Effects of soil heterogeneity and preferential flow on the water flow and isotope transport in an experimental hillslope.

Soil water movement plays vital roles in hillslope runoff generation and groundwater and surface water interaction. However, there are still knowledge gaps about the impacts of soil heterogeneity and preferential flow on the internal water flow and transport process. In this study, the vertical soil heterogeneity focused on the variations in soil retention capacity, and the consideration of lateral preferential flow emphasized the higher hydraulic conductivity. We combined isotopic tracing and numerical modeling in an artificial hillslope, focusing on monitored processes of the artificial rainfall and isotopic tracing experiment. The results showed that the soil moisture quickly accumulated at the bottom of the hillslope during rainfall events, while the 2H enrichment occurred in the topsoil derived from enriched isotope injection in the second artificial rainfall. The evaporation process slowed down the mixing of new water in the topsoil and old water in the lower layer. We found that the vertical soil heterogeneity had significant influences on the internal water and isotope transport paths within the hillslope. The lateral preferential flow played an important role in the water flux and transport time to the seepage face. The coupling of isotopic tracing, which reflects the water transport and mixing with the hillslope, effectively improved the model simulation and mechanism analysis of hillslope water flow. Our findings provide new insights into the mechanisms governing soil water flow and transport dynamics in hillslopes, taking into account vertical soil heterogeneity and lateral preferential flow.

Methane emissions and microbial communities under differing flooding conditions and seasons in littoral wetlands of urban lake.

Wetlands are the largest natural sources of methane (CH4) emissions worldwide. Littoral wetlands of urban lakes represent an ecotone between aquatic and terrestrial ecosystems and are strongly influenced by water levels, environmental conditions, and anthropogenic activities. Despite these littoral zones being potential "hotspots" of CH4 emissions, the status of CH4 emissions therein and the role of physicochemical properties and microbial communities regulating these emissions remain unclear. This study compared the CH4 fluxes, physicochemical properties, and CH4-cycling microbial communities (methanogens and methanotrophs) of three zones (a non-flooded supralittoral zone, a semi-flooded eulittoral zone, and a flooded infralittoral zone) in the littoral wetlands of Lake Pipa, Jiangsu Province, China, for two seasons (summer and winter). The eulittoral zone was a CH4 source (median: 11.49 and 0.02 mg m-2 h-1 in summer and winter, respectively), whereas the supralittoral zone acted as a CH4 sink (median: -0.78 and -0.09 mg m-2 h-1 in summer and winter, respectively). The infralittoral zone shifted from CH4 sink to source between the summer (median: -10.65 mg m-2 h-1) and winter (median: 0.11 mg m-2 h-1). The analysis of the functional genes of methanogenesis (mcrA) and methanotrophy (pmoA) and path analysis showed that CH4 fluxes were strongly regulated by biotic factors (abundance of the mcrA gene and alpha diversity of CH4-cycling microbial communities) and abiotic factors (ammonia nitrogen, moisture, and soil organic carbon). In particular, biotic factors had a major influence on the variation in the CH4 flux, whereas abiotic factors had a minor influence. Our findings provide novel insights into the spatial and seasonal variations in CH4-cycling microbial communities and identify the key factors influencing CH4 fluxes in littoral wetlands. These results are important for managing nutrient inputs and regulating the hydrological regimes of urban lakes.

PAFAH2 suppresses synchronized ferroptosis to ameliorate acute kidney injury.

Synchronized ferroptosis contributes to nephron loss in acute kidney injury (AKI). However, the propagation signals and the underlying mechanisms of the synchronized ferroptosis for renal tubular injury remain unresolved. Here we report that platelet-activating factor (PAF) and PAF-like phospholipids (PAF-LPLs) mediated synchronized ferroptosis and contributed to AKI. The emergence of PAF and PAF-LPLs in ferroptosis caused the instability of biomembranes and signaled the cell death of neighboring cells. This cascade could be suppressed by PAF-acetylhydrolase (II) (PAFAH2) or by addition of antibodies against PAF. Genetic knockout or pharmacological inhibition of PAFAH2 increased PAF production, augmented synchronized ferroptosis and exacerbated ischemia/reperfusion (I/R)-induced AKI. Notably, intravenous administration of wild-type PAFAH2 protein, but not its enzymatically inactive mutants, prevented synchronized tubular cell death, nephron loss and AKI. Our findings offer an insight into the mechanisms of synchronized ferroptosis and suggest a possibility for the preventive intervention of AKI.

Data-driven assessment of soil total nitrogen on the Qinghai-Tibet Plateau.

The investigation of soil total nitrogen (STN) holds significant importance in the preservation and sustainability of Earth's ecosystems. The Qinghai-Tibet Plateau (QTP), renowned as the world's most expansive plateau and characterized by its exceptionally delicate ecosystem, demands an in-depth exploration of its STN content. In this study, we use a machine learning approach to extrapolate point-scale measured STN stocks to the entire QTP and calculated STN storage from 0 to 2 m. Our results show that the XGB algorithm performs well in modeling STN despite variations in simulation accuracy for specific depth ranges. The spatial distribution of STN across the QTP exhibits pronounced heterogeneity, especially for the 0-50 cm soil layer, with relatively higher STN stocks in the southeast and lower stocks in the northwest of QTP. The vertical distribution reveals a gradual decrease in STN storage with increasing depth. The 0-50 cm soil layer holds the highest STN stocks, averaging around 0.78 kg/m2, which is almost the sum of STN stocks in the 50-100 cm and 100-200 cm soil layers. Meanwhile, the STN stocks are smaller in permafrost zone than that in non-permafrost zone. We also investigate the impact factors that control the spatiotemporal distribution of STN. It indicates that vegetation, precipitation, temperature, and elevation are the major factors for STN distribution, while physical properties of the soil have a relatively smaller impact. These findings are crucial for understanding the distribution and evolution of STN on the QTP.

The role of halogens in Au-S bond cleavage for energy-differentiated catalysis at the single-bond limit.

The transformation from one compound to another involves the breaking and formation of chemical bonds at the single-bond level, especially during catalytic reactions that are of great significance in broad fields such as energy conversion, environmental science, life science and chemical synthesis. The study of the reaction process at the single-bond limit is the key to understanding the catalytic reaction mechanism and further rationally designing catalysts. Here, we develop a method to monitor the catalytic process from the perspective of the single-bond energy using high-resolution scanning tunneling microscopy single-molecule junctions. Experimental and theoretical studies consistently reveal that the attack of a halogen atom on an Au atom can reduce the breaking energy of Au-S bonds, thereby accelerating the bond cleavage reaction and shortening the plateau length during the single-molecule junction breaking. Furthermore, the distinction in catalytic activity between different halogen atoms can be compared as well. This study establishes the intrinsic relationship among the reaction activation energy, the chemical bond breaking energy and the single-molecule junction breaking process, strengthening our mastery of catalytic reactions towards precise chemistry.

Transcriptome analysis and identification of genes related to environmental adaptation of Grylloprimevala jilina Zhou & Ren 2023.

Grylloprimevala jilina is a true cave insect living in the dark areas of caves. It has the characteristics of sparse skin pigmentation, degeneration of the compound eyes and monocular eyes, and obvious preference for high-humidity and low-temperature environments. Given the highly specialized, rare, and limited distribution, G. jilina is considered an endangered species and also a first-level national protected insect in China. Cave creatures often undergo dramatic morphological changes in their sensory systems to adapt to the cave environment. Most previous studies mainly focused on morphological adaptive changes in cave insects, and only a few studied the changes at the gene level. In this study, we performed transcriptome analysis of G. jilina and constructed phylogenetic trees of genes that are related to environmental adaptation, including chemosensory, visual-related, reproduction-related, temperature adaptation-related, and winged morph differentiation-related genes. Besides, the expression levels of environmental adaption-related genes in different tissues, including antennae, heads, thoraxes, abdomens, legs, and tails, were analyzed. The results showed the loss of chemosensory genes and vision-related genes, the conservation of reproduction-related genes and temperature adaptation-related genes, and the conservation of wing-related genes despite the loss of wings, and the results were consistent with other cave insects. The identification and expression study of genes possibly related to the environmental adaptability in G. jilina provided basic data for the protection of this endangered species and increased knowledge about insect evolution in general.

Simulation and prediction of changes in maximum freeze depth in the source region of the Yellow River under climate change.

The source region of the Yellow River (SRYR) is located at the edge of the Qinghai-Tibet Plateau (QTP), which is completely covered by frozen ground. Due to relatively higher temperatures, the frozen ground in the SRYR is particularly fragile and susceptible to the impacts of global climate change. This study discusses the maximum freeze depth (MFD) of frozen ground in the SRYR, including analysis of measured data at the stations, comparison of simulation models, and projection of future changes. The MFD of frozen ground recorded at nine meteorological stations within the SRYR ranged from a few tens of centimeters to more than two meters. The decreasing trend of MFD was recorded except for a few stations from 1997 to 2017, with a maximum rate of -22.8 cm/10a. The decreasing rate of MFD for the whole SRYR from 1997 to 2017 is -10.8 cm/10a. Furthermore, we assessed the performance of three simulation methods: Stefan equation, multiple linear regression, and BP neural network predicting the MFD using the measured data. The Stefan equation exhibited limited accuracy in simulating the MFD, while the BP neural network demonstrated remarkable performance, with a correlation coefficient R of 0.949. In addition, we evaluated the applicability of different global climate models (GCMs) in the SRYR, identified the optimal model, and combined it with the BP neural network model to predict future MFD change. Among the five climate models, the BCC-CSM2-MR model and ensemble model fit the measured precipitation and air temperature well. The projected results based on the BCC-CSM2-MR model and ensemble model indicate that the MFD of different stations in the SRYR and the whole region will still tend to decrease in the future. Our results contribute to understanding the response of cold region frozen ground to climate change and provide available data.

Capture of colloidal fine suspended particle by aquatic vegetation under rainfall.

The capture of colloidal fine suspended particles by vegetation plays an important role in water quality of the shallow aquatic system under rainfall. Quantifying impact of rainfall intensity and vegetation condition on this process remains poorly characterized. In this study, the colloidal particle capture rates under three rainfall intensities, four vegetation densities and with submerged or emergent vegetation were investigated in different travel distance in a laboratory flume. Considering vegetation as porous media, non-Darcy's law with rainfall as a source term, was coupled with colloid first-order deposition model, to simulate the particle concentration changes with time, determining the particle deposition rate coefficient (kd), representing capture rate. We found that the kd increased linearly with rainfall intensity; but increased and then decreased with vegetation density, suggesting the existence of optimum vegetation density. The kd of submerged vegetation is slightly higher than emergent vegetation. The single collector efficiency (η) showed the same trend as kd, suggesting colloid filtration theory well explained the impact of rainfall intensity and vegetation condition. Flow hydrodynamic enhanced the kd trend, e.g., the theoretical strongest flow eddy structure represented in the optimum vegetation density. This study is helpful for the design of wetland under rainfall, to remove colloidal suspended particles and the hazardous material, for the protection of the downstream water quality.

Co-transport of arsenic and micro/nano-plastics in saturated soil.

Contaminants can co-exist and migrate together in the environment, causing complex (and sometimes unexpected) transport dynamics which challenge the efficient remediation of individual contaminants. The co-transport dynamics, however, remained obscure for some contaminants, such as arsenic and micro/nano-plastics (MNPs). To fill this knowledge gap, this study explored the co-transport dynamics of arsenic and MNP particles in saturated soil by combining laboratory experiments and stochastic model analysis. Isothermal adsorption and sand column transport experiments showed that the adsorption of arsenic by MNP particles followed the Freundlich model, with a maximum adsorption of 2.425 mg/g for the MNP particles with a diameter of 100 nm. In the presence of MNP particles, the efflux concentration of arsenic ions declined due to adsorption, where the decline rate decreased with the increasing MNP size and increased with the increasing adsorption capacity. Experimental results also showed that the 100 nm nano-plastic particles prohibited arsenic transport in saturated sand columns, while the 5 µm microplastics enhanced arsenic transport due to electrostatic adsorption and media pore plugging. A tempered time fractional advective-dispersion equation was then proposed to quantify the observed breakthrough curves of arsenic. The results showed that this model can reliably capture the co-transport behavior of arsenic with MNPs in the saturated soil with all coefficients of determination over 0.97, and particularly, the small MNP particles facilitated anomalous transport of arsenic. This study therefore improved the understanding and quantification of the co-transport of arsenic and MNPs in soil.

Lower Compositional Variation and Higher Network Complexity of Rhizosphere Bacterial Community in Constructed Wetland Compared to Natural Wetland.

Macrophyte rhizosphere microbes, as crucial components of the wetland ecosystem, play an important role in maintaining the function and stability of natural and constructed wetlands. Distinct environmental conditions and management practices between natural and constructed wetlands would affect macrophytes rhizosphere microbial communities and their associated functions. Nevertheless, the understanding of the diversity, composition, and co-occurrence patterns of the rhizosphere bacterial communities in natural and constructed wetlands remains unclear. Here, we used 16S rRNA gene high-throughput sequencing to characterize the bacterial community of the rhizosphere and bulk sediments of macrophyte Phragmites australis in representative natural and constructed wetlands. We observed higher alpha diversity of the bacterial community in the constructed wetland than that of the natural wetland. Additionally, the similarity of bacterial community composition between rhizosphere and bulk sediments in the constructed wetland was increased compared to that of the natural wetland. We also found that plants recruit specific taxa with adaptive functions in the rhizosphere of different wetland types. Rhizosphere samples of the natural wetland significantly enriched the functional bacterial groups that mainly related to nutrient cycling and plant-growth-promoting, while those of the constructed wetland-enriched bacterial taxa with potentials for biodegradation. Co-occurrence network analysis showed that the interactions among rhizosphere bacterial taxa in the constructed wetland were more complex than those of the natural wetland. This study broadens our understanding of the distinct selection processes of the macrophytes rhizosphere-associated microbes and the co-occurrence network patterns in different wetland types. Furthermore, our findings emphasize the importance of plant-microbe interactions in wetlands and further suggest P. australis rhizosphere enriched diverse functional bacteria that might enhance the wetland performance through biodegradation, nutrient cycling, and supporting plant growth.

Changes in permafrost spatial distribution and active layer thickness from 1980 to 2020 on the Tibet Plateau.

The Tibetan Plateau (TP) is experiencing extensive permafrost degradation due to climate change, which seriously threatens sustainable water and ecosystem management in the TP and its downstream areas. Understanding the evolution of permafrost is critical for studying changes in the water cycle, carbon flux, and ecology of the TP. In this study, we mapped the spatial distribution of permafrost and active layer thickness (ALT) at 1 km resolution for each decade using empirical models and machine learning methods validated with borehole data. A comprehensive comparison of model results and validation accuracy shows that the machine learning method is more advantageous in simulating the permafrost distribution, while the ALT simulated by the empirical model (i.e., Stefan model) better reflects the actual ALT distribution. We further evaluated the dynamics of permafrost distribution and ALT from 1980 to 2020 based on the results of the better-performing models, and analyzed the patterns and influencing factors of the changes in permafrost distribution and ALT. The results show that the permafrost area on the TP has decreased by 15.5 %, and the regionally average ALT has increased by 18.94 cm in the 2010s compared to the 1980s. The average decreasing rate of permafrost area is 6.33 × 104 km2 decade-1, and the average increasing rate of ALT is 6.31 cm decade-1. Permafrost degradation includes the decreasing permafrost area and the thickening active layer mainly related to the warming of the TP. Spatially, permafrost area decrease is more susceptible to occur at lower latitudes and lower altitudes, while ALT increases more dramatically at lower latitudes and higher altitudes. In addition, permafrost is more likely to degrade to seasonally frozen ground in areas with deeper ALT.

Increasing evapotranspiration decouples the positive correlation between vegetation cover and warming in the Tibetan plateau.

Plant growth generally responds positively to an increase in ambient temperature. Hence, most Earth system models project a continuous increase in vegetation cover in the future due to elevated temperatures. Over the last 40 years, a considerable warming trend has affected the alpine ecosystem across the Tibetan Plateau. However, we found vegetation growth in the moderately vegetated areas of the plateau were negatively related to the warming temperatures, thus resulting in a significant degradation of the vegetative cover (LAI: slope = -0.0026 per year, p < 0.05). The underlying mechanisms that caused the decoupling of the relationship between vegetation growth and warming in the region were elaborated with the analysis of water and energy variables in the ecosystem. Results indicate that high temperatures stimulated evapotranspiration and increased the water consumption of the ecosystem (with an influence coefficient of 0.34) in these degrading areas, significantly reducing water availability (with an influence coefficient of -0.68) and limiting vegetation growth. Moreover, the negative warming effect on vegetation was only observed in the moderately vegetated areas, as evapotranspiration there predominantly occupied a larger proportion of available water (compared to the wet and highly vegetated areas) and resulted in a greater increase in total water consumption in a warmer condition (compared to dry areas with lower levels of vegetation cover). These findings highlight the risk of vegetation degradation in semi-arid areas, with the degree of vulnerability depending on the level of vegetation cover. Furthermore, results demonstrate the central role of evapotranspiration in regulating water stress intensity on vegetation under elevated temperatures.

NosZI microbial community determined the potential of denitrification and nitrous oxide emission in river sediments of Qinghai-Tibetan Plateau.

Denitrification in river sediments is the hotspot of nitrogen removal and nosZI gene is essential for reducing nitrous oxide (N2O) emissions. However, few studies tried to link nosZI communities with variations of denitrification rates in sediments along the high-elevation rivers. Here, we investigated the spatial variation of potential denitrification rates of sediments along a section (hereafter YJ) of the middle reaches of the Yarlung Zangbo River in the Qinghai-Tibetan Plateau. We also used the real-time quantitative PCR (qPCR) and high-throughput sequencing techniques to evaluate the abundance and composition of nosZI-containing microbial groups. The influences of physicochemical factors and denitrifier communities on potential denitrification rates were further revealed through structural equation modeling. The obtained results indicated that potential denitrification rates and N2O/(N2O + N2) ratio in the sediments along YJ section were greatly different. Moreover, the alpha diversity and composition of nosZI-containing microbial community in river sediments differed remarkably, mainly driven by the ammonia nitrogen (NH4+-N), organic matter (OM) and pH in sediments. The relative abundances of Zoogloeaceae, Oxalobacteraceae, Rhodospirillaceae and Bradyrhizobiaceae significantly differed among five groups (P < 0.05). Structural equation modeling further suggested that nitrogen nutrients directly influenced the potential denitrification rates, while total phosphorus (TP) showed indirect effects on potential denitrification rates through modulating denitrifier abundances and nosZI community. The abundance and composition of nosZI community were powerful predictors in regulating denitrification rates and N2O/(N2O + N2) ratio. Our findings highlight that the nosZI-containing microbial groups play a non-negligible role in nitrogen removal and N2O mitigation in high-elevation river sediments.

Contrasting Patterns of the Resident and Active Rhizosphere Bacterial Communities of Phragmites Australis.

Rhizosphere microbes play a key role in maintaining plant health and regulating biogeochemical cycles. The active bacterial community (ABC) in rhizosphere, as a small fraction of the rhizosphere resident bacterial community (RBC), has the potential to actively participate in nutrient cycling processes at the root-sediment interface. Here, we investigated the ABC and RBC within the rhizosphere of Phragmites australis (P. australis) subjected to different environmental conditions (i.e., seasons and flooding conditions) in Lake Taihu, China. Our results indicated that RBC exhibited significantly higher alpha diversity as well as lower beta diversity than ABC. The active ratios of 16S rRNA to 16S rDNA (also RNA/DNA) of the bacterial communities in summer and winter suggested a lower proportion of potential active taxa in the rhizosphere bacterial community during summer. Network analysis showed that negative correlations in each network were observed to dominate the species correlations between the rhizosphere and bulk sediment bacterial communities. Our results revealed that niche differentiation and seasonal variation played crucial roles in driving the assembly of ABC and RBC associated with the rhizospheres of P. australis. These findings broaden our knowledge about how rhizosphere bacterial communities respond to environmental variations through changing their diversity and composition.

Colloidal transport and deposition through dense vegetation.

The effectiveness of submerged synthetic aquatic vegetation on removal of colloids from flowing water was investigated to explore retention of particulate nonpoint source pollutants in aquatic systems. In colloid transport experiments, the deposition rate coefficient of colloids in dense vegetation is often taken as spatially constant. This assumption was tested by experiments and modeling aimed at quantifying changes in colloid retention with travel distance in submerged synthetic aquatic vegetation. Experiments were performed in a 10-m long, 0.6-m wide flume with a 5-cm water depth under different fluid velocities, initial colloid concentrations, and solution pH values. A model accounting for advection, dispersion and first-order kinetic deposition described the experimental data. The colloid deposition rate coefficient showed a power-law decrease with travel distance, and reached a steady state value before the end of the flume. Measured changes in colloid properties with transport distance (ζ potential and size) could not explain the observed decrease. While gravity was shown to contribute to the decrease, its impact was too weak to explain the decreasing power law trend, suggesting that processes operating in granular media to produce similar outcomes may also apply to submerged vegetation.

Some (Fish Might) Like It Hot: Habitat Quality and Fish Growth from Past to Future Climates.

Current expectation is that projected climate change may have adverse effects on fish habitats and survival. The analysis leading to these concerns is typically done at large scale with limited possibility to quantify the local biological response and compare with previous conditions. Our research investigated the effects of recorded climate conditions on Chinook salmon (Oncorhynchus tshawytscha) spawning and rearing habitats and growth responses to the local climate and compared those conditions to predicted responses to a climate change. The study site was a 7 km long reach of Bear Valley Creek, an important spawning stream for this US Endangered Species Act listed species, in the Pacific Northwest of United States. We used 2D numerical modeling supported by accurate, high-resolution survey data to calculate flow hydraulics at various discharges from base to bankfull flows. For past and future conditions, computed flow hydraulics were combined with habitat suitability indices (SI) to compute spawning and rearing habitat suitability. Information on habitat suitability along with fish density and stream water temperature informed a growth model to quantify the potential fish size, an index of survival rates and fitness. Our results indicate that yearly-averaged rearing habitat quality remains similar to historic, but the timing of high- and low-quality habitat periods shift within the calendar year. Future spawning habitat quality may be significantly reduced during the seasonal period to which Chinook have currently adapted their spawning behavior. The growth model indicates an increase in anticipated size of Chinook salmon for predicted future climate conditions due to water temperature increase. Consequently, future climate conditions may have a substantial negative impact on spawning and limited impact on rearing conditions due to flow reduction and thus quality and extent of available habitat. However, the expected warmer stream water temperatures may benefit rearing, because of increased fish size in these high elevation streams.

Dynamics and inhibition of MLL1 CXXC domain on DNA revealed by single-molecule quantification.

CpG islands recruit MLL1 via the CXXC domain to modulate chromatin structure and regulate gene expression. The amino acid motif of CXXC also plays a pivotal role in MLL1's structure and function and serves as a target for drug design. In addition, the CpG pattern in an island governs spatially dependent collaboration among CpGs in recruiting epigenetic enzymes. However, current studies using short DNA fragments cannot probe the dynamics of CXXC on long DNA with crowded CpG motifs. Here, we used single-molecule magnetic tweezers to examine the binding dynamics of MLL1's CXXC domain on a long DNA with a CpG island. The mechanical strand separation assay allows profiling of protein-DNA complexes and reports force-dependent unfolding times. Further design of a hairpin detector reveals the unfolding time of individual CXXC-CpG complexes. Finally, in a proof of concept we demonstrate the inhibiting effect of dimethyl fumarate on the CXXC-DNA complexes by measuring the dose response curve of the unfolding time. This demonstrates the potential feasibility of using single-molecule strand separation as a label-free detector in drug discovery and chemical biology.

Effects of shading levels on the composition and co-occurrence patterns of bacterioplankton and epibiotic bacterial communities of Cabomba caroliniana.

Epibiotic bacterial community colonized on the plant leaf plays important roles in promoting plant growth and nutrient absorption, but is sensitive to environmental changes. As one of the most important environmental factors affecting the growth of plants and photosynthetic microorganisms, light may affect the diversity, composition, and interactions of the epibiotic bacterial community. Submerged plants in the aquatic ecosystem may be more sensitive to light intensity variations compared to the terrestrial plants since they usually receive less light. However, the effects of light on the interactions between the submerged plants and their epibiotic microbial communities remain uncertain. Here we used the 16S rRNA gene high-throughput sequencing to investigate the diversity and composition of the bacterioplankton and epibiotic bacterial communities of the Cabomba caroliniana under four different shading levels. A total of 24 water and leaf samples were collected from the experimental microcosms near Lake Taihu. We found the epibiotic bacterial community possessed a higher diversity than that of the bacterioplankton community, although the alpha diversity of the bacterioplankton community was more susceptible to different levels of shading. SourceTracker analysis revealed that with the increase of shading, the colonization of bacterioplankton to epibiotic bacteria decreased. Network analysis showed that the bacterial community network at 50% shading level had the lowest modularity and highest clustering coefficient compared to the bacterial community networks of other shading levels. Our findings provided new understandings of the effects of different light intensities on the epibiotic bacterial communities of submerged macrophytes.

Holocene monsoon dynamics at Kunlun Pass on the northeastern Qinghai-Tibet Plateau.

Various proxy records have been used for the understanding of environmental and climate variations during the Holocene. Here, for the first time, we use meteoric 10Be isotope measurements performed on sediments from a drill core collected at the Kunlun Pass (KP) on the northeastern Qinghai-Tibet Plateau (NETP) to investigate hydroclimate changes during the Holocene. The 10Be flux suggests relative low levels in the Early Holocene, followed by a sharp increase to high values at around 4 ka BP (4 ka BP = 4000 years before present). Afterwards, the 10Be flux remains on a high level during the Late Holocene, but decreases slightly towards today. These 10Be deposition patterns are compared to moisture changes in regions dominated by the Indian Summer Monsoon (ISM), East Asian Summer Monsoon (EASM), and the Westerlies. Different from the gradual changes in monsoon patterns, the 10Be data reveal low levels during the Early Holocene until ~4 ka BP when an obvious increase is indicated and a relative high level continues to this day, which is relatively more in agreement with patterns of the Westerlies. This finding provides a new evidence for a shift in the dominant pattern of atmospheric circulation at the KP region from a more monsoonal one to one dominated by the Westerlies. Our results improve the understanding of non-stationary interactions and spatial relevance of the EASM, the ISM and the Westerlies on the Qinghai-Tibet Plateau.