Investigating the Potential Use of RADARSAT-2 and UAS imagery for Monitoring the Restoration of Peatlands

Lori White,Jon Pasher,Shari Hayne,Ridha Touzi,Jason Duffe,Mark Mcgovern

doi:10.3390/rs12152383

Abstract

The restoration of peatlands is critical to help reduce the effects of climate change and further prevent the loss of habitat for many species of flora and fauna. The objective of this research was to evaluate RADARSAT-2 satellite imagery and high-resolution Unmanned Aerial Systems (UASs) to determine if they could be used as surrogates for monitoring the success of peatland restoration. Areas of peatland that were being actively harvested, had been restored from past years (1994–2003), and natural shrub bog in Lac St. Jean, Quebec were used as a test case. We compared the Freeman–Durden and Touzi decompositions by applying the Bhattacharyya Distance (BD) statistic to see if the spectral signatures of restored peatland could be separated from harvested peat and natural shrub bog. We flew Unmanned Aerial Surveys (UASs) over the study site to identify Sphagnum and Polytrichum strictum, two indicator species of early peatland restoration success. Results showed that the Touzi decomposition was better able to separate the spectral signatures of harvested, restored, and natural shrub bog (BD values closer to 9). Symmetric scattering type αs1, Helicity |τ1,2,3|, a steep incidence angle, and peak growing season appear to be important for separating the spectral signatures. We had moderate success in detecting Sphagnum and Polytrichum strictum visually by using texture and pattern but were unable to use colour due to differences in sun angle and clouds during the UAS flights. Results suggest that RADARSAT-2 data using the Touzi decomposition and UAS imagery show potential for monitoring peatland restoration success over time.

Highlights

Canada has an estimated 123 million hectares of peatlands, which provide a variety of ecosystem services, such as unique habit for a variety of flora and fauna, and water storage, purification and flow control
The analysis of the Bhattacharyya Distance (BD) (Tables 2–4) values for both the FD and the ICTD demonstrates that the spectral signature of the restored peat became more similar to that of natural shrub bog (BD values closer to 0) the longer since it was restored
The BD values decreased gradually to 0.5 and 0.6 in the 15 July 2015, and 22 August 2015, FQ4 images respectively for peat restored in 1994–1995, indicating the spectral signature was very similar to that of natural shrub bog

Summary

Introduction

Canada has an estimated 123 million hectares of peatlands, which provide a variety of ecosystem services, such as unique habit for a variety of flora and fauna, and water storage, purification and flow control. The Canadian peat industry has been working along with academics and government agencies to reduce and mitigate the effects of peat harvesting disturbances for several years These efforts include developing and implementing field peatland restoration methods for post-harvest sites with the goal of re-establishing a Sphagnum moss cover. Restoration activities include drainage ditch blocking and berm construction to alter the hydrologic regime and the application of Sphagnum seed stock, and applying a mulch cover [5]. These activities can raise the water table, increase the soil pore water pressure, and decrease evapotranspiration [5,6,7], enabling the Sphagnum seed stock to generate a new moss carpet

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Conclusion