Biomass and net primary productivity in savannas, Gran Sabana, Canaima National Park, Venezuela
Bibiana
Alejandra
Bilbao, Departamento de Estudios Ambientales, Universidad Simón Bolívar, Caracas, Venezuela, bibiana_bilbao@hotmail.com
(Presenting)
Zamira
Hasmy, Departamento de Estudios Ambientales, Universidad Simón Bolívar, Caracas, Venezuela, zahas@hotmail.com
Alejandra
Verónica
Leal, Departamento de Estudios Ambientales, Universidad Simón Bolívar, Caracas, Venezuela, aveleal@yahoo.com
Carlos
Luis
Méndez, Departamento de Estudios Ambientales, Universidad Simón Bolívar, Caracas, Venezuela, carlosmendez@etheron.net
Eduardo
Zambrano, Departamento de Estudios Ambientales, Universidad Simón Bolívar, Caracas, Venezuela, ezambrano@usb.ve
José
Manuel
Moreno, Facultad de Ciencias del Medio Ambiente, Universidad de Castilla- La Mancha, Toledo, España, JoseM.Moreno@uclm.es
In Canaima National Park (30000 km2), Venezuela, the use of fire for hunting and shifting agriculture is a common practice by natives. Stabilization of population at towns and villages has led to increased fire frequency, causing the conversion of many forest areas to open savanna. The patterns of accumulation of biomass in this ecosystem and the productivity processes thereon associated are poorly known. In this study we measured the annual dynamics of net primary productivity (NPP) in a tropical savanna located in Gran Sabana, CNP. During five consecutive years above (AB) and belowground biomass (BB) was periodically harvested. ANPP varied annually, leading to net accumulation or decrease of AB (with maximum of 1100 g DM m-2). Positive ANPP ranged between 187 to 537 g DM m-2 year-1, and was related to the length of the growing season and total annual precipitation. Unlike in other tropical savannas, these low values were not related to the positive annual hydrological balance. No seasonal fluctuations in the decomposition rates (~1.2 mg DM g-1 day-1) were observed, which were rather low. Grasses had the highest species richness; however sedges accumulated greater AB. Dominant grasses and sedges present a high accumulation of BB (~1214 g DM m-2) and a peculiar development of big aerial rhizomes that represent 42 % of AB. In general, these results evidence the low NPP and biomass accumulation capacity of these savannas after fire. One year after fire only 50% of the total biomass is recovered. Thus, fire recurrence can occur only at 2 or more years after fire.
Submetido por Bibiana Alejandra Bilbao em 24-MAR-2004
Tema Científico do LBA: CD (Armazenamento e Trocas de Carbono)