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Leaf litter decomposition rates increase with rising mean annual temperature in Hawaiian tropical montane wet forests.

Authors
  • Bothwell, Lori D1
  • Selmants, Paul C2
  • Giardina, Christian P3
  • Litton, Creighton M2
  • 1 Natural Sciences Division, University of Hawaii at Hilo , Hilo, HI , USA.
  • 2 Department of Natural Resources and Environmental Management, University of Hawaii at Manoa , Honolulu, HI , USA.
  • 3 Institute of Pacific Islands Forestry, Pacific Southwest Research Station, USDA Forest Service , Hilo, HI , USA.
Type
Published Article
Journal
PeerJ
Publisher
PeerJ
Publication Date
Jan 01, 2014
Volume
2
Identifiers
DOI: 10.7717/peerj.685
PMID: 25493213
Source
Medline
Keywords
License
Unknown

Abstract

Decomposing litter in forest ecosystems supplies nutrients to plants, carbon to heterotrophic soil microorganisms and is a large source of CO2 to the atmosphere. Despite its essential role in carbon and nutrient cycling, the temperature sensitivity of leaf litter decay in tropical forest ecosystems remains poorly resolved, especially in tropical montane wet forests where the warming trend may be amplified compared to tropical wet forests at lower elevations. We quantified leaf litter decomposition rates along a highly constrained 5.2 °C mean annual temperature (MAT) gradient in tropical montane wet forests on the Island of Hawaii. Dominant vegetation, substrate type and age, soil moisture, and disturbance history are all nearly constant across this gradient, allowing us to isolate the effect of rising MAT on leaf litter decomposition and nutrient release. Leaf litter decomposition rates were a positive linear function of MAT, causing the residence time of leaf litter on the forest floor to decline by ∼31 days for each 1 °C increase in MAT. Our estimate of the Q 10 temperature coefficient for leaf litter decomposition was 2.17, within the commonly reported range for heterotrophic organic matter decomposition (1.5-2.5) across a broad range of ecosystems. The percentage of leaf litter nitrogen (N) remaining after six months declined linearly with increasing MAT from ∼88% of initial N at the coolest site to ∼74% at the warmest site. The lack of net N immobilization during all three litter collection periods at all MAT plots indicates that N was not limiting to leaf litter decomposition, regardless of temperature. These results suggest that leaf litter decay in tropical montane wet forests may be more sensitive to rising MAT than in tropical lowland wet forests, and that increased rates of N release from decomposing litter could delay or prevent progressive N limitation to net primary productivity with climate warming.

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