Pollen monitoring in the central Rila Mountains, Southwestern Bulgaria: comparisons between pollen traps and surface samples for the period 1993-1999

Modern pollen deposition is monitored for the Central Rila Mountains, Southwestern Bulgaria, by means of pollen traps, moss samples and lake surface sediments. Results are presented for three sampling sites from different vegetation belts along an altitudinal transect (1000-1900 m) for a seven-year period of observations (1993-1999). Both the annual influx and percentage values of the main arboreal and non-arboreal taxa are presented and discussed in relation to pollen production and dispersal distance. The greatest proportion of the pollen being deposited originates from Pinus diploxylon-type (P. sylvestris and P. mugo) irrespective of its abundance in the local vegetation. The influx values of the endemic Balkan species Pinus peuce (Pinus haploxylon-type pollen) are several times lower than those of P. diploxylon-type. Abies alba and Picea abies have a representation in the deposited pollen assemblage which is comparable with the distribution and abundance of those species in the surrounding vegetation. Although the monitoring series is too short to confirm it, the cyclical flowering of Fagus sylvatica seems to be reflected in the trap results. The amount of pollen of low altitude species, which is deposited in the sub-alpine zone is very high. The data obtained from the different depositional media are compared. That the moss samples reflect pollen deposition from more than one year is evidenced by the absence of the distinct peak years seen in the trap results. In the light of these results the interpretation of previously analysed fossil pollen assemblages from the same study area may need to be revised. (C) 2001 Elsevier Science B.V. All tights reserved.