BIOMASS STRUCTURE AND DRY-MATTER DYNAMICS OF SUBTROPICAL ALLUVIAL ANDEXOTIC LIGUSTRUM FORESTS AT THE RIO-DE-LA-PLATA, ARGENTINA

Biomass, litterfall, litter standing crop, and decomposition was studi ed in a native subtropical alluvial forest locally known as Selva Marg inal (SM) and an exotic Ligustrum lucidum forest (LF) at the Reserva I ntegral de Punta Lara, Buenos Aires Province, 34-degrees-47'S and 58-d egrees-1'W. The alluvial forest site was at the southern limit of dist ribution of subtropical forests in South America. The Ligustrum forest was invading disturbed areas. Total biomass was 147.7 Mg/ha (86% abov eground and 14% belowground) in the SM, and 71.4 Mg/ha (93% and 7%, re spectively) in the LF. Litterfall was 10.3 Mg/ha.yr and 13.8 Mg/ha.yr respectively. Annual leaf decomposition rate was greater for Ligustrum (k = 4.07) than for SM species (k = 1.48). The mean residence time of aboveground biomass was 12 yr for the SM and 5 yr for the LF. The k1 values (litterfall/standing crop) were 1.9 and 2.0 for SM and LF respe ctively. The influence of coastal road and wall in the hydroperiod, na tive forested wetland ecosystem survival and exotic forest invasion is discussed.