The sedimentary record in the Late Palaeoproterozoic‐Neoproterozoic Bayan Obo rift belt can provide critical insight into tectonic evolution of Columbia and the North China Craton. In this study, we present new U–Pb geochronology, Hf isotopic analyses from the Bayan Obo Group, the Mesoproterozoic kimberlite, and gabbro to constrain the depositional age and potential provenance information of the Bayan Obo Group. We show that the Dulahala‐Jianshan, Bilute, and Baiyinbaolage formations were deposited at ca. 1.81–1.7 Ga, ca. 1.58–1.35 Ga, and ca. 1.25–1.0 Ga, respectively. Our data suggest the following potential provenance for sediments within the Bayan Obo Group: (a) The Khondalite Belt, Yinshan Block, and crystalline basement complex of the North China Craton to the south were the most potential provenance of the Dulahala and Jianshan formations during the initial deposition of Bayan Obo Group; (b) The Yinshan Block, and crystalline basement complex of the North China Craton, and local intermediate‐acid igneous rocks were the most potential provenance of the Bilute Formation; and (c) the local gabbro and volcanic rocks were the most potential provenance of the Baiyinbaolage Formation. Based on regional geologic constraints and the sedimentary history, we propose that the Northern Marginal Rift System probably represented several distinct rifting events. Furthermore, the Bayan Obo and Huade rift belts were active more recently than 1.0 Ga, which suggests that these rift systems were not only related to the rifting of the Columbia supercontinent. We propose that the Bayan Obo rift belt also records the rifting related to the breakup of Rodinia with the deposition of Qingbaikou System (Tonian) strata.

Heavy metals are extremely harmful materials to marine ecosystems and human health. To determine the anthropogenic contributions and ecological risks in Weitou Bay, China, the spatiotemporal variations in the concentrations of heavy metals in surface sediment were investigated during spring 2008 and 2017. The results indicated that high concentrations of pollutants were generally located near the river mouths and along the coast of industrial areas. Principal component analysis indicated that heavy metal contents were mainly affected by industrial waste drainage, urban development, natural weathering and erosion, and interactions between organic matter and sulfides. The potential ecological risk assessment demonstrated that, in 2008, 82% of the sampling sites were at low risk, while 18% were at moderate risk. The situation had deteriorated slightly by 2017, with 73%, 18%, and 9% of stations in Waytou Bay at low, moderate, and very high risk, respectively. Cd was the most harmful metal, followed by Hg. These two elements accounted for more than 80% of the potential ecological risk index (RI) value. The present work analyzed the source of heavy metals, identified the major pollution elements and high risk areas, and provides guidance for pollution control and ecological restoration in Weitou Bay.

The impact of inter-and intraspecific neighboring plants on mixed legume-grass communities has rarely been explored in relation to seeded species patch size. In this study, two native perennial species, the legume alfalfa (Medicago sativa L.) and the grass tall fescue (Festuca arundinacea L.), were investigated as monocultures and in mixture. A three-year growth experiment was conducted to investigate the effects of plant-plant competitive interactions on fine-scale seeding patterns: monoculture, three different conspecific patch sizes (1.0, 0.5, and 0.25 m side length of squares) and a control in which the seeds were mixed and scattered (i.e., patches were not formed) as in conventional seeding. The results demonstrated significant differences in the mutual effect intensity in all conspecific patch sizes, indicating the presence of grass-legume interactions on mixed plant communities. Smaller patch sizes resulted in better facilitation by higher neighbor effect intensity when compared with a larger patch size and the conventional mixture. Seedings in the smallest patch size of 0.25 m × 0.25 m showed intra-and interspecific competition and significantly improved aboveground productivity compared with the other patch sizes. We directly quantified the variation of species neighbor effect intensity between grass and legume mixtures among different species patch sizes at seeding. Integrating this knowledge into species interaction models in plant community ecology could greatly enhance our understanding of species coexistence in grasslands as well as provide opportunities for manipulating competition to achieve specific agronomic aims.

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