Long-Term Changes of the Phosphorus Status of Two German Scots Pine Ecosystems: Effects of Atmospheric N Deposition and Fertilization.

Long-term changes of the phosphorus status of two German Scots pine ecosystems: Effects of atmospheric N deposition and fertilization For two Scots pine (Pinus sylvestris) stands in S Germany with different atmospheric N deposition and N status (Pfaffenwinkel: moderate N deposition, Pustert: large N deposition), the nutritional status of P and other nutrients has been monitored (bi)annually during the recent 44 years. In both stands, amelioration experiments had been established in 1963 to develop appropriate strategies (NPKMg fertilization + liming; PKMg fertilization, liming, tillage, and introduction of lupine) to increase the poor stand growth at the sites. P amendments were carried out in 1964 and 1967. Concentrations and stocks of total P, citric acid-extractable phosphate, NH4F-extractable phosphate, and other bioelements in the topsoil of the control plots of both sites were quantified 1984, 1994, and 2004. In 2004, the ameliorated plots were included in the soil inventory. The stands at the control plots of both sites showed a systematic deterioration in P nutrition during recent decades, which was particularly pronounced at the Pustert site. At both sites the observed changes of total P concentrations and stocks and of the C/P or N/P ratios in the topsoil could not explain the negative trends in stand P nutrition. In contrast, the concentrations and stocks of citric acid-extractable phosphate in the topsoil decreased in recent years, and reflected the changes of the P nutritional status of the stands. At Pfaffenwinkel, the effects of P fertilization were visible even more than 35 years after the P amendments: foliar P concentrations and topsoil stocks of citric acid-extractable phosphate were increased in 2004 at the fertilized plots compared to the control plots. At Pustert, P fertilization effects on foliar P concentrations disappeared in the mid 1980ies, and the various experimental variants do not show any systematic difference in their topsoil stocks of citric acid-extractable phosphate.