Application of urease-producing microbial community in seawater to dust suppression in desert.

In order to solve the dust problem caused by sandstorms, this paper aims to propose a new method of enriching urease-producing microbial communities in seawater in a non-sterile environment. Besides, the difference of dust suppression performance of enriched microorganisms under different pH conditions was also explored to adapt the dust. The Fourier-transform infrared spectrometry (FTIR) and Scanning electron microscopy (SEM) confirmed the formation of CaCO3. The X-ray diffraction (XRD) further showed that the crystal forms of CaCO3 were calcite and vaterite. When urease activity was equivalent, the alkaline environment was conducive to the transformation of CaCO3 to more stable calcite. The mineralization rate at pH = 10 reached the maximum value on the 7th day, which was 97.49 ± 1.73%. Moreover, microbial community analysis results showed that the relative abundance of microbial community structure was different under different pH enrichment. Besides, the relative abundance of Sporosarcina, a representative genus of urease-producing microbial community, increased with the increase of pH under culture conditions, which consistent with the mineralization performance results. In addition, the genus level species network diagram also showed that in the microbial community, Sporosarcina was negatively correlated with another urease-producing genus Bacillus, and had a reciprocal relationship with Atopostipes, which means that the urease-producing microbial community was structurally stable. The enrichment of urease-producing microbial communities in seawater will provide empirical support for the large-scale engineering application of MICP technology in preventing and controlling sandstorms in deserts.

Effects of rotation grazing time on the characteristics of soil seed bank in desert steppe.

Exploring the characteristics of soil seed bank under seasonal grazing plays an important role in the reasonable use of desert steppe. We examined seed bank species composition, density, vertical distribution, diversity in the soil of 0-5, 5-10, 10-15 cm soil layers and the relationship with vegetation and soil environmental factors in Ningxia desert steppe. The treatments included enclosure (FY), traditional time rotation grazing (FG), delayed to start rotation grazing (YG), early to end rotation grazing (TG), delayed to start and early to end rotation grazing (YT) and free grazing (ZY). The results showed that there were nine families and 21 species in the soil seed bank in the study area. The species composition of soil seed bank in TG seed bank with 13 species was the largest, while FY and ZY soil seed banks had the least, with 8 species, respectively. The den-sity of ZY soil seed bank was significantly higher than that of FY, YG, TG and YT. The number of perennial species seeds in the soil seed bank of FY was the largest, reaching 32.0%, while that in the ZY was the least, only 12.4%, mainly with sexually reproduced annual weeds. Soil seed bank was mainly concentrated in the 0-5 cm surface layer. With increasing soil depth, the size of soil seed bank decreased. The dominance and diversity of soil seed bank were the highest in FY, while the dominance, diversity and uniformity were the lowest in ZY. The similarity between soil seed bank and aboveground vegetation was generally low. In contrast, the FG and ZY seed banks had higher similarity with vegetation, and the FY was the lowest. Soil moisture, organic matter, total nitrogen concentration, total phosphorus concentration, and soil bulk density were the main soil factors affecting soil seed bank. Compared with traditional whole year free grazing, seasonal four-zone rotation grazing could increase species richness and abundance of perennial plants in soil seed bank of desert steppe, as well as the total species richness, diversity and uniformity of the seed bank. Although the effect sof seasonal four-zone rotation grazing on seed bank was not as good as the long-term enclosure grassland, it was of great significance to the utilization and protection of desert steppe.