分类： 农、林、牧、渔 >> 土壤学 提交时间： 2019-03-28 合作期刊: 《干旱区科学》
摘要： The aboveground primary production is a major source of carbon (C) and nitrogen (N) pool and plays an important role in regulating the response of ecosystem and nutrient cycling to natural and anthropogenic disturbances. To explore the mechanisms underlying the effect of spring fire and topography on the aboveground biomass (AGB) and the soil C and N pool, we conducted a field experiment between April 2014 and August 2016 in a semi-arid grassland of northern China to examine the effects of slope and spring fire, and their potential interactions on the AGB and organic C and total N contents in different plant functional groups (C3 grasses, C4 grasses, forbs, Artemisia frigida plants, total grasses and total plants). The dynamics of AGB and the contents of organic C and N in the plants were examined in the burned and unburned plots on different slope positions (upper and lower). There were differences in the total AGB of all plants between the two slope positions. The AGB of grasses was higher on the lower slope than on the upper slope in July. On the lower slope, spring fire marginally or significantly increased the AGB of C3 grasses, forbs, total grasses and total plants in June and August, but decreased the AGB of C4 grasses and A. frigida plants from June to August. On the upper slope, however, spring fire significantly increased the AGB of forbs in June, the AGB of C3 grasses and total grasses in July, and the AGB of forbs and C4 grasses in August. Spring fire exhibited no significant effect on the total AGB of all plants on the lower and upper slopes in 2014 and 2015. In 2016, the total AGB in the burned plots showed a decreasing trend after fire burning compared with the unburned plots. The different plant functional groups had different responses to slope positions in terms of organic C and N contents in the plants. The lower and upper slopes differed with respect to the organic C and N contents of C3 grasses, C4 grasses, total grasses, forbs, A. frigida plants and total plants in different growing months. Slope position and spring fire significantly interacted to affect the AGB and organic C and N contents of C4 grasses and A. frigida plants. We observed the AGB and organic C and N contents in the plants in a temporal synchronized pattern. Spring fire affected the functional AGB on different slope positions, likely by altering the organic C and N contents and, therefore, it is an important process for C and N cycling in the semi-arid natural grasslands. The findings of this study would facilitate the simulation of ecosystem C and N cycling in the semi-arid grasslands in northern China.
分类： 核科学技术 >> 核材料与工艺技术 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： The effect of humic acid (HA) on the diffusion of Re(VII) was investigated in compacted Gaomiaozi (GMZ) bentonite by the through- and out- diffusion method. The effective diffusion coefficient, De, and accessible porosity, acc, were measured in order to evaluate the impact of humic acid on Re(VII) diffusion. The De value was in the range of (5.28.3)10-12 m2/s. The diffusion of Re(VII) was enhanced in the presence of HA, and the De value increased with the increase of ageing time, indicating that the formation of HA-Re complexes was slow. Moreover, the acc was in the range of (0.06 0.16), which is less than the total porosity. It implies that the HA-Re complexes are anions.
分类： 生物学 >> 生物物理学 提交时间： 2016-05-12
Liu, Mi
Wu, Aiping
Jiang, Taijiao
Liu, Mi
Wu, Aiping
Jiang, Taijiao
Liu, Mi
Wu, Aiping
Jiang, Taijiao
Liu, Mi
Hua, Sha
Wu, Aiping
Jiang, Taijiao
Zhao, Xiang
Li, Xiyan
Lan, Yu
Wang, Dayan
Shu, Yuelong
Hua, Sha
Du, Xiangjun
摘要： The influenza A (H1N1) virus causes seasonal epidemics that result in severe illnesses and deaths almost every year. A deep understanding of the antigenic patterns and evolution of human influenza A (H1N1) virus is extremely important for its effective surveillance and prevention. Through development of antigenicity inference method for human influenza A (H1N1), named PREDAC-H1, we systematically mapped the antigenic patterns and evolution of the human influenza A (H1N1) virus. Eight dominant antigenic clusters have been inferred for seasonal H1N1 viruses since 1977, which demonstrated sequential replacements over time with a similar pattern in Asia, Europe and North America. Among them, six clusters emerged first in Asia. As for China, three of the eight antigenic clusters were detected in South China earlier than in North China, indicating the leading role of South China in H1N1 transmission. The comprehensive view of the antigenic evolution of human influenza A (H1N1) virus can help formulate better strategy for its prevention and control.
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