LONG-TERM STUDY OF FORMERLY LITTER-RAKED SCOTS PINE ECOSYSTEMS IN NE BAVARIA - RECENT CHANGES IN SOIL CHEMICAL-PROPERTIES AND STAND NUTRITION

For two sites in NE Bavaria (Germany) forested with mature stands of S cots Pine (Pinus sylvestris L.) characterized by acidic soils derived from acidic parent material (phyllite-Pfaffenwinkel, and cretaceous se diments-Pustert) and substantial devastation due to intense litter-rak ing in the past, recent changes in the chemical status of the topsoil (acidification, N eutrophication) and in the nutritional status of the pine stands were investigated. Changes in topsoil chemistry were quan tified by comparing the results of soil inventories carried out in 197 4, 1982/1984, and 1994. Changes in the nutrition of the forest stands were assessed by repeated analyses of half-year old needles conducted at least every second year from 1964 to 1994. For both sires, a consid erable acidification of the topsoil horizons was noticed. The pH value decreased significantly between 0.1 to 0.2 units (all horizons of Pfa ffenwinkel, O layer of Pustert) and about 0.3 to 0.4 units (mineral so il of Pustert). Additionally, we found a significant decrease in base saturation and in the amounts of exchangeable Ca (only for Pustert) an d Mg (both sires) in the topsoil. Only in the O layer of Pfaffenwinkel the C/N ratio decreased slightly between 1982/84 and 1994, whereas th e C/N ratio of all other studied horizons remained constant or increas ed. The nutritional scarus of tile Scots Pine stands on both sires cha nged in a similar way. In contrasting ro the situation in the early 19 60ies, the N deficiency dissappeared and needle growth increased drama tically in the course of the monitoring period. Both, the average weig ht and the N levels of half-year old needles increased significantly w ithin 20 years for 25 by 33%, and 13 by 18%, respectively. On the othe r hand, the Ca concentrations decreased for 16 Ly 27%. K and P showed only minor, insignificant changes; tile Mg concentrations developed di fferently at both sites. For Pfaffenwinkel, an increasing risk of Ca s hortage particularly in warm and dry years is postulated, if the obser ved trend oi a decreasing pool of plant-available Ct in the topsoil co ntinues in the future.