Changes in Soil C, N, and P Concentrations and Stoichiometry in Karst Trough Valley Area under Ecological Restoration: The Role of Slope Aspect, Land Use, and Soil Depth

Abstract

This study aims to investigate the roles of slope aspect, land use and soil depth in altering the soil organic carbon (C), total nitrogen (N), and total phosphorus (P) traits in the karst trough valley area experiencing extensive ecological restoration. A total of 54 soil samples were collected at 0–10, 10–20, and 20–30 cm soil depths from secondary forest, plantation forest, and grassland on the relatively more shaded east-facing slope and the contrasting west-facing slope, respectively. The independent and interactive effects of slope aspect, land use, and soil depth on soil C, N, and P concentrations and stoichiometry were determined. The results show that soil C and N concentrations were markedly higher on the east-facing slope than on the west-facing slope, and soil P concentrations showed an opposite trend, leading to significant differences in soil C:P and N:P but not in C:N ratios between the two aspects. Soil C and N concentrations were not affected by land use, and soil P concentration was significantly higher in plantation forest than in secondary forest and grassland. Soil C and N concentrations significantly decreased with increasing soil depth, but soil P concentration presented no significant changes with soil depth. Both the land use and soil depth did not differ in terms of their elemental stoichiometry. There were no significant interactive effects of slope aspect, land use and soil depth on soil C, N, and P traits. Our results indicate that soil C, N, and P changes are more sensitive to slope aspect rather than land use and soil depth in the karst trough valley area under ecological restoration.

Spatial variability of soil physicochemical properties under different land uses impacted by erosion on karst hillslopes in Southwest China

“…In addition, soil chemical properties were significantly affected by soil depth, except for the total K content at 10–20 cm in forestland at the upper and lower slope positions, and all of the soil chemical indicators decreased with soil depth. In agreement with our results, previous studies also reported that most soil nutrient contents decreased with increasing soil depth (e.g., Li et al, 2021; Ma et al, 2015). This was likely because surface soil nutrients can be improved through the decomposition of livestock waste, plant residue or the application of fertilizer (McLauchlan, 2006).…”

“…Soil erosion may vary with differences in runoff discharge, vegetation density, land use, distinct slope position and aspect (Li et al, 2021), which can lead to losses of soil nutrient elements and induce spatial variation in soil C, N, P and K among the three slope positions. Soil P and K are essential nutrients for crop and plant growth (Ma et al, 2015).…”

Variations in soil carbon, nitrogen, and phosphorus concentrations and stoichiometry with stand age in Acacia hybrid plantations in Southern Vietnam

“…Soil depth is a vital factor that influences the contents of soil nutrients (SC, SN, and SP) (Xu et al 2019). Several previous investigations have shown that SC and SN contents were relatively greater in the top layer than those in the deeper layer, while SP concentrations did not significantly differ among soil depths, resulting in marginal variations in their stoichiometric ratios (Luo et al 2020;Li et al 2021). This contradicts the present study.…”

Characteristics of Soil C, N, and P Stoichiometry as Affected by Land Use and Slope Position in the Three Gorges Reservoir Area, Southwest China

“…Similarly, in this study, soil BD in SF was significantly higher than in OP and CL, due largely to the relatively less soil disturbance in SF relative to the human activities (i.e., fertilization and cultivation) in OP and CL, resulting in highly compacted soil [56]. This result was also supported by the significant relationships between soil BD and C and N concentrations, which were found in other studies [52,57]. The highest EC was determined in OP, which was in line with the findings of Samani et al [58], probably owing to the decomposition of litter and chemical fertilizer that produced amounts of soluble ions in soils and raised the EC level in the OP [58].…”