Examining the relationship between invasive plants and urbanization in Auburn, Alabama

Background/Question/Methods

The spread of invasive species in riparian areas is an international problem which has resulted in significant loss of native species in riparian areas worldwide, including the east Alabama region. To address disturbances caused by invasive species occurrence, managing agencies and municipalities need reliable information regarding the occurrence, extent, and dispersal of invasive species and how land use may increase the spread of these species. It is also essential to inform and assist land owners to identify and report emerging invasive species in riparian areas. The objective of this study was to find the frequency of occurrence and dominance of invasive shrubs by surveying the extent of Ligustrum sinense (Chinese privet), Elaeagnus pungens (Silverthorn), and Tridica sebifera(Chinese tallow tree) in riparian corridors across a land use gradient in east Alabama. We expected to see the highest levels of invasive species in the city center with decreasing levels radiating outward into rural areas. By using a modified version of Braun-Blanquet method, 46 riparian forests were surveyed. To examine the relationship between land use/land cover (LULC) change and distribution of target invasive plants, aerial photographs and land use maps were also used. A total of 46 study sites were overlaid on digital maps and analyzed by considering urban, forest, and agricultural land use and their reletionship with occurance of target invasive shrubs in Auburn, Alabama. 

Results/Conclusions

The results of analyses showed that urbanization, specifically housing density can increase the occurrence of fragmentation in urban areas, and this may allow increased spread of invasive plant species which are adaptive to forest edge, disturbance, and propagule pressure in riparian forest. The results of LULC change spatial analyses also suggested that riparian areas close to urban developments were more susceptible to invasion by the surveyed target invasive species. Chinese privet and Silverthorn were more abundant in the city center with decreasing occurrance radiating outward into rural landscapes, where Chinese Tallow tree was more common in sites outside the Auburn urban core.