Doctor of Philosophy (PhD)
Geography & Anthropology
This research focused on the Roseau cane (Phragmites australis) dieback assessment in the lower MRD of Louisiana and introduced a comprehensive and systematic multi-source remote sensing method for assessing wetland and Roseau cane dieback and habitat dynamics analysis from three scale levels from large-scale to small scale.
Large-scale historical vegetation/land change analyses were conducted in the lower MRD based on Landsat in the past two decades (2001 - 2021). A strong increasing trend of vegetation was found since 2005. Around 51 km2 ofdieback area was detected which accounts for 11% of the overall vegetation coverage. This research showed that 65.8% of the dieback occurred in the Roseau cane area from 2010 to 2019 while the Roseau cane only accounted for 49.7% of overall vegetation coverage in 2010. The result proved that Roseau cane was more vulnerable to dieback in the lower MRD compared with other wetland vegetation.
A Roseau cane habitat classification scheme for two main passes in the lower MRD based on the mid-scale Worldview image is proposed. Through Support Vector Machine (SVM) classification method, the two variants of Roseau cane, the Delta Phragmites and European Phragmites can be separated in the study area. The results shared around 79% of agreement with the Landsat-derived classification result. In addition, the results indicated no significant differences between them in the detected areas where dieback occurred between 2019 and 2021.
Furthermore, this research monitored small-scale Roseau cane habitat dynamics in a selected drone mapping site in Pass-A-Loutre from the fall of 2020 to May 2022. This research developed a new sampling strategy based on drone which effectively solves the limited accessibility challenge in the coastal environment. The experimental results demonstrate that SVM could produce a reliable habitat mapping accuracy of over 85%. The massive death of vegetation coverage indicated that the hurricane event had a severe impact on small-scale ecosystems, however, this research didn't observe a significant difference in damage level among the wetland vegetation species. The landscape indices used in this study can be used as a reference for the analysis of ecosystem landscape patterns in other small scales studies.
Shang, Nan, "Studies of Roseau Cane Dieback in the Lower Mississippi River Delta Based on Remote Sensing Data Including Landsat, Worldview, and Drone" (2022). LSU Doctoral Dissertations. 6009.