Succession of soil macro-faunal biodiversity in forests converted from croplands after long-term coastal reclamation

Abstract

Abstract The long-term succession of the soil macro-faunal community after reclamation at coastal areas is not well understood, especially at the time scale of centuries. The objective of this work was to analyze soil development by measuring its principal physico-chemical properties and study the macro-faunal biodiversity succession along the successional trajectory created by intermittent reclamation. We hypothesized that soil macro-faunal taxonomic and functional diversity, richness, and density would increase after long-term reclamation, and that macro-faunal succession was related to dike age. In July 2014, sites of varying dike age (30, 50, 100, and 200 years) were used to represent a successional trajectory of Fluvisol soils at a reclaimed coast at Yancheng, China. The selected habitats were planted with 14–17 years old poplar (Populus euramericana) or dawn redwood (Metasequoia glyptostroboides) trees. With increasing dike age, soil nutrient status improved over the successional trajectory, as indicated by the increased soil organic carbon (SOC) concentration, total nitrogen (TN), and total phosphorous (TP). Soil salt concentration (SSC), pH, and carbon-nitrogen (C/N) ratio continuously decreased, as did soil bulk density (BD), the latter of which had a smaller coefficient of variation than the other properties did. Over the first 100 years of macro-faunal succession, taxonomic richness, abundance, Margalef’s richness index, and the Shannon-Weaver diversity index increased significantly, but did not differ significantly between the habitats with dike ages of 100 and 200 years. Significant differences in the measured communities’ characters were detected between forests planted with different trees when the dike age was 50 years but not when it was 30 years. Differences in macro-faunal community structure were primarily related to SOC and SSC, which were considerably related to dike age. The taxonomic richness and abundance of functional groups varied significantly among habitats and was related to changes in food resources in the soil environment. The abundance and taxonomic richness of phytophagous and saprophagous species increased with increasing dike age; no significant differences were noted in taxonomic richness of omnivorous species and predator abundance. The results thus supported our hypotheses. In conclusion, long-term macro-faunal community succession was affected by dike age, land use, and soil development after reclamation, and the soil macro-faunal biodiversity tended to increase with increasing dike age.