Seaira - Salinity testing of plants.

I certainly have a few ways that I could develop and arrange this project. I am interested in plant life and the ecosystems affected by them in the coastal dune areas and mangroves. Currently through my own research I have been practicing basic identification of native species to this area, as well as the non-native invasive species that interact with the natural ecosystem. I am curious to see how the native species deal with salinity within the soil substrate. Upon my initial research for this project I found that plants are placed into categories of salt intolerant, glycophytes, and salt tolerant plants, halophytes. Realizing this I became curious as to what happens when salt water encroaches on areas of agriculture where the majority of the crops are glycophytes.
For my project I would like to sample plants species at different locations and test the salinity to see how far away from the actual beach salt encroaches. I would ideally like to use GIS (Geographic Information System) software to create a map of my findings, and maybe even shed light on areas that are being affected by saltwater encroachment.
Through my research I also discovered that secondary salinity in a soil substrate, or plants root systems can occur naturally, through sediment weathering or through human disruption of the native plant species. When agricultural activity takes place native plant species are removed and more shallow rooted plants are put in their place. During this process the water table is able to rise bringing with it NaCl to the soils surface. Having large root systems from native shrubs and trees keeps the water table at appropriate levels from root absorption.
I still need a few suggestions or some advice to make this project viable. Here are my considerations; Do I test one species of plant, or many? Do I test agricultural plants, or native ones? Should I test the soil substrate for saline properties, or the plant itself?
Native plants and ecosystems play an important role in the health of soil salinity and pH. Through this research hopefully I can find alternative solutions to help agriculture thrive while maintaining a proper balance, and possibly observe how salt water encroachment is affecting the local environment.
I plan to record my findings with a bar graph to compare different saline levels in plants, or possibly a scatter plot graph to show a correlation between distance from the shoreline, and recorded salinity levels. And finally to show my testing sites and findings I would like to transfer my data into GIS software for future usage.