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In order to investigate the properties of metal to metal charge transfer (MMCT) influenced by the relative energy level between the bridging unit and the terminal unit, two groups of heterotrimetallic cyanido–metal-bridged complexes, trans-[Cp(dppe)Fe-CN-Ru(MeOpy)4-NC-Fe(dppe)Cp][X]n (1[X]n; n = 2, 3, or 4; X = PF6 or BF4) (Cp = cyclopentadiene, dppe = 1,2-bis(diphenylphosphino)ethane, MeOpy = 4-methoxypyridine) and [Cp*(dppe)Fe-CN-Ru(MeOpy)4-NC-Fe(dppe)Cp*] [X]n (2[X]n; Cp* = 1,2,3,4,5-pentamethylcyclopentadiene; n = 2, 3, or 4; X = PF6 or BF4) were synthesized and fully characterized. The crystallography data suggest different oxidation sites in the ground state for one-electron oxidation products 13+ and 23+, and the electrochemical and Mössbauer spectra suggest that in the one-electron oxidation compounds 13+, the charge is delocalized all along the trimetal backbone Fe–Ru–Fe, while in 23+, the charge is rather delocalized between the two metal parts Fe–Ru. Further oxidation of N3+ gives N4+ (N = 1 or 2), during which a spin transfer towards the terminal units is observed in both series. [ABSTRACT FROM AUTHOR]

Controlling drainage during the growth stage is one of the means to provide suitable water and fertilizer conditions for crops, alleviate environmental pollution, and increase crop yield. Therefore, in this study, we studied three drainage treatments: free drainage (FD) and growth-stage subsurface controlled drainage (CD) at depths of 40 cm (CWT1) and 70 cm (CWT2). We used the HYDRUS-2D model to simulate the dynamic changes of NO3-N in the 0–100 cm soil layer as well as NO3-N uptake by crops, leaching after irrigation and fertilization, and loss through subsurface pipes in 2020 (model calibration period) and 2021 (model validation period). The degree of agreement between the simulated and measured values was high, indicating a high simulation accuracy. CD increased the soil NO3-N content and crop NO3-N uptake, and decreased NO3-N leaching and loss. We observed significant differences in the soil NO3-N content after irrigation at the budding stage of oilseed sunflower between CD and FD, with the largest difference seen for the 0–40 cm soil layer. CD increased crop yield, and the average oilseed sunflower yield of the CWT1 and CWT2 treatments increased by 4.52% and 3.04% relative to the FD treatment (p < 0.05). CD also enhanced nitrogen use efficiency. In moderately salinized soil, CD at 40 cm (CWT1) reduced the nutrient difference in vertical and horizontal directions while retaining water and fertilizer. CWT1 stabilized the groundwater depth, reduced the hydraulic gradient of groundwater runoff, and decreased the drainage flow rate. The NO3-N leaching and loss dropped, which promoted crop nitrogen uptake and utilization, improved nitrogen use efficiency, reduced nitrogen loss, and had a positive effect on protecting the soil and water environment. The results demonstrate that CD is a suitable drainage method for the experimental area. [ABSTRACT FROM AUTHOR]

Dissolved organic carbon (DOC) is an important function of soil organic carbon and sensitive to environmental disturbance. Few studies have explored the variations in soil DOC dynamics and effects on soil physicochemical properties following prescribed burnings. In this study, Pinus koraiensis plantation forests in Northeast China were selected and subjected to prescribed burning in early November 2018. Soil DOC and different soil physicochemical and biological properties in the 0–10 cm and 10–20 cm soil layers were sampled six times within two years after a prescribed burning. In this study, some soil physicochemical (SOC, TN, and ST) and microbial biomass properties (MBC) recovered within two years after a prescribed burning. Compared to the unburned control stands, the post-fire soil DOC concentrations in the upper and lower soil layers increased by 16% and 12%, respectively. Soil DOC concentrations varied with sampling time, and peaked one year after the prescribed burning. Our results showed that soil chemical properties (NH 4 +-N and pH) rather than biological properties (microbial biomass) were the main driving factors for changes in post-fire soil DOC concentrations. Current study provides an important reference for post-fire and seasonal soil C cycling in plantation forests of Northeast China. • Soil DOC concentrations peaked one year after the prescribed fire. • Increased soil DOC after two years of prescribed burning. • Soil NH 4 +-N and pH were the main drivers for changes in post-fire soil DOC. [ABSTRACT FROM AUTHOR]

Soil organic carbon (SOC) is an important component of the ecosystem carbon pool, and fire is one of the important disturbances in forest ecosystems. With global warming, there has been a gradual increase in boreal forest fires, which has a nonnegligible impact on the SOC dynamics in forests. The CENTURY model was employed in our study to simulate the changes in SOC stocks in boreal forests of the Great Xing'an Mountains, China under different fire severity conditions. Fire severity was represented by the metric of difference normalized burn ratio (dNBR) derived from 30-m Landsat-8 imageries. Changes in forest SOC stocks following fire disturbance were predicted under four future Representative Concentration Pathway (RCP) scenarios (RCP2.6, RCP4.5, RCP6.0, and RCP8.5). We found that the CENTURY model had good results in simulating the SOC stocks in the postfire of China's boreal forests. Forest SOC dynamics responded differently to fire severities and the larger SOC loss was associated with increasing fire severity. Importantly, a feedback mechanism was found between climate change and SOC stocks, which reduces SOC stocks with increasing temperatures. High-severity forest fires tended to cause serious damage to the SOC pool and delay forest SOC recovery time; after such events, forest SOC stocks cannot be fully recovered to the prefire levels (6.74% loss). In addition, higher CO2 emissions and warmer temperatures significantly affected the recovery of SOC stocks after fire disturbance, resulting in larger SOC losses. Overall, we projected losses of 10.14%, 12.06%, 12.41%, and 15.70% of SOC stocks after high-severity fires in four RCP scenarios, respectively. Our findings emphasize the importance of fire disturbance and climate change on future dynamics of SOC stocks in China's boreal forests, providing a scientific basis for future boreal forest management and fire management. [ABSTRACT FROM AUTHOR]

Controlled drainage is an important measure to improve salinized soil in arid and semi-arid areas. However, free drainage during the growth period leads to excessive water loss, and crops lack water in the later growth period, resulting in crop yield reduction. Therefore, in arid and semi-arid areas, soil salts should be leached during the non-growing period, and drainage should be controlled during the growing period to ensure that crops have adequate water absorption and utilization, improve soil water availability for optimal water supply and salinity control. In this study, through field trials in 2020 and 2021, 3 treatments were set up. The depth of free drainage (FD) is common subsurface pipe drainage and the controlled drainage in the growth period were 40 cm (CWT1) and 70 cm (CWT2), respectively, and the drainage depth in the non-growing period was 100 cm. Using the HYDRUS-2D model to simulate the dynamic changes of soil water and salts in the 0–100 cm range, the calibration and validation of the HYDRUS-2D model were performed using the measured soil water and salt content values of 2020 and 2021. The results showed that the simulated soil water and salt contents agreed well with the measured contents. Controlled Drainage (CD) is a new agricultural drainage management practice that involves periodically increasing the outlet elevation of subsurface drainage pipes, CD significantly increased the water content of the 0–100 cm soil layer—especially at 0–40 cm depth—after growth stage irrigation. Under FD, CWT1, and CWT2, the 2-year mean soil water content of the 0–40 cm soil layer after growth stage irrigation in 2020 and 2021 was respectively 0.263, 0.278, and 0.267 cm3 cm−3, with the latter two values being higher by 5.70 % and 1.52 % than the former value, respectively. Soil water uptake by sunflower after irrigation mainly occurred in the 0–40 cm soil layer, which contributed 55.88–78.51 % of the total soil water uptake. Soil re-salinization occurred in the late growth stage (the flowering stage) under different treatments, with a mean re-salinization rate (relative to the period before spring irrigation) of 29.29 %, 33.48 %, and 30.34 % under FD, CWT1, and CWT2, respectively. Although the re-salinization rate was relatively high under CWT1 and CWT2, it had a low effect on crop growth as well as crop yield. HYDRUS-2D simulation was performed to compare different drain depths in the growth stage in order to determine the optimal drain depth for sunflower in moderately saline soils. To this end, the following metrics were considered for the main root zone (0–40 cm): soil water content, soil salt content, soil de-salination rate during spring irrigation, and soil re-salination rate in the late growth stage. Reduce soil salt content during spring irrigation, increase soil water content after irrigation during growth period, and minimize soil salt return rate in late growth stage, that is, to provide suitable water conditions for crop growth and minimize salt stress. The optimal drain depth during the growth stage was ultimately determined to be 50 cm. • The HYDRUS-2D model was calibrated and validated using 2-year experimental data. • Different (free, controlled) drainage treatments affect soil water-salt dynamics. • Controlled drainage can significantly increase soil water content from 0 to 40 cm. • Controlled drainage treatment of soil salt return is relatively serious. • Controlled drainage treatment can improve crop yield and water productivity. [ABSTRACT FROM AUTHOR]

In this work, we report a pair of asymmetric cyanido-bridged binuclear Ru-CN-Ru-Cl complexes, [Cp*(dppe)RuII-CN-RuII/III(bpy)2Cl]n+[BF4]n (1n+[BF4]n, n = 1, 2; Cp* = 1,2,3,4,5-pentamethylcyclopentadiene, dppe = 1,2-bis(diphenylphosphino)ethane, bpy = 2,20-bipyridine), and 12+ with RuII-CN-RuIII is the one-electron oxidized product of 1+ with RuII-CN-RuII. Both the complexes are well characterized. The investigations indicate that 12+ is a completely delocalized (Class III) mixed-valence complex, confirmed by theoretical calculations. To the best our knowledge, 12+ is the first example of the structurally characterized asymmetric cyanido-bridged Class III mixed-valence complex. [ABSTRACT FROM AUTHOR]

Soil salinization affects more than 25% of land globally. Subsurface pipe drainage is known for its effectiveness in improving saline–alkali land. The red clay layer (RCL) hinders soil improvement in the Hetao Irrigation District of Inner Mongolia, China. The soil water and salt migration rules at different buried depths and RCL were studied based on the field subsurface pipe drainage test and simulation using the DRAINMOD-S model (Version 6.1). The following implications can be drawn from the results: (1) Although the RCL affected the accuracy of the model, the calibrated statistical results met the application requirements, and the DRAINMOD-S model can be used to analyze subsurface pipe drainage under different distribution conditions of the RCL. (2) The RCL can reduce the drainage efficiency of the subsurface pipe, specifically when the distribution is shallow. (3) The soil desalting rate increased with an increase in the buried depth of the subsurface pipe. The desalination effect of shallow soil was better than that of deep soil. The RCL reduced the drainage and salt removal efficiency of the subsurface pipe. Burying the subsurface pipe as far above the RCL as possible should be considered. Thus, it is feasible to apply the DRAINMOD-S model to relevant studies. [ABSTRACT FROM AUTHOR]

This paper aims to put forward an emission flux method for calculating the amount of CO2 carbon emission in coalfield fires. In this method, the area of coalfield fires is an essential modeling parameter. In order to obtain this basic data, the thermal infrared remote sensing data on January 24,2011 obtained by Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) were used to inverse the surface temperature of fires in Wuda coalfield, Inner Mongolia, China. Then a Self-Adaptive Gradient Based Thresholding method was applied to segment the thermal infrared image by a threshold, the mean temperature of the extreme gradient points for the temperature image. This threshold was applied to delineate the coalfield fire areas. The total area of coalfield fires in Wuda coal field was estimated as 239.6 hm² in January 2011. Through the emission flux method and basic parameters generated by the density model of the fissures in the coalfield, the amount of CO2 carbon emissions by coalfield fires in Wuda coalfield was estimated and the result shows that the annual equivalent carbon dioxide emission in Wuda coalfield fires is up to 37. 9 x 104 tons. [ABSTRACT FROM AUTHOR]

The occurrence of shallow saline water tables in arid zones provides for groundwater-fed natural vegetation and for a substantial amount of irrigated crops' water needs. This is the case of the Hetao plain, upper Yellow River Basin, Inner Mongolia, China, where one of the major irrigation systems of China and the World is installed. As reviewed, numerous irrigation and water management studies have been developed in Hetao and the upstream irrigated plain of Yinchuan, Ningxia. These studies have demonstrated the need for controlling salts through the autumn irrigation and the appropriate irrigation methods and scheduling. Moreover, studies evidenced the need for adopting irrigation schedules that consider groundwater contribution during the crop cycle but most of these studies were empirical, resulting difficult to transfer results. When models adopted were mechanistic, they are difficult to use for irrigation scheduling purposes comparatively with soil water balance (SWB) models. Thus, the current study used two sets of five static water table lysimeters cropped with maize and having water table depths (WTD) fixed between 0.85 and 2.25 m. It was therefore possible to observe the daily capillary rise fluxes from the water table, the dynamics of water and salts and to calibrate the SWB model SIMDualKc. Results show that the average electrical conductivity of the saturated extract of the soil ranged from 3.10 to 4.69 dS m−1 with the higher values observed when WTD was smaller, while the electrical conductivity of irrigation water ranged 1.73–1.87 dS m−1. Results also show that shallower WTD required less irrigation water but caused higher salinity impacts on crop growth and yields. Thus, the best WTD were around 1.75–2.00 m when basin irrigation was adopted in 2017 and 2018. In these crop seasons, the simulated groundwater contribution to actual crop evapotranspiration (ET c act) was up to 37% in the lysimeters having a shallow WTD (1.25 m), while in the lysimeters with deeper WTD (2.00–2.25 m) it was about 11% of the ET c act. Contrastingly, in 2019, when maize was not irrigated, the average groundwater contribution represented 73% and 49% of ET c act in the lysimeters with shallow and deep WTD, respectively. Results were obtained when a large leaching autumn irrigation (200 mm) was performed. Those experiments showed that, solutions for using basin flooding irrigation are ready but still require that irrigation scheduling is adjusted to provide for appropriate use of the saline groundwater contribution, which may be performed with the model SIMDualKc, as demonstrated by the high goodness-of-fit indicators used to evaluate the referred simulations. • Soil water contents and capillary rise from a saline shallow water table (WT) were measured using static WT lysimeters. • Observations were used to calibrate/validate the SIMDualKc model. • Impacts of WT depth on crop ET, soil salinity, maize growth and yield were assessed. • Best results for crop transpiration and yield were obtained for the WT depth at 2 m. • Groundwater contribution with shallower WT promoted salinity build-up in the rootzone. [ABSTRACT FROM AUTHOR]

• Different responses of soil respiration (R s) components to forest fire. • Soil heterotrophic respiration (R h) increased significantly in burned plots (24%). • Soil autotrophic respiration (R a) decreased significantly in burned plots (66%). • The ratio of R h to R s significantly increased in burned plots (39%). • Fire led to R s C efflux increased during the spring freeze–thaw cycles period (28%). • MBC (microbial biomass carbon) was the dominant biotic driver of R s in burned plots. Fire plays a critical part in regulating soil carbon (C) budgets in forest ecosystems. However, few studies have focused on the effects of fire on soil respiration (R s) and its heterotrophic (R h) and autotrophic (R a) components. In this study, we examined the response of R s , R h , and R a to fire and the driving factors that affect R s after a fire disturbance in a Dahurian larch (Larix gmelinii) forest in northeastern China. Fire disturbance significantly increased R h by approximately 24% and significantly reduced R a by approximately 66% in burned plots compared to unburned plots. The ratio of R h to R s significantly increased from 0.57 in the unburned plots to 0.79 in the burned plots. Fire disturbance also led to cumulative R s C efflux increasing by approximately 10% and 28% during the growing season and the period of spring freeze–thaw cycles (FTC) in the burned plots. Furthermore, using structural equation modelling, we showed that T 5 (soil temperature at 5 cm depth) was the main abiotic factor affecting R s in both unburned and burned plots. Fine root biomass (FR) was the dominant biotic driver of R s in the control plots, whereas microbial biomass carbon (MBC) was the dominant biotic driver of R s in burned plots. Our findings demonstrated a significant discrepancy in the response of R s components to fire disturbance. Forest fires can cause considerable losses of soil C in a cold temperate forest ecosystem, which suggests that proactive management of forest regeneration should be carried out after forest fire disturbances. [ABSTRACT FROM AUTHOR]

By using organic geochemistry and organic petrology methods comprehensively, the contrastive study of gas measured data of coal bed methane and gas hydrate samples from Muri coalfield in Qilian Mountain permafrost area was carried out,the comparability and similarity of the both were revealed. Based on the hydrocarbon source rock evaluation and geological conditions analysis, the hydrocarbon gas sources of natural gas hydrate was discussed, which was considered that the gas hydrate in Muri coalfield belongs to the mixed gas genesis with dominant coal-typed gas, Jurassic coal seam, carbon mudstone and oil shale are major gas source rocks, and the Carboniferous dark marlite, the Lower Permian dark limestone and the Upper Triassic dark mudstone are minor gas source rocks. Gas hydrate prospecting target in Qinghai-Tibetan Plateau permafrost should concentrate on the middle metamorphic phase (condensate-wet gas zone) of coal distribution area, the western part of Muri coalfield, Wuli coal-bearing region in the southern Qinghai and Tumen coal-bearing region in the northern Tibetan are the optimum target areas. [ABSTRACT FROM AUTHOR]