HOLOCENE VEGETATION AND WATER-LEVEL HISTORY IN 2 BOGS OF THE CORDILLERA-DE-TALAMANCA, COSTA-RICA

Pollen records of Holocene sediment cores from the Costa Rican Cordill era de Talamanca (La Chonta bog, 2310 m and La Trinidad bog, 2700 m) s how the postglacial development of the montane oak forest zone from ca . 9500 to 1500 yr BP. During the early Holocene (ca. 9500-7000 yr BP), alder vegetation covered the La Chonta and La Trinidad bogs and their adjacent hills. The upper forest line is inferred to be at 2800-3000 m elevation. A Podocarpus-Quercus forest characterised the middle Holo cene (ca. 7000-4500 yr BP). The upper forest line is located at > 3000 m reaching the present-day altitudinal distribution. A Quercus forest characterised the late Holocene (ca. 4500-1500 yr BP). Compared to mo dern conditions, the early Holocene has similar average temperatures, but the moisture level was probably higher. Pollen evidence for the la te Holocene indicates drier environmental conditions than today. In or der to improve the paleoecological interpretation, we described the lo cal vegetation and used moss samples as pollen traps at both montane b ogs along strong soil moisture gradients.