Natural Grasslands Outperform Artificial Shrublands and Forestlands in Soil Ecological Environment Improvement in Severely Degraded Areas

Abstract

Unsustainable land use leading to soil degradation has become one of the most pressing global environmental issues, threatening the foundation of human existence. Vegetation restoration can restore degraded soils by increasing soil organic carbon (SOC), soil stability, and soil water content (SWC), creating a favorable living environment. However, few studies have simultaneously examined the impacts of vegetation restoration on these three factors. This study collects soil samples from croplands (control), grasslands, shrublands, and forestlands at depths of 0–20, 20–40, and 40–60 cm to investigate the effects of different vegetation types on SOC, soil stability, and SWC. A comprehensive soil quality index (CSQI), derived from a weighted summation method, indicates the overall impacts of vegetation restoration on these factors. The results showed that vegetation restoration significantly increased SOC stocks and mean weight diameter only in the 0–20 cm layer, with no significant difference among the vegetation types. Shrublands and forestlands significantly increased SWC in the 0–20 cm layer, while all vegetation types decreased SWC in the 20–40 and 40–60 cm layers, with grasslands showing the least reduction. This is primarily because shrublands and forestlands require more water to sustain their higher biomass. Across the entire profile (0–60 cm), grasslands exhibited the highest CSQI, indicating they have the most beneficial effect on the soil ecological environment. The main factors influencing soil CSQI variation in the 0–60 cm depth include aggregate composition, soil nitrogen, and litter biomass. Therefore, grasslands emerge as the optimal vegetation type in the central of the Loess Plateau, effectively sequestering SOC and enhancing soil stability while minimizing soil water consumption.