分类： 地球科学 >> 地理学 提交时间： 2020-11-25 合作期刊: 《干旱区科学》
摘要： Seed germination profoundly impacts plant community composition within the plant life cycle. Snow is an important source of water for seed germination in the temperate deserts of Central Asia. Understanding how seed germination responds to variations in snow cover in relation to seed traits and plant ecological characteristics can help predict plant community sustainability and stability in Central Asia under a scenario climate change. This study investigated the seed germination of 35 plant species common to the Gurbantunggut Desert in Central Asia under the three snow treatments: (1) snow addition; (2) ambient snow; and (3) snow removal. Two-way analysis of variance (ANOVA) tests were performed to assess interactions among the impacts of snow treatments, seed traits and plant ecological characteristics on seed germination. Phylogenetic generalized least-squares (PGLS) model was used to test the relationships between seed traits and seed germination. The results demonstrated that snow variations had no significant impacts on seed germination overall. Seed germination under the snow addition treatment was similar with that under the ambient snow treatment, irrespective of seed traits and plant ecological characteristics. Snow removal only had negative impacts on seed germination for certain groups of seed traits and plant ecological characteristics. Seed mass positively affected seed germination, showing a linear increase of arcsin square root-transformed seed germination with log-transformed seed mass. Seed shape also profoundly impacted seed germination, with a higher germination percentage for elongated and flat seeds. Seed germination differed under different plant life forms, with semi-shrub species showing a significantly higher germination percentage. Most importantly, although snow treatments, seed traits and plant ecological characteristics had no interactive effects on seed germination overall, some negative impacts from the snow removal treatment were detected when seeds were categorized on the basis of seed mass and shape. This result suggests that variations of snow cover may change plant community composition in this temperate desert due to their impacts on seed germination.
分类： 地球科学 >> 地理学 提交时间： 2021-04-22 合作期刊: 《干旱区科学》
摘要： Winter snowpack is an important source of moisture that influences the development of biological soil crusts (BSCs) in desert ecosystems. Cyanobacteria are important photosynthetic organisms in BSCs. However, the responses of the cyanobacterial community in BSCs to snowpack, snow depth and melting snow are still unknown. In this study, we investigated the cyanobacterial community composition and diversity in BSCs under different snow treatments (doubled snow, ambient snow and removed snow) and three snow stages (stage 1, snowpack; stage 2, melting snow; and stage 3, melted snow) in the Gurbantunggut Desert in China. In stages 1 and 2, Cyanobacteria were the dominant phylum in the bacterial community in the removed snow treatment, whereas Proteobacteria and Bacteroidetes were abundant in the bacterial communities in the ambient snow and doubled snow treatments. The relative abundances of Proteobacteria and Bacteroidetes increased with increasing snow depth. The relative abundances of Cyanobacteria and other bacterial taxa were affected mainly by soil temperature and irradiance. In stages 2 and 3, the relative abundance of Cyanobacteria increased quickly due to the suitable soil moisture and irradiance conditions. Oscillatoriales, Chroococcales, Nostocales, Synechococcales and unclassified Cyanobacteria were detected in all the snow treatments, and the most dominant taxa were Oscillatoriales and Chroococcales. Various cyanobacterial taxa showed different responses to snowpack. Soil moisture and irradiance were the two critical factors shaping the cyanobacterial community structure. The snowpack depth and duration altered the soil surface irradiance, soil moisture and other soil properties, which consequently were selected for different cyanobacterial communities. Thus, local microenvironmental filtering (niche selection) caused by snow conditions may be a dominant process driving shifts in the cyanobacterial community in BSCs.
分类： 生物学 >> 生态学 提交时间： 2023-06-13 合作期刊: 《干旱区科学》
摘要：Drought is a critical limiting factor affecting the growth and development of plants in arid and semi-arid areas. Photosynthesis, one of the most important physiological processes of plants, can be significantly inhibited by drought. Photosystem II (PSII) is considered the main attack target when photosynthesis is affected by drought. To clarify how PSII components of the ephemeral plant Erodium oxyrhinchum (grown in the Gurbantunggut Desert, China) respond to drought treatment, we evaluated the functional activity of PSII by determining chlorophyll fluorescence and gas exchange parameters under different drought treatment levels (control (400 mL), moderate drought (200 mL), and severe drought (100 mL)). Under moderate drought treatment, significant decreases were found in net photosynthetic rate (Pn), effective quantum yield of PSII (Y(II)), relative electron transfer rate of PSII (rETR(II)), oxygen-releasing complex, probability of an absorbed exciton moving an electron into the electron transport chain beyond primary quinone receptor QA– (Φ(Eo)), probability of a trapped exciton moving an electron into the electron transport chain beyond primary quinone receptor QA– (ψ(Eo)), and performance index of PSII (PIabs). Compared to control treatment, marked increases were observed in water use efficiency (WUE), relative variable fluorescence at the J step (VJ), initial fluorescence (Fo), and dissipated energy per active reaction center (DIo/RC) under moderate drought treatment, but there were no substantial changes in semi-saturated light intensity (IK), active reaction centers per cross-section (RC/CS), and total performance index of PSII and PSI (PItotal, where PSI is the photosystem I). The changes of the above parameters under severe drought treatment were more significant than those under moderate drought treatment. In addition, severe drought treatment significantly increased the absorbed energy per active reaction center (ABS/RC) and trapping energy per active reaction center (TRo/RC) but decreased the energy transmission connectivity of PSII components, RC/CS, and PItotal, compared to moderate drought and control treatments. Principle component analysis (PCA) revealed similar information according to the grouping of parameters. Moderate drought treatment was obviously characterized by RC/CS parameter, and the values of Fo, VJ, ABS/RC, DIo/RC, and TRo/RC showed specific reactions to severe drought treatment. These results demonstrated that moderate drought treatment reduced the photochemical activity of PSII to a certain extent but E. oxyrhinchum still showed strong adaptation against drought treatment, while severe drought treatment seriously damaged the structure of PSII. The results of this study are useful for further understanding the adaptations of ephemeral plants to different water conditions and can provide a reference for the selection of relevant parameters for photosynthesis measurements of large samples in the field.
分类： 地球科学 >> 地球科学史 提交时间： 2020-10-20 合作期刊: 《干旱区科学》
摘要： In forest ecosystems, interactions between overstory trees and understory herbs play an important role in driving plant species diversity. However, reported links between overstory tree and understory herb species diversity have been inconsistent, due to variations in forest types and environmental conditions. Here, we measured species richness (SR) and diversity (Shannon-Wiener (H') and Simpson's (D) indices) of overstory trees and understory herbs in the protected Tianshan Wild Fruit Forest (TWFF), Northwest China, to explore their relationships along the latitudinal, longitudinal, elevational, and climatic (current climate and paleoclimate) gradients in 2018. We found that SR, and H' and D diversity indices of overstory trees and understory herbs exhibited a unimodal pattern with increasing latitude and elevation (P<0.05) and negative associations with longitude (P<0.01). Along the climatic gradients, there were U-shaped patterns in SR, and H' and D diversity indices between trees and herbs (P<0.05). SR, and H' and D diversity indices for overstory tree species were positively associated with those for understory herbs (P<0.01). These findings indicate that overstory trees and understory herbs should be protected concurrently in the TWFF to increase effectiveness of species diversity conservation programs.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-05-02
Ding, ZH [Ding, Zhihui][ 1 ]
Deng, QH [Deng, Qihuang][ 1 ]
Shi, DW [Shi, Diwei][ 1 ]
Zhou, XB [Zhou, Xiaobing][ 1 ]
Li, Y [Li, Yong][ 1 ]
Ran, SL [Ran, Songlin][ 2 ]
Huang, Q [Huang, Qing][ 1 ]
摘要： Hexagonal Columnar ZrB2 powders were obtained from irreg- ular commercial powder at low temperature using microwave heating technique. It was confirmed that the raw ZrB2 powders first underwent dissolution process in the glassy coating, fol- lowed by re-crystallization. A growth mechanism involving selective attachment is proposed to explain the formation of the hexagonal tubules.
提交时间： 2017-05-02
Liu, WL [Liu, Wulong][ 1,2 ]
Qiu, CJ [Qiu, Changjun][ 1 ]
Zhou, J [Zhou, Jie][ 2 ]
Ding, ZH [Ding, Zhihui][ 2 ]
Zhou, XB [Zhou, Xiaobing][ 2 ]
Du, SY [Du, Shiyu][ 2 ]
Ha, YH [Ha, Young-Hwan][ 3 ]
Huang, Q [Huang, Qing][ 2 ]
摘要： Porous Ti2AlN ceramic, which was measured to be 3.23 g/cm3 about 74.9% of its theoretical value, was successfully synthesized and simultaneously consolidated from starting raw materials of Ti, Al, and TiN powders with a near-stoichiometric molar ratio of
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