Abstract The purpose of this study was to characterize the physiological response of Synechococcus elongatus, a brackish-water cyanobacterium, to salt stress. S. elongatus was grown in artificial sea water medium with different salinities. The response was measured by analysis of extracellular polymeric substances (EPS) and membrane lipids. The EPS yields were positively correlated (r2 = 0.99) with the salinity. The ratio of unsaturated to saturated fatty acids (U/S) increased with salinity in the range of 2.1‰ to 31.5‰ and decreased at 52.5‰. A positive linear correlation (r2 = 0.92) was observed between the average chain length (ACL) of fatty acids and the salinity. These data indicate that S. elongatus adapted to salt stress by the secretion of EPS and by adjusting the membrane fluidity through the changes in ACL or desaturation of fatty acids. These variations in EPS and fatty acids may be used as geochemical biomarkers in sediments to unravel changes in the salinity of ancient evaporative environments. Keywords: Synechococcus salinityfatty acidEPSACLbiomarker Acknowledgments The analytical work was carried out in the Geomicrobiology Laboratory, State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (Wuhan). We thank Dr. Shucheng Xie for the constructive comments on the manuscript. This work was jointly supported by the grant from Natural Science Foundation of China (40730209, 41130207), the 973 Program (2011CB808800), the Program for New Century Excellent Talents in University (NCET-08-0831), the Provincial Program for Outstanding Youth of Hubei (2008CDB373), and the Special Fund for Basic Scientific Research of Central Colleges, China University of Geosciences (Wuhan) (CUG090103 and CUGL100502).
In our country, the Yellow River Basin ecological protection and development are put forward under the background of high quality. Among the 14 large-scale coal bases in our country, 9 coal bases are located in the Yellow River Basin, and the Shenfu-Dongsheng Coalfield, which is currently the largest under development, is located here. The region is in the process of coal mining, and the movement of overlying strata will cause the stress redistribution and coal seam in overlying aquifers also due to the effect of pore water pressure along the seepage of rock fracture and damage of overlying aquifer, so in the same formation, stress and the coupled action of seepage flow will produce mutual influence. This article through the early stage of the theoretical results discussed the application of numerical simulation method for simulating 2301 face, and the effect of stress on seepage is concluded. It is proved that the numerical simulation analysis has an important reference value for the coupling problem of stress and seepage. At the same time, the protective mining of aquifers is the basic condition for the surface ecological protection of the area, and it also provides a theoretical basis for the restoration of the ecological environment in the coal mining areas of the Yellow River Basin.
Studies of ecological boundaries are important and have become a rapidly evolving part of contemporary ecology. The ecotones are dynamic and play several functional roles in ecosystem dynamics, and the changes in their locations can be used as an indicator of environment changes, and for these reasons, ecotones have recently become a focus of investigation of landscape ecology and global climate change. As the interest in ecotone increases, there is an increased need for formal techniques to detect it. Hence, to better study and understand the functional roles and dynamics of ecotones in ecosystem, we need quantitative methods to characterize them. In the semi-arid region of northern China, there exists a farming-pasturing transition resulting from grassland reclamation and deforestation. With the fragmentation of grassland landscape, the structure and function of the grassland ecosystem are changing. Given this perspective; new-image processing approaches are needed to focus on transition themselves. Hyperspectral remote sensing data, compared with wide-band remote sensing data, has the advantage of high spectral resolution. Hyperspectral remote sensing can be used to visualize transitional zones and to detect ecotone based on surface properties (e. g. vegetation, soil type, and soil moisture etc). In this paper, the methods of hyperspectral remote sensing information processing, spectral analysis and its application in detecting the vegetation classifications, vegetation growth state, estimating the canopy biochemical characteristics, soil moisture, soil organic matter etc are reviewed in detail. Finally the paper involves further application of hyperspectral remote sensing information in research on local climate in ecological boundary in north farming-pasturing transition in China.
Nitrification represents one of the key steps in the global nitrogen cycle. While originally considered an exclusive metabolic capability of bacteria, the identification of the Thaumarchaeota revealed that ammonia-oxidizing archaea (AOA) are also important contributors to this process, particularly in acidic environments. Nonetheless, the relative contribution of AOA to global nitrification remains difficult to ascertain, particularly in underexplored neutrophilic and alkalinophilic terrestrial systems. In this study we examined the contribution of AOA to nitrification within alkaline (pH 8.3–8.7) cave environments using quantitative PCR, crenarchaeol lipid identification and measurement of potential nitrification rates. Our results showed that AOA outnumber ammonia-oxidizing bacteria (AOB) by up to four orders of magnitude in cave sediments. The dominance of Thaumarchaeota in the archaeal communities was confirmed by both archaeal 16S rRNA gene clone library and membrane lipid analyses, while potential nitrification rates suggest that Thaumarchaeota may contribute up to 100% of ammonia oxidation in these sediments. Phylogenetic analysis of Thaumarchaeota amoA gene sequences demonstrated similarity to amoA clones across a range of terrestrial habitats, including acidic ecosystems. These data suggest that despite the alkaline conditions within the cave, the low NH3 concentrations measured continue to favor growth of AOA over AOB populations. In addition to providing important information regarding niche differentiation within Thaumarchaeota, these data may provide important clues as to the factors that have historically led to nitrate accumulation within cave sediments.
By the methods of classic statistics and geostatistics, this paper analyzed the spatial heterogeneity of soil moisture at 0-50 cm depth in different sampling grain sizes (1 m x 1 m and 2 m x 2 m) at the cropland-grassland boundary in agro-pastoral transitional zone of North China. In study area, the soil moisture at 0-10 cm, 10-20 cm, 20-30 cm, 30-40 cm, and 40-50 cm depths of cropland, grassland, and cropland-grassland boundary presented moderate variance, and the coefficient of variation (CV) of grassland was higher than that of cropland. The CV increased with soil depth, and a significant linear regression relation (P < 0.05) was observed between them in sampling grain size 1 m x 1 m. In sampling grain size 1 m x 1 m, the spatial heterogeneity of soil moisture at different depths was obviously higher at cropland-grassland boundary than in cropland and grassland, which had a moderate to strong spatial dependency, and the range (A0) was 7.65-30.99 m; whereas in sampling grain size 2 m x 2 m, the spatial distribution of soil moisture at cropland-grassland boundary had both the moderate to strong spatial dependency and the pure nugget effect, and the A0 was 4.16-18.86 m, suggesting that there existed ecological edge effect of soil moisture at cropland-grassland boundary.
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