Macrophyte community diversity and composition respond to ecosystem conservation and local environmental factors. In this study, we developed a multidimensional diversity framework for macrophyte communities, including the taxonomic and functional alpha and beta diversity. We used the framework to explore the relationships among water level regimes and these diversity parameters in a case study of China's Baiyangdian Lake. Analysis of indicators of hydrologic alteration divided the water level from 1959 to 2019 into four regimes (dry, <6.42 m; low, 6.42–7.23 m; medium, 7.23–8.19 m; high, >8.19 m). Alpha and beta diversity were significantly higher in the medium regime than in the low and high regimes. Redundancy analysis indicated that the maximum water depth significantly affected taxonomic alpha diversity, and total nitrogen (TN) and chemical oxygen demand (COD) concentration significantly affected functional alpha diversity, respectively. Mantel tests showed that TN, Secchi depth (SD), and water depth in the high water level regime significantly increased the total beta diversity and turnover components. TN was the main factor that increased total taxonomic beta diversity. Water level regime mainly influenced interspecific relationships by changing the TN and COD concentration. The water level should be maintained between the medium and high water level regimes to promote restoration of the macrophyte community and improve ecosystem stability. The biodiversity evaluation framework would provide a deeper insight into the hydrological process management for restoration of aquatic macrophyte communities in shallow lakes. 相似文献
To enhance the utilization efficiency of farmland irrigation water and reduce the leakage of water conveyance channels, the leakage process of channels was simulated dynamically. The simulated results were compared with data measured in laboratory experiments, and the performance of the model was evaluated. The results indicated that the simulated values of the model were consistent with the observation values, and the R2 values varied between 0.91 and 0.99. In addition, based on the laboratory experiments, a water supply system (Mariotte bottles) and soil box were built using plexiglass. Three influencing factors, namely, the channel form, soil texture and channel cross-sectional area, were varied to observe and calculate the resulting cumulative infiltration amount, infiltration rate and wetting front migration distance. HYDRUS-3D software was used to solve the three-dimensional soil water movement equation under different initial conditions. The results demonstrated that the U-shaped channel was more effective than the trapezoidal channel in increasing the utilization efficiency of the water resources. A U-shaped channel with a small channel cross-sectional area should be adopted and the soil particle size should be prioritized in the construction of water conveyance channels for farmlands. The simulation results were in agreement with the observed results, which indicates that HYDRUS-3D is a reliable tool that can accurately simulate the soil moisture movement in water conveyance channels. The research results can provide a reference for the design and operation of farmland irrigation systems. 相似文献
Journal of Geographical Sciences - The risk posed by natural disasters can be largely reflected by hazard and vulnerability. The analysis of long-term hazard series can reveal the mechanisms by... 相似文献
The volcanic rocks of the Xiong'er Group are situated in the southern margin of the North China Craton(NCC).Research on the Xiong er Group is important to understand the tectonic evolution of the NCC and the Columbia supercontinent during the Paleoproterozoic.In this study,to constrain the age of the Xiong'er volcanic rocks and identify its tectonic environment,we report zircon LA-ICP-MS data with Hf isotope,whole-rock major and trace element compositions and Sr-Nd-Pb-Hf isotopes of the volcanic rocks of the Xiong'er Group.The Xiong'er volcanic rocks mainly consist of basaltic andesite,andesite.dacite and rhyolite,with minor basalt.Our new sets of data combined with those from previous studies indicate that Xiong'er volcanism should have lasted from 1827 Ma to 1746 Ma as the major phase of the volcanism.These volcanics have extremely low MgO.Cr and Ni contents,are enriched in LREEs and LILEs but depleted in HFSEs(Nb,Ta,and Ti),similar to arc-related volcanic rocks.They are characterized by negative zircon ε_(Hf)_(t) values of-17.4 to 8.8,whole-rock initial ~(87)Sr/~(86)Sr values of 0.7023 to 0.7177 andε_(Nd)(t) values of-10.9 to 6.4.and Pb isotopes(~(206)Pb/~(204)Pb =14.366-16.431,~(207)Pb/~(204)Pb =15.106-15.371,~(208)Pb/~(204)Pb= 32.455-37.422).The available elemental and Sr-Nd-Pb-Hf isotope data suggest that the Xiong'er volcanic rocks were sourced from a mantle contaminated by continental crust.The volcanic rocks of the Xiong'er Group might have been generated by high-degree partial melting of a lithospheric mantle that was originally modified by oceanic subduction in the Archean.Thus,we suggest that the subduction-modified lithospheric mantle occurred in an extensional setting during the breakup of the Columbia supercontinent in the Late Paleoproterozoic,rather than in an arc setting. 相似文献
防风林带结构是影响防风效能的主要因素。建立不同宽度、不同株行距林带防风效能与林带后距离之间的统计模型,可以为防风林建设提供指导性意见。通过风洞实验,在11 m·s-1风速下,对4种宽度、5种株行距林带的背风面0~10H(H为林带高度)的风速进行测定,采用曲线参数估计法、傅立叶模型、SSF模型(Sum of Sin Functions),构建了不同结构林带防风效能与林带后距离间的统计模型。结果表明:傅立叶模型拟合不同宽度林带的防风效能与林带后距离的关系效果最优,可决系数(R2)均在98%以上;SSF模型拟合不同株行距林带的防风效能与林带后距离的关系效果最优(R2>0.98)。根据构建的统计模型,风速为11 m·s-1左右时,林带宽度8 m(两行一带)的防风林的防风效能存在明显优势;5种株行距的林带中,株行距为8 m×8 m的防风林带本试验条件下防风效果最好。 相似文献
In thermal-related engineering such as thermal energy structures and nuclear waste disposal, it is essential to well understand volume change and excess pore water pressure buildup of soils under thermal cycles. However, most existing thermo-mechanical models can merely simulate one heating–cooling cycle and fail in capturing accumulation phenomenon due to multiple thermal cycles. In this study, a two-surface elasto-plastic model considering thermal cyclic behavior is proposed. This model is based on the bounding surface plasticity and progressive plasticity by introducing two yield surfaces and two loading yield limits. A dependency law is proposed by linking two loading yield limits with a thermal accumulation parameter nc, allowing the thermal cyclic behavior to be taken into account. Parameter nc controls the evolution rate of the inner loading yield limit approaching the loading yield limit following a thermal loading path. By extending the thermo-hydro-mechanical equations into the elastic–plastic state, the excess pore water pressure buildup of soil due to thermal cycles is also accounted. Then, thermal cycle tests on four fine-grained soils (natural Boom clay, Geneva clay, Bonny silt, and reconstituted Pontida clay) under different OCRs and stresses are simulated and compared. The results show that the proposed model can well describe both strain accumulation phenomenon and excess pore water pressure buildup of fine-grained soils under the effect of thermal cycles.
Spatial distribution (horizonal and vertical) of groundwater microbial communities and the hydrogeochemistry in confined aquifers were studied approximately along the groundwater flow path from coteau to plain in the Nomhon area, Qinghai‐Tibet plateau, China. The confined groundwater samples at different depths and locations were collected in three boreholes through a hydrogeological section in this arid and semi‐arid area. The phylogenetic analysis of 16S rRNA genes and multivariate statistical analysis were used to elucidate similarities and differences between groundwater microbial communities and hydrogeochemical properties. The integrated isotopic geochemical measurements were applied to estimate the source and recharge characteristics of groundwater. The results showed that groundwater varied from fresh to saline water, and modern water to ancient water following the flowpath. The recharge characteristics of the saline water was distinct with that of fresh water. Cell abundance did not vary greatly along the hydrogeochemical zonality; however, dissimilarities in habitat‐based microbial community structures were evident, changing from Betaproteobacteria in the apex of alluvial fan to Gammaproteobacteria and then to Epsilonproteobacteria in the core of the basin (alluvial‐lacustrine plain). Rhodoferax, Hydrogenophaga, Pseudomonas, and bacterium isolated from similar habitats unevenly thrived in the spatially distinct fresh water environments, while Sulfurimonas dominanted in the saline water environment. The microbial communities presented likely reflected to the hydrogeochemical similarities and zonalities along groundwater flowpath. 相似文献
Sinonovacula constricta is one of the important economic aquaculture species in China. In this study, we constructed genetic linkage maps of S. constricta based on 300 microsatellite markers derived from RAD-seq using an F1 full-sib family. The female map contained 204 microsatellites assigned to 22 linkage groups, which covered 1529.5 cM with an average interval of 10.3 cM. The male consisted of 187 microsatellites in 19 linkage groups corresponding to the haploid chromosome number(n(28)19), which spanned 1429.3 cM with an average interval of 8.7 cM. The genome coverage was approximately 83.5% and 81.4%, respectively. An integrated map was constructed according to the common markers in parental linkage groups, which had a total length of 1683.8 cM with an average interval of 7.3 cM. The genome coverage of the integrated map was approximately 86.3%. The genetic linkage map would form the foundation for further studies on the quantitative trait loci(QTL), as well as accelerating the breeding process of this species. 相似文献