Abstract
In this study, the effects of slope aspects and depths on soil organic carbon (SOC), soil total nitrogen (STN), and soil total phosphorus (STP) were quantified in disturbed restoration regions of Gaolan County, located in the Gansu Province of semi-arid loess Plateau of China. Soil samples were collected at 0–10, 10–20, 20–40, 40–60, 60–80, and 80–100 cm on southern, southwestern, western, northwestern, and northern slope aspects of three hills. A total of 75 soil profiles and 450 soil samples were analyzed. Results showed that the SOC, STN, and STP content varied from 1.65 to 12.87 g/kg, 0.45 to 1.53 g/kg, and 0.07 to 0.78 g/kg, and the SOCD, STND, and STPD at 0–100 cm varied from 3.9 to 9.5 kg/m2, 0.58 to 1.35 kg/m2, and 0.33 to 0.56 kg/m2, which increased from the southern to northern slope aspects. The SOC, STN, and STP contents and SOCD, STND, and STPD were mainly in the 0–60 and 60–100 cm soil layers. The vertical descent rate was γSOC > γSTN > γSTP for both content and density. For a single soil nutrient, the decline rate of its content and density on the northern slope aspect was greater than that on the southern slope aspect, that is γN > γ All > γS. The correlation degree between soil properties and SOC and STN content were above 0.6, the overall correlation with STP content was <0.6. These results confirmed that topography (slope aspects) was the most significant factor controlling the distribution patterns of SOC, STN, and STP in hill ecosystems. Overall, the northern slope aspect (vs. southern slope aspect) was more favorable to the preservation of SOC, STN, and STP. Accordingly, in the Loess Plateau and similar fragile environments, soil nutrient protection and vegetation restoration are selective to some extent.
Highlights
The semi-arid area of the Loess Plateau is one of the most fragile zones in the Chinese Loess Plateau region, but it is a key area of vegetation construction in the Loess Plateau [1]
The soil organic carbon (SOC) content showed a significantly decreasing trend with soil depth at all sampling positions, and the SOC content at 0–10 cm was about 2–3 times larger than that at 80–100 cm
The results show (Figures 2, 3) that the SOC, soil total nitrogen (STN), and soil total phosphorus (STP) contents and SOCD, STND, and STPD on the northern slope aspects are significantly higher than other slope aspects, and STN and STP gradually increase from the southern to northern slope aspects, which is consistent with the research results of Lenka et al [26] and Huang et al [3]
Summary
The semi-arid area of the Loess Plateau is one of the most fragile zones in the Chinese Loess Plateau region, but it is a key area of vegetation construction in the Loess Plateau [1]. The content of soil organic matter, litter redistribution, and long-term accumulation of soil nutrients will affect the carbon process of community and ecosystem and the biochemical cycle of mineral elements [5, 6], and affect the stability and sustainability of the whole ecosystem. Topographic indexes can well justify the spatial variability of crops, indicating the importance of these factors by influencing the distribution of moisture during the process of crop production in the study region. The enhancements of crop components in the lower slope positions could be attributed to an increase in soil depth and plant available water as well as to the accumulation of further soil organic matter and nutrient elements, including nitrogen and potassium, in such positions as a result of soil redistribution [10]. Topographic attributes and vegetation indexes were to be influential parameters and would be an indication of soil microorganisms for soil quality assessment and management practices [11]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
