A comparison of mangrove and marsh influences on soil respiration rates: A mesocosm study

Abstract

Due to reductions in freeze events, mangroves have been rapidly encroaching into previously salt marsh-dominated coastal wetlands along the northeastern shores of Florida, USA. This shift in dominant wetland vegetation type may have significant implications for belowground processes such as soil organic matter decomposition and respiration. Using a full factorial greenhouse mesocosm experiment, we investigated the effects of plant type (no plant, Avicennia germinans, or Spartina alterniflora) and soil type (sand, mangrove-derived soil, or marsh-derived soil) on estimated heterotrophic soil respiration rates. While we predicted that A. germinans mangrove seedlings would increase heterotrophic respiration, we found that mangrove seedlings did not increase heterotrophic respiration when compared to control (no plant) treatments. Additionally, we found that heterotrophic respiration was higher in marsh-derived soils than in mangrove-derived soils for both control and mangrove plant treatments. Our findings suggest that the stage of mangrove invasion and the level of root development may influence changes in heterotrophic soil respiration.