PARENT SESSION
Poster Session # 13: Biogeochemistry, Photosynthesis, and Respiration.
Tuesday, August 5 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.
Leaf litter addition effects upon soil nutrients in a wet tropical forest.
Conner, Cristin*,1, Wood, Tana1, Lawrence, Deborah1, 1 University of Virginia, Charlottesville, VA
ABSTRACT- Plant growth and soil organic matter in lowland tropical rain forests are widely considered to be limited by phosphorus (P). Litterfall is a major source of P return to the soil; hence, the relationship between litter inputs and soil nutrient content is an important component of nutrient cycling in these systems. We investigated soil-litter interactions in a tropical lowland rain forest in Costa Rica. In order to evaluate this relationship, we experimentally manipulated litter along an age gradient in forest recovering from pasture. At each of six sites, we removed litter from a 400m2 area and added it to a 100m2 area with two replicates per site. This is equal to a four-fold increase in litterfall. We sampled soil to 5cm depth in addition and control plots monthly for a period of 7 months after litter addition. Soils were air-dried and digested using a modified Kjeldahl digestion. The digestate was then analyzed colorometrically for total P. Secondary forest sites had significantly higher total P than mature forest sites (1.02 mg/g in secondary versus 0.62 mg/g in mature; p<0.05). Total P was highest in June and as the rainy season progressed, P decreased in both the control and litter addition plots regardless of forest age. Thus, the decline in total soil P is likely related more to environmental factors than to the amount of litter being decomposed. Further research should focus on the influence of environmental factors such as soil moisture and pH that might influence this process.
Key words: litter addition, nutrient cycling