Subjects: Geosciences >> Geography submitted time 2024-03-01 Cooperative journals: 《干旱区研究》
Abstract： To study the important effects of the water-holding capacity of litter in plantation plants in coal minedumps on soil and water conservation and ecosystem restoration in mining areas, litter accumulation amount, thethickness, water-holding rate, water-holding capacity, and water absorption rate of different decomposition stageswere investigated in four typical plantations of the same age (Populus simonii, Ulmus pumila, Pinustabulaeformis, and Robinia pseudoacacia forests) in the Antaibao opencast coal mine reclamation area, throughfield investigation and soaking extraction. The results showed that the litter accumulation amount in the P.simonii forest was higher than that in the R. pseudoacacia and U. pumila forests (P < 0.05). The water-holdingcapacity and litter rate at different decomposition degrees changed logarithmically with immersion time (P <0.01). The order of the water absorption rate of litter was R. pseudoacacia forest > U. pumila forest > P. simoniiforest > P. tabulaeformis forest, and the water absorption rate showed a significant power function withimmersion time (P < 0.01). In conclusion, the litter of the P. simonii forest had the strongest water- holdingcapacity, whereas the R. pseudoacacia forest had the fastest water absorption rate. Therefore, from theperspective of the water conservation capacity of litter, P. simonii forest should be prioritized and mixed with theR. pseudoacacia forest, which is more conducive to water conservation in the reclamation area of opencast coalmines.
Subjects: Geosciences >> Space Physics submitted time 2016-05-04
Abstract： Coronal mass ejections (CMEs) and corotating interaction regions (CIRs) are two significant contributors to interplanetary disturbances and geomagnetic disturbances, which also play as major drivers of geomagnetic storms to modulate the geo-space environment. In order to comprehensively investigate the characteristic temporal features of the solar wind activity and associated geomagnetic activity, a large amount of solar wind data and geomagnetic activity indices are analyzed in detail. Firstly, using the public data of solar wind parameters and geomagnetic activity indices provided by the NASA OMNIWeb, the MATLAB codes are developed to deal with a number of key parameters including IMF B-z solar wind velocity, solar wind proton density, solar wind dynamic pressure, Dst, AE, and Kp for the entire Solar Cycle 23 from 1996 to 2008. The complete database with a full list of 269 CME events and 456 CIR events is identified. Case event studies and superposed epoch analyses are implemented to carefully investigate the statistical features of four important solar wind parameters (IMF 13,, solar wind speed, solar wind proton density, and solar wind dynamic pressure) and three major geomagnetic indices (Dst, AE, and Kp) associated with the two types of solar disturbances. Secondly, the minimum of Dst index is utilized to differentiate 355 isolated geomagnetic storms occurring during the Solar Cycle 23. These storms are further categorized according to the magnitude of Dst minimum into 145 weak storms, 123 moderate storms, 70 strong storms, 12 severe storms, and 5 extreme storms. Finally, superposed epoch analysis is applied to evaluate the statistics of solar wind parameters and geomagnetic indices corresponding to magnetic storms with different intensities. It is found that in general the linearly fitted slope of N-sw/P-dyn (where N-sw is the solar wind proton density and P-dyn the dynamic pressure) with respect to epoch time remains positive for CME events but negative for CIR events, which can act as a feasible means to distinguish CME and CIR events. On average, compared to CIR events, CME events have larger magnitudes of southward IMF B solar wind dynamic pressure, AE and Kp indices but smaller Dst(min). In principle, CMEs bear higher possibility to drive extremely intense (i. e., super) geomagnetic storms. The overall variations of Dst tend to be similar to some extent for different levels of geomagnetic storms, however, Dst decreases faster for stronger storms. There are a large number of differences between CME and CIR events and their driven geomagnetic storms as well. Therefore, CME-driven storms and CIR-driven storms should be studied separately. The established database of CME and CIR events and geomagnetic storms and the quantitative statistical information in combination can provide a useful aid for better understanding the responses of Earth's plasma sheet, radiation belts, and ring current to various solar activities.
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