|The effect of habitat heterogeneity and burial depth on seed retention in salt marshes|
Jingkun, X. (2021). The effect of habitat heterogeneity and burial depth on seed retention in salt marshes
. BSc Thesis. NIOZ Royal Netherlands Institute for Sea Research: Yerseke. 26 pp.
Globally, coastal salt marshes provide a variety of important ecosystem services such as biodiversity conservation, carbon reserves, wave attenuation, and shoreline stabilization. However, with the impact of climate change, sea level rise, and human activities, salt marsh ecosystems are under constant threats. In the dynamic environment of tidal flats, the retention of salt marsh seeds in suitable habitats is the prerequisite for the colonization of salt marsh seedlings. Process-based research on it will help to identify the bottlenecks that limit the formation of salt marshes and can provide scientific basis and theoretical support for formulating reasonable salt marsh system restoration and reconstruction schemes. Here, we explore how the heterogeneity of habitat (including elevation, sedimentary dynamic, benthos disturbance) and the depth of burial affect seed retention of typical saltmarsh pioneer species. Five salt marsh habitats (Zuidgors, Hoofdplaat, Baalhoek, Keetenisse, and Baarland) with different disturbance regimes located at the Westerschelde in the Netherlands were used as the research sites. Three pioneer plants (Aster tripolium, Scirpus maritimus, and Spartina anglica) were used as model species. Two rounds of field manipulation experiments demonstrated that: 1) The retention of surface seeds mainly depends on the specific hydrodynamic disturbance in different habitats. 2) The bed elevation changes can cause the loss of salt marsh seeds that are on the surface of sediments and burial depth less than 10 mm. 3) The burial depth is the main factor affecting the retention of salt marsh seeds. The salt marsh seeds can stably preserve in the sediments and form a lasting seed bank when they are buried more than 20 mm. 4) There is no significant difference in seed retention ratio between species. 5) The predation of benthos is not the main factor that causes the loss of seeds. Our findings provide novel insight relevant to the bottleneck of seed retention and seedling establishment, with important implications for understanding the effects of climate change on critical state transitions and enabling human-aided restoration.