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

Author:

Bendavid Nadav S.12ORCID,Alexander Heather D.3,Davydov Sergei P.4,Kropp Heather5,Mack Michelle C.6,Natali Susan M.7,Spawn‐Lee Seth A.8,Zimov Nikita S.4,Loranty Michael M.1ORCID

Affiliation:

1. Department of Geography Colgate University Hamilton NY USA

2. Now at: School of the Environment, Yale University New Haven CT USA

3. College of Forestry, Wildlife, and Environment Auburn University Auburn AL USA

4. Pacific Geographical Institute Far East Branch Russian Academy of Sciences, Northeast Science Station Cherskiy Russia

5. Environmental Studies Program Hamilton College Clinton NY USA

6. Center for Ecosystem Science and Society Northern Arizona University Flagstaff AZ USA

7. Woodwell Climate Research Center Falmouth MA USA

8. Department of Geography University of Wisconsin Madison WI USA

Abstract

AbstractIn 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.

Funder

National Science Foundation

Publisher

American Geophysical Union (AGU)

Subject

Paleontology,Atmospheric Science,Soil Science,Water Science and Technology,Ecology,Aquatic Science,Forestry

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