Effects of Exotic Cordgrass Spartina alterniflora on Soil Physical and Chemical Characteristics in the Haihe River Estuary, China

An exotic grass Spartina alterniflora was introduced in China almost 30 years ago, and since then it has become an urgent topic due to its invasiveness in the coastal zone of China. We investigated consequences of S. alterniflora invasion on inter-tidal ecosystem processes in Haihe River estuary salt marsh of Tianjin, China. Soil pH, salinity, buck density, soil organic C, total N, C/N, soil microbial biomass C (SMBC), and soil microbial biomass N (SMBN) were determined, respectively. Moreover, correlations between soil buck density, organic C, total N, C/N, SMBC, and SMBN were also measured. The results showed that soil pH, salinity, and buck density in Spartina salt marsh were significant lower than mudflat. However, soil organic C, total N, SMBC, and SMBN were significantly higher in Spartina salt marsh than mudflat. With the extension of sampling time, soil pH, salinity, organic C, total N, SMBC, and SMBN increased, except for soil buck density. Soil organic C and total N were positively related with SMBC and SMBN regardless of Spartina salt marsh or mudflat. Therefore, invasion of S. alterniflora improved soil physical and chemical properties in estuary salt marsh. Furthermore, it is necessary to take soil microorganism into account when evaluating effects of S. alterniflora on soil physical and chemical properties.