Effect of burrowing crabs on retention and accumulation of soil carbon and nitrogen in an intertidal salt marsh

Abstract

Ecosystem engineers that affect other organisms by creating, modifying, maintaining or destroying habitats have received widespread attention. Understanding natural ecosystems and the way in which ecosystem engineers shape the environment is important to ecological restoration based on key ecosystem processes. Increasing studies has shown that crabs in intertidal salt marsh can act as ecosystem engineers, affecting the geomorphological processes and spatial heterogeneity of tidal flat. In this study, field investigations and manipulative experiments were conducted to explore how crab burrowing activity affects intertidal microtopography and soil carbon and nitrogen in the intertidal salt marshes. The results showed that crab burrowing activity is one of the key factors influencing concave-convex microtopography, which could intercept plant detritus and subsequently influencing the retention and accumulation of soil carbon and nitrogen. When compared to areas of flat microtopography with few or no crab burrows, soil organic carbon content (SOC), soil inorganic carbon content (SIC), total carbon content (TC), and total nitrogen content (TN) in adjacent areas of concave-convex microtopography with high density crab burrows were all significantly higher. Artificial simulation of ecosystem engineering processes could also change the geomorphological features of tidal flats and improve the retention and accumulation of soil carbon and nitrogen, which could also attract more crabs to burrow and settle down, then generate and maintain the concave-convex microtopography. Taken together, the results of this study provide scientific and effective implication and guidance for the restoration of coastal salt marshes.