Ulmus pollen at Sibisa Swamp, North Sumatra (Ulmaceae)

Ulmus pollen characterised by a four-pored morphology was reported from samples of various ages taken from the radiocarbon dated pollen sites of Pea Sim-sim and Tao Sipinggan and in one sample from the undated Pea Sijajap record (Maloney, 1984). All these sites are located on the Toba Plateau, south of Lake Toba, over 50 km away from the nearest existing sources (Touw & Van Steenis, 1968) of Ulmus lancaeafolia Roxb. ex Wall. Sibisa Swamp is situated east of Lake Toba, at 98°58'E, 2°33'N, near the tourist resort of Prapat and much closer to the Karo Highlands source. It is in an area of fresh-looking volcanic topography at an altitude of c. 1300 m. The site was discovered and cored by Flenley and Morley in 1972 (cf. Morley et al., 1973). They described the vegetation of the swamp as somewhat disturbed and including a variety of species characteristic of swamps in central Sumatra, of which three: Eleocharis sp., Xyris cf. capensis and Blechnum orientale were listed. The writer made additional borings in 1973 but the longest was only 1.50 m deep. It can be added that the centre of the swamp was dominated by Eleocharis ochrostachys Steud. with some Xyris capensis Thunb. and that the Blechnum orientale L. formed an outer vegetation ring. The deepest boring was made at the centre of the site. Samples were taken at 5 cm intervals but complete cores sections were not sent back to the laboratory and larger samples selected for possible 14 C dating have, unfortunately, been mislaid over time.