Substrate age and precipitation effects on Hawaiian forest canopies from spaceborne imaging spectroscopy

Gregory P. Asner, Kimberly M. Carlson, Roberta E. Martin

Research output: Contribution to journalArticle

32 Scopus citations

Abstract

We used spaceborne imaging spectroscopy provided by the Earth Observing-1 Hyperion sensor to quantify the relative importance of precipitation and substrate age that control ecosystem development and functioning in Metrosideros polymorpha rainforests of Hawaii. Four hyperspectral vegetation indices provided metrics of forest canopy structure, biochemistry and physiology to compare along gradients of annual rainfall (750 to > 6000 mm year- 1) and substrate age (0 to 250,000 years). The canopy greenness index NDVI increased with annual precipitation and substrate age, but saturated in forests with rainfall of 3000 mm year- 1. Precipitation and substrate age were roughly equal contributors to the observed greenness of the forests. A canopy water content index (NDWI) also increased with precipitation and substrate age, but did not reach a maximum until very wet (> 5000 mm year- 1) forest conditions were encountered on the oldest substrates. The water index appears superior to the NDVI in capturing spatial and climate-substrate driven variations in canopy structure. The photochemical reflectance index (PRI) indicated highest light-use efficiency levels in canopies on the most developed substrates and at annual precipitation levels of 3-4500 mm year- 1. A leaf carotenoid index (CRI) suggested a maximum canopy photosynthetic capacity at ∼ 4000 mm rainfall year- 1 on the oldest substrates. These results quantify the sensitivity of rainforest canopies to changing precipitation and soil conditions, and they corroborate plot-scale analyses in native Hawaiian forests ecosystems. Structural and functional studies of remote rainforest regions are possible with spaceborne imaging spectroscopy, and could be used to understand the dynamics of rainforests with climate change.

Original languageEnglish (US)
Pages (from-to)457-467
Number of pages11
JournalRemote Sensing of Environment
Volume98
Issue number4
DOIs
StatePublished - Oct 30 2005
Externally publishedYes

Keywords

  • Canopy chemistry
  • Earth Observing-1
  • Hawaii
  • Hyperion
  • Hyperspectral remote sensing
  • Metrosideros polymorpha
  • Rainforest

ASJC Scopus subject areas

  • Soil Science
  • Geology
  • Computers in Earth Sciences

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