A novel moisture adjusted vegetation index (MAVI) to reduce background reflectance and topographical effects on LAI retrieval.

Gaolong Zhu,Yibo Liu,Weimin Ju,J M Chen,Lalit Kumar

doi:10.1371/journal.pone.0102560

Abstract

A new moisture adjusted vegetation index (MAVI) is proposed using the red, near infrared, and shortwave infrared (SWIR) reflectance in band-ratio form in this paper. The effectiveness of MAVI in retrieving leaf area index (LAI) is investigated using Landsat-5 data and field LAI measurements in two forest and two grassland areas. The ability of MAVI to retrieve forest LAI under different background conditions is further evaluated using canopy reflectance of Jack Pine and Black Spruce forests simulated by the 4-Scale model. Compared with several commonly used two-band vegetation index, such as normalized difference vegetation index, soil adjusted vegetation index, modified soil adjusted vegetation index, optimized soil adjusted vegetation index, MAVI is a better predictor of LAI, on average, which can explain 70% of variations of LAI in the four study areas. Similar to other SWIR-related three-band vegetation index, such as modified normalized difference vegetation index (MNDVI) and reduced simple ratio (RSR), MAVI is able to reduce the background reflectance effects on forest canopy LAI retrieval. MAVI is more suitable for retrieving LAI than RSR and MNDVI, because it avoids the difficulty in properly determining the maximum and minimum SWIR values required in RSR and MNDVI, which improves the robustness of MAVI in retrieving LAI of different land cover types. Moreover, MAVI is expressed as ratios between different spectral bands, greatly reducing the noise caused by topographical variations, which makes it more suitable for applications in mountainous area.

Highlights

In recent decades, numerous spectral vegetation indices (VIs) derived from remotely sensed data have been developed to monitor the Earth’s vegetation cover and retrieve vegetation parameters such as leaf area index (LAI), fractional vegetation cover, biomass, and photosynthetic activity [1,2,3,4]
3.1 Relationships between VIs and LAI Seven VIs including normalized difference vegetation index (NDVI), Soil adjusted vegetation index (SAVI), Optimized soil adjusted vegetation index (OSAVI), Modified soil adjusted vegetation index (MSAVI), reduced simple ratio (RSR), modified normalized difference vegetation index (MNDVI), and moisture adjusted vegetation index (MAVI), full descriptions found in Table 1, are selected and calculated from the Thematic Mapper (TM) surface reflectance image to investigate their sensitivity to LAI
We develop a new three-band moisture adjusted vegetation index (MAVI)

Summary

Introduction

Numerous spectral vegetation indices (VIs) derived from remotely sensed data have been developed to monitor the Earth’s vegetation cover and retrieve vegetation parameters such as leaf area index (LAI), fractional vegetation cover, biomass, and photosynthetic activity [1,2,3,4] These VIs are often algebraic combinations of spectral reflectance in the red and near infrared (NIR) wavebands, for example, the most commonly used simple ratio (SR) [5] and normalized difference vegetation index (NDVI) [6]. It has been recognized that taking ratios between different spectral bands has the advantage of reducing unwanted noise caused by topography

Methods

Results

Conclusion