PARENT SESSION
Oral Session # 60: Invasive Species V: Genetics; Chemical Cycling Effects.
Presiding: S Miao
Wednesday, August 6. 1:30 PM to 5:00 PM, SITCC Meeting Room 204.
Decomposition and nutrient dynamics in native and exotic Hawaiian understory plant litter.
Allison, Steven*,1, Vitousek, Peter1, 1 Stanford University, Stanford, CA, USA
ABSTRACT- We studied decomposition rates and nutrient dynamics in 15 understory plant litter types from the Hawaiian islands in control and N + P fertilized plots. The 15 litter types included 6 exotic species, 4 types of stem material, and 5 fern species. Using measurements of initial litter chemistry, litter nutrient dynamics, and mass loss over time, we investigated the potential for changes in litter inputs to affect ecosystem nutrient cycling. We found a 100-fold variation in litter decay rates, with native leaf litter decaying at rates of 0.2-2.3 yr-1 and exotic leaf litter at rates of 1.4-9.4 yr-1. Angiosperm litter decayed more rapidly than fern litter, and leaves generally decayed more rapidly than stems. Fertilization increased the decay rates of exotic litter types, but left most native litter decay rates unchanged. Only litter from 3 native ferns and litter from an exotic ginger was able to retain or immobilize N after 100 days of decomposition. All litter types except the recalcitrant native ferns lost > 50% of initial P during decomposition. Fertilization increased nutrient immobilization or delayed the onset of nutrient loss for most litter types. If native understory plants are displaced by invasives, nutrient cycling rates could increase dramatically due to rapid decomposition and nutrient release in exotic litter. Rapid decay rates and acceleration of exotic litter decomposition in response to nutrient additions could create a positive feedback between invasion, decomposition, and nutrient cycling rates.
Key words: litter decomposition, invasive species, Hawaii, fertilization