Soil Conditions and Potential Soil Amendments For Use in Restoring High Intertidal Areas in Southern California Tidal Marshes

摘要

Restoration of high intertidal habitat zones is difficult due to infrequency of inundation and development of high salinities. This is especially true in the arid southwestern coastal region, and when surface soils are removed as part of the restoration leaving subsoils as the primary substrate for revegetation. A study was undertaken to examine soils within a suite of reference wetlands in southern California and to determine what soil amendments might be useful for improving restoration soils. Surface soils from six reference sites and subsoils from the San Dieguito Lagoon restoration site were analyzed for pH, salinity, organic matter, soil texture, and bulk density. San Dieguito soils were found to have higher pH and bulk density, but lower salinity, organic content and clay content than reference marsh soils. Based on these results, growth experiments were then conducted incorporating various soil additions. Pickleweed (Salicornia virginica) cuttings were planted in six experimental treatments: Biosol (a commercial organic matter soil amendment), clay, diatomaceous earth, topsoil, kelp, or compaction. Two different trends were identified as a result of growth experiments. While pickleweed cuttings in the Biosol-amended soils exhibited much higher levels of growth (over 4 times as great as control plants), their overall survival was low (64% compared to control 77%). The highest survival was exhibited by pickleweed in topsoil-amended soils (92%). The experimental results indicate that organic matter and topsoil amendments may have a beneficial effect on wetland restoration plantings, by increasing both the short-term growth rate and overall survival of planted materials. Field studies are required to confirm this result.