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Stipa shanxiensis, a cryptic species within Stipa grandis that originated from central and western China, is described based on morphological, genomic, and ecological data from field and common garden experiments. Stipa shanxiensis morphologically resembles S. grandis, although phylogenetically it is closely related to the less morphologically similar Stipa baicalensis and Stipa krylovii. Of the eight significant morphological differences between S. shanxiensis and S. grandis, the two, cauline ligules longer than 2 cm with a filiform apex, and hairs shorter than 0.2 mm on the adaxial surface of the cauline uppermost leaves can be used to distinguish the species. Results from a common garden experiment verified that the two diagnostic characteristics were relatively stable and less morphologically plastic in response to environmental variation. Furthermore, a significant ecological divergence was found between S. shanxiensis and S. grandis, such that the former preferred warmer and more humid climates, and their predicted distribution was generally separated. Taken together, our results highlight that the integrative taxonomic approach was valuable for recognizing a new cryptic species in Stipa. In particular, we find that common garden experiments involving the effects of growth stage and characteristic position helped to morphologically diagnose cryptic species. These findings may also facilitate our understandings of ecological adaption and phenotypic plasticity in response to environmental change. [ABSTRACT FROM AUTHOR]

The experiment studied the effect of Arbuscular mycorrhizal fungi (AMF) function in the grasses and legumes mixture. A mixed sowing experiment of Medicago varia Martin. cv. Caoyuan No.3 and Agropyron mongolicum Keng. cv. Mengnong No. 1 was carried out on four years grassland. The paper researched AMF infection, soil nitrogen and phosphorus nutrients situation. The results showed that the total yield of mixed sowing was 24.3% higher than that of monoculture alfalfa and 46.9% higher than that of monoculture ice grass, and the plant height of mixed sowing ice grass was higher than that of monoculture ice grass. The pH value of rhizosphere soil of mixed grassland was significantly lower than that of non-rhizosphere soil. The vesicle infection rate of mixed sowing ice grass was significantly higher than that of monoculture ice grass. The total nitrogen of mixed sowing soil was higher than that of alfalfa monoculture or ice grass monoculture. The available P content in rhizosphere soil was higher than that in non-rhizosphere soil. The experiment indicates that the soil yield can be increased with the increase of Arbuscular fungi infection rate, the increase of nitrogen and phosphorus content in rhizosphere soil, and the decrease of soil pH value. [ABSTRACT FROM AUTHOR]

Great attention has been paid to accelerate the start-up period and enhance floc properties and structural stability in activated sludge reactors with the aid of inorganic chemical agents such as calcium ion. The laboratory-scale sequencing batch reactors (SBRs) were operated continuously for 35 days to investigate the effect of calcium ion (Ca 2+ ) on the physicochemical properties and evolution of extracellular polymeric substances (EPS) of activated sludge during set-up period. When compared to the control (non-calcium ion addition), the addition of 150 mg·L -1 Ca 2+ to the influent significantly increased the mixed liquid suspended solids (MLSS) and the mixed liquid volatile suspended solids (MLVSS) by 89.6% and 75.6% on 28 d, respectively, and decreased the sludge volume index (SVI) by 47.9% following SBRs set-up. Compared with the control system, the contents of EPS, polysaccharides (PS) and proteins (PN) were increased by 76.4%, 28.8% and 31.6% under the condition of Ca 2+ dosage of 150 mg·L -1 . The PS/PN ratio was 68.8 for Ca 2+ addition, compared to only 36.6 for the control reactor. Analysis using three-dimensional excitation emission matrix fluorescence spectroscopy and Fourier transform infrared spectrum revealed that Ca 2+ addition changed the compositional characteristics of EPS. Results from this study provided a fundamental knowledge basis for the improvement of the settling properties of activated sludge with calcium ion addition.