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Geo-information Science and Remote Sensing Thesis Report GIRS-2020-32 Assessing Utilization Intensity of Rangelands Based on Remote Sensing-Derived Carrying Capacity Models and Stocking Density: A case study in Bulgan, Mongolia Sietse van der Woude, [email protected] 2020 ne 23, Ju ii iii Assessing Utilization Intensity of Rangelands Based on Remote Sensing-Derived Carrying Capacity Models and Stocking Density: a case study in Bulgan, Mongolia Sietse van der Woude, [email protected] Registration number: 95 09 12 973 010 Supervisors: dr. NE Tsendbazar (Geo-Information Science & Remote Sensing, WUR) dr.ir. JGPW Clevers (Geo-Information Science & Remote Sensing, WUR) A thesis submitted in partial fulfilment of the degree of Master of Science at Wageningen University and Research Centre, The Netherlands. 23-06-2020 Wageningen, The Netherlands Thesis code number: GRS-80436 Thesis Report: GIRS-2020-32 Wageningen University and Research Centre Laboratory of Geo-Information Science and Remote Sensing iv Abstract Rangelands cover a large proportion of the earth’s surface, upon which a great deal of biodiversity, but also livelihoods of people depend. Rangeland management on varying scales has been able to benefit from the implementation of remote-sensing based information. However, the interests of different scales of rangeland management, from local to international, have differing requirements for remote-sensing based data in terms of cost, accuracy and speed in order to asses rangeland utilization intensity. In this research, the accuracy of a MODIS Net Primary Productivity-based model (process-based model) developed for Azerbaijan for aboveground carrying capacity in rangelands was compared to that of locally-trained a Landsat 8 surface reflectance-based empirical (Cubist) model. These models were coupled with stocking density estimates derived from summer herder locations to identify areas in which overgrazing had occurred. This was performed for the study area of Bulgan province, Mongolia. It was shown that the performance of the process-based model when applied to Bulgan resulted in low accuracy, however the model performed comparably to the model developed in a previous study for Azerbeijan. Despite this, the mean of the biomass predictions differed significantly from the mean of the observed values (p < 0.05). The empirical model delivered better performance than the process-based model and did not result in significant differences between the means of predictions and observed biomass values (p > 0.05). Due to overprediction of biomass by the process-based model, overgrazing was not estimated to be as extensive by the process- based model as by the empirical model. However, the process-based model and validation strategies could be further fine-tuned until the accuracy of an NPP-based model could be comparable to that of a strictly empirical model and applicable for use in inter-regional or international comparison of overgrazing levels. Keywords: rangeland, biomass, overgrazing, forage, degradation, Landsat, Modis v Acknowledgements I thank my parents, Cees and Christel, for putting up with me moving back home during difficult times, keeping my spirits up, and all the lovely meals and express-zo’s without which I would have not even been close to finishing my thesis. I would like to thank Nandika Tsendbazar and Jan Clevers for their guidance, tips and flexibility, especially in transitioning from working in the office and working at home. Finally, I would like to thank all my friends for always providing a listening ear and encouragement when I needed it. vi Contents Abstract ..................................................................................................................................... iv Acknowledgements .................................................................................................................... v List of Figures ............................................................................................................................ viii List of Tables ............................................................................................................................... x 1. Introduction ............................................................................................................................ 1 1.1. Context & Background ..................................................................................................... 1 1.2. Problem Definition .......................................................................................................... 4 1.3. Objectives ........................................................................................................................ 7 Research questions:............................................................................................................ 7 4. Methodology .......................................................................................................................... 8 4.1. Study Area ....................................................................................................................... 8 4.2. Data ............................................................................................................................... 10 4.2.1. Process-based model ............................................................................................. 10 4.2.2. Empirical model ...................................................................................................... 11 4.2.3. Sustainably usable biomass .................................................................................... 14 4.2.4. Forage Intake .......................................................................................................... 15 4.3. Models ........................................................................................................................... 16 4.3.1. Process-based model ............................................................................................. 16 4.3.2. Empirical model ...................................................................................................... 18 4.4. Validation ....................................................................................................................... 21 4.4.1. Cross-validation ...................................................................................................... 21 4.4.2. NDVI-adjustment of process-based model ............................................................ 21 4.4.3. Performance Metrics .............................................................................................. 22 4.5. Workflow ....................................................................................................................... 23 4.5.1. Aboveground biomass prediction using empirical model ...................................... 24 4.5.2. Aboveground biomass prediction using process-based model ............................. 24 4.5.3. Forage intake prediction ......................................................................................... 25 4.5.4. Further processing and overlay of outputs ............................................................ 26 4.6. Software ........................................................................................................................ 27 5. Results .................................................................................................................................. 27 5.1. Process-based model..................................................................................................... 27 5.1.1. Performance ........................................................................................................... 27 5.1.2. Biomass predictions: Process-Based model ........................................................... 31 vii 5.2. Empirical model ............................................................................................................. 33 5.2.1. Exploratory analysis ................................................................................................ 33 5.2.2. Model selection and performance ......................................................................... 34 5.2.3. Biomass predictions: Empirical model ................................................................... 39 5.3. Forage Intake ................................................................................................................. 42 5.4. Overgrazing .................................................................................................................... 44 5.4.1. Relative grazing pressure: Overview ...................................................................... 44 5.4.2. Ecoregion and local-scale differences in overgrazing ............................................. 47 6. Discussion ............................................................................................................................. 50 6.1. Model performance ...................................................................................................... 50 6.2 Carrying capacity and forage intake ............................................................................... 53 6.3. Overgrazing .................................................................................................................... 55 7. Conclusion ...........................................................................................................................