MCA: Interactions between density dependence and environmental stress in plant-microbial symbioses

Tulane University, New Orleans LA

Investigators

Abstract

Just as humans live with bacteria on the inside and outside of their bodies, plants have bacteria inside their tissues and on their surfaces. Some of these bacteria are beneficial and some are pathogenic (cause disease) to the plants. Plants cannot move as much as humans, however, so pathogenic bacteria can sometimes accumulate around mature plants and this might be detrimental to young seedlings. In addition, there might be environmental gradients, like air temperature or salinity, that change how the pathogens build up. This project explores the interplay between plant-pathogen accumulation and salinity gradients, using two freshwater swamp tree species that act as a storm barrier along the Gulf of Mexico and Atlantic coasts. We will test hypotheses about plant pathogens and salinity, and we will add beneficial bacteria to plants that are growing in an alternative substrate, crushed glass from recycle centers, for coastal restoration. Broader impacts include engaging community organizations and providing data to a local start-up for glass recycling. Negative feedback occurs when microorganisms in the soil accumulate around a mature tree and provide a negative growth environment for young seedlings of the same species. This phenomenon has been shown across many kinds of habitats, but much less is known about how increased stress from the environment interacts with negative feedback. This knowledge gap is a problem as climate-related stressors are increasing in many habitats. We address this knowledge gap in the context of sea level rise and hurricane intensity, using freshwater swamp trees as our focal species. Broadly we ask: what is the relationship between negative feedback and increasing salinity stress? There is a possibility of both facilitation or interference in our study system of plant-symbiont interactions, and these outcomes may change with stress. Two greenhouse experiments will test the effects of negative density dependence along a salinity gradient and in crushed, recycled glass. We predict that seedlings will benefit from growing in heterospecific soil when stress is low but will benefit from growing in conspecific soil when stress is high. Because negative feedback is observed in so many habitats, our research findings may have a large impact on our understanding of ecological processes related to stress. For broader impacts, we are engaging community organizations and providing data to a local start-up for glass recycling. The Mississippi Delta provides billions in economic value for the US. Using recycled materials that would otherwise go to a landfill, will increase the ability to replenish swamps and restore hydrology in areas that are becoming more and more saline. This project is jointly funded by the Population and Community Ecology program and the Established Program to Stimulate Competitive Research (EPSCoR). This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.