Microspatial ecotone dynamics at a shifting range limit: plant-soil variation across salt marsh-mangrove interfaces

Area of Science:

• Coastal Ecology
• Plant Ecology
• Climate Change Ecology

Background:

• Climate change, specifically reduced winter temperature extremes, facilitates mangrove range expansion into salt marshes.
• Ecotone dynamics, like the salt marsh-mangrove interface in the northern Gulf of Mexico, offer insights into ecological responses to climate-driven range shifts.
• Understanding these shifts is crucial for predicting future ecological implications of global climate change.

Purpose of the Study:

• To assess aboveground and belowground plant-soil dynamics across the salt marsh-mangrove ecotone.
• To quantify micro-spatial patterns in horizontal extent of mangrove expansion.
• To investigate the influence of salt marsh characteristics and vegetation on soil properties.

Main Methods:

• Studied vegetation and rooting dynamics of mangrove trees (large and small) along transects from mangrove canopy into salt marsh.
• Quantified horizontal reach of roots beyond the aboveground mangrove boundary.
• Analyzed the impact of salt marsh species and structure on mangrove seedling dynamics and vegetation influence on soil properties.

Main Results:

• Vegetation and rooting dynamics showed distinct horizontal extents, with mangrove root expansion reaching up to 8 meters beyond the aboveground limit.
• A positive correlation was observed between mangrove tree height and the extent of root systems.
• Soil carbon density and organic matter did not significantly differ across the salt marsh-mangrove interface.

Conclusions:

• Mangrove root systems extend significantly further into salt marshes than their aboveground canopy, indicating a substantial belowground expansion.
• Vegetation structure and local hydrology are key factors influencing mangrove seedling establishment and dynamics.
• Studying both aboveground and belowground ecotone dynamics is essential for predicting ecological consequences of climate change-induced range expansions.