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Abstract
In 1983, the Pennsylvania State University engaged in a spray irrigation system for the disposal of treated wastewater on 209 hectares of farm and forest land in State Game Lands 176. The system was designed to distribute 5 centimeters of wastewater 52 weeks per year. Differences in species composition and structure have been observed between the irrigated and non-irrigated. In 1997, to monitor the long-term effects of wastewater irrigation on plant community and soil conditions in forested ecosystems, 20 pairs of irrigation and non-irrigation plots were established, and density and species composition of tree, shrub, and herbaceous plants were inventoried. Soil samples of A and B horizons were also taken for each 20 x 20 meters plot. At each plot, plants components included (1) overstory stems on 20 x 20 meters plot, (2) sapling-sized stems on four 10 x 10 meters subplots, (3) seedling-sized stems on four 2 x 2 meters subplots, (4) shrub species coverage on four 10 x 10 meters subplots, and (5) herbaceous plants coverage on sixteen 1 x 1 meters subplots. Initial results indicate striking differences in species composition, in densities of trees and shrubs, and in shrub and herbaceous coverage values, between the irrigated and non-irrigated forested communities. Total numbers of combined tree and shrub species in the non-irrigated overstory, sapling-sized, and seedling-sized components were 15, 47, and 33 species, respectively, compared to 17, 29, and 10 species, respectively, for the irrigated components. Overstory, sapling-sized, and seedling-sized stem densities were 536, 2,823, and 107,316 stems/hectares, respectively, for the nonirrigated and 361, 706, and 1,127 stems/hectares, respectively, for the irrigated components. Shrub and herbaceous coverage values were 17 and 80 percent, respectively, in the irrigated area, compared to 61 and 30 percent, respectively, in the non-irrigated area. The fertility levels in soil A and B horizons were also very different for the two areas. For both A and B soil horizons, the irrigated area had higher pH, higher phosphorus, magnesium, and calcium contents, and lower exchangeable acidity than the non-irrigated area. These data suggest that modifications to either the plant community species base or the methods of wastewater distribution will be needed to maintain forested ecosystems in the wastewater irrigation area of State Game Lands 176.
Parent Publication
Citation
Larrick, David S.; Bowersox, Todd W. 1999. Long-term effects of wastewater irrigation on forested ecosystems at Pennsylvania State Game Lands 176. In: Stringer, Jeffrey W.; Loftis, David L., eds. 1999. Proceedings, 12th central hardwood forest conference; 1999 February 28-March 1-2; Lexington, KY. Gen. Tech. Rep. SRS-24. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 293 p
