PARENT SESSION
Oral Session #33: Biodiversity and Ecosystem Function: Nutrients, soils, microbes.
Presiding: K. Brown
Tuesday, August 6. 8:00 AM to 11:30 AM. Grand Ballroom Central, Radisson.

Nutrient retention in tropical plantations: costs and benefits of enhanced plant life-form diversity.

BIGELOW, SETH^*,1,3, EWEL, JOHN^2,3, ¹ Institute of Ecosystem Studies, Millbrook, NY³ University of Florida Department of Botany, Gainesville, FL² USDA-FS Institute of Pacific Islands Forestry, Honolulu, HI

ABSTRACT- Richness of plant life forms has been hypothesized to affect ecosystem attributes such as retention of nutrients. To test this, we designed a field experiment incorporating perennial plants at a lowland site in the humid tropics. Three indigenous tree species were grown alone and in combination with interplanted palms and heliconias. Nutrient retention was assessed by applying a water balance to concentrations of nutrients in soil water from ceramic cup samplers at a depth of 1.1 m. For one tree species there was no effect of increased life form diversity on nutrient retention, and for the other trees effects of increased diversity were not consistently observed until ~6 yr after stand establishment. In comparison to single-species stands, multi-species stands of Cedrela showed diminished leaching losses of NO₃ but elevated losses of Ca and Mg. Multi-species stands of Hyeronima showed lower leaching losses of Ca and Mg than single-species stands but did not differ in NO₃ losses. Beneficial effects of increased life-form diversity on ecosystem nutrient retention are contingent on species characteristics, duration of interaction, and nutrient. All three factors must be understood, lest augmentation of life-form diversity lead to increased nutrient losses.

KEY WORDS: plant life-form diversity, nutrient leaching, tropical tree plantation, water balance