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Microbial abundance and diversity in river ecosystems are being increasingly investigated, yet a synthesized understanding is still lacking. Here, studies of microbial abundance and diversity along global rivers are systematically reviewed based on 814 investigations performed across 8376 sites. We found that riverine microbial investigations are extremely heterogeneous regarding the spatiotemporal distribution of the sampling sites, the environmental media concerned, the microbial groups and indices targeted, the methods used, and the physicochemical properties examined. More than 72.23% of the studies were performed in the last 8 years, with most studies conducted in Europe, China, and the United States, while other regions were poorly investigated. Most studies have examined microbes in water, but very few studies have systematically investigated microbes in water, sediments, and riparian soils. Bacteria are the most studied microbial taxonomic groups; microbes with resistance genes and nitrogen cycling genes are the most studied microbial functional groups. High-throughput sequencing has greatly expanded our understanding of microbial diversity along rivers. Nevertheless, the ecological implications of microbial diversity are still poorly understood. Regarding physicochemical properties, researchers tend to examine environmental parameters that are critical for shaping microbial communities, such as pH, nitrogen, and phosphorus. Future research should pay more attention to rivers that have not been well studied, especially large rivers. Additionally, microbial studies along rivers should be conducted in a more systematic way, taking the underinvestigated environmental media, microbial groups, microbial indices, and physicochemical properties into consideration. Advanced microbiology techniques, such as multiple omics technologies, should be increasingly applied.

Rural China faces a shortage of safe drinking water. There are significant challenges associated with small centralized water supply systems and decentralized water supply systems. Many rural residents use point-of-use water treatment systems to ensure the safety of their drinking water. The actual water purification effect and applicability of these water treatment systems in small centralized and decentralized water supply systems need to be determined urgently. In this study, the water quality index (WQI) method was applied for the first time in rural areas to evaluate the effectiveness of point-of-use water treatment systems. A total of 67 reverse osmosis water treatment systems were tested. The rate of compliance with drinking water standards of the decentralized water supply was low (37%). Compared with untreated water, the use of a reverse osmosis water treatment system improved the rate of compliance with drinking water standards, but this effect was not satisfactory (8%). Among the factors potentially affecting the purified water quality of point-of-use water treatment systems (e.g., service time of the water treatment system, service time of the filter element, and type of water source), the service time of the filter element had the most significant influence on the water quality. If the filter element had not been replaced for a long period, the removal effect of the water treatment system on the total hardness, sulfide, copper, and ammonia nitrogen was significantly affected, reducing the quality of the purified water. To ensure the safety of drinking water, it is recommended to replace the filter element of a reverse osmosis water treatment system at least once a year.

A composting experiment with sewage sludge and green waste was conducted to explore the effects of aeration directions (i.e., upward and downward) on static composting systems. The compost properties, including humification indexes and organic matter loss rate, and microbial diversity during the composting, were determined. Results showed that the downward aeration promoted the homogenization of temperature and moisture of the static composting system, thereby stimulating microbial metabolism and accelerating mineralization and humification. Microbial community profiles significantly changed among the composting phases. The humification dynamics were significantly correlated with the relative abundance of multiple microbial functional groups. However, no significant effects of aeration direction on the microbial community profiles were observed. The findings indicate that downward aeration is promising to improve the quality of static compost production, by stimulating microbial metabolism rather than altering microbial community profiles.

Medicinal plants are more vulnerable to threats than non-medicinal plants. In China, a large number of medicinal plants are threatened by human activities and climate change, which greatly affect the conservation of species diversity, genetic resources and sustainable development of the traditional Chinese medicine industry. In this study, we established the first database for the distributions of 535 threatened medicinal plant species in China at the county level. Using this database, we explored geographic patterns, identified biodiversity hotspots and determined the conservation gaps for these threatened medicinal plants. Threatened medicinal plants were widely distributed in 1709 counties across the whole country. The species richness was higher in southern than in northern China. Using the “top 5% richness algorithm” and the “complementary algorithm”, we identified 213 counties as biodiversity hotspots for threatened medicinal plants in China. However, based on further conservation gap analysis, we found that 30 hotspot counties were not covered by any type of nature reserve (complete conservation gaps), and 27 more hotspot counties were not covered by national or provincial nature reserves in mainland China. We suggest that new nature reserves should be established for the 30 complete conservation gaps, while range, level or management strategies for the current nature reserves should be improved for the remaining 27 conservation gaps to promote the conservation of threatened medicinal plants in China.

China is very rich in biodiversity, however, it is also characterized by a long history of civilization. As a result, China has a large number of threatened species. Recently the Chinese government evaluated the living status of plants, and published the China Biodiversity Red List: Higher Plants. However, little is known about how threatened plants are distributed and conserved in China. In this study, we developed a fine resolution distribution database for 3244 threatened plants, explored richness patterns and evaluated the in situ conservation status of the threatened plants by overlapping the species distribution with terrestrial national and provincial nature reserves (NNRs and PNRs) in China. We found the greatest richness of threatened plants in the southwestern region of mainland China (mainly Yunnan, southeastern Xizang and western Sichuan), northwestern Guangxi, northern Guangdong, Hainan Island and the mountainous region of Taiwan, while the lowest richness was found in Qinghai, Hebei, Shandong, Jiangsu and Chongqing Provinces. On average, NNRs covered 18.8%, and NNRs and PNRs together covered 27.5%, of threatened plant distribution areas. However, 827 threatened plants (including 627 species endemic to China) were not covered by NNRs and 397 threatened plants (including 293 endemic to China) were not covered by either NNRs or PNRs. We proposed that nature reserves specifically designed for threatened plants need to be established in South China, especially in the Yunnan, Guizhou, Guangxi, Xinjiang Hainan, and Zhejiang Provinces.

Orchidaceae, the orchid family, is one of the species richest families and the most endangered plant groups. Most orchids are narrowly distributed in specific habitats because of their mycorrhizal specificity, pollinator specialization and limited seed germination rate; compared to plants from other families, orchids are extremely susceptible to habitat disturbance. However, little is known about how orchids are distributed and how they are protected at large scales. In this study, we developed a distribution database for all the 1449 orchid species in China. Using this database, we explored patterns of orchid richness in relation to climate, net primary productivity and habitat heterogeneity in China. We then evaluated the in situ conservation status of the orchids in China by overlapping the species distribution and the terrestrial national and provincial nature reserves (NNRs and PNRs) in C\hina. We found that 90% of orchid species in China were distributed in 258,800 km

Dendrobium officinale, endemic to China, is a rare and endangered medicinal herb. As a result of its high economic value, slow growth, and diminishing wild population, protected cultivation is preferred. However, little information is available on its growing environment and photosynthetic characteristics. In this study, the photosynthetic patterns of D. officinale were investigated under various environmental conditions by measuring the net CO2 exchange rates continuously for several days or weeks. Under non-stressed growth chamber conditions with 12-hour light and 12-hour dark periods, D. officinale had concomitance of C3 and crassulacean acid metabolism (CAM) photosynthesis patterns. Different degrees of CAM in D. officinale, expressed as the percentage of CO2 exchanges in the dark period to the daily amount of CO2 exchanges, were observed depending on environmental conditions. With decreasing substrate water content, a typical CAM pattern was found, and concomitance of C3 and CAM patterns was found again when plants were rewatered. The accumulation of leaf titratable acidity during a dark period increased as substrate dried out but decreased again as plants were rewatered. A shorter light–dark cycle (4-hour light and 4-hour dark periods) led to a C3 pattern alone. The substrate moisture and light–dark cycle were inducible factors for switching between C3 and CAM patterns in D. officinale. These results indicate that D. officinale is a facultative CAM plant and the C3 pathway can be induced by controlling the growing environment. Further studies are needed to identify the optimal environmental conditions to enhance the growth of D. officinale.