Soil quality assessment in low human activity disturbance zones: a study on the Qinghai-Tibet Plateau.

The Qinghai-Tibet Plateau, located at the Third Pole and known as the "Asian water tower," serves as a crucial ecological barrier for China. Grasping the soil quality on the Qinghai-Tibet Plateau holds paramount importance for the rational and scientific exploitation of soil resources within the region and is essential for vegetation restoration and ecological reconstruction. This study, conducted in Maqin County, Qinghai Province, collected 1647 soil samples (0-20 cm) within a study area of 6300 km2. Sixteen soil indicators were selected that were split into beneficial (N, P, S, and B), harmful (Cr, Hg, As, Pb, Ni, and Cd), and essential (Cu, Zn, Se, Ga, K, and Ca) elements. The Soil Quality Index (SQI) was computed to assess soil quality across diverse geological contexts, land cover classifications, and soil profiles. The results indicate that the overall SQI in the study area was comparatively high, with most regions having an SQI between 0.4 and 0.6, categorized as moderately to highly satisfactory. Among the different geological backgrounds, the highest SQI was found in the Quaternary alluvium (0.555) and the lowest in the Precambrian Jinshuikou Formation (0.481). Regarding different land-use types, the highest SQI was observed in glacier- and snow-covered areas (0.582) and the lowest in other types of grassland (0.461). The highest SQI was recorded in typical alpine meadow soil (0.521) and the lowest in leached brown soil (0.460). The evaluation results have significant reference value for the sustainable utilization and management of soil in Maqin County, Qinghai Province, China.

Ecological risk assessment and transmission of soil heavy metals in pastoral areas of the Tibetan plateau based on network environment analysis.

The Qinghai-Tibet Plateau is distinguished by its diverse ecosystems and biodiversity, which are highly dependent on their soil. In this study, a comprehensive analysis was conducted to assess the ecological risks in Maqin County, located on the Qinghai-Tibet Plateau, along with the local background values of soil elements, level of element enrichment, and source appointment of soil elements. The findings show that the background soil element levels in Maqin County were greater than the average soil content values in China. The soils in the study area exhibited pollution levels ranging from weak to moderate. The positive matrix factorization (PMF) model was employed to successfully categorized soil elements into four sources: F1 (natural sources), F2 (grazing sources), F3 (volcanic and rock fracture sources), and F4 (intrusive and deep rock source). Based on the characteristics of the ecological communities and the network environmental analysis model, ecological risks were directly introduced through vegetation and soil microorganisms, with subsequent transmission to other components of the ecosystem through the food chain. The integrated risks associated with vegetation, herbivores, soil microorganisms, and carnivores were 0.0106, 0.00193, 0.0282, and 0.00132, respectively. Notably, soil microorganisms were found to be the primary contributors to the total ecological risk in the study area. Furthermore, network environmental analysis and human health risk models revealed that F1, F2, F3, and F4 accounted for 16.85 %, 8.90 %, 21.76 %, and 52.49 % of the input risk of vegetation and soil microorganisms, respectively. Particularly, F4 emerged as the largest contributor to human health risks. This study provides valuable information for the preservation of the ecological environment in pastoral areas, contributing to the global promotion of sustainable ecological practices.