The effects of water depth on estimating Fractional Vegetation Cover in mangrove forests

Younes, Nicolas, Joyce, Karen E., Northfield, Tobin D., and Maier, Stefan W. (2019) The effects of water depth on estimating Fractional Vegetation Cover in mangrove forests. International Journal of Applied Earth Observation and Geoinformation, 83. 101924.

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Abstract

Maps of mangroves have often been limited to showing the presence or absence of mangrove trees and seldom have studies shown an important indicator of ecosystem integrity such as vegetation cover. Fractional Vegetation Cover (FVC) is used to assess ecosystem health, land cover and carbon stocks, hence accurately measuring FVC is an important task for scientists and land managers. Many methods have been proposed to measure FVC and simple linear models are commonly used. We created an experiment that allowed us to: 1) acquire very detailed hyperspectral imagery (1 mm pixel size) from a simulated mangrove forest, 2) measure the effect of water depth on FVC estimations, and 3) compare the relationship of eight spectral bands and indices with FVC using linear and non-linear models. After acquiring the imagery we corrected for dark signal and a white reference, performed spectral and spatial resampling, and created linear and non-linear models across four pixel sizes. Our results suggest that 1) linear and beta models have similar performance across all pixel sizes; 2) Soil Adjusted Vegetation Index (SAW), Modified Soil Adjusted Vegetation Index2 (MSAVI2) and Enhanced Vegetation Index (EVI) perform better than the Normalized Difference Vegetation Index (NDV), and, 3) our models perform better at fine pixel sizes than coarse scales. We tested our results on high-resolution satellite imagery with similar results and, therefore, recommend using SAW, EVI or MSAVI2 when predicting FVC instead of NDVI.

Item ID: 60699
Item Type: Article (Research - C1)
ISSN: 1872-826X
Keywords: Fractional vegetation cover, Beta regression, Linear regression, Tidal influence, Tidal height, Water effect size, Remote sensing
Copyright Information: © 2019 Elsevier B.V. All rights reserved.
Funders: James Cook University Postgraduate Research Fellowship, Wet Tropics Management Authority Student Research Grant
Date Deposited: 16 Oct 2019 07:41
FoR Codes: 09 ENGINEERING > 0909 Geomatic Engineering > 090905 Photogrammetry and Remote Sensing @ 50%
05 ENVIRONMENTAL SCIENCES > 0502 Environmental Science and Management > 050206 Environmental Monitoring @ 50%
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