Search

In June 2020, needle blight symptoms on Pinus thunbergii were discovered in Bazhong City, Sichuan Province, China. Fungal isolates were obtained from the pine needles of P. thunbergii. After examining morphological characteristics and conducting multi-locus (ITS, ACT, TUB2 and RPB2) phylogenetic analyses, the isolates SC1–SC5 were determined to be a new species, Biscogniauxia sinensis. Genealogical Concordance Phylogenetic Species Recognition with a pairwise homoplasy index test was used to further verify the results of the phylogenetic analyses. The morphology and phylogenetic relationships between this new species and other related Biscogniauxia species were discussed. To our knowledge, this is also the first report of Biscogniauxia sinensis associated with pine needle blight on P. thunbergii in China. The needle damage of P. thunbergii associated with Biscogniauxia sinensis will detrimentally affect the carbon absorption and photosynthetic efficiency of P. thunbergii, further reduce the absorption of nutrients by Japanese black pine and may lead to the imbalance of pine forest conditions, which will have a negative impact on the forest ecological system. [ABSTRACT FROM AUTHOR]

The Xiaojiang fault system (XJFS), located to the southeast of the Tibetan Plateau, has a complicated tectonic history and is an ideal location to study the Tibetan Plateau in terms of its deep material transport mechanism and the effects of past tectonic events. In this study, broadband and long-period magnetotelluric data were collected above this fault system and inverted to build a 3-D resistivity model of the lithosphere. As shown in the model, at upper-middle crustal depths, three high-resistivity anomalies separate the strike-slip faults located in the study area, which may be the remnants of the Emeishan large igneous province that was destroyed and modified by Cenozoic crustal activity. The lower crust is characterized by significant low-resistivity anomalies that extend downward to the upper mantle. The low-resistivity anomalies in the upper crust may be caused by brines or/and conductive minerals (e.g., graphite and sulfides), and the possible reason for the low-resistivity anomalies that were imaged in the lower crust and upper mantle may be the presence of hydrogen in nominally anhydrous minerals and partial melts. According to the seismic activity distribution and resistivity structure, we propose dividing the seismic activity of the study area into three categories: tectonic earthquakes, earthquakes with no active faults on the surface, and other scattered earthquakes with no general features. Seismic activities are controlled by tectonic activities, fluid transportation, and the adjustment of the Earth's stress field. It is believed that there is a mutually reinforcing relationship between seismic activity and deep fluids. Fluids could lower the frictional force in faults, promote movement, and thus induce earthquakes; on the other hand, seismic activities and the long-term strike-slip movements of faults could generate heat and increase the connectivity of fluids, which decreases the strength of the crust and facilitates the flow of fluids. Based on the resistivity model, it is demonstrated that the present tectonic activity in the XJFS is complicated and characterized by rigid block extrusion along strike-slip faults in the upper crust, ductile deformation with channel flow in the lower crust, and the upwelling of mantle materials. In combination with previous studies, our results indicate that the weak crustal materials from the Tibetan Plateau are blocked by (1) the lithosphere modified by the Emeishan plume and (2) the South China block when flowing through the Sichuan-Yunnan block. Therefore, these weak materials turn to the southwest direction along the XJFS, then pass through the Red River fault and enter the Indochina block. [ABSTRACT FROM AUTHOR]

The bedding surfaces of shale in the Longmaxi formation are well developed. To study the influence of bedding surfaces on the mechanical properties of shale, we have carried out uniaxial and triaxial compression tests on shale specimens of Longmaxi formation in Southern Sichuan, China. The results shows that when the samples are subjected to compression, the properties of shale, including strength characteristics, elastic parameters, and fracture mode in the shale samples, are characterized by strong anisotropy. The confining pressure effect is due to the existence of well-developed bedding surfaces in shale. The results provide a theoretical basis for horizontal wellbore stability analysis and hydraulic fracturing design in shale gas wells. [ABSTRACT FROM AUTHOR]

The Longmenshan (LMS) southern section is the front of the eastwards material migration from the Qinghai–Tibet Plateau. To understand whether the 2022 Ms6.1 Lushan earthquake was a strong aftershock of the 2013 Ms7.0 Lushan earthquake and why the aftershocks of the two earthquakes were concentrated relative to the 2008 Wenchuan earthquake, a three-dimensional electrical structural model of the Lushan earthquake region is established based on magnetotelluric (MT) array data. The model shows high-conductor layers (HCL) in the Songpan–Ganzi terrane (SGT) middle crust, Sichuan Basin (SCB) shallow surface, western Sichuan foreland depression (WSCFD) and LMS Moho. The analysis suggests that the HCL in the study area at a depth of 10 km is caused by saline fluids in the fracture zone or porous sedimentary rock voids, while the high-conductor body in the middle and lower crust and upper mantle is caused by partial melting of rocks. The Lushan earthquake area is subject to compressional deformation horizontally as the eastwards migration of Qinghai–Tibet Plateau material is blocked by the SCB and vertically by the upwards extension of high-conductor plastic material at depth. The aftershocks of the Lushan earthquake area are mainly confined within the Baoxing–Zhonglin–Daxing–Lushan high-conductor region, which has noticeable electrical structural differences compared to the overall high-resistivity structure of the LMS southern section; these differences explain why the aftershocks of the two earthquakes did not expand in the northeast and southwest directions of LMS. Because the 2022 and 2013 Lushan earthquakes both occurred in the same high-conductor region in the deep part of the Dachuan–ShuangShi fault to the Danyi blind fault, the 2022 Lushan earthquake was a strong aftershock of the 2013 Lushan earthquake in terms of electrical structural characteristics. • A 3D crust–mantle electrical model at south section of Longmenshan was established. • Aftershocks of Lushan earthquake mainly distributed in the high-conductor region. • 2022 Lushan earthquake was a strong aftershock of the 2013 Lushan earthquake. [ABSTRACT FROM AUTHOR]