Modelling Semiarid Water-Soil-Vegetation Systems in a Changing Climate

Description

Water-soil-vegetation dynamic nexuses affect, and are affected by, both human activity and climate change. For a given area, inappropriate land management practices can result in soil and vegetation degradation, which in turn will likely alter natural hydrologic processes, leading to more frequent and severe flooding and drought. In response, an altered hydrologic condition tends to prompt soil erosion by wind and water, which can cause further vegetation degradation or even loss. Such nexuses will likely become more interwoven in changing climate because the non-stationary climate can further deteriorate the already-altered hydrologic condition. So far, our understanding is incomplete regarding how such nexuses maintain or break equilibriums between water, soil, and/or vegetation in terms of eco-environmental resilience. This book: 1) conceptualises the interrelated physical processes of water-soil-vegetation systems; 2) introduces mathematical models for simulating the processes; and 3) develops a variety of modelling cases of selected systems across the world. Currently, there are no books focusing on this topic though some incomplete information has been scattered in various peer-reviewed journals and project reports. This book provides a systematic elucidation of this important topic and serves as a one-stop information source. Upon reading this book, the reader can apply the materials to conduct advanced research on this topic and develop practical measures in protecting fragile vegetation ecosystems and confronting climate change. The broader application is to prevent land degradation and desertification as induced by climate change and human activities (e.g., development and grazing). Recommended for researchers and graduate students. Key Features: Includes both fundamental principles and practical applicationsEmphasizes semiarid water-soil-vegetation nexuses rather than individual processesDeciphers dynamics and interrelations of the physical processes of semiarid water-soil-vegetation systemsAddresses impacts of climate change from practical management perspectivesMaximizes readability by including illustrations, pictures, and annotated equations. PRELIMS.pdf Preface Acknowledgements Author biography Xixi Wang CH001.pdf Chapter 1 Overview 1.1 Problems and challenges 1.2 Hypotheses and questions 1.3 Modeling framework 1.4 The structure of this book References CH002.pdf Chapter 2 Physical processes 2.1 Characteristics of semi-arid ecosystems 2.2 Water–heat–carbon cycles 2.2.1 Bare land surface with loose topsoil 2.2.2 Bare land surface with physical crust 2.2.3 Bare land surface with biocrust 2.2.4 Vegetated land surface 2.3 The abiotic and biotic properties of semi-arid soils 2.3.1 The abiotic properties 2.3.2 The biotic properties 2.4 Land–atmosphere interactions 2.5 Soil water dynamics 2.6 Vegetation community composition 2.7 Equilibrium and shift 2.8 Summary and discussion References CH003.pdf Chapter 3 Conceptualizations 3.1 Approximation of semi-arid ecosystems 3.2 Ground-surface processes 3.2.1 Interception 3.2.2 Penetration 3.2.3 Evaporation 3.2.4 Effluent 3.3 Rootzone processes 3.3.1 Water source and sink 3.3.2 Carbon source and sink 3.4 Below-rootzone processes 3.5 Plant growth and senescence 3.5.1 Growth 3.5.2 Senescence and net growth 3.6 Topsoil erosion 3.6.1 Aeolian erosion 3.6.2 Fluvial erosion 3.6.3 Effects of physical and biological crusts on erosion 3.7 Summary and discussion References CH004.pdf Chapter 4 Mathematical models 4.1 Overview 4.2 Comparisons of existing models 4.2.1 HYDRUS-1D 4.2.2 SWAT 4.2.3 SWAP 4.2.4 Comparisons 4.3 Model selection 4.4 Development of new algorithms 4.4.1 Physical crusts 4.4.2 Biocrusts 4.4.3 Low-moisture soils 4.4.4 Dry soil layers 4.4.5 The SWAP-E model 4.5 Measures of model performance 4.5.1 Empirical judgement 4.5.2 Visualization plot 4.5.3 Statistics 4.6 Model parameterization and calibration 4.6.1 Initial parameter values 4.6.2 Sensitivity analysis 4.6.3 Optimization of sensitive parameters 4.6.4 Parameter uncertainty and model robustness 4.6.5 Relevant computer programs 4.7 Summary and discussion Declaration References CH005.pdf Chapter 5 Case studies 5.1 Study sites 5.1.1 The Balagaer River watershed in North China 5.1.2 The HSL site in North China 5.1.3 The upper Cowhouse Creek watershed in USA 5.2 Long-term soil moisture responses to climate and livestock grazing 5.2.1 Background 5.2.2 Materials and methods 5.2.3 Results 5.2.4 Discussion 5.2.5 Conclusions 5.3 The effects of climate and livestock grazing on precipitation consumption 5.3.1 Introduction 5.3.2 Materials and methods 5.3.3 Results 5.3.4 Discussion 5.3.5 Conclusions 5.4 Topsoil erosion as influenced by climate and vegetation coverage 5.4.1 Background 5.4.2 Model formulization 5.4.3 Materials and methods 5.4.4 Results and discussion 5.4.5 Conclusions 5.5 Retardation effects of a dry soil layer on soil water evaporation 5.5.1 Introduction 5.5.2 Data and methods 5.5.3 Results 5.5.4 Discussion 5.5.5 Summary and conclusions 5.6 Grass productivity as influenced by climate and livestock grazing 5.6.1 Background 5.6.2 Model development 5.6.3 Materials and methods 5.6.4 Results and discussion 5.6.5 Conclusions 5.7 Interactive effects of land use and soil on water and sediment yields 5.7.1 Background 5.7.2 Materials and methods 5.7.3 Results and discussion 5.7.4 Summary and conclusions 5.8 The effects of biocrusts on water balance and soil erosion 5.8.1 Introduction 5.8.2 Materials and methods 5.8.3 Results 5.8.4 Discussion 5.8.5 Conclusions 5.9 Resilience and degradation of semi-arid ecosystems 5.9.1 Introduction 5.9.2 The WERT 5.9.3 Methods 5.9.4 Results 5.9.5 Discussion 5.9.6 Conclusions 5.10 Summary and general conclusions References CH006.pdf Chapter 6 Overall conclusions and discussion 6.1 Major findings 6.2 Broad discussion 6.3 Further research References APP1.pdf Chapter APP2.pdf Chapter APP3.pdf Chapter