July 2016

Dr. Thoralf Meyer and doctoral student Thomas B. Christiansen presented research for the public in Maun, Botswana on July 25th, 2016 at Maun Lodge. These monthly research talk sessions are organized by local researcher, Dr. Emily Bennitt and help inform the public about on-going research in Botswana. Below are the summaries of the two presentations:

Title:  Who is Who: Fingerprinting Environmental Conditions from Space
Authors: Drs. Thoralf Meyer & Kelley A. Crews
Department of Geography and the Environment, The University of Texas

Summary: Savannas are complex arid or semi-arid biomes, covering approximately 20 % of the terrestrial surface of the earth, providing substantial ecosystem service, such as carbon storage, firewood, rangeland and protection against soil erosion. They are ecosystems best described as systems prone to constant change in productivity, diversity and abundance of species and structure. Due to this complexity, savannas are extremely heterogeneous ecosystems where despite past and current research, the ongoing processes between abiotic and biotic environment remain purely understood. This is amplified, especially in light of increasing anthropogenic influences, increase in human population and climate change. This study contributes to the ongoing scientific debate about the role of savannas as a carbon sink or source. One main factor determining this relationship is the role of woody vegetation. We have assessed multiple drivers of shrub encroachment and their impact on diversity and abundance of woody vegetation across the rainfall gradient of the Kalahari Transect, located in western Botswana. This study underlines the importance to study the combination of multiple drivers and their effect on species with similar functional and structural traits. We further developed allometric relationship to estimate biomass using different morphological parameters, therefore providing a useful tool to estimated biomass on multiple scales, ranging from a plot scale to a local scale when active remote sensing systems are employed. To overcome the challenges associated with the quantification of biomass across large tracks of land, we took on the challenge to extract biomass using a two dimensional passive remote sensing system where we leveraged excessive field derived measurements and validation methods to test the performance of various spectral unmixing techniques in heterogeneous savanna environments. Multiple Endmember Spectral Mixture Analysis and the Moderate Imaging Spectroradiometer Enhanced Vegetation Index product were used to derive a relationship that indicates woody vegetation structure using the fractional cover of green vegetation contained in a MODIS pixel. By combining the unmixing process, EVI, Phi and the allometric relationships described above, I was able to successfully quantify biomass across the Kalahari region in Botswana.

Title: Incorporating Three-Dimensional Vegetation Structure in Environmental Studies
Speaker: Thomas Brandt Christiansen, Ph.D. Student
Department of Geography and the Environment, The University of Texas at Austin

Summary: Ecological sampling is vital for understanding our environment in order to inform land management strategies and policies about the health of the ecosystems in Botswana. Several platforms can be used to monitor changes in vegetation form and function. Field measurements can be taken to gain insights into factors such as vegetation abundance, diversity, and structure. These data can then be related to satellite images and products, such as land-use and land-cover maps, flooding patterns, and burned areas, in order to monitor changes over time across broader scales.

This research talk presented a new method which combines structural vegetation field measurements with a developed computer visualization program in order to further our understanding of ecosystem structure. The method utilizes belt transects with vegetation plots (e.g. 10 by 30 meters) at even spacing along the transect (e.g. every 500 meters) where all woody vegetation is measured in three dimensions and the location of each tree is noted in Cartesian space. The number of stems and diameter of stems is also measured along with identifying the species. The field data are then entered into an excel spreadsheet back in the office. These data files are used as input for our developed computer visualization program (using Interactive Data Language) which allows the assessment of structural vegetation patterns across space. This new method enables the assessment of differences in vegetation structure across different land management areas, impact of disturbances and changes over time (such as woody plant encroachment or impacts of elephant damage) in vegetation structure, habitat availability and diversity for biodiversity.

Figure: Example of how we can use this new model to assess differences in vegetation structure between two plots.