REMOTE SENSING TO CHARACTERISE VEGETATION FUEL MOISTURE CONTENT IN THE UK UPLANDS ABDULBASET HAMED A. BADI Ecosystems and Environment Research Centre School of Science, Engineering & Environment University of Salford Salford, M5 4WT, UK Submitted in Partial Fulfilment of the Requirements of the Degree of Doctor of Philosophy, April 2019 Contents Contents .................................................................................................................................. i List of tables .......................................................................................................................... v List of figures ....................................................................................................................... vi Dedication ............................................................................................................................. ix Acknowledgments ................................................................................................................. x Declaration............................................................................................................................ xi List of Acronyms ................................................................................................................. xii Abstract ............................................................................................................................... xiii CHAPTER 1: INTRODUCTION ...................................................................................... 1 1.1 Introduction .................................................................................................................. 1 1.2 Research aims and objectives ...................................................................................... 3 1.3 Original contribution of the research ........................................................................... 9 1.4 Structure of research .................................................................................................. 10 CHAPTER 2: LITERATURE REVIEW ........................................................................ 13 2.1 Introduction. ............................................................................................................... 13 2.2 UK upland vegetation and wildfires .......................................................................... 13 2.2.1 Importance of uplands ......................................................................................... 14 2.2.2 Plant communities in upland areas ...................................................................... 16 2.2.3 Wildland fires in context ..................................................................................... 17 2.2.4 Fire risk modelling approaches ........................................................................... 20 2.3 Vegetation fuel properties .......................................................................................... 25 2.3.1 Wildland vegetation fuel properties .................................................................... 25 2.3.2 Importance of fuel moisture content ................................................................... 27 2.3.3 Vegetation water content ..................................................................................... 29 2.3.4 Measured fuel moisture content .......................................................................... 30 2.4 Characterising vegetation with remote sensing ......................................................... 31 2.4.1 Electromagnetic radiation ................................................................................... 32 2.4.2 Atmospheric interactions..................................................................................... 33 2.5 Remote sensing and vegetation biophysical properties ............................................. 35 2.5.1 Spectral properties of leaf and canopy ................................................................ 35 2.5.1.1 Leaf reflectance ............................................................................................ 35 2.5.1.2 Canopy reflectance ....................................................................................... 38 i 2.5.1.3 Soil reflectance ............................................................................................. 41 2.5.2 Vegetation Indices ............................................................................................... 42 2.5.2.1 Normalized Difference Water Index (NDWI) .............................................. 44 2.5.2.2 Moisture Stress Index (MSI) ........................................................................ 44 2.5.3 Remote sensing of vegetation moisture content .................................................. 45 2.6 Radiative Transfer Models ......................................................................................... 47 2.6.1 Scattering by arbitrary inclined leaves (SAIL) model ........................................ 49 2.6.2 Model of leaf optical properties spectra (PROSPECT) ...................................... 49 2.7 Conclusion ................................................................................................................. 50 CHAPTER 3: LABORATORY EXPERIMENT AND RADIATIVE TRANSFER MODELLING .................................................................................................................... 52 3.1 Introduction ................................................................................................................ 52 3.2 Laboratory experiments ............................................................................................. 53 3.2.1 Preparation of vegetation samples....................................................................... 53 3.2.2 ASD measurement protocol ................................................................................ 54 3.2.3 Experiment 1: Spectral reflectance with FMC variation ..................................... 56 3.2.3.1 Results .......................................................................................................... 57 3.2.4 Experiment 2: Effects of soil background ........................................................... 60 3.2.4.1 Results .......................................................................................................... 61 3.2.5 Experiment 3: Different ‘solar’ zenith angles ..................................................... 64 3.2.5.1 Results .......................................................................................................... 64 3.3 Radiative Transfer Modelling .................................................................................... 66 3.3.1 Simulating the relationship between FMC and VI .............................................. 68 3.3.1.1 Results .......................................................................................................... 69 3.3.2 Simulating the effects of different soil backgrounds .......................................... 71 3.3.2.1 Results .......................................................................................................... 71 3.3.3 Simulating the effects of different solar zenith angles ........................................ 73 3.3.3.1 Results .......................................................................................................... 73 3.4 Conclusion ................................................................................................................. 75 CHAPTER 4: STUDY AREA, FIELD WORK AND IMAGE DATA ANALYSIS .... 76 4.1 Introduction ................................................................................................................ 76 4.2 Study area .................................................................................................................. 76 4.3 Climate ....................................................................................................................... 79 4.4 Vegetation .................................................................................................................. 81 ii 4.5 Wildfires in the Peak District ..................................................................................... 84 4.6 Fieldwork study area .................................................................................................. 88 4.6.1 Sampling design .................................................................................................. 89 4.6.2 Vegetation and soil sampling .............................................................................. 93 4.7 Laboratory work ........................................................................................................ 94 4.7.1 FMC and soil moisture measurements ................................................................ 94 4.8 Remote sensing data sets ........................................................................................... 94 4.8.1 Atmospheric correction ....................................................................................... 95 4.8.1.1 Sen2Cor ........................................................................................................ 96 4.8.1.2 LEDAPS ....................................................................................................... 96 4.8.2 Spectral measurements ........................................................................................ 96 4.8.3 Surface reflectance