Zhenxing Bian

Iron ore tailings have been shown to promote the formation of soil aggregate cementing agents through weathering, thereby influencing soil aggregate formation in reclaimed land. However, their mechanism of action under different reclamation methods remains unclear. This study established a field station in the semi-arid region of Northern China to investigate three typical iron ore tailing reclamation methods, including topsoil blending type (DT), sublayer moisture conservation type (JT), and thick-layer tailings type (FT), with adjacent farmland as the control (CK). The analysis of soil organic carbon (SOC) components, soil inorganic carbon (SIC), iron/aluminum oxides, and aggregate composition and stability in the reclaimed soils revealed the evolution patterns of cementing materials and the potential mechanisms driving aggregate formation. The results indicate that the reclamation process promotes the weathering of tailings, with a significant increase in free iron oxide (Fed) content ranging from 19.09% to 41.93%. Iron oxides released from iron ore tailings influenced the reclaimed topsoil through plant litter return processes, resulting in a significantly higher amorphous iron oxide (Feo) content compared to CK. Additionally, the content of crystalline aluminum oxide (Alc) in the DT topsoil showed a significant increase, reaching 2.82 g/kg. The variation in organic and inorganic cementing agents significantly influences aggregate composition and stability, with soil particulate organic carbon (POC), crystalline iron oxide (Fec), Alc, and amorphous aluminum oxide (Alo) identified as the primary agents affecting aggregate formation (p < 0.05). After five years of reclamation, the proportion of DT macroaggregates (>0.25 mm) increased to 42.10%, and both the mean weight diameter (MWD) and the geometric mean diameter (GMD) increased significantly to 2.21 mm and 0.43 mm, respectively. In contrast, JT macroaggregates and microaggregates (0.053–0.25 mm) decreased to 26.88% and 29.01%, respectively, and aggregate stability significantly declined. FT macroaggregates and their stability showed no significant difference compared to CK. The study shows that after years of reclamation, both DT and FT reclamation methods have reached normal farmland levels in terms of aggregate formation and stability, making them practical and valuable reclamation solutions.

Understanding the responses of soil biota to global changes is crucial for the maintenance of ecosystem functions. The impact of global changes on the diversity of soil microbial communities in severely degraded grassland ecosystems invaded by a single poisonous weed remains unclear. This study conducted a control experiment on degraded grasslands with Sophora alopecuroides as a single dominant species and examined soil microorganism response to nitrogen addition, watering, and mowing. Our results showed that: (1) Nitrogen addition, watering, mowing, nitrogen‐water interaction, and nitrogen‐mowing interaction significantly reduced soil bacterial diversity, while there were no significant effects on soil fungal diversity. Nitrogen, watering, mowing, and their interaction increased the proportion of fungi in the microbial co‐occurrence network. (2) Nitrogen addition, watering, and mowing significantly affected the bacterial and fungal community composition, and fungivores nematodes abundance had a significant effect on the abundance of fungi and bacteria dominant phyla. (3) Nitrogen addition had indirect effects on bacterial richness and diversity mainly through nitrate nitrogen and soil pH. The abundance of fungivores nematodes had direct and significant negative effects on bacterial diversity and fungal richness. The results revealed that fungivores nematodes are higher trophic level soil fauna that influence fungi and bacteria, but the mechanism was still unclear. Nitrogen addition, watering, and mowing affect the changes in microbial diversity and the stability of food webs by increasing soil nutrients, changing the aboveground poisonous weed structure, and affecting soil fauna, which can contribute new perspectives for the restoration of degraded grassland with severe invasion of poisonous weeds.

As urbanization progresses at an accelerating pace, the depletion of natural resources and environmental degradation are becoming increasingly severe. Constructing ecological security patterns (ESPs) has become a crucial strategy for mitigating environmental stress and promoting sustainable social development. Currently, the methods for constructing ESPs remain under exploration. Particularly, in the identification of ecological sources, insufficient emphasis has been placed on trade-offs among ecosystem services (ESs). This study focuses on Liaoning Province, situated in China’s northeast revitalization area—a region with a developed heavy industry and abundant ecological resources. The InVEST model was employed to assess ESs, and the ordered weighted average (OWA) method was utilized to identify ecological sources. By integrating both natural and social factors, the ecological resistance surface was constructed, and circuit theory was applied to determine ecological corridors, ultimately leading to the development of an ESP. The results show that (1) between 2010, 2015, and 2020, water yield continued to increase, habitat quality continuously declined, soil conservation tended to decrease and then gradually increase, and carbon storage tended to increase and then decrease. The four ESs show similar spatial features, characterized by elevated levels in the eastern and western areas and a comparatively reduced level in the central region; (2) a total of 179 ecological sources were identified, covering 26,235.34 km². The overall distribution showed a concentration in the east, with a fragmented and dispersed pattern in the southwest. The identification of 435 ecological corridors, with an overall length totaling 8794.59 km, resulted in a network-like distribution pattern. Additionally, 65 ecological pinch points and 67 barrier points were identified; and (3) a “four zones, three corridors, and two belts” pattern of ecological protection and restoration has been proposed. The findings offer valuable insights for Liaoning Province and other rapidly developing regions facing escalating environmental pressures.