We examined the effects of soil nutrient availability and tissue chemistry on decomposition of both fine roots (<2 mm diameter) and leaves in three sites along a forest chronosequence in the Hawaiian Islands. These sites form a natural fertility gradient, with the youngest and oldest sites having lower nutrient availability than the intermediate-aged site. Nitrogen (N) limits aboveground net primary productivity (ANPP) in the youngest site, while phosphorus (P) limits ANPP in the oldest site. Both root and leaf litter decomposed most slowly in the 4.1-Myear-old site. We also investigated root decomposition in fertilized plots at the youngest and oldest sites; when roots were produced and decomposed in fertilized plots, root decomposition rates increased with N and P additions at the 4.1-Myear-old site. At the 300-year-old site, however, root decomposition rates did not respond to N or P additions. Roots decomposed faster than leaves at the more infertile sites, in part because of lower lignin-to-nitrogen ratios in roots than in leaf litter. Decomposing roots immobilized more nutrients than did decomposing leaves, and may serve an important role in retaining nutrients in these forests.
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Acknowledgements We thank Jack Ewel, Jack Putz, Peter Vitousek, and Kim Williams for advice on experimental aspects of this study; Peter Vitousek for logistical support of many kinds; and Heraldo Farrington for help in the field. We are grateful to Hawai’i Volcanoes National Park, the state of Hawaii Division of Forestry and Wildlife, and the Department of Parks and Recreation in Kaua’i for providing access to field sites. Lodging and logistical assistance on Kauai was graciously provided by the Joseph Souza Center in Kokee State Park. Doug Turner (Stanford University) provided the N and P analysis and Brad Dewey (University of Minnesota-Duluth) provided carbon fraction analyses. Many helpful comments on this manuscript were made by Nick Comer-ford, Jack Ewel, Steve Mulkey, Jack Putz, Ted Schuur, Whendee Silver, and Kim Williams. This research was supported by grants to R.O. from the National Science Foundation and the National Geographic Society and a NSF post-doctoral fellowship to S.E.H.
Copyright 2004 Elsevier Science B.V., Amsterdam. All rights reserved.
- Lignin-to-nitrogen ratios
- Metrosideros polymorpha
- Nutrient accumulation
- Nutrient limitation