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Habitat consist of the physical, chemical, and biological features that support the survival and growth of aquatic organisms, and the maintenance of biological processes and ecological function. However, habitat is spatially and temporally heterogeneous and displays spatial autocorrelation, mean that at large spatial scales, the maintenance of ecological function is complex. Consequently, it is difficult to characterize and interpret habitat characteristics, especially over large space-time scales. Although a wide variety of habitat monitoring methods have been proposed, there is still lack of well-developed methods for long-term tracking and monitoring of habitat changes at the watershed scale. Here, the characteristics of watershed habitats and the importance of monitoring in environmental management were explored based on the concept, purpose, and significance of habitat monitoring. Several monitoring methods were summarized and compared, and the key scientific limitations and requirements of habitat monitoring (e.g., spatial scale, survey scope, characteristic parameters, data acquisition, etc.) evaluated. Based on this, key aspects for successful habitat monitoring in China are proposed as baseline information for the research and application of habitat monitoring for watershed-scale ecological space management.

Periphytic algae are often used as an indicator to evaluate water quality. Here, the community structure of periphytic algae and its relationship with environment factors were analyzed in the main stream of the Songhua River during the summers of 2014 to 2019. The status and trends in ecological water quality were also evaluated based on bioassessments. Phytoplankton species belonging to 4 phyla and 58 genera were recorded, including 28 Bacillariophyta genera, 17 Chlorophyta genera, 10 Cyanophyta genera, and 3 Euglenophyta genera; Bacillariophyta, Chlorophyta, and Cyanophyta accounted for 48.28%, 29.31%, and 17.24% of the community, respectively. Cell densities varied between 1.29×10 4 and 8.42×10 4 ind·cm -3 , with an average of 4.35×10 4 ind·cm -3 . The dominant genera were Cyclotella, Melosira, Asterionella, Cymbella, Synedra, Pinnularia, Navicula , and Scenedesmus . The physicochemical water quality showed notable changes during the past six-year monitoring period. Specifically, the dissolved oxygen content increased year on year; ammonia nitrogen, total phosphorus, and total nitrogen first increased and then decreased; and, overall, water quality significantly improved in 2019. Relationship between periphytic algae and environmental factors was further examined using redundancy analysis (RDA), which showed that time was the main factor driving the succession of algal community structure. Dissolved oxygen (DO), ammonia nitrogen (NH 4 + -N), total nitrogen (TN), total phosphorus (TP), five-day biochemical oxygen demand (BOD), and chemical oxygen demand (COD) were also important environmental variables affecting algal community structure.

The magnetic and electrical properties of complex oxide thin films are closely related to the phase stability and cation ordering, which demands that we understand the process-structure-property relationships microscopically in functional materials research. Here we study multiferroic thin films of double-perovskite La 2 NiMnO 6 epitaxially grown on SrTiO 3 , KTaO 3 , LaAlO 3 and DyScO 3 substrates by pulsed laser deposition. The effect of epitaxial strains imposed by the substrate on the microstructural properties of La 2 NiMnO 6 has been systematically investigated by means of advanced electron microscopy. It is found that La 2 NiMnO 6 films under tensile strain exhibit a monoclinic structure, while under compressive strain the crystal structure of La 2 NiMnO 6 films is rhombohedral. In addition, by optimizing the film deposition conditions a long-range ordering of B-site cations in La 2 NiMnO 6 films has been obtained in both monoclinic and rhombohedral phases. Our results not only provide a strategy for tailoring phase stability by strain engineering, but also shed light on tuning B-site ordering by controlling film growth temperature in double-perovskite La 2 NiMnO 6 films.

Low (α)- and high-temperature (β) forms of BiTaO 4 have attracted much attention due to their dielectric and photocatalytic properties. In the present work, a third form, the so-called HP-BiTaO 4 , was synthesized at high temperature and pressure. The phase evolution, phase transformations, and dielectric properties of α- and β-BiTaO 4 and HP-BiTaO 4 ceramics are studied in detail. β-BiTaO 4 ceramics densified at 1300 °C with the microwave permittivity ε r ≈ 53, the microwave quality factor Q f ≈ 12070 GHz, and the temperature coefficient of resonant frequency τ f ≈ -200 ppm/°C. HP-BiTaO 4 ceramics were synthesized at 5 GPa and 1300 °C followed by annealing at 600 °C. In contrast with the α phase, HP-BiTaO 4 exhibited ε r ≈ 195 at 1 kHz to 10 MHz, accompanied by a low dielectric loss of ∼0.004. The relation between structure and dielectric properties is discussed in the context of Shannon's additive rule and bond theory.