[Soil microbial carbon pump conceptual framework 2.0]. / 土壤微生物碳泵概念体系2.0.

Microorganisms are essential actors in the biogeochemical cycling of elements within terrestrial ecosystems, with significant influences on soil health, food security, and global climate change. The contribution of microbial anabolism-induced organic compounds is a non-negligible factor in the processes associated with soil carbon (C) storage and organic matter preservation. In recent years, the conceptual framework of soil microbial carbon pump (MCP), with a focus on microbial metabolism and necromass generation process, has gained widespread attention. It primarily describes the processes of soil organic C formation and stabilization driven by the metabolic activities of soil heterotrophic microorganisms, representing an important mechanism and a focal point in current research on terrestrial C sequestration. Here, we reviewed the progress in this field and introduced the soil MCP conceptual framework 2.0, which expands upon the existing MCP model by incorporating autotrophic microbial pathway for C sequestration and integrating the concept of soil mineral C pump. These advancements aimed to enrich and refine our understanding of microbial-mediated terrestrial ecosystem C cycling and sequestration mechanisms. This refined framework would provide theoretical support for achieving China's "dual carbon" goals.

[Accumulation of microbial necromass carbon and their contribution to soil organic carbon in different vegetation types on the Loess Plateau, Northwest China]. / é»„åœŸé«˜åŽŸä¸åŒæ¤è¢«ç±»åž‹åœŸå£¤å¾®ç”Ÿç‰©æ®‹ä½“ç¢³çš„ç§¯ç´¯åŠå ¶å¯¹æœ‰æœºç¢³çš„è´¡çŒ®.

Microbial necromass carbon (MNC) is an important contributor to soil organic carbon (SOC). Soil carbon storage has increased significantly since the return of farmland to forestland (grassland) on the Loess Plateau. However, the contribution of MNC to SOC accumulation in different vegetation types and the influence factors remain unclear. Herein, we used the biomarker (amino sugar) technique to determine the MNC content and analyzed the influencing factors in 0-5 cm and 5-20 cm soil layers of natural grassland, shrubland (Caragana microphylla), and forestland (Quercus liaodongensis) in the Loess Plateau. The results showed that: 1) the soil pH decreased significantly from grassland to shrubland and then to forestland within the same soil layer. However, the SOC, total nitrogen (TN), microbial biomass carbon (MBC), and microbial biomass nitrogen (MBN) contents showed a reverse trend, with forestland displaying the highest values followed by shrubland and then grassland. The 0-5 cm had significantly higher values than the 5-20 cm depth. 2) The MNC contents varied 0.69-16.41 g·kg-1 in the two soil horizons of the three vegetation types. There were significant increases in the contents of bacterial necromass carbon (BNC), fungal necromass carbon (FNC), and MNC in the 0-5 cm soil from grassland, shrubland to forestland. The contents of MBC were 1.9 times higher in forestland than in shrubland, and 3.2 times higher in shrubland than in grassland. In the 5-20 cm soil layer, the contents of FNC and MBC were significantly higher in the forestland than in the shrubland and grassland. The FNC content was significantly higher than that of the BNC, ranging from 1.16 to 9.83 times greater than the BNC. 3) The contribution of MNC to SOC was 0.6 and 0.7 times higher in shrubland and forestland than in grassland, respectively, with FNC accounting for 15.2%-42.7%, and BNC accounting for 1.4%-7.4%. 4) pH, TN, MBC, and MBN were important factors that influenced MNC accumulation. In summary, the variation in vegetation type altered soil nutrients, microbial activity, and soil pH, resulting in forestland and shrubland being more beneficial to the formation and accumulation of MNC, which was dominated by fungi, compared to grassland.

[Distribution, Risk, and Influencing Factors of Microplastics in Surface Water of Huangshui River Basin].

In order to explore the distribution of microplastics in the freshwater environment of Qinghai-Tibet Plateau, 63 surface water samples were collected in Huangshui River basin of Qinghai province during the wet season, and the distribution characteristics and main influencing factors of microplastics in the surface water were analyzed by means of metallographic microscope, Fourier infrared spectroscopy, field investigation, and image data analysis. The potential ecological risks of microplastics were evaluated using risk index (H) and pollution load index (PLI) models. The abundance of microplastics in surface water ranged from 665-8780 n·m-3, with the highest average abundance of 5414 n·m-3 in Huangyuan County. The abundance of microplastics increased from upstream to downstream. The main colors of microplastics were transparent (67%) and black (17%), and the particle size was less than 50 µm (70%). Polyethylene (66%) and polypropylene (12%) were the main polymer types. The abundance of microplastics was positively correlated with cultivated land area, precipitation, and ultraviolet intensity, but the opposite results were observed in dissolved oxygen, redox potential, and wind speed. Additionally, the potential ecological risk of surface water in the Huangshui River basin was relatively low.

[Influence of Land Use and Land Cover Patterns on Water Quality at Different Spatio-temporal Scales in Hehuang Valley].

Based on the measured water quality data of Huangyuan County, Huzhu Tu Autonomous County, and Minhe Hui Tu Autonomous County in Hehuang Valley of Qinghai province in the normal and wet seasons, the effects of land use and land cover patterns on regional seasonal water quality were analyzed using remote sensing technology and mathematical statistics. The results showed that:① the concentrations of total nitrogen and total phosphorus in the surface water of Hehuang Valley were high. Water pollution areas (Class Ⅳ and Ⅴ) were mainly concentrated in the lower reaches of the river and the junction of tributaries. ② The explanation rate of land use to water quality in the normal season was higher than that in the wet season. The optimal scale was the 200 m buffer scale in the normal season, and farmland and towns were the main influencing factors. The optimal scale in the wet season was the 5 km buffer scale, and the main influencing factor was the forest. ③ In the normal season, the proportion of farmland was positively correlated with the concentration of total nitrogen and permanganate index but negatively correlated with the concentration of total phosphorus. The proportion of town area was positively correlated with the water quality index. The proportion of grassland area in the wet season was positively correlated with the permanganate index. The proportion of forestland area was negatively correlated with water quality index in both periods. Farmland, grassland, and town areas were the "source" landscape of pollutants, but farmland also played a role in intercepting pollutants to a certain extent. Forest land was the "sink" landscape of pollutants. ④ The pattern of forestland in the 200 m buffer zone in the normal season had a high explanatory rate for water quality, and the largest patch index (LPI) and patch density (PD) were the main factors. The study showed that it is an important measure to purify the surface water quality of Hehuang Valley by rationally planning the proportion of residential land and cultivated land and improving the coverage rate and aggregation degree of forestland around the riparian zone.

Bistriazoles with a Biphenyl Core Derivative as an Electron-Favorable Bipolar Host of Efficient Blue Phosphorescent Organic Light-Emitting Diodes.

High-quality host materials are indispensable for the construction in the emitting layer of efficient organic light-emitting diodes (OLEDs), especially in a guest and host system. The good carrier transport and energy transfer between the host and emitters are out of necessity. In this work, a wide bandgap and bipolar organic compound, 2,2'-bis(4,5-diphenyl-(1,2,4)-triazol-3-yl)biphenyl (BTBP), conjugating two electron-transporting triazole moieties on a hole-transporting biphenyl core, was synthesized and characterized. The wide bandgap of 4.0 eV makes the promise in efficient energy transfer between the host and various color emitters to apply as the universal host, especially for blue emitters. The close electron and hole mobilities perform the same order of 10-5 cm2·V-1·s-1, identified as bipolar behavior and benefited for carrier balance at low bias. Although carrier transportation belongs to bipolar behavior at a low electrical field, the electron mobility is much faster than the hole one at a high electrical field and belongs to electron-transporting behavior. Employing the BTBP as the host matrix mixed with a phosphor dopant, iridium(III)bis[4,6-di-fluorophenyl-pyridinato-N,C2]picolinate, a high-efficiency sky-blue phosphorescent organic light-emitting diode (OLED) was achieved with a maximum current efficiency of 65.9 cd/A, maximum power efficiency of 62.8 lm/W, and maximum external quantum efficiency of 30.2%.

[Effects of Converting Farmland into Forest and Grassland on Soil Nitrogen Component and Conversion Enzyme Activity in the Mountainous Area of Southern Ningxia].

The effects of the policy of converting farmland to forest and grassland on soil nitrogen content and conversion enzyme activity were studied. Caragana intermedia, Prunus davidiana, Medicago spp., and Stipa bungeana and a corn control were examined to determine the concentrations of seven soil nitrogen components and the activity of two nitrogen conversion enzymes. The main factors affecting soil nitrogen distributions and transformation was also explored using redundancy analysis (RDA). The results showed that:① Compared with the corn soil, the content of particulate organic nitrogen, light fraction organic nitrogen, microbial biomass nitrogen, and ammonium nitrogen in the Stipa bungeana soil increased by 35.3%, 83.3%, 64.2%, and 110.0%, respectively; soluble organic nitrogen and ammonium in the Medicago spp. soil increased by 0.7% and 67.5%, respectively; the asparaginase and protease activities in the Stipa bungeana soil increased by 360% and 144.8%, respectively, indicating that conversion of farmland to forest and grassland has a promoting effect on nitrogen components and conversion enzyme activity; ②The content of organic nitrogen, light organic nitrogen, particulate organic nitrogen, and soluble organic nitrogen in the Prunus davidiana soil was 3.7%, 133.3%, 70.6%, and 28.1% higher than that of the corn soil, respectively. The light fraction organic nitrogen content of the Caragana intermedia soil and microbial biomass nitrogen content of the Prunus davidiana soil was 16.7% and 49.6% higher than that of the corn soil, respectively. Protease activity in the Caragana intermedia and Prunus davidiana soils was higher than in the corn soil, further indicating that the conversion of farmland to forest and grassland promotes the accumulation of nitrogen components and enhances conversion enzyme activity; ③ The RDA and environmental factor explanation rate results indicated that soil water content, pH, and soil organic carbon were the key factors affecting nitrogen distribution and transformation in the mountainous area of southern Ningxia. Overall, the results show that converting farmland into forest and grassland has changed conversion enzyme activity and has promoted the accumulation of nitrogen components in soils. This provides a theoretical basis for ecological restoration and soil quality management in the Loess Plateau.

[Effects of the Farmland-to-Forest/Grassland Conversion Program on the Soil Bacterial Community in the Loess Hilly Region].

This study investigated the effects of the program aimed at converting farmland into forest or grassland on the soil bacterial diversity in the Loess Hilly region. Corn land was selected as the experimental control, and Caragana intermedia land and Stipa bungeana land were selected as the experimental lands. Soil from three different land use types were selected as subjects. The soil bacterial communities were analyzed using a high throughput sequencing technique (MiSeq). The sequence region was 16S rRNA V3-V4 variable region. The α diversity, community composition, and relative abundances of the soil bacterial groups were analyzed, in order to explore the effects of soil physical and chemical properties on the bacterial community structure. The results showed that the structure and diversity of the microbial communities differed under the different land use types. At the phylum level, the dominant phyla were Proteobacteria, Actinobacteria, Acidobacteria, Chloroflexi, Gemmatimonadetes, and Firmicutes. At the class level, α-Proteobacteria, Actinobacteria, Acidobacteria, ß-Proteobacteria, Thermoleophilia, Gemmatimonadetes, Bacilli, and δ-Proteobacteria were predominant. Compared to the corn land, Proteobacteria and Actinobacteria were the dominant bacteria in the Caragana intermedia land, while Actinobacteria and Acidobacteria were the dominant bacteria in the Stipa bungeana land. Soil bacterial diversity was the highest in the shrub land. RDA analysis revealed that soil organic matters and total nitrogen were the most influential environmental factors. It was shown thus that the program of converting farmland into forest or grassland has significantly improved the soil fertility and environmental conditions, and the composition of the soil bacterial community has also been appreciably changed.

[Ecological stoichiometry of leaf and litter of herbaceous plants in loess hilly and gully regions, China]. / 黄土丘陵区草本植物叶片与枯落物生态化学计量学特征.

This study was conducted in the forest, forest-steppe and steppe vegetation zones along the Yanhe River Basin, where the leaf and litter samples from four dominant herbaceous plants including Lespedeza davurica, Stipa bungeana, Artemisia sacrorum, Artemisia giraldii were taken. By measuring the concentrations of carbon (C), nitrogen (N), phosphorus (P) and potassium (K), we measured the concentrations and their ratios to explore the limit and resorption of nutrient in the herbaceous plants. The results showed that the leaf N/P of four herbaceous plants was all lower than 14, suggesting their growth was mainly limited by N content. Except for L. davurica, the mean nutrient resorption efficiency of K, N and P in the other three plants was 79.9%, 48.7% and 32.5%, respectively. The higher nutrient resorption efficiency and K concentration in the leaf were beneficial for soil water competition of A. sacrorum and A. giraldii. The litter C/N in A. sacrorum was significantly lower than that in S. bungeana and A. giraldii, which was easy to decompose to benefit the nutrient recycling. This resulted in the wide distribution of A. sacrorum in the three vegetation areas.

[Soil Bacterial Communities Under Different Vegetation Types in the Loess Plateau].

In this study, we collected soil samples from four different arborcommunities and four herb communities, which represented two vegetation ecosystems in the northwest of the Loess Plateau. Our objectives were to determine the diversity of soil bacterial communities and the affecting factors with the method of 454 high-throughput pyrosequencing technology. The results showed that the structures of the microbial communities differed in terms of both the predominant phylum and the relative abundance of each phylum. At the phylum level, the dominant phyla were Proteobacteria, Actinobacteria, Acidobacteria, Chloroflexi and Planctomycetes. At the class level, Actinobacteria, α-Proteobacteria, Acidobacteria, ß-Proteobacteria and Planctomycetacia were predominant. The relative abundance of Actinobacteria in grass vegetation ecosystem was more abundant than that in forest vegetation ecosystem. Proteobacteria in forest vegetation ecosystem were more abundant. Soil pH was significantly correlated with the relative abundance of Actinobacteria. Soil organic matter,soil total N and soil total P were the key factors affecting soil Proteobacteria. These results will provide useful information for the diversity of soil bacteria and guide the practice of vegetation restoration in the Loess Plateau.

[Characteristics and Coupling Relationship of Soil Carbon and Nitrogen Transformation During In-situ Mineralization Cultivation in Forestlands in the Mountain Area of Southern Ningxia].

The study aimed to investigate the characteristics and relationship between soil carbon and nitrogen transformation of artificial forestlands, which is one type of vegetation restoration in the mountain area of Southern Ningxia. Soil samples were collected every two months in a year from three forestlands, and the characteristics of soil organic carbon, dissolved carbon, microbial biomass carbon, organic nitrogen, inorganic nitrogen, soil ammonification, nitrification and mineralization rates, microbial immobilization rates and coupling of soil carbon and nitrogen were studied by the in-situ closed-top PVC tube incubation methods. The results showed that: in the process of in-situ incubation, the most obvious changes of carbon and nitrogen were in 61-120 days which was mainly affected by soil moisture; There were significantly positive correlations between the soil organic carbon and the total nitrogen, microbial biomass carbon and microbial biomass nitrogen, dissolved carbon and dissolved nitrogen; Transformation rates of soil organic carbon had significant effects on the soil ammonification, nitrification and microbial immobilization rates. It can be well simulated by model of linear regression equation; Microbial quotient, MBN/SON were significantly increased in soil of Caragana korshinskii land. Net nitrification rates, net mineralization rates in Caragana korshinskii land were significantly higher than that in Prunus davidiana and Prunus mandshurica lands.

[Variation of soil nitrogen during in situ mineralization process under different grasslands in the mountainous area of southern Ningxia, Northwest China].

Variations in organic nitrogen, microbial biomass nitrogen, soluble organic nitrogen, NH4(+) -N, NO3(-) -N, NO2(-) -N and N mineralization were investigated under three different grasslands in the mountainous area of southern Ningxia, Northwest China (natural grassland, artificial turf and abandoned land) using the close-top tube incubation method. Microbial biomass nitrogen, soluble organic nitrogen, NH4(+)-N, NO3(-)-N, NO2(-)-N and N mineralization exhibited significant seasonal variations. The nitrogen levels remained essentially unchanged from April to June, significantly decreased in July-August, rebounded after August, and were lowest in August. The organic nitrogen content remained unchanged in the whole training process. The soil mineralization rates, nitrification and ammonification rate were lowest in June-August. The ratios of each N fraction to total N responded differently to seasonal changes. The ratios of organic N, NO2(-) -N to total N did not change, in contrast, the ratios of nitrate N, microbial biomass nitrogen and soluble organic nitrogen, to total soil N decreased from April to August, and increased from August to December. The soil organic matter, pH, and bulk density were closely related to soil N. There was a significant positive correlation among the six N fractions. The soil nitrogen content of the different grassland types followed the order of natural grassland > abandoned land > artificial turf.

[Effects of different aspects on soil microbial biomass and dissolved organic carbon of the loess hilly area].

Soil samples from different aspects (southern slope and northern slope) under the same vegetation in two typical vegetation zones (forest vegetation zone and steppe vegetation zone) of Yanhe basin in the loess hilly area were chosen and analyzed, in order to investigate the content and correlation of soil microbial biomass carbon (SMBC), soil microbial biomass nitrogen (SMBN), soil microbial biomass phosphorus (SMBP) and dissolved organic carbon (DOC). The results show that, in 0-10 cm soil layer of forest vegetation zone, SMBC in southern slope and northern slope are 532.1-792.5 mg x kg(-1) and 333.6-469.8 mg x kg(-1), SMBN are 53.66-87.31 mg x kg(-1) and 47.58-61.38 mg x kg(-1) respectively, both of them are higher in southern slope than those in northern slope, but in steppe vegetation zone, SMBC and SMBN in southern slope are lower than those in northern slope, with SMBC of southern slope and northern slope are 68.90-75.34 mg x kg(-1) and 65.29-128.67 mg x kg(-1), SMBN are 13.94-18.61 mg x kg(-1) and 13.00-20.10 mg x kg(-1) respectively, SMBP in both vegetation zones have a different variation trend compared with SMBC and SMBN; the ratio of SMBC to the sum of SMBC plus DOC (SMBC + DOC) in southern slope of forest vegetation zone reaches the maximum value in two vegetation zones, which is 77.74%. In steppe vegetation zone, this ratio both decreases from northern slope to southern slope and 0-10 cm soil layer to 10-30 cm soil layer. The difference of soil moisture and temperature between different aspects under the same vegetation have a significant effect on soil microbial biomass, it also makes the ratio of SMBC to SMBC + DOC different, SMBC + DOC can reflect soil carbon availability better than SMBC, there might be an obvious change in soil microbial communities in 0-10 cm soil layer of different aspects in forest vegetation zone.

[Effects of grape seed addition in swine manure-wheat straw composting on the compost microbial community and carbon and nitrogen contents].

Taking substrates swine manure and wheat straw (fresh mass ratio 10.5:1) as the control (PMW), a composting experiment was conducted in a self-made aerated static composting bin to study the effects of adding 8% grape seed (treatment PMW + G) on the succession of microbial community and the transformation of carbon and nitrogen in the substrates during the composting. Seven samples were collected from each treatment, according to the temperature of the compost during the 30 d composting period. The microbial population and physiological groups were determined, and the NH4(+)-N, NO3(-)-N, organic N, and organic C concentrations in the compost were measured. Grape seed addition induced a slight increase of bacterial count and a significant increase of actinomycetes count, but decreased the fungal count significantly. Grape seed addition also decreased the ratio of bacteria to actinomycetes and the counts of ammonifiers and denitrifiers, but increased the counts of nitrifiers, N-fixing bacteria, and cellulose-decomposing microorganisms. The contents of NH4(+)-N and organic C decreased, while that of NO3(-)-N increased obviously. The NO3(-)-N content in the compost was positively correlated with the actinomycetes count. During composting, the compost temperature in treatment PMW + G increased more rapidly, and remained steady in thermophilic phase, while the water content changed little, which provided a stable and higher population of actinomycetes and nitrifiers in thermophilic phase, being beneficial to the increase of compost nitrate N.