Variations of the soil macrofauna community and corresponding influencing factors in the newly reclaimed coastal area: A case study in Yangtze Estuary, China

Intensive reclamation activity has reshaped global coastal ecosystems. Soil macrofauna, an effective proxy for ecosystem health, has the potential to predict coastal reclamation ecological impact. Previous studies have primarily focused on the long-term (≥ 30 years) soil macrofaunal succession in reclaimed areas. However, composition of the soil macrofauna and its environmental drivers in newly reclaimed areas (< 30 years) remain uncertain. We selected Hengsha Dongtan in the Yangtze Estuary to conduct the study, and four different regions (reclaimed for 13, 8, 4, and 1 year, respectively) were employed to investigate soil macrofaunal composition and corresponding environmental drivers. The results showed that: (1) Terrestrial species millipedes (Paradoxosomatidae sp.), chinch bugs (Dimorphopterus spinolae), and wolf spiders (Pirata subpiraticus) were dominant. Millipedes, chinch bugs, wolf spiders, ants (Myrmecina sp.), and rove beetles (Stenus melanarius and Paederus fuscipes) were major species contributing to the average dissimilarity among regions. (2) The taxonomic composition of soil macrofauna varied over time after reclamation, which showed that the number of species, density, and biomass of soil macrofauna in region 1 (reclaimed for 13 years) was higher than that in regions 2, 3, and 4 (reclaimed for 8, 4, and 1 year). (3) The functional composition of soil macrofauna varied over time after reclamation. The number of species, density, and biomass of the phytophagous and saprophagous groups increased over time, whereas those of the predatory group decreased gradually. (4) Soil pH and total organic carbon content, together with land use, appeared to be key factors that determine soil macrofaunal composition. Overall, our study illustrates the response of soil macrofauna to changes in environmental factors and land use in newly reclaimed areas. Future studies should expand the range of potential factors and comprehensively analyze the mechanisms that maintain soil macrofaunal diversity in reclaimed areas.