Search Results (40)

To study the structure and distribution characteristics of the phytoplankton community in the Huaihe River Basin, Yangtze River Basin, and Taihu Lake Basin in Jiangsu Province, 126 sampling sites were set up in 35 rivers in the region, and samples were collected during the wet season (August–September) in 2023. Based on the monitoring results of phytoplankton, the study selected 20 candidate indicators and conducted range screening, discriminative ability analysis, and correlation analysis. Finally, seven core indicators were determined to construct the Phytoplankton Biological Integrity Index (P-IBI) evaluation system. The rating standards were determined by the ratio method, and the phytoplankton integrity of Jiangsu Province was evaluated. The differences were analyzed. As the results showed, the overall health status of rivers in Jiangsu Province was general. From the point of view of the basin scope, the Huaihe River Basin and the Yangtze River Basin were in sub-healthy state, and the Taihu Lake Basin was general. There were significant differences in the phytoplankton density community structure in the Yangtze River, Huaihe River, and Taihu Lake Basins. Phytoplankton integrity was positively correlated with total nitrogen and nitrate nitrogen, but not with other environmental factors. Nitrogen is the main factor affecting the integrity of river phytoplankton in Jiangsu Province. Full article

Sediment is a core part of lake ecosystems, and its organic matter (OM) content is a key indicator of lake ecological health and regional carbon cycling. OM provides nutrients for phytoplankton and algae in water, thereby influencing the degree of lake eutrophication. However, excessively high OM content may trigger water eutrophication, alter sediment’s physical and chemical properties, and ultimately threaten the stability and health of ecosystems. This study innovatively selected Poyang Lake, Taihu Lake, Qinghai Lake, and Hulun Lake from China’s four major geographical regions to systematically investigate sediments’ OM content, sources, and distribution characteristics at different times. The results showed that the organic matter content of sediments in lakes from different regions varied significantly and was influenced by multiple factors, such as watershed characteristics, eutrophication levels, human activities, and climate change. Poyang Lake and Taihu Lake, characterized by high levels of agricultural activities and urbanization within their basins, exhibit significant fluctuations in organic matter content, with total organic carbon (TOC) levels ranging from 0.35% to 2.9% and 0.7% to 2.4%, respectively. In contrast, Qinghai Lake and Hulun Lake, influenced by natural conditions and ecological policies, show relatively stable TOC levels, ranging from 1.3% to 2.75% and 1.25% to 3.58%, respectively. By analyzing sediments’ OM content and combining methods such as organic carbon, nitrogen isotopes, and organic C/N ratios, it is possible to effectively assess the ecological health of lakes, provide critical data support for pollution control, and play a significant role in carbon cycle management. Full article

This study aims to evaluate the growth characteristics of six Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) provenances (S1–S6) from different climatic regions in subtropical China in order to select superior provenances with strong adaptability, fast growth, and reasonable biomass allocation. These results will provide references for genetic improvement and resource utilization of Chinese fir plantations. A total of 385 trees, aged 26 to 48 years, were selected from the Chinese fir gene bank in Anhui. Wood core sampling was used to obtain tree ring width and early/latewood width data. Growth rate, fast-growth period, and biomass allocation of each provenance were analyzed using methods such as the logistic growth equation, BAI (basal area increment), latewood percentage, and biomass estimation. The fast-growth period of Chinese fir starts from the 2nd to the 4th year, with significant growth occurring around the 14th year and growth stabilizing between 30 and 50 years. Provenance S2 showed clear advantages in growth rate and biomass, while S6 was relatively weak. BAI analysis revealed that the provenances reached their growth peak around 10 years of age, with a gradual decline afterward, but S2 maintained higher growth levels for a longer period. Root-shoot ratio analysis showed that S2 had the most balanced ratio, promoting stable growth and efficient water and nutrient absorption, while S6 had a higher root-shoot ratio, indicating growth limitations. Furthermore, S2 demonstrated continuous biomass increase after 30 years, indicating excellent growth potential. This study provides quantitative analysis of the growth characteristics and adaptability of different Chinese fir provenances, offering scientific support for the construction and breeding of Chinese fir plantations, and contributing to enhancing the productivity and ecological adaptability of Chinese fir plantations for sustainable resource utilization. Full article

Intraluminal photoacoustic (PA) imaging has the potential for providing physiological and functional information in wide-ranging clinical applications. Along with endoluminal ultrasound transducers, these applications require compact light delivery devices which can deliver high-energy ns-pulsed laser to the target region. In this work, we describe the design, method of fabrication and characterization of a new compact, side-fire optical fiber that can deliver high-energy laser pulses for PA imaging. Side-fire illuminators were fabricated using UV laser ablation to create windows on the side of a 1.5 mm diameter single core, multi-mode optical fiber with a reflective silver coating and a beveled end. Devices with 10 mm, 20 mm, and 30 mm window lengths were fabricated and their beam profiles characterized. Elongated side-fire fibers with −6 dB beam size up to 30.79 mm × 5.5 mm were developed. A side-fire to total output ratio of up to 0.69 and a side fire efficiency of up to 40%, relative to a standard front-fire fiber, were achieved. We evaluated the effects of high-energy ns-pulsed light propagation on the fiber by coupling the fiber to 18 mJ or 100 MW/cm² (at 750 nm) beam from a Q-switched laser. The PA imaging with the fiber was demonstrated by detecting India ink targets embedded in chicken breast tissue over the full length of a 20 mm illumination window and over a 100° angle and by visualizing in vivo the rat ear vasculature. Full article

Ultrapotassic lamprophyre dykes in southern Xizang provide important insight into the deep processes and nature of the source region. In this study, the lamprophyre dykes in the Bangbule area of southern Xizang were investigated to understand their petrogenesis and source mantle characteristics. The lamprophyres, based on their mineral and chemical compositions, are classified into two types: type-1, mainly comprising biotite and clinopyroxene, and type-2, featuring annite, phlogopite, and clinopyroxene as phenocrysts. Mica ⁴⁰Ar-³⁹Ar dating indicates their formation in the early Oligocene (29.5 ± 0.2 Ma). Geochemically, both lamprophyre types show extremely high Sr [(⁸⁷Sr/⁸⁶Sr)_i = 0.713936–0.716999] but low and consistent Nd [(¹⁴³Nd/¹⁴⁴Nd)_i = 0.511991–0.512012] isotopic ratios. Type-1 lamprophyres are more enriched in SiO₂, Al₂O₃, and total alkalis (Na₂O + K₂O) but have lower ^TFe₂O₃, CaO, and MgO contents, as well as Mg^# values, compared to type-2, underscoring the differentiated nature of type-1. Geochemical evidence shows that the Bangbule lamprophyre originated from the partial melting of the lithospheric mantle metasomatized by subducted Indian continental crust-derived melts, followed by fractional crystallization. The phenocrysts of clinopyroxene, phlogopite, and K-feldspar exhibit disequilibrium textures and complex zoning between their cores and mantles, suggesting magma replenishment and mixing during their formation. The cores of the clinopyroxene and phlogopite phenocrysts exhibit low Mg^# values, while their mantles show high Mg^# values, indicating magma replenishment between later mafic and early evolved (ultrapotassic) magmas. Accordingly, an open magma chamber model that experienced fractional crystallization and replenishment was proposed for the generation of diverse lamprophyre dykes in Xizang. Full article

This study analyzes the dynamics of China’s fruit industry using a range of analytical tools, including the location Gini coefficient, industry concentration ratio, spatial autocorrelation index, specialization index, and the industry gravity model. It explores the industry’s evolving characteristics and trends since the economic reforms, culminating in a trajectory map that highlights shifts in the industry’s gravitational center. This study also offers a qualitative analysis of the factors influencing the agglomeration and relocation of fruit production centers. The findings show a steady increase in both total output and yields per unit area within China’s fruit industry over time. Although the overall degree of agglomeration has decreased, regional agglomeration effects remain significant. Furthermore, the data reveal significant spatial autocorrelation in fruit production, indicating a long-term westward shift in core production areas. Different geographic areas exhibit varying levels of gradational shifts, with marked differences in production concentration patterns across different fruit types. This study provides a comprehensive framework for understanding production agglomeration, integrating interdisciplinary methods from statistics and geography. Full article

A novel concept of cold neutron source employing chessboard or staircase assemblies of high-aspect-ratio rectangular para-hydrogen moderators with well-developed and practically fully illuminated surfaces of the individual moderators is proposed. An analytic approach for calculating the brightness of para-hydrogen moderators is introduced. Because the brightness gain originates from a near-surface effect resulting from the prevailing single-collision process during thermal-to-cold neutron conversion, high-aspect-ratio rectangular cold moderators offer a significant increase, up to a factor of 10, in cold neutron brightness compared to a voluminous moderator. The obtained results are in excellent agreement with MCNP calculations. The chessboard or staircase assemblies of such moderators facilitate the generation of wide neutron beams with simultaneously higher brightness and intensity compared to a para-hydrogen-based cold neutron source made of a single moderator (either flat or voluminous) of the same cross-section. Analytic model calculations indicate that gains of up to approximately 2.5 in both brightness and intensity can be achieved compared to a source made of a single moderator of the same width. However, these gains are affected by details of the moderator–reflector assembly and should be estimated through dedicated Monte Carlo simulations, which can only be conducted for a particular neutron source and are beyond the scope of this general study. The gain reduction in our study, from a higher value to 2.5, is mostly caused by these two factors: the limited volume of the high-density thermal neutron region surrounding the reactor core or spallation target, which restricts the total length of the moderator assembly, and the finite width of moderator walls. The relatively large length of moderator assemblies results in a significant increase in pulse duration at short pulse neutron sources, making their straightforward use very problematic, though some applications are not excluded. The concept of “low-dimensionality” in moderators is explored, demonstrating that achieving a substantial increase in brightness necessitates moderators to be low-dimensional both geometrically, implying a high aspect ratio, and physically, requiring the moderator’s smallest dimension to be smaller than the characteristic scale of moderator medium (about the mean free path for thermal neutrons). This explains why additional compression of the moderator along the longest direction, effectively giving it a tube-like shape, does not result in a significant brightness increase comparable to the flattening of the moderator. Full article

Paphiopedilum micranthum, an IUCN Red List species, is discontinuously distributed in the karst limestone mountain of southwest China and exhibits ecological specialization, typically through lithophytic and terrestrial ecotypes. Whether the distribution of rhizosphere bacteria and fungi in these different habitats is random or reflects soil preferences requires further investigation. A total of 73 samples from the core distribution areas in China, representing all habitats in two sites, were analyzed for soil differences by comparing edaphic properties and microbial community structure based on high-throughput sequencing of bacterial 16S rRNA genes and fungal ITS region sequences, alongside soil physiochemical data. The results showed no significant differences in microbial community richness and diversity across the heterogeneous habitats. However, significant differences in taxa were observed across various habitats. Dominant bacterial phyla included Actinobacteriota, Proteobacteria and Acidobacteriota, with dominant genera such as Crossiella, Pseudonocardia, 67-14, Mycobacterium and RB41. The primary fungal phyla were Basidiomycota and Ascomycota, featuring prominent genera such as Phlegmacium, Archaeorhizomyces, Trechispora, and Lepiota. There were 16 bacterial genera and 13 fungal genera associated with nitrogen transformation and fixation. Alkali-hydrolyzed nitrogen (AN) was identified as a main driver of soil bacterial and fungal community variation. Based on an analysis of soil physicochemical properties, ammonium nitrogen content was consistently higher than nitrate nitrogen across different habitats. Furthermore, across all heterogeneous habitats, P. micranthum showed no significant differences in nitrate nitrogen, ammonium nitrogen, or their ratio. The nitrogen-use efficiency of P. micranthum ranged from 7.73% to 9.87%, with the highest efficiency observed in the terrestrial habitat of Shedu. These results suggest that P. micranthum prefers habitats rich in organic matter and nitrogen, showing a preference for ammonium nitrogen uptake in natural conditions. Heterogeneous habitats affect plant nitrogen-use efficiency as well as changes in microbial community composition. Full article

The quality of rice, evaluated using multiple quality-related traits, is the main determinant of its market competitiveness. In this study, two japonica rice varieties with significant differences in quality-related traits were used as parents to construct two populations, BC₃F₂ and BC₃F_2:3, with Kongyu131 (KY131) as the recurrent parent. A genetic linkage map was constructed using the BC₃F₂ population based on 151 pairs of SSR/InDel polymorphic markers selected between the parents. Grain-shape-related traits (grain length GL, grain width GW, and length-to-width ratio LWR), chalkiness-related traits (white-core rate WCR, white-belly rate WBR, white-back rate BR, and chalkiness rate CR), and amylose content (AC) were investigated in the two populations in 2017 and 2018. Except for BR and CR, the traits showed similar characteristics with a normal distribution in both populations. Genetic linkage analysis was conducted for these quality-related traits, and a total of 37 QTLs were detected in the two populations. Further validation was performed on the newly identified QTLs with larger effects, and three grain shape QTLs and four chalkiness QTLs were successfully validated in different environments. One repeatedly validated QTL, qWCR3, was selected for fine mapping and was successfully narrowed down to a 100 kb region in which only two genes, LOC_0s03g45210 and LOC_0s03g45320, exhibited sequence variations between the parents. Furthermore, the variation of LOC_Os03g45210 leads to a frameshift mutation and premature protein termination. The results of this study provide a theoretical basis for positional cloning of the qWCR3 gene, thus offering new genetic resources for rice quality improvement. Full article

National parks (NPs) are the flagship protected areas in China’s conservation network and play a key role in the ecological protection of core objects and important natural landscapes. However, the shortage of spatial optimization methods based on quantitative indicators has limited the spatially explicit identification of national parks. Therefore, in this study, we selected the main area of the Tarim River (MTR) in Xinjiang as an example to optimize the spatial boundary of a national park. We constructed an evaluation system based on representativeness, ecological importance, and the foundation of the existing protected area. Subsequently, we comprehensively employed a species distribution model to simulate the habitat of the primary conservation targets. Additionally, we spatially optimized the region using an integer linear model, considering multiple scenarios. The results of this study show that fewer than 30% of the existing protected areas in the MTR protect conservation objects. Using different protection objects and quantitative goals, the spatial optimization results for the eight protection scenarios show that the most effective national park establishment scenario covers a total area of 15,009.3 km², which is 8157.5 km² more than the protected area already in place and would include the Tarim Populus National Nature Reserve and Luntai Tarim Populus Forest Park. The opportunity cost to be paid for protection according to this boundary is approximately USD 115.14 million. The protection ratios of each protection object for the expanded park are more than 50%, which is 27.7% higher than the protection effect produced by the existing protected area, so we recommend that Tarim National Park be set up on the basis of this boundary. Full article

The fall armyworm, Spodoptera frugiperda J.E. Smith (Lepidoptera: Noctuidae), is an agricultural pest native to tropical and subtropical regions of the Americas, with considerable potential for global invasion and seasonal migration. Although genetically modified (GM) plants have shown positive impacts on the economy and the environment as they synthesize proteins that act as natural insecticides and are primarily intended to protect the crops from damage by specific pests, potential effects of Bt toxins on non-target organisms can occur. This experiment aimed to evaluate the potential impacts on the parasitoid Palmistichus elaeisis (Hymenoptera: Eulophidae), using the pupae of Spodoptera frugiperda (Lepidoptera: Noctuidae) as hosts, which were fed with transgenic maize genotypes such as Herculex^®, expressing Cry1F protein, and PowerCore^®, expressing Cry1F, Cry1A.105, and Cry2Ab2 proteins, or their non-transgenic isohybrid. The experiment was conducted in a completely randomized design with ten replicates. Spodoptera frugiperda larvae were fed ad libitum with transgenic and non-transgenic maize until the pupal stage and then individually exposed to six P. elaeisis females for 78 h. The total number of adults, emerged males, tibia size, cephalic capsule size, and parasitoid body size were not influenced by host feeding. However, the number of emerged females from the Herculex^® and PowerCore^® treatments was lower than that for the isohybrid treatment. The sex ratio and longevity of parasitoids emerging from PowerCore^® were 1.05 and 1.26 times lower, respectively, than that of those from the isohybrid. Furthermore, the number of dead P. elaeisis within the host pupa was 10.56 times higher in the PowerCore^® genotype. Combining Bt proteins within pyramided genotypes should cause minimal impacts and promote the conservation and integration of beneficial insects. The results of this study provide helpful information for developing effective and compatible integrated pest management (IPM) strategies. Full article

We aimed to study the effects of mycorrhizal and extraradical hyphae on soil physical and chemical properties and enzyme activity characteristics in a subtropical plantation and to explore its indicative effect on the effectiveness of soil nutrients. In this study, three native afforestation tree species, Cunninghamia lanceolata, Schima superba, and Liquidambar formosana, with different biological characteristics, root functional traits, and nutrient acquisition strategies in subtropical regions were selected as the research objects. Based on the method of in-growth soil cores, the nylon mesh with different pore sizes was used to limited the root system and hypha into the soil column. The soil physical and chemical properties of five kinds of hydrolase related to the carbon (C), nitrogen (N), and phosphorus (P) cycles were determined in this study. The correlation of different tree species, roots, and mycelia with soil physicochemical properties, enzyme activity, and stoichiometric ratios was analyzed. The results revealed that mycorrhizal treatment significantly affected the soil total carbon (TC) and pH but had no significant effect on hydrolase activity and its stoichiometric ratio. Tree species significantly affected soil physical and chemical properties, soil β-1,4-N-acetylglucosaminidase (NAG), β-1,4-glucosidase (βG), and cellobiohydrolase (CB) activities and soil enzyme stoichiometric ratios. The soil enzyme activity and stoichiometric ratio of the Chinese fir forest had higher values than in monoculture broad-leaved stands of both Schima superba and Liquidambar formosana. There was no significant interaction effect of mycorrhizal treatments and tree species on all soil properties, enzyme activities, and stoichiometric ratios. In addition, the soil enzyme activity and stoichiometric characteristics were mainly affected by the pH. In this study, the soil enzyme activity ratios In(BG + CB):In(AP) and In(NAG + LAP):In(AP) were lower values than the global scale, while the ratios of In(βG + CB):In(NAG + LAP) were higher than the average, indicating that the soil microorganisms in this area were limited by C and P. Moreover, the soil enzyme activity and chemical metrology characteristics were mainly affected by the pH change. In conclusion, differences in litter quality and root functional traits of tree species affected the soil enzyme activity and its stoichiometric characteristics through the shaping of the forest environment by organic matter input, and the influence of pH was the main regulating factor. Full article

Studying the accumulation rules of organic matter (OM) in paleo-ocean sediments can not only enhance our understanding of how OM becomes enriched in ancient oceans but also provide guidance for the exploration of shale gas in unconventional shale strata. A breakthrough has been made in shale gas exploration in the early Cambrian Qiongzhusi Formation in South China. However, less attention has been paid to the intraplatform basin of the Yangtze Platform, and the factors controlling organic matter enrichment in this special region remain unclear. This study focuses on a continuous drilling core across the full well section of the Qiongzhusi Formation in the intraplatform basin of the Yangtze Platform. Through the comprehensive analysis of total organic carbon (TOC), major and trace elements, and Mo isotopes, this study investigates the controlling factors for OM enrichment with δ^98/95Mo ratios utilized to identify the existence of euxinic bottom water. The examined 240 m long core can be divided into four units, where the TOC values of the lower Units 1 and 2 (0.2–5.0 wt.%) average higher than the upper Units 3 and 4 (0.2–2.5 wt.%). Redox indicators (U/Th, Ni/Co, EF(Mo)—EF(U)) indicate an increasing oxidation of bottom waters from the bottom upwards. δ^98/95Mo data further confirm the presence of weakly euxinic conditions in Units 1 and 2, addressing the ongoing controversy surrounding bottom water redox environments. Primary productivity indicators (Ni/Al, Cu/Al) suggest a relatively low average productivity level within the intraplatform basin. The upwelling indicators EF(Co) * EF(Mn) of different profiles in the Yangtze Platform suggest that low productivity within the intraplatform basin can be mainly attributed to the absence of upwelling. Consequently, this study proposes an organic matter enrichment mechanism for the Qiongzhusi Formation in the intraplatform basin, which emphasizes the significance of the redox environment in the formation of high-quality hydrocarbon source rocks in restricted environments that lack upwelling, setting it apart from the deep ocean. These findings have the potential to provide valuable insights for the exploration of high-quality hydrocarbon source rocks in other similar regions. Full article

Sub-hourly heavy precipitation events (SHHPs) associated with regional low-pressure (RegL) systems in Portugal are a natural hazard that may have significant socioeconomic implications, namely in agriculture. Therefore, in this paper, their dynamic and thermodynamic drivers are analysed. Three weather stations were used to isolate SHHPs from 2000 to 2022. Higher precipitation variability is found in southern Portugal, with a higher ratio of extreme events on fewer rainy days. This study shows that these SHHP events are associated with low-pressure systems located just to the west of the Iberian Peninsula. These systems exhibit a cold core, particularly strong at mid-levels, and a positive vorticity anomaly, which is stronger in the upper troposphere, extending downward to low levels. These conditions drive differential positive vorticity advection and, therefore, rising motion to the east of the low-pressure systems. Moreover, at low levels, these systems promote moisture advection over western Iberia, also generating instability conditions, which are assessed by instability indices (Convective available potential energy, the Total-Totals index, and the K-index). The combination of these conditions drives heavy precipitation events. Lastly, the total column cloud ice water revealed higher values for the heavier precipitation events, suggesting that it may be a useful predictor of such events. Full article

The study investigated the composition and content of Σ₁₅PAH in the surface and core sediments from Dachan Bay (DCB) in Shenzhen city and discussed the effects of urban development and regional energy structure on the marine environment through the spatial distribution, vertical profile, and sources of Σ₁₅PAH. The results indicated that the concentrations of Σ₁₅PAH in the sediments of DCB ranged between 299 ng/g and 2336 ng/g in the surface sediments and between 65 ng/g and 994 ng/g in the core sediments. The horizontal spatial distribution of PAHs content with decreasing concentrations from the coastal to central areas implied the land-based input of PAHs. The vertical profile of high PAHs concentration in 0 cm–60 cm suggested that the PAHs pollution is attributed to the urban development of Shenzhen since 1950, especially after the 1980s. According to features of the low molecular weight (LMW)/high molecular weight (HMW), PAHs diagnostic ratios and their relationships with total organic carbon (TOC) and oil, the pyrogenic PAHs were mainly from the combustion of petroleum and byproducts in the surface and 0 cm–60 cm sediments but from the combustion of biomass in 60 cm–190 cm sediments, which corresponded with the variation of energy structure in surrounding areas. This study suggested that urban development and regional energy structure have a great impact on PAHs distribution in DCB and further controls of land-based pollutant emissions are still needed. Full article