Insight into bacterial and archaeal community structure of Suaeda altissima and Suaeda dendroides rhizosphere in response to different salinity level.

IMPORTANCE: Suaeda play an important ecological role in reclamation and improvement of agricultural saline soil due to strong salt tolerance. At present, research on Suaeda salt tolerance mainly focuses on the physiological and molecular regulation. However, the important role played by microbial communities in the high-salinity tolerance of Suaeda is poorly studied. Our findings have important implications for understanding the distribution patterns and the driving mechanisms of different Suaeda species and soil salinity levels. In addition, we explored the key microorganisms that played an important ecological role in Suaeda rhizosphere. We provide a basis for biological improvement and ecological restoration of salinity-affected areas.

Great gerbil burrowing-induced microbial diversity shapes the rhizosphere soil microenvironments of Haloxylon ammodendron in temperate deserts.

In the Gurbantunggut Desert of northwest China, the main habitat of Rhombomys opimus (great gerbil) is under the thickets of Haloxylon ammodendron, the main construction species. In the long-term coexistence, continuous gerbil activities (burrowing, defecating, and gnawing) limited the growth of H. ammodendron, affected the root microenvironment under the H. ammodendron forest, and weakened the desert ecosystem. However, there is a lack of general understanding about the response of desert soil microhabitats to such gerbil disturbance. Accordingly, this study examined the effects of different intensities of gerbil disturbance (none, mild, moderate, or severe disturbances) on soil nutrients content and used high-throughput sequencing to explore the change in diversity and structure of microbial communities (bacteria and fungi) in H. ammodendron rhizosphere at different soil depths (0-20, 20-40, and 40-60 cm). In the arid desert ecosystem, compared with the soil fungal community, the alpha diversity of the soil bacterial community was significantly affected by gerbil disturbance. Meanwhile, both soil depth and gerbil disturbance significantly impacted the beta diversity and relative abundance of soil bacterial and fungal communities. In addition, gerbil disturbance significantly altered the soil characteristics affecting the distribution and composition of soil microbial communities in H. ammodendron rhizosphere, especially the soil bacterial community. This survey provides evidence that remold impact of gerbil disturbance on soil microenvironment of H. ammodendron rhizosphere in desert ecosystems in northwest China, which helps to further understand the potential correlations with changes in the microbial community at a regional scale.

[GIS-based measurement of Haloxylon ammodendron tree ring]. / 基于GIS的梭梭年轮测量方法.

Tree ring data is of significance for reconstructing climate and predicting environmental dynamics. In order to accurately measure spacing and other parameters of Haloxylon ammodendron tree ring, we first assigned coordinate system to the scanned H. ammodendron disc PS images based on GIS, and then completed the H. ammodendron tree ring spacing measurement by using ENVI image classification software and GIS measuring tool. The measurement accuracy was proved by WinDENDRO tree ring analysis system. The results showed that there was no significant difference between those two methods (P=0.63), and that the difference of paired mean value was 0.87 µm, indicating that the measured results were accurate and reliable. The constructed method in this study could be used to measure the spacing of H. ammodendron tree ring, which lay the foundation for the automatic measurement of tree ring parameters such as area and perimeter. Our method could replace the current professional tree ring analysis system for some ring parameter measurement. The study would contribute to the dendroclimatology analysis and the investigation on age structure of H. ammodendron population.

[Spatiotemporal variation of growing season length of vegetation in China.] / 中国植被生长期的时空变化.

We analyzed the variation trend of growing season length (GSL) of different periods in provinces (regions) of China and the corresponding movement velocity of GSL isolines at 150, 200, 250, 300 and 350 days, based on daily mean temperature data of 822 meteorological stations from 1951 to 2017. In this study, the definition of GSL given by the world meteorological organization was adopted, together with Slope, Hurst and Mann-Kendall indices. The results showed that the GSL in northern China changed significantly during 1951-2017. The extension of GSL was faster in the north than the south, and faster in high-altitude areas than low-altitude ones. The trend of future GSL change in most regions of China converged with the current extension trend. The extension of GSL in northern provinces (regions) was generally 0.1-0.2 d·a-1, of which the fastest was Tibet with a speed of 0.44 d·a-1. The period 1981-2000 was the most changeable time of GSL in Chinese provinces (regions). The growing season start (GSS) of all provinces (regions) contributed more to the GSL extension, except for Xinjiang, whose GSL extension was dominated by the growing season end (GSE). In the high-latitude or high-altitude provinces, GSL was more sensitive to the change of mean annual temperature. The higher the mean annual temperature, the longer the GSL. Since 1951, China's GSL isolines of 150, 200, 250, 300 and 350 days showed notable variations. The fastest movement velocity was the 200 days isoline in Northeast China with an average northward movement velocity of 6.11 km·a-1. The general principle of the movement of China's GSL isoline was that the higher the value of the isoline, the slower the northward movement, with even a southward shift in part of the 350 days isoline. The extension of GSL in China would result in the northward shift of crop planting boundary and the extension of natural vegetation growth period. However, the specific impacts of this change on the quality, crop yield, and ecosystem carbon sequestration need further research.