Five decades of rapid forest spread in the Pieria Mountains (N. Greece) reconstructed by means of high-resolution pollen analysis and aerial photographs

The rapid spread of pine forests on the western side of the Pieria Mountains (N. Greece) began in 1945 and was facilitated by the recession of human activity and the siliceous geological substrate of the area. The pine expansion is visible not only in the vegetation maps for the years 1945, 1960 and 1992 but is also reflected in pollen data acquired from the high resolution analysis of a peat sequence covering the period 1945–1997, according to 210Pb and 137Cs dating. A possible inflation of the calculated PAR values due to discrepancies in the dating model is suspected and indirectly traced from the comparison of the Pinus mean PAR values for the most recent eight years of the monolith with those of a Tauber trap placed in the same mire. The presence of a high pollen producer such as pine enables the calculation of reliable PAR values, despite any discrepancies in the age-depth model. The Pinus PAR values “quantify” better the expansion of this timberline species, while pollen percentages reflect the same event in a “qualitative” way, i.e. as part of the general vegetation changes that take place in the area.