Document: ERI-3-59-79

Effects of introduced trees on soils in a Hawaiian montane rainforest.

LEVY, E.T.* and P.M.VITOUSEK

Stanford University, Stanford, CA 94305, USA ¹

Abstract:
We evaluated a series of monospecific tree stands planted in the 1930's on the island of Hawai'i to test how 14 different tree species affect soil properties. The tree stands are planted on the same substrate with similar climate, so any differences between plots can likely be attributed to tree species. Nitrogen fixing trees had N concentrations in litterfall more than two times greater than any other species resulting in a significant increase in net nitrification rates in soils under N-fixers. The concentration of N in litterfall was a better predictor of net nitrification rates (R² = 0.475) than pH (R² = 0.064). Native forests had significantly greater plant available nitrogen than all introduced species, which may result from immobilization of N in the biomass of fast-growing introduced trees, or greater leaching of N in the low-diversity tree plantations. We also analyzed Sr isotopic composition of leaf samples to differentiate between trees in their ability to obtain nutrients from depth. Access to rock-derived pools of nutrients deep in the soil may be particularly important in highly weathered tropical ecosystems where the supply of phosphorus or base cations often limit growth.

Keywords: plant-soil interactions, N cycling, nitrification, Sr isotopes, introduced species

This abstract is being presented at: 2:45 PM in session:
Oral Session #13: N Fixation and Biochemical Patterns.