PARENT SESSION
Oral Session #15: Ecosystem Ecology. Presiding: J. Jenkins.
Monday, August 6, 2001. 1:00 PM to 4:45 PM. Hall of Ideas F.
Parent material controls on ecosystem carbon stocks and nutrient cycling.
Giardina, Christian1, Dockersmith, Ingrid1, Voung, Richard2, Sanford, Robert2, Tsib, Feliz3, 1 2 3
ABSTRACT- Parent material can exert a large influence on nutrient cycling, plant productivity and species composition, but this influence is poorly quantified in seasonally dry tropical forests. In western Belize, broad-leaved forest and pine woodland grow in soils derived from limestone and granite parent materials, respectively. Nutrient poor Entisols derived from limestone supported a diverse flora with 27 tree species across test plots, while extremely nutrient poor Ultisols derived from granite supported one-third the number of species. Above and belowground productivity, assessed by quantifying total standing biomass in 38 yr old stands formed after synchronous stand-replacing disturbances, were also influenced by parent material. Broad-leaved forests accumulated 30% greater aboveground woody biomass (74 and 58 Mg/ha, respectively), and maintained 100% greater fine and intermediate root biomass to 50 cm (640 and 270 g/m2, respectively). Forest floor standing stock was slightly higher in broad-leaved forest than pine woodlands (490 and 419 g/m2, respectively). In line with biomass estimates, nitrogen availability and phosphorus fractions, as determined in the field with buried resin bags and in laboratory assays, were 3 to 7 fold higher in broad-leaved forest than in pine woodland soils. At this tropical site, parent material appears to exert a large-scale influence on the biogeochemistry and species composition of native forest ecosystems.
KEY WORDS: tropical forest, parent material, carbon, nutrients