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Plant and Soil Responses to Chronic Nitrogen Additions at the Harvard Forest, Massachusetts
Author(s) -
Aber John D.,
Magill Alison,
Boone Richard,
Melillo Jerry M.,
Steudler Paul
Publication year - 1993
Publication title -
ecological applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.864
H-Index - 213
eISSN - 1939-5582
pISSN - 1051-0761
DOI - 10.2307/1941798
Subject(s) - nitrification , hardwood , leaching (pedology) , nitrogen , environmental science , ammonium , mineralization (soil science) , human fertilization , nitrogen cycle , agronomy , nitrate , growing season , experimental forest , soil water , ecology , chemistry , biology , soil science , organic chemistry
Data are presented on changes in plant and soil processes in two forest types (red pine plantation and oak—maple forest) at the Harvard Forest, Petersham, Massachusetts, in response to 3 yr of chronic N fertilization. The hardwood stand exhibited greater N limitation on biological function than the pine stand prior to fertilization as evidenced by a lower net N mineralization rate, nearly undetectable rates of net nitrification, and very low foliar N content. N additions were made in six equal applications throughout the growing season, and consisted of 5 and 15 g°m — 2 °yr — 1 of N as ammonium nitrate. The pine stand showed larger changes than the hardwood stand for extractable N, foliar N, nitrification, and N leaching loss. Retention of added N was essentially 100% for all but the high application pine plot from which significant N leaching occurred in the 3rd yr of application. From 75 to 92% of N added to fertilized plots was retained in the soil, with larger fractions retained in the hardwood stand than the pine stand for all treatments. As hypothesized, the stands are exhibiting highly nonlinear patterns of nitrogen output in response to continuous nitrogen inputs. The implications of this nonlinearity for regional eutrophication of surface waters and atmospheric deposition control policy are discussed.