Shrubs Compensate for Tree Leaf Area Variation and Influence Vegetation Indices in Post-Fire Siberian Larch Forests

Nadav S. Bendavid, Heather D. Alexander, Sergei P. Davydov, Heather Kropp, Michelle C. Mack, Susan M. Natali, Seth A. Spawn-Lee, Nikita S. Zimov, Michael M. Loranty

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

In post-fire Siberian larch forests, where tree density can vary within a burn perimeter, shrubs constitute a substantial portion of the vegetation canopy. Leaf area index (LAI), defined as the one-sided total green leaf area per unit ground surface area, is useful for characterizing variation in plant canopies. We estimated LAI with allometry for trees and tall shrubs (>0.5 and <1.5 m) across 26 sites with varying tree stem density (0.05–3.3 stems/m2) and canopy cover (4.6%–76.9%) in a uniformly-aged mature Siberian larch forest that regenerated following a fire ∼75 years ago. We investigated relationships between tree density, tree LAI, and tall shrub LAI, and between LAI and satellite observations of Normalized Difference and Enhanced Vegetation Indices (NDVI and EVI). Across the density gradient, tree LAI increases with increasing tree density, while tall shrub LAI decreases, exhibiting no patterns in combined tree-shrub LAI. We also found significant positive relationships between tall shrub LAI and NDVI/EVI from PlanetScope and Landsat imagery. These findings suggest that tall shrubs compensate for lower tree LAI in tree canopy gaps, forming a canopy with contiguous combined tree-shrub LAI across the density gradient. Our findings suggest that NDVI and EVI are more sensitive to variation in tall shrub canopies than variation in tree canopies or combined tree-shrub canopies in these ecosystems. The results improve our understanding of the relationships between forest density and tree and shrub leaf area and have implications for interpreting spatial variability in LAI, NDVI, and EVI in Siberian boreal forests.

Original languageEnglish (US)
Article numbere2022JG007107
JournalJournal of Geophysical Research: Biogeosciences
Volume128
Issue number3
DOIs
StatePublished - Mar 2023

Keywords

  • boreal forest
  • leaf area index
  • shrubs
  • siberia
  • trees
  • vegetation indices

ASJC Scopus subject areas

  • Forestry
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Atmospheric Science
  • Palaeontology

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