The theoretical basis for the hypothesis that the growth rate of Balsam poplar trees is positively correlated with the proximity to water sources and moisture availability touches on several ecological principles. First the water cycle, the adaptations of poplar trees that can tolerate seasonal flooding and high water content soil. The gradient of resources or disturbances, suggesting that the availability of resources (like water) influences the distribution and abundance of a species and diversity. The ecology of a riparian environment, the conditions that are influenced by the abundance of water.
Ideas that underpin this research for me is the successional dynamics and species diversity. Poplar trees seem to play a role in the succession of riparian environments. there ability to colonize disturbed areas, lead me to believe they have successional qualities in those areas, making the area more habitable for other species to grow.
three keywords to describe my project would be Riparian ecology, Resource gradient, Balsam Poplar diversity.
Sounds like a great start for ideas for the intro for your paper