ICOM1 Abstract

DE ANDRADE, ZITA, GLADYS ESCALANTE, ERASMO MENESES & RAFAEL HERRERA. Centro de Ecologia, Instituto Venezolano de Investigaciones Cientificas, IVIC, Apartado 21827, Caracas 1020-A, Venezuela. -Soil mycorrhizal potential in a seasonally flooded forest in Venezuela The objective of this work was to assess the soil mycorrhizal potential and the AMF spores types communities at different locations along a gradient in a seasonally flooded forest at Mapire river: the studied field plot is localized near Mapire, Anzo‡tegui State, South-East of Venezuela. Soil sampling was carried out during February and May, 1992, in three zones along a gradient perpendicular to the course of the river. Flooding reaches a maximum of up to 12 m and last up to 8 months (MAX) near the river's normal border; approximately 100 m away from the river's normal border an intermediate zone occurs where the flooding reaches a maximum of up to 5 m and lasts for up to 5 months (MED); and there is a third zone which is the zone where flooding reaches a maximum of 1 m for 1 or 2 months (MIN). Soil samples (0-20 cm) were taken from each site. Spores were isolated from soil by wet-sieving and decanting and centrifuged with sucrose solution (750 g/L). The soil mycorrhizal potential was estimated using the Porter's most probable number (MPN) method. Soil mycorrhizal potential was found to be the lowest in MAX site both for February and for May. At MIN site, the number of colonizing propagules was found intermediate and the highest values were those found in MED for both sampling times. The values reported here are in general lower than those for other tropical ecosystems. Many species of AM fungi were found particularly those belonging to Scutellospora spp. and Glomus spp.