Long-term sloping cultivation reduced core microbiota related to nitrogen fixation and soil hydrocarbon degradation.

Sloping farmland increases soil erosion, but little is known about how soil erosion impacts microbial structures and functions in sloping farmland. Using high-throughput sequencing, we conducted a six-year in-situ experiment with gradients of 0° (CK), 5° (S1), 10° (S2), and 15° (S3) to investigate the effects of sloping farmland on soil microbial diversities, compositions, and functions related to nitrogen and carbon resource acquisition. The results showed that the S1, S2, and S3 treatments significantly decreased SOM and NO3- levels by 33.0%∼47.3% and 37.0%∼49.6%, respectively, in comparison to the CK treatment. The S1, S2, and S3 treatments had similar impacts on diversities and compositions of bacterial and fungal communities. Moreover, the S1, S2, and S3 treatments had same enriched and depleted core microbiota. Long-term sloping cultivation filtered these core microbiota mainly by reducing SOM and NO3- and increasing AK and AP. Compared with the CK treatment, the S1, S2, and S3 treatments significantly reduced the relative abundances of potential functions of nitrogen fixation, hydrocarbon degradation, and fermentation by 46.9%∼54.5%, 74.7%∼83.5%, and 28.1%∼54.1%, respectively. Sloping treatments reduced functions related to nitrogen fixation and soil hydrocarbon degradation mainly because the loss of SOM reduced the relative abundances of core microbiota. Generally, long-term sloping cultivation reduced core microbiota related to nitrogen fixation and soil hydrocarbon degradation mainly due to the loss of SOM. Our findings provided implications for the management and reclamation of sloping farmland.

Sediment properties control riverine methane emissions: A case study of the Liao river in northern China.

River and stream sediments act as biogeochemical reactors for greenhouse gases, particularly methane. However, understanding how riverbed sediment properties influence river carbon emissions remains relatively unclear. The Liao River in northern China is a typical watershed with heterogeneous water and sediment sources, characterized by varying sediment properties. In this study, we surveyed CH4 and CO2 emissions from its mainstem and tributaries during flood and dry seasons. We found consistent seasonal patterns in CH4 and CO2 emissions, with peaks occurring during the flood season. The average CH4 and CO2 fluxes were 1.64 ± 1.80 mmol m-2 d-1 and 59.66 ± 44.60 mmol m-2 d-1, respectively. Notably, the percentage of sediment silt was significantly correlated with CH4 concentration and flux (R2 = 0.12-0.30, p < 0.05). Fine particles dominated the availability of sediment organic matter and redox conditions, which were related to riverine CH4 production and emissions. Structural equation modeling revealed that both grain size and the percentage of TOC (total organic carbon) directly influenced riverine CH4 and CO2 emissions. The organic content and redox conditions of the riverbed sediment collectively explained 65% of riverine CH4 emissions, while grain size composition indirectly controlled CH4 emissions by altering sediment substrate quality and redox conditions. In contrast, river CO2 emissions were only weakly dependent on anaerobic metabolism in riverbed sediments. These findings enhance our understanding of the sources and metabolic mechanisms of riverine CH4 and CO2 emissions and offer potential improvements for estimating carbon fluxes in regional or global riverine networks by considering riverbed sediment properties.

Land use and urbanization indirectly control riverine CH4 and CO2 emissions by altering nutrient input.

Urban rivers are recognized as significant sources of methane (CH4) and carbon dioxide (CO2) emissions. Despite this, the influence of land use and urbanization on carbon emissions across rural-urban rivers at the watershed scale has been insufficiently explored. This study utilized in-situ surveys of the Liao River in northern China to investigate the spatial and temporal variations of CH4 and CO2 emissions and their relationship with urbanization and its potential controlling factors. The findings revealed that CH4 emissions peaked in fall, whereas CO2 emissions were highest in summer. The average fluxes of CH4 and CO2 at the water-gas interface were 1387.22 ± 2474.98 µmol·m-2·d-1 and 52.78 ± 54.44 mmol·m-2·d-1, respectively. Water quality parameters accounted for 80.49 % of the total variation in CH4 and CO2 concentrations and fluxes. Structural equation modeling indicated that TN, TP, DTC, and conductivity had direct effects on riverine CH4 and CO2 emissions, with standardized direct effects of 0.50 and 0.49, respectively. Nutrient input emerged as the primary driver, increasing CH4 and CO2 concentrations and fluxes, particularly in urban-adjacent river sections likely receiving higher nutrient loads. This study underscores that land use and urbanization indirectly influence riverine CH4 and CO2 emissions by modifying nutrient inputs. Effective land use management and nutrient input control are recommended strategies to mitigate riverine CH4 and CO2 emissions.

Spatial distribution characteristics of denitrification functional genes and the environmental drivers in Liaohe estuary wetland.

Genes nirS, nirK, and nosZ are specific for the denitrification process, which is associated with greenhouse gas N2O emission. The abundances and diversities of community containing these three genes are usually used as a common index to reflect the denitrification process, and they would be affected by differences in environmental factors caused by changes from warm to cold conditions. The quantification of denitrification in natural wetlands is complex, and straightforward identification of spatial distribution and drivers affecting the process is still developing. In this study, the bacterial communities, gene diversities, and relative abundances involved in denitrification were investigated in Liaohe Estuary Wetland. We analyzed the relative abundances, diversities, and communities of bacteria containing the three genes at warm and cold conditions using Illumina MiSeq sequencing and detected the potential environmental factors influencing their distribution by using a random forest algorithm. There are great differences in the community composition of the bacteria containing genes nirS, nirK, and nosZ. All the abundant taxa of nirS and nirK communities belonged to phylum Proteobacteria. Compared with the community composition of bacteria containing nirS and nirK, the community of bacteria containing nosZ is more diverse, and the subdivision taxa of phylum Euryarchaeota was also abundant in the community containing nosZ. The distribution characteristics of the relative abundance of nirS and nirK showed obvious differences both at warm and cold climate conditions. The oxidation-reduction potential, nitrite nitrogen, and salinity were detected as potential variables that might explain the diversity of nirS. The total nitrogen and nitrite nitrogen were the important variables for predicting the relative abundance of nirS at warm climate condition, while oxidation-reduction potential and pH contributed to the diversity of nirS at cold condition. The bulk density of sediment was detected as a potential variable affecting the relative abundance of nirK at warm and cold conditions, and diversity of nirK at warm condition, while nitrite nitrogen was detected as an important environmental factor for predicting the diversity of nirK at cold condition. Overall, our results show that the key environmental factors, which affect the relative abundance, diversity, and community of bacteria containing the functional denitrification genes, are not exactly the same, and the diversities of nirS, nirK, and nosZ have a higher environmental sensitivity than their relative abundances.

Optimization of landscape pattern in the main river basin of Liao River in China based on ecological network.

As a main stream method of landscape pattern optimization, the ecological network plays an important role in maintaining ecosystem stability, improving landscape connectivity, and promoting landscape sustainable development. Based on landscape connectivity index and morphological spatial pattern analysis (MSPA), a comprehensive evaluation system of ecological patches was constructed in the main river basin of Liao River, and ecological sources were extracted. According to the habitat characteristics of the study area, the ecological cumulative resistance surface was constructed, and the ecological corridors and nodes were extracted by the minimum cumulative resistance (MCR) model. The ecological network of the study area was comprehensively evaluated by using the network analysis method, and the importance level of the ecological corridor was divided by the gravity model, so as to put forward the optimization suggestions of the landscape pattern based on the ecological network. The results showed that the ecological network in the main river basin of Liao River is composed of 20 ecological sources, 108 ecological corridors, and 72 ecological nodes, with the distribution characteristics of dense east and sparse west. The main landscape components are cropland and woodland. The closure degree, line point rate, and connectivity index of the ecological network are 0.27, 1.50, and 0.51, respectively, and the cost ratio is 0.23. In the optimization of landscape pattern, priority should be given to the restoration of primary ecological sources and ecological corridors, followed by the ecological construction of secondary and tertiary ecological sources and ecological corridors, the rational use of engineering technology for habitat remodeling, and the adoption of the "patch-corridor-substrate" model to improve the stability and landscape connectivity of the regional ecosystem. The construction of ecological network in the main river basin of Liao River is of great significance to regional ecological security and biodiversity conservation, and provides data support for optimizing the landscape pattern of the basin and promoting regional sustainable development.

Analysis of driving forces on wetland ecosystem services value change: A case in Northeast China.

Social development and changes in natural conditions have seriously affected the ecosystem services value (ESV) of wetlands. It is important for social sustainable development and human welfare to identify and evaluate the driving factors that lead to changes in ESVs. Based on the land use data of Northeast China (NEC) from 1980 to 2015, the Emergy method and Logarithmic Mean Divisia Index decomposition analysis (LMDI) was applied to calculate the main ESVs of wetlands and clarify the contributions of different driving factors to ESVs changes. The results showed that the value of provision services (ESVp) and cultural services (ESVc) increased significantly, while the value of regulation services (ESVr) and supporting services (ESVs) decreased. Overall, the ESV of wetlands increased by 7.31 × 1022 solar emjoules (sej), with a growth rate of 127.73%. The most obvious factors driving ESV changes were the wetland supporting factor (△GA), per capita GDP factor (△PG), and protection investment factor (△T). The combined average contribution weight of the three factors was above 50%. From the perspective of driving force category, social-economic development effect had the greatest impact on ESVs, with average contribution weights ranging from 45.18% to 54.59%, followed by human activity effect, average contribution weights ranging from 33.45% to 40.14%, and the influence of natural factor effect was relatively small. The research results would provide a reference for protecting and improving the ESV of the wetland ecosystem.

Ensemble warming projections in Germany's largest drinking water reservoir and potential adaptation strategies.

The thermal structure in reservoirs affects the development of aquatic ecosystems, and can be substantially influenced by climate change and management strategies. We applied a two-dimensional hydrodynamic model to explore the response of the thermal structure in Germany's largest drinking water reservoir, Rappbode Reservoir, to future climate projections and different water withdrawal strategies. We used projections for representative concentration pathways (RCP) 2.6, 6.0 and 8.5 from an ensemble of 4 different global climate models. Simulation results showed that epilimnetic water temperatures in the reservoir strongly increased under all three climate scenarios. Hypolimnetic temperatures remained rather constant under RCP 2.6 and RCP 6.0 but increased markedly under RCP 8.5. Under the intense warming in RCP 8.5, hypolimnion temperatures were projected to rise from 5 °C to 8 °C by the end of the century. Stratification in the reservoir was projected to be more stable under RCP 6.0 and RCP 8.5, but did not show significant changes under RCP 2.6. Similar results were found with respect to the light intensity within the mixed-layer. Moreover, the results suggested that surface withdrawal can be an effective adaptation strategy under strong climate warming (RCP 8.5) to reduce surface warming and avoid hypolimnetic warming. This study documents how global scale climate projections can be translated into site-specific climate impacts to derive adaptation strategies for reservoir operation. Moreover, our results illustrate that the most intense warming scenario, i.e. RCP 8.5, demands far-reaching climate adaptation while the mitigation scenario (RCP 2.6) does not require adaptation of reservoir management before 2100.

The distribution and enrichment characteristics of copper in soil and Phragmites australis of Liao River estuary wetland.

The aims of the present investigation were to reveal the distribution and enrichment characteristics of copper in soil and Phragmites australis of Liao River estuary wetland. The concentrations of copper in root, stem, leaf, and ear of Phragmites australis as well as in soil were determined to study the absorption capacity of copper by wild Phragmites australis of Liao River estuary wetland. The study was carried out at test pool of the Shenyang Agricultural University, and the experimental materials (soil, irrigating water and Phragmites australis) were derived from Liao River estuary wetland. The concentrations of copper in soil and Phragmites australis were 16.4441 to 49.0209 mg/kg and 0.8621 to 89.5524 mg/kg, respectively. The results indicated that the enrichment coefficients of copper in different tissues of Phragmites australis changed with the growth of Phragmites australis. The results revealed that the enrichment coefficients of copper in the whole Phragmites australis were greater than 1 at each growing stage of the Phragmites australis. The results also showed that the transfer coefficients of Phragmites australis to copper changed with the growth of Phragmites australis. The results revealed that the Phragmites australis had a good removal effect on copper from soil and had some characteristics of copper hyperaccumulator.

The average concentration function of dissolved copper in Hun River, Liaoning province, Northeastern China.

Water samples were collected from Hun River to research the change in the concentration of dissolved copper and its distribution as well as accumulation during the dry season in 2013. The mean concentrations of dissolved copper in Hun River were 0.1057-0.1533 mg/l during the dry season. The results indicated that the most severe dissolved copper pollution were associated with the mining area, industrial area, and living area along the Hun River. The results also indicated that controlling the sources of copper pollution effectively reduced the concentration of dissolved copper in Hun River. The concentration function about time and spatial coordinate, average concentration function about time coordinate, average concentration function about spatial coordinate, and bounded mean oscillation space were used to evaluate the extent of copper pollution in Hun River. The error function, quartiles, and curve fitting tool were performed to determine the stations with high concentration of dissolved copper in Hun River. We furthermore obtained the upper and lower bounds of the error between two kinds of bounded mean oscillation spaces to explore the migration of copper pollution in Hun River. The results of the average concentration function and bounded mean oscillation space revealed that the long-term control measures of copper pollution and short-term control measures of copper pollution, the control of copper pollution in large watershed, and the control of copper pollution in small watershed in Hun River should be combined with each other. The strict policy and pollution control strategy should be implemented to ensure that the water of the Hun River meets the natural environment standard for the growth of aquatic life and human.

Heavy metal concentrations in water and soil along the Hun River, Liaoning, China.

Water and soil samples were collected along the Hun River to study the concentrations of Cr, Cu and Zn during the dry season, medium season and wet season in 2013. The concentrations of Cr, Cu, and Zn in Hun River were 0.0010 to 0.1298, 0.0057 to 0.1533 and 0.0162 to 0.5004 mg/L, respectively. The concentrations of Cr, Cu, and Zn in soil from around the Dahuofang reservoir were 0.0033 to 0.2149, 0.0054 to 0.2218 and 0.0135 to 0.3544 mg/g, respectively. The results indicated that the concentrations of Cr, Cu and Zn in water from the Hun River and soil from around the Dahuofang reservoir were significantly different at different sample stations and seasons. The pollution indexes of Cr, Cu and Zn in water and soil along the Hun River were calculated using principal component analysis in order to enact future measures against heavy metal pollution. According to the pollution characteristics of heavy metals along the Hun River, a treatment strategy was formulated to provide a scientific basis for the prevention and control of heavy metal pollution along the Hun River.

Identifying and Classifying Pollution Hotspots to Guide Watershed Management in a Large Multiuse Watershed.

In many locations around the globe, large reservoir sustainability is threatened by land use change and direct pollution loading from the upstream watershed. However, the size and complexity of upstream basins makes the planning and implementation of watershed-scale pollution management a challenge. In this study, we established an evaluation system based on 17 factors, representing the potential point and non-point source pollutants and the environmental carrying capacity which are likely to affect the water quality in the Dahuofang Reservoir and watershed in northeastern China. We used entropy methods to rank 118 subwatersheds by their potential pollution threat and clustered subwatersheds according to the potential pollution type. Combining ranking and clustering analyses allowed us to suggest specific areas for prioritized watershed management (in particular, two subwatersheds with the greatest pollution potential) and to recommend the conservation of current practices in other less vulnerable locations (91 small watersheds with low pollution potential). Finally, we identified the factors most likely to influence the water quality of each of the 118 subwatersheds and suggested adaptive control measures for each location. These results provide a scientific basis for improving the watershed management and sustainability of the Dahuofang reservoir and a framework for identifying threats and prioritizing the management of watersheds of large reservoirs around the world.