Plant effects on burrowing crab morphology in a Chinese salt marsh: Native vs. exotic plants

Burrowing crabs are conspicuous components of many salt marshes yet factors influencing burrow morphology have received little attention. We studied the effects of marsh plants on crab burrows and found significant variation of crab burrow morphology along a successional gradient from mudflat to vegetated marshes (either exotic Spartina alterniflora or native Phragmites australis marsh). Mudflat soil had lower water content, but higher bulk density than vegetated marshes. Burrows in vegetated marshes had more openings and branching and higher width–depth ratios, but smaller openings and lower depth, length, and total volume than on mudflats. S. alterniflora marshes had less rhizome biomass, but higher fine root biomass than P.australis marshes found at higher elevations, and burrows in S. alterniflora marshes were shallower, shorter, had smaller volumes, but had larger surface openings than P.australis marshes. Young S. alterniflora marshes had higher aboveground biomass, but lower stem density, rhizome and fine root biomass, and burrows were deeper, longer, and larger than in old S. alterniflora marshes. These data suggest that plant properties influence burrow morphologies and that burrow morphologies change during salt marsh succession due to changing root distributions and soil properties.