Combination of plant species and water depth enhance soil quality in near-natural restoration of reclaimed wetland

Plant introduction and hydrological management are essential strategies for near-natural wetland restoration. However, the combined effects of plant species and water depth on soil quality restoration remain poorly understood. The wetland ecosystem is crucial for Earth ecosystem health and sustainable development, but it faces challenges due to environmental change and human activities leading to soil quality degradation. In this study, we conducted a five-year near-natural restoration experiment covering approximately 2071 m² area in the Changbai Mountains region of northeastern China to assess the impact of plant species and water depth combinations on soil quality dynamics in reclaimed wetlands. Through an ecological engineering project, a meticulous controlled experiment was implemented to investigate the impact of different plant species and water depth combinations on soil quality in near-naturally restored wetlands. Over the five-year restoration period, we observed significant improvements in soil quality indicators, including pH, bulk density, soil organic carbon content, and labile organic carbon fractions. Soil pH and bulk density both showed a decreasing trend, with notable variations influenced by the combination of plant species and water depth. Particularly significant drops were observed in wetlands where Lythrum salicaria L. was introduced at 10 cm water depth and Iris wilsonii C. H. Wright was introduced at 30 cm water depth. Meanwhile, soil organic carbon content also appeared optimal restoration effects in the aforementioned combinations, highlighting the regulatory effect of these combinations on soil quality regulation. Linear regression modeling demonstrated a significant positive correlation between soil organic carbon and both above-ground and below-ground biomass, highlighting the interplay between vegetation dynamics and soil quality restoration. Our study provides valuable insights into the complex dynamics of soil quality restoration in reclaimed wetlands and underscores the importance of considering plant species-water depth combinations in restoration planning. By understanding these dynamics, restoration practitioners can make informed decisions to enhance the sustainability of wetland ecosystems and their invaluable ecological services.