分类： 生物学 >> 生态学 提交时间： 2025-07-17 合作期刊: 《干旱区科学》
摘要： Grassland is a key component of the ecosystem in the Qinghai Lake Basin, China. Understanding the effects of climate change and human activities on grassland productivity significantly improves ecological conservation and promotes sustainable vegetation growth in this area. Based on the net primary productivity (NPP) products of MOD17A3HGF (a moderate-resolution imaging spectroradiometer (MODIS) product that provides annual NPP at 500 m resolution) and meteorological data, we analyzed the spatial and temporal evolution of grassland NPP and its interaction with climate factors in the Qinghai Lake Basin from 2001 to 2022 via partial correlation and trend analysis methods. We also used the deflecting trend residual method and scenario analysis method to quantitatively assess the relative contributions of climatic factors and human activities to grassland NPP. The results revealed that: (1) during the past 22 a, grassland NPP increased considerably, with a gradient change from the northwest to the southeast of the study area; (2) sunshine duration, precipitation, and temperature positively influenced grassland NPP, with sunshine duration exerting a stronger effect on grassland NPP than precipitation and temperature; and (3) 98.47% of the grassland in the study area was restored, with an average contribution of 65.00% from human activities and 35.00% from climatic alterations. Compared with climate change, human-induced factors had a greater effect on grassland NPP in this area. The results of the study not only provide important scientific support for ecological restoration and sustainable development of the basin but also offer new ideas for research on similar ecologically fragile areas.
分类： 天文学 >> 天文学 提交时间： 2024-08-14 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： Sulfur chemistry in the formation process of low-mass stars and planets remains poorly understood. The protoplanetary disks are the birthplace of planets and its distinctive environment provides an intriguing platform for investigating models of sulfur chemistry. We analyzed the Atacama Large Millimeter/submillimeter Array observations of CS 7–6 transitions in the HD 163296 disk and performed astrochemical modeling to explore its sulfur chemistry. We simulated the distribution of sulfur-containing molecules and compared it with observationally deduced fractional column densities. We have found that the simulated column density of CS is consistent with the observationally deduced fractional column densities, while the simulated column density of C2S is lower than the observationally deduced upper limits on column densities. This results indicate that we have a good understanding of the chemical properties of CS and C2S in the disk. We also investigated the influence of the C/O ratio on sulfur-containing molecules and found that the column densities of SO, SO2, and H2S near the central star are dependent on the C/O ratio. Additionally, we found that the N[CS]/N[SO] ratio can serve as a promising indicator of the disk's C/O ratio in HD 163296. Overall, the disk of HD 163296 provides a favorable environment for the detection of sulfur-containing molecules.
提交时间： 2017-05-02
Zhou, M [Zhou, Ming][ 1 ]
Tian, T [Tian, Tian][ 1 ]
Li, XF [Li, Xuanfu][ 1,2 ]
Sun, XD [Sun, Xudong][ 1 ]
Zhang, J [Zhang, Juan][ 1,2 ]
Cui, P [Cui, Ping][ 1 ]
Tang, J [Tang, Jie][ 3 ]
Qin, LC [Qin, Lu-Chang][ 1,4 ]
摘要： Liquid-phase exfoliation of tetraethylammonium graphite intercalation compound [TEA-GIC] has been prepared by high-power tip-sonication of graphite in aqueous TEA solution. The release of gaseous species due to the decomposition of TEA under microwave irr
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