Agricultural terraces are a manifestation of man's ability to transform nature during the past thousands of years, and they have played an important role in the development of human society. The Ganjia Basin in Xiahe County, Gansu Province, is located in the northeastern Tibetan Plateau. A large area of banded landscape is distributed on the hills and piedmonts in the Ganjia Basin, which is claimed to be composed of large-scale abandoned ancient terraces. Based on fieldwork, satellite remote sensing data and GIS analysis in the present study, we found that the ancient terraces cover an area of 42.2 km² and are mainly distributed on slopes between 2936 and 3326 m a.m.s.l. (meters above mean sea level) on both sides of the Yangqu River and its tributaries in the basin. Additionally, we analyzed various environmental proxies, including magnetic susceptibility (MS), grain size, the contents of total organic carbon (nitrogen) (TOC, TN), and palynological assemblages, from three representative sections of ancient agricultural terraces (GJAT-1, GJAT-1, and GJAT-3), and compared them with the MS values and clay content of a natural profile with accurate chronological control in the Ganjia Basin. The results indicate that the terraces are reclaimed paleosols dating to the Late Holocene (3000 kyr BP), and that the homogeneous MS values of the top 25-35 cm of the terrace profiles differ from those of the natural soil section, which confirms the existence of a cultivation layer in the terraces. However, the increases in the contents of TOC and TN above the cultivated layer, and the fact that the trend of MS in the terrace profile is broadly in line with the natural profile, indicate that the terraces were only used for a short interval and have been abandoned for a relatively long time. Combined with historical documentary evidence, we infer that the ancient Xiahe agricultural terraces were constructed as a result of the "Gongjianshou (bowman) militia farming" policy during the Northern Song China (1074-1125 CE). Climate reconstructions for the Northern Hemisphere and northern China demonstrate that the temperature was higher and that the precipitation increased during this interval, providing a favorable environment for agricultural production. Overall, our results provide a typical example of societal adaptation to climate change in the past.

Global climate change and human activities have profoundly affected regional hydrological processes. Attribution recognition of streamflow and sediment change is particularly important to understand the theory and practice of ecological protection and for high-quality development of watersheds. Based on the Budyko hypothesis and fractal theory, we used the elastic coefficient method to analyze the attribution of streamflow and sediment changes in the upper (typical hilly and valley region), middle (earth-rock mountain forest region and tableland region), and lower (Weibei loess tableland agricultural region) portions of the Beiluo River Basin from the 1960s to the 2010s. Results showed that runoff depth in the upper, middle, and lower reaches of Beiluo River decreased significantly from 35, 32, and 34 mm in the 1960s to 19, 24, and 6 mm in the 2010s, with a decrease rate of 0.3, 0.2, and 0.4 mm/a, respectively. The upstream sediment transport decreased significantly, while the sediment transport of the middle reaches decreased insignificantly; the downstream sediment transport also decreased significantly from 99, 8, and 3 million tons in the 1960s to 10, 3, and 0.3 million tons in the 2010s, with decreasing rates of 1.5, 0.04, and 0.1 million t/a, respectively in the 60 years. In contrast to the 1960s, the runoff change in the upstream region has been gradually affected by human activities since the 1970s, and its degree has gradually increased as the contribution rate of human activities in the 2010s reached 66.3%. Runoff variation in the middle reaches was mainly determined by climate change, with the contribution rates of rainfall and potential evapotranspiration being 77.0% and 20.2%, respectively. The decrease of runoff in the downstream region was mainly affected by human activities, and the contribution rate was as high as 64.3% in the 2010s. In contrast to the 1960s, the change of sediment yield in the basin was always dominated by human activities, and the contribution rates of human activities to the reduction of sediment discharge in the upper, middle, and lower reaches in the 2010s were 80.7%, 59.2%, and 92.7%, respectively. Measures such as returning farmland to forests on slope and engineering practices in valley contributed 39.0% and 42.7%, respectively, of the reduction in sediment transport in the upstream region. The estimation results of the contribution of human activities in the middle and lower reaches reflect the response of regional runoff and sediment transport in high vegetation cover areas and in irrigated agricultural areas.

The chemical protection mechanism of soil organic carbon (SOC) was explored to quantify the distribution of organic carbon protected by iron (Fe) and aluminum (Al) minerals in two alpine soils. Selective extraction methods were used in mountain podzolic (MP) soil and alpine meadow (AM) soil to investigate the distribution of SOC, as well as Fe and Al contents of SOC associated with crystalline metal oxides extracted by (dithionite-HCl, DH), short-range-order minerals extracted by (hydroxylamine-HCl, HH) and organo-mineral complexes extracted by (Na-pyrophosphate, PP). Results showed that the carbon concentrations extracted by DH, HH, and PP in MP soils were (10.91±6.23) g/kg, (5.92±1.66) g/kg, and (8.76±2.29) g/kg, respectively. These oxides, minerals, and complexes accounted for 20.92%, 12.07%, and 19.93% of SOC, respectively. Comparatively, the carbon concentrations for DH, HH, and PP in AM soils were (9.05±1.33) g/kg, (5.52±1.02) g/kg, and (9.12±3.21) g/kg, accounting for 21.04%, 12.47%, and 19.34% of SOC, respectively. The distribution of carbon contents and their proportions to SOC extracted through three extractants showed an order of PP > DH > HH in the A horizon and an order of DH > PP ≈ HH in the B horizon, for both MP and AM soils. An increase in soil depth, together with increasing abundance of secondary minerals and crystalline minerals in deeper soils, leads to organo-mineral associations changing from being dominated by organo-metal complexes to being dominated by the crystalline mineral-associated organic carbon. PP-extracted carbon contents and its relative proportion to SOC were higher in the A horizon than those in the B horizon, whereas DH- and HH- extracted carbon contents and their proportions to SOC were generally lower in the A horizon than those in the B horizon. These differences were more pronounced in MP because of its special soil property. The distribution of metal (Al+Fe) contents extracted by the three extractants showed the order DH > HH > PP in both soil types. However, the molar ratio of carbon-to-metal showed the order DH < HH < PP, suggesting that as the degree of mineral crystallization increases, the interaction between minerals and carbon changed from precipitation dominant to adsorption dominant. A correlation analysis of DH, HH, PP, and SOC suggested that the accumulation of SOC was driven to a certain extent by the association of crystalline Fe and Al minerals and organic matter in MP, as well as the association of short-range-order minerals and organic matter as well as organo-metal complexes in AM soils. The organomineral associations are, to some extent, driving the accumulation of SOC in alpine mountain soils in western Sichuan. The distribution of organic carbon associated with minerals and the accumulation ways of organic carbon is different across various soil types.

The moon is the only natural satellite of the earth and the main celestial body in deep space exploration at current stage. The study on lunar surface morphology can not only help understand the structure and composition of the moon but also provide direct and reliable evidence on the origin and evolution history of the moon. Compared with the geomorphic classification of the earth, research on lunar morphology started late and developed slowly. Although researchers have been concentrated in lunar morphology study, there is still lack of research with regards to the distribution characteristics of morphological indicators and their combination with lunar morphological classification schemes. Based on the characteristic analysis of surface elevation in lunar mare, we found that the division criteria of -2500 m and -1500 m can better distinguish the inner region of the lunar mare and the crater rim crests and highland. The study on the impact craters shows that a contour line of 3000 m can better highlight the boundary of some impact craters in the highland. Besides, the boundary of South Pole Aitken is mostly situated at an elevation of about 1000 m. Thus, four thresholds of -2500 m, -1500 m, 1000 m and 3000 m are proposed as the classification criteria in lunar morphological classification scheme, and the lunar surface is divided into five geomorphic types: extremely low altitude, low altitude, medium altitude, high altitude and extremely high altitude.