Soil Moisture Rather than Soil Nutrient Regulates the Belowground Bud Bank of Rhizomatous Species Psammochloa villosa in Arid Sand Dunes

In arid and semi-arid sand dune ecosystems,belowground bud bank plays an important role in population regeneration and vegetation restoration.However,the responses of belowground bud bank size and composition to sand burial and its induced changes in soil environmental factors have been rarely studied.In arid sand dunes of Northwestern China,we investigated belowground bud bank size and composition of the typical rhizomatous psammophyte Psammochloa villosa as well as three key soil environmental factors(soil moisture,total carbon and total nitrogen)under different depths of sand burial.Total buds and rhizome buds increased significantly with increasing burial depth,whereas tiller buds first increased and then decreased,with a peak value at the depth of 20-30 cm.Soil moisture increased significantly with sand burial depth,and was positively correlated with the number of all buds and rhizome buds.Soil total carbon concentration first increased and then decreased with sand burial depth,and total nitrogen concentration was significantly lower under deep sand burial than those at shallow depths,and only the number of tiller buds was positively correlated with soil total nitrogen concentration.These results indicate that soil moisture rather than soil nutrient might regulate the belowground bud bank of P.villosa,and that clonal psammophytes could regulate their belowground bud bank in response to sand burial and the most important environmental stress(i.e.,soil moisture).These responses,as the key adaptive strategy,may ensure clonal plant population regeneration and vegetation restoration in arid sand dunes.

Improving Strength of Carbon Fiber Grafted Carbon Nanotube Reinforced Thermoplastic Composites by 3D-Printed Molding

To improve the strength of carbon fiber(CF) reinforced Polycaprolactam(PA6) composites, controlled amounts of carbon nanotubes(CNTs) were grafted onto the surface of CF to prepare the hybrid reinforcement(HR). We used HR to fabricate laminate and H-sample to test the interfacial bonding strength(IBS) of the composites by means of a novel process called three-dimensional printed molding(3 D-PM). By using the melt drop printing method, we measured the contact angles between PA6 and CF(without sizing) and between PA6 and HR. The IBS and the mechanical properties of the composites were obtained by the tensile test. The experimental result indicated that CF grafted by 0.25% weight fraction of CNT or more could develop a special microstructure similar to the micro-pits on the surface of CF, which improved the wettability of CF and PA6 due to the increased surface area and the roughness of CF. When the weight fraction of CNT reached 0.25%, the IBS increased by 41.8%, the tensile strength by 130%, and the interfacial shear strength(IFSS) by 238%. The interfacial dimple fracture was observed by Scanning Electron Microscope(SEM), which revealed that the composites were able to absorb more deforming energy before fracture. The modified surface microstructure of CF would prevent crack propagation at the interface and increase the mechanical properties of thermoplastic composites(TPCs).

Effects of Thermal Compressive Strain on the Orientation Recovery for Ultra-Thin CNT-Filled Polypropylene Molding

Due to the strong shearing field during processing,untra-thin injection molded CNT-filled polypropylene(PP) always forms a strong CNT orientation along the flow direction,which results in its anisotropic conductivity.In order to evaluate the mechanism on recovery of the orientation,we processed the molding under the condition of different thermal compressive strains with modified hot-rolling machine.The stability of the molding's conductivity after rolling was studied under the action of alternated loading.The disoriented behavior of the microstructures during rolling was observed by SEM and 2 D-WAXD,and the degree of orientation of CNT was calculated.The conductivity of the sample was measured using a standard two-terminal DC resistor.The results showed that the deformation resistance in the rolling direction was greater than that in the transverse deformation under the action of large thermal compressive strain.The samples would mainly deform in the transverse direction and not elongate in the direction of the rolling,which could speed up the recovery of the orientation structure and reduce the anisotropy of the conductivity.The recovery speed of the orientation was related to the level of the thermal compressive strain.After the hotrolling processing,the stability of the sample's conductivity under the alternating load was improved because of the effect induced by polymer strengthening.

2021年世界鞘翅目现生类群分类年鉴

本文整理并总结了世界鞘翅目2021年发表的新分类阶元、新组合、新异名、分类阶元升级和降级等情况,并单独梳理了中国2021年鞘翅目新增分类群。通过在线数据库检索及相关同行补充,最终共获得了相关文献1,114篇。2021年,世界鞘翅目新分类阶元共计3,375个,包括2个新亚科,1个超族,9个新族,3个新亚族,178个新属,36个新亚属,3,070个新种和76个新亚种,另有1,071个新组合,485个新异名,70个分类阶元升级,26个分类阶元降级。新发表的物种中,隐翅虫科534种,金龟科461种,二者约占总数的31.6%。世界鞘翅目新物种发现数量最多的国家是中国,共发现新属13个,新亚属4个,新种635个,新亚种6个,发表中国新记录亚科2个,新记录属13个,新记录亚属1个,新记录种112个和新记录亚种6个。2021年发表的中国鞘翅目新种有204个隶属于金龟科,新物种发现数量最高的省级行政区是云南省(172个新种及亚种)。