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This study reports the effects of a long-term tillage and crop residue experiment on the soil microbial ecology of a Loess soil located in Gansu Province, western China. Tillage and residue management treatments were imposed on a nine-year continuous rotation of maize (Zea mays L. cv Zhongdan No. 2), winter wheat (Triticum aestivum L. cv Xifeng No. 24) and soybean (Glycine max L. cv Fengshou No. 12). After nine years, there were significant effects on topsoil (0-10 cm) carbon, nitrogen, microbial activity, microbial composition and function. The retention of crop residues compared to residue removal significantly improved all measures of chemical and biological soil fertility. The values of average well color development (AWCD), a measure of the metabolic utilization of organic compounds, for the residue retention treatments were always higher than those with residue removal treatments, and the differences increased with increasing incubation time. Principal component analysis indicated that crop residue retention significantly altered topsoil microbial activity and community functional diversity. Our research clearly demonstrates that retention of crop residues significantly enhances soil microbial metabolic capacity, compared to no tillage, and can therefore contribute to sustainable agriculture on the Loess Plateau. Promotion of conservation agriculture has the potential to rehabilitate soil fertility and improve agricultural sustainability and food security on the region.

We reconstructed a multiproxy record of the Holocene climate changes from a 9.53 m core from Bosten Lake in the southern Xinjiang of northwestern China based on a chronology supported by nine AMS 14C dates in the hope that the previous reconstructions can be improved. Our data exhibited three timescales of variation in the water salinity of the lake. First, the upward-increasing parallel trends of major salinity proxies suggest that the salinity has been gradually increasing in the past ~8000 years. This constant increase in the salinity is most likely to have resulted from the shrinking of glacial cover in the central Tianshan Mountains where the inflowing river (i.e. Kaidu River) originated. Second, the C/S ratio and carbonate-based salinity proxies suggest that the lake was formed around ~8060 cal. yr BP and reached its maximum depth around ~7250 cal yr BP. The lake level then declined to the mid- and late-Holocene average level around ~6370 cal. yr BP and has varied drastically around a relatively constant mean during the past ~6370 years. Third, the past ~8060 yr history of the Bosten Lake can be divided into five salinity stages. That is, three high salinity intervals are separated by two low salinity intervals. The two low salinity stages occurred between ~6370 and ~5170 cal. yr BP and between ~3000 and ~2170 cal. yr BP. Each one of the three high salinity stages can be further divided into less saline and more saline substages. Specifically, less saline time intervals are: substage 2-1 (~8060—~7250 cal. yr BP), substage 4-2 (~4370—~3830 cal. yr BP) and substage 6-2 (~1250—~0 cal. yr BP). Also, saltier time intervals are: substage 2-2 (~7250—~6370 cal. yr BP), substage 4-1 (~5170—~4370 cal. yr BP), substage 4-3 (~3830—~3000 cal. yr BP) and substage 6-1 (~2170—~1250 cal. yr BP). It should be stressed that the phase relationships between the carbonate-based salinity proxy and diatom-based temperature proxy suggest that the salinity was mainly controlled by temperature. Finally, the comparison between the Bosten Lake salinity record and the high northern latitudinal climate pattern suggests that the lower salinity and cooler periods in Bosten Lake area correspond with abrupt climatic events (i.e. cooling events) in the high northern latitudes.

Biosensors based on terahertz (THz) metasurfaces have recently attracted widespread attention. However, few have been reported so far because it is a challenge to achieve ultrasensitive multidimensional detection in the THz spectrum. Here, we propose a novel THz biosensor that consists of a metasurfaces and a metal oxide semiconductor-like structure (MOSLS), which is based on patterned graphene–polyimide–perovskite. We varied the photoconductivity of the MOSLS via the electrostatic doping effect. The biosensor could detect whey protein down to a concentration limit of 6.25 ng/mL. Significant responses in frequency, phase, and transmission amplitude were all detected for different protein concentrations. The transmission value difference, frequency shift, and phase difference increased with the concentration of whey protein, clearly demonstrating multidimensional biosensing. Moreover, by applying lasers with different wavelengths, we have realized reversible biosensing in THz region for the first time. These results are very promising for applications of THz metasurfaces in the field of biosensing.

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