Characteristics of carbon, nitrogen, and phosphorus in soil aggregates under different restoration methods on cut slopes in the Qinghai-Tibet Plateau mining area

This study systematically compared soil aggregate stability and carbon-nitrogen-phosphorus nutrient characteristics among three restoration methods for cut slopes (three-dimensional netting [TCS], frame beams [FCS], and galvanized wire mesh [GCS]) relative to unrestored cut slopes (UCS) in the Jiama Mining Area, Tibet. Microsoft Excel 2022 was used for data organization, while statistical analyses were conducted with SPSS 20.0. Statistical comparisons of restoration treatments for soil properties (nutrient indicators, enzyme activities) employed one-way ANOVA with Tukey's HSD multiple comparisons.
TCS exhibited significantly higher SOC content than FCS, GCS, and UCS. For aggregates smaller than 0.25 mm, FCS exhibited significantly higher SOC values than other restoration methods. While bulk soil SOC contents were significantly elevated in FCS and TCS compared to GCS and UCS, GCS and UCS did not differ significantly from each other. TCS exhibited significantly higher TN contents in most aggregate size classes compared to other treatments. Among the three restoration methods, only GCS exhibited lower TN contents than UCS across all aggregate size fractions. In bulk soil, TN contents in GCS and UCS showed no significant difference but were both significantly lower than those in TCS and FCS, with TCS also showing significantly higher TN content than FCS. A significant increase in TP content was observed in macroaggregates from TCS and FCS compared with GCS and UCS. Within the microaggregates fraction, TP concentrations were significantly elevated in FCS and UCS relative to TCS and GCS. TP concentrations in the < 0.053 mm fraction were significantly elevated in FCS relative to other treatments. In bulk soil, UCS had the highest TP content, significantly higher than that in TCS and GCS.
TCS exhibited significantly higher soil saccharase (SAC) activity across all aggregate size fractions compared to the other cut slopes. In aggregates smaller than 2 mm, both FCS and GCS exhibited higher SAC activity than UCS. Statistical analysis detected no significant variation in bulk soil SAC activity between GCS and UCS treatments. Both TCS and FCS exhibited higher urease (URE) activity than GCS and UCS. UCS exhibited significantly higher URE activity than GCS only in the microaggregates fraction. TCS exhibited significantly higher alkaline phosphatase (ALP) activity than the other cut slopes. Except in the microaggregates fraction, where FCS, GCS, and UCS showed no significant differences in ALP activity. In bulk soil, ALP activity differed significantly among the four slope types, with the hierarchy: TCS > FCS > GCS > UCS. Across bulk soil and > 0.053 mm aggregates, catalase (CAT) activity was significantly lower in GCS compared to other slope types. TCS demonstrated significantly higher CAT activity than other restoration methods in both bulk soil and < 2 mm aggregates, while FCS and GCS showed no significant difference.