Biomass estimation of wetland vegetation in Poyang Lake area using ENVISAT advanced synthetic aperture radar data

Jingjuan Liao,Guozhuang Shen,Lei Dong

doi:10.1117/1.jrs.7.073579

Abstract

Biomass estimation of wetlands plays a role in understanding dynamic changes of the wetland ecosystem. Poyang Lake is the largest freshwater lake in China, with an area of about 3000 km 2 . The lake’s wetland ecosystem has a significant impact on leveraging China’s environmental change. Synthetic aperture radar (SAR) data are a good choice for biomass estimation during rainy and dry seasons in this region. In this paper, we discuss the neural network algorithms (NNAs) to retrieve wetland biomass using the alternating-polarization ENVISAT advanced synthetic aperture radar (ASAR) data. Two field measurements were carried out coinciding with the satellite overpasses through the hydrological cycle in April to November. A radiative transfer model of forest canopy, the Michigan Microwave Canopy Scattering (MIMICS) model, was modified to fit to herbaceous wetland ecosystems. With both ASAR and MIMICS simulations as input data, the NNA-estimated biomass was validated with ground-measured data. This study indicates the capability of NNA combined with a modified MIMICS model to retrieve wetland biomass from SAR imagery. Finally, the overall biomass of Poyang Lake wetland vegetation has been estimated. It reached a level of 1.09×10 9 , 1.86×10 8 , and 9.87×10 8 kg in April, July, and November 2007, respectively.

Highlights

Wetlands are an important component of global ecosystems because of their role in maintenance of environmental quality and biodiversity
Biomass distributions of Poyang Lake wetlands in April, July, and November 2007 were mapped using ENVISAT advanced synthetic aperture radar (ASAR) data and Michigan Microwave Canopy Scattering (MIMICS)-fed neural network analysis (Fig. 8)
This study focused on the application of neural network algorithms (NNAs) combined with the MIMICS model to retrieve wetland vegetation biomass with ENVISAT ASAR alternative polarization data

Summary

Introduction

Wetlands are an important component of global ecosystems because of their role in maintenance of environmental quality and biodiversity. Wetland biomass is a key index to the health of the wetland ecosystem and provides quantitative information for understanding its ecological and environmental functions.[1] Conventional methods of in situ estimation are often time consuming, labor intensive, and difficult to implement, especially in remote areas. Isolated plot measurements cannot provide spatial distribution of biomass in large areas. The advantages of remote-sensing techniques, such as repetition of data collection, a synoptic view, a digital format that allows fast processing of large quantities of data, and high correlations between spectral bands and vegetation parameters, make it an efficient source for large-area biomass estimation, especially in areas of difficult access. Remote sensing–based biomass estimation has increasingly attracted scientific attention.[2]

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