Skip to main content
2023 ESA Annual Meeting Main banner
Icon Legend
This session is not in your schedule.
This session is in your schedule. Click again to remove it.
Back

Organized Oral Session

Session: : Where Land Meets Water: Biogeochemical Cycling at the Terrestrial-Aquatic Interface

OOS 27-4 - Gaining a predictive understanding of coastal forest responses to pulse salinity and inundation disturbance

Tuesday, August 8, 2023
2:15 PM – 2:30 PM PDT
Location: 258
This study investigates the impacts of extreme freshwater and estuarine-water flooding events on coastal forest soil carbon (C) cycling at ecosystem scales as part of the Terrestrial Ecosystem Manipulation to Probe the Effects of Storm Treatments (TEMPEST) project in Maryland, USA. TEMPEST uses a large-unit, un-replicated experimental design, with three 2,000 m2 plots serving as control, freshwater, and estuarine-water treatments. In June 2022, the two treatment plots each received 300 m3 of either freshwater or estuarine-water over ~9 hours which approximated a 15-cm rainfall event and saturated the upper soil (0-30 cm) for ~5 hours. A crucial component of coastal forests' response will be how soils respond to changing hydrological conditions, but this is highly uncertain, and no previous ecosystem-scale experiment has looked at this question. We separated the root-and-rhizosphere and soil heterotrophic components of CO2 and CH4 flux with an exclusion approach and determined their responses to temperature, moisture, and electrical conductivity variation at seasonal and episodic scales.

Plant root-and-rhizosphere and soil heterotrophic fluxes varied seasonally and were greatest in the growing season. On shorter timescales, discrete inundation events shaped soil heterotrophic flux patterns, but not those of the root-and-rhizosphere, and resulted in temporary suppression of total soil respiration and CH4 uptake. Soil heterotrophs may have been more sensitive to episodic change because they are in surface litter and soil where the greatest impacts of pulse inundation events occurred, while roots in surface soil are part of deeper-rooted plant systems that may require larger and/or prolonged moisture pulses that penetrate the soil profile to trigger physiological responses. Our initial results suggest that temperate coastal soils are resilient to extreme but one-time hydrologic disturbance and any belowground responses will be driven largely by soil heterotrophs. The impact of multi-year, repeated events remains uncertain and will be addressed by TEMPEST in the years to come.