Author: Wenjie Liu
Liu, Wenjie, 2025 Geospatial Modelling of Three-dimensional Structure and Ecohydrological Processes of Semi-arid Woodlands, Flinders University, College of Science and Engineering
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Semi-arid woodlands are important part of terrestrial ecosystems. Woodlands not only provide provisioning services (timber, fuel, food), but also regulating services like soil stabilization, air and water quality improvement, local microclimate regulation, and carbon sequestration. In the face of escalating climate change and human activities, conservation and sustainable management are vital for ensuring the long-term resilience of these ecosystems.
Remote sensing technology enables large-scale, high-frequency monitoring of terrestrial ecosystem dynamics. However, widely utilized satellite missions such as MODIS, Landsat, and Sentinel offer only low to moderate resolution data, while high-resolution imagery, although available, is prohibitively expensive. Additionally, all these satellite systems are prone to cloud contamination, leading to data gaps. Those factors constrain our ability to accurately observe woodland ecosystems at the tree scale. Moreover, current approaches to remote sensing-based ecosystem monitoring often simplify woodlands by treating them as flat surfaces, with a predominant focus on canopy-level processes, thereby neglecting the complex physical interactions occurring beneath the canopy.
The overarching aim of this study is to explore the above mentioned challenges and investigate the three-dimensional structure and ecohydrological processes of the semi-arid woodlands. Understanding woodland 3D structure is crucial for monitoring forest changes, supporting carbon emission reduction initiatives, enhancing forest fire management, and providing essential data for climate adaptation and sustainable forest management. Besides, forest canopy significantly influences the radiation transmission thereby controls the sub-canopy surface energy budget. Exploring the overstory vegetation attributes improves our knowledge of understorey ecohydrological processes, which enhances our comprehension of the overall ecosystem's energy and water balance.
In the first part of this research, the role of local environments in shaping vegetation attributes within semi-arid woodlands is investigated. Topographic factors such as elevation, slope, and aspect are crucial in determining the distribution, composition, and structure of vegetation. The objective of this study is to quantify how topography influences vegetation attributes and identify the key driving factors. Understanding these relationships is important for improving our ability to predict vegetation dynamics and inform reforestation and afforestation efforts in semi-arid regions.
The second part aims to develop a radiation model for simulating the distribution of solar radiation within the woodland’s understorey surface. By incorporating local topographic features and canopy shading effects, this model provides a detailed representation of how solar radiation is distributed beneath the canopy across varying environmental conditions. The accurate simulation of understorey radiation is crucial for understanding microclimate dynamics and the subsequent impact on vegetation growth and ecosystem processes.
The third part of this research is on modelling and mapping understorey evapotranspiration (ET), which are fundamental to the water balance and energy flux within woodland ecosystems. The study aims to quantify understorey ET and assess its contribution to the overall water flux of semi-arid woodlands. This detailed mapping of ET processes will enhance our understanding of water resource dynamics in these ecosystems and support the development of more effective conservation and management strategies.
In summary, this study offers a comprehensive analysis of the influence of topography on the structure of the studied semi-arid woodlands. It also provides valuable insights into the distribution patterns of solar radiation and ET within these ecosystems. The research framework and methodology developed in this study can be transferred to other regions, enabling broader applications. These findings contribute to guiding sustainable management practices, helping to ensure the resilience of semi-arid woodlands in the face of environmental challenges.
Keywords: Australia, Remote sensing, UAV, Topography, Radiation modelling, Evapotranspiration
Subject: Hydrology thesis
Thesis type: Doctor of Philosophy
Completed: 2025
School: College of Science and Engineering
Supervisor: Huade Guan