4	Red maple	59.8	Red maple	80.7	<.0001
Southeastern mixed	Pines	40.9	Loblolly pine	47.9	Loblolly pine	20.5	<.0001
Southeastern mixed	Other gymnosperms	3.6	Pond cypress	2.8	Pond cypress	2.3	0.0085
Southeastern mixed	Oaks	20.7	White oak	15.0	Water oak,Quercus nigra	16.1	<.0001
Southeastern mixed	Other angiosperms	34.8	Sweetgum, Liquidambar styraciflua	34.3	Sweetgum	61.1	0.0005
Northern mixed	Pines	7.7	Jack pine	8.9	Red pine	2.7	0.2194
Northern mixed	Other gymnosperms	25.9	Northern white-cedar	30.5	Northern white-cedar	37.2	<.0001
Northern mixed	Oaks	6.1	Northern red oak	4.8	Northern red oak	1.8	<.0001
Northern mixed	Other angiosperms	60.3	Quaking aspen	55.8	Red maple	58.3	<.0001
Prairies/savannas	Pines	1.9	Loblolly pine	3.0	Loblolly pine	2.3	0.0706
Prairies/savannas	Other gymnosperms	0.9	Eastern redcedar	4.4	Eastern redcedar	5.5	N/A
Prairies/savannas	Oaks	36.4	White oak	26.4	Post oak,Quercus stellata	13.8	<.0001
Prairies/savannas	Other angiosperms	60.8	American elm, Ulmus americana	66.2	American elm	78.5	<.0001
Prairies	Pines	4.0	Ponderosa pine, Pinus ponderosa	3.7	Ponderosa pine	2.0	N/A
Prairies	Other gymnosperms	3.2	Eastern redcedar	22.7	eastern redcedar	43.0	N/A
Prairies	Oaks	8.4	Bur oak, Quercus macrocarpa	11.5	Bur oak	4.1	N/A
Prairies	Other angiosperms	84.4	Eastern cottonwood,Populus deltoides	62.0	Green ash	50.9	0.4571