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.
Highlights
The biogeochemical cycles of carbon (C), nitrogen (N), and phosphorus (P) are usually interconnected through their coupled responses to primary production, respiration, and decomposition [1,2]
Soil P concentration was significantly higher in plantation forest (PF) than in secondary forest (SF) and GL (Figure 2h)
Soil C and N concentrations were higher on the east-facing slope than on the relatively more sunlit west-facing slope, while soil P concentration showed the opposite trend, leading to significant differences in soil C:P and N:P but not in C:N between two aspects
Summary
The biogeochemical cycles of carbon (C), nitrogen (N), and phosphorus (P) are usually interconnected through their coupled responses to primary production, respiration, and decomposition [1,2]. The C:N:P stoichiometric ratio is the significant indicator for characterizing the nutrient cycling, and its shifts affect the capacity to regenerate the natural vegetation after the anthropogenic abandonment [3,4,5]. It has been suggested that C, N, and P cycles vary greatly in soils because of the effects by various factors such as topography, vegetation types, and human activities [6,7]. Due to the effects of those influencing factors, soil C, N, and P concentrations are markedly changed, and their coupled stoichiometric ratios are probably disrupted, indicating the potential differences occurring in the ecological interactions and processes in different soil ecosystems [8,9,10]. Sidari et al [15] found lower soil C and N contents on the south-facing slope rather than the relatively more shaded northern aspect, and the
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