POTASSIUM TRENDS IN RED PINE PLANTATIONS AT PACK-FOREST, NEW-YORK

Trees are believed to cause improvement of nutrient availability in impoverished soils; however, evidence for this ameliorative capacity has generally been only circumstantial. Long-term monitoring of chemical changes in forest soils on nutrient-poor, agriculturally degraded sites may provide evidence of amelioration by trees. At the Pack Forest in the southeastern Adirondack Mountains of New York, soil and foliar K were periodically measured from 1949 to 1987 in red pine (Pinus resinosa Ait.) plantations established in the late 1920s to early 1930s. These plantations were established two decades after the area had been abandoned following a century of exploitive agriculture, when the inherently nutrient-poor site was further impoverished for K by crop removal. For unfertilized plantations, both Ap horizon exchangeable K and K in current-year foliage increased from the 1950s to the 1980s; the rate of soil K increase was 250 g ha-1 yr-1. For K-fertilized stands, Ap horizon and foliar K were constant throughout the measurement period. High potential for the parent material to supply K, coupled with conservative biogeochemical cycling, can account for the increase and maintenance of K in this agriculturally degraded system.