LONG-TERM FERTILIZATION AND SOIL MOISTURE INTERACT TO INFLUENCE PLANT AND BACTERIAL COMMUNITIES IN A LOW NUTRIENT WETLAND

Abstract

Human activities such as urbanization and intensive agriculture modify nutrient and water cycles in significant ways. Changes to nutrient and water cycles can cause disruptions to plant-microbe mutualisms, especially in low-nutrient wetland ecosystems. Due to ongoing nutrient and moisture variations, the succession of plant and microbial communities may diverge in unexpected ways. In this study, I investigated how long-term fertilization and hydrologic alterations affect associations between wetland plants and soil microbial communities in a historically low-nutrient coastal plain wetland. I hypothesized that long-term fertilization and drier ditched conditions influenced patterns in plant and bacterial communities to different degrees. I tested this hypothesis at a long-term nutrient addition (N-P-K fertilizers) and disturbance (mowing) experiment (established in 2003) located at East Carolina University's West Research Campus in Greenville, North Carolina. Specifically, I examined the relationship between plant communities and bacterial communities (based on amplicon sequencing of the 16S rRNA gene) in mowed plots undergoing nutrient enrichment and varying soil moisture conditions from 2014 to 2020. Results revealed that nutrient enrichment and ditch effects influenced plant and bacterial community succession to different degrees. In addition, bacterial diversity was higher in wetter fertilized soils than drier unfertilized soils over time. Plant communities were distinct due to hydrology, especially in unfertilized plots, while fertilization influenced bacterial communities more than hydrology. In addition, total soil carbon was correlated to bacterial community patterns. Because of nutrient enrichment and drying conditions, changes to wetland plants and soil bacterial community patterns could imply an increasingly competitive rather than cooperative relationship between plants and soil microbes.