EFFECTS OF ADDED NITROGEN ON TREES AND SOIL OF DECIDUOUS FORESTS IN SOUTHERN NEW YORK (SUGAR, MAPLE, WHITE, ASH, BLACK, CHERRY)

Nitrogen fertilization rate trials were established in eight second-growth deciduous forest stands in southcentral New York to examine the effects of added N on tree growth and soil chemical properties. The experiments were located in mixed-species stands having no history of cultivation or fire, of pole- and small sawlog-sized trees, on well to somewhat poorly drained acid soils typical of the better, but not the best northern hardwood sites. Basal area growth of individual trees over 30 years was determined from measurements of annual rings on cores extracted from dominant and codominant trees.; Basal area growth response of sugar maple (Acer saccharum Marsh.) and white ash (Fraxinus americana L.) during the 10 years of the experiment was diminished relative to results from other fertilization studies. The diminished level of response of white ash in the present study was attributed to better N status of the soils. Results of sugar maple and black cherry (Prunus serotina Ehrh.) supported the hypothesis that no deficiency of nitrogen existed at the locations studied. Factors thought to have contributed to the more favorable N status were the lack of fire or other major disturbances, and increased atmospheric inputs of nitrogen since the 1940's in the Northeastern United States.; Intensive sampling of soils at four locations revealed no increase in organic weight or total N content of the forest floor or mineral soil, 0-10 cm. There was no change in the calculated nitrogen as a percentage of organic matter, such as would have accompanied long-term storage of fertilizer N in the organic matter. Significantly lower concentrations and weights of Ca, Mg, and K in the mineral soil (0-10 cm) favored a hypothesis of nitrate leaching. Significantly lower pH in the mineral soil of fertilized plots was further support of the hypothesis of nitrate leaching.