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Soil moisture remarkably influences soil organic carbon (SOC) decomposition and is one of the key variables in ecological models influencing changes in soil carbon (C) storage. However, the mechanisms determining the impact of soil moisture on SOC decomposition in coastal wetlands are poorly understood. We collected and incubated soil samples from a coastal wetland of the Yellow River Delta, China, to investigate the response of SOC decomposition (the sum of CO2–C and CH4–C) to soil moisture. Soil samples were incubated at 20%, 60%, 100%, 140% and 180% water holding capacity (WHC), respectively. Compared to drought condition (20% WHC), moist (60% and 100% WHC) and flooding (140% and 180% WHC) conditions were observed with significantly higher SOC decomposition, explained by increased soil microbial biomass and altered soil physical parameters (pH and electronic conductivity (EC)). Excluding the effect of drought, we found decreased SOC decomposition with increased microbial biomass in flooding conditions compared to moist conditions. Structural equation modeling analysis showed that SOC decomposition and soil C storage were associated with changes in soil environment and soil microbial biomass resulted from soil moisture variation. This study highlights the importance of soil moisture in soil carbon dynamics, which is enlightening for the evaluation of soil C cycling with a decline of soil moisture under a warmer climate in coastal wetlands.

PurposeClimate warming and sea level rise have the potential to change the salt level of soil in tidal wetlands. And it is important to clarify the process and the mechanism of decomposition of soil organic carbon in a tidal wetland under varying salinities. The aim of this study was to evaluate the impacts of soil salinity on the decomposition rate of organic carbon (DROC) and dissolved organic carbon (DOC) in a tidal wetland.Materials and methodsTwo types of soil (surface soil in Suaeda salsa and bare tidal flat) were collected, air-dried, and homogenized. After adding different content of salt (0 g/L, 3 g/L, 6 g/L, 9 g/L, and 12 g/L), the soils were incubated for 28 days at stable room temperature (25 ± 2 °C) and added by deionized water to maintain the stability of soil moisture. The gases (CO2 and CH4) emission rates of each salt treatment were measured during 28-day incubation. DROC was determined by the sum of daily CO2-C emission rates and daily CH4-C emission rates in this study.Results and discussionSalt addition inhibited the process of gas emissions and DROC. Gases emission rates and DROC of two types of soil showed similar temporal trends, with distinctive drop in the beginning of experiment and no significant decrease followed. Significant difference of DOC among salt treatments was found in the bare tidal flat soil. Variations of partial correlation between DROC and soil salinity and DOC showed similar trends (e.g., in days 9–18, the positive effect of DOC on DROC was greatly promoted (R2 = 0.80, p < 0.001), and the negative effect of soil salinity was highly improved (R2 = 0.93, p < 0.001)). Soil properties, in particular DOC, may be primary factors accounting for the discrepancy of gases emission rates and DROC of two types of soil.ConclusionsIncreased soil salinity had a negative effect on DROC during 28-day incubation. The impact of soil salinity and DOC on DROC were varied in different phases of laboratory experiment (soil salinity generally had increasingly negative relationship with DROC, but DOC showed most significantly positive relationship in the middle stage of incubation). Both the formation and consumption of DOC may be valuable for more detail research regarding to decomposition of soil organic carbon.

Tidal salt marshes, as “blue carbon” ecosystems, play a critical role in mitigation of global climate change since their large soil organic carbon (SOC) pool. Drying-rewetting cycles induced by periodic tides have profound influence on soil carbon cycling in tidal salt marshes. However, the magnitude and mechaanism of the effects of drying-rewetting frequency on SOC loss in tidal salt marshes is still uncertain. Here, we conducted a mesocosm experiment to identify how drying-rewetting frequency changes alter the vertical (CO 2 and CH 4 ) and lateral (dissolved organic carbon) carbon losses of soils in a tidal salt marsh in the Yellow River Delta (YRD). We found that increasing soil moisture inhibited CO 2 emission but stimulated CH 4 emission in a tidal salt marsh. Soil dissolved organic carbon (DOC) was produced in the drying phase and rewetting lead to the loss of DOC. Soil moisture and salinity change induced by drying-rewetting cycles were the critical factors controlling vertical organic carbon loss in a tidal salt marsh. DOC had significant effects on CO 2 emissions. Changes of tidal action and drying-rewetting cycle induced by global change can affect the pathway of carbon loss in a tidal salt marsh.

Aims Climate change (extreme rainfall) and water management activities have led to variation in hydrological regimes, especially inundation, which may alter the function and structure of wetlands as well as wetland-atmosphere carbon (C) exchange. However, the degree to which different inundation depths (standing water depth above the soil surface) affect ecosystem CH 4 fluxes, ecosystem respiration (R eco ) and net ecosystem CO 2 exchange (NEE) remains uncertain in wetland ecosystems. Methods We conducted a field inundation depth manipulation experiment (no inundation, i.e. only natural precipitation; 0, water-saturated; 5, 10, 20, 30 and 40 cm inundation depth) in a freshwater wetland of the Yellow River Delta, China. The CH 4 fluxes, R eco and NEE were measured with a static chamber technique during the growing seasons (May–October) of 2018 and 2019. Results Inundation depth significantly increased plant shoot density, above-water level leaf area index (WLAI), above-water level plant shoot height (WHeight), aboveground and belowground biomass of the dominant grass Phragmites australis in both years. Meanwhile, inundation depth increased the CH 4 fluxes, R eco (except for 0 cm) and NEE compared to no inundation, which could be attributed partly to the increased plant productivity (shoot density, WLAI, WHeight, biomass). Additionally, the CH 4 fluxes, R eco or NEE exhibited parabolic responses to inundation depth. Furthermore, global warming potential (GWP) was significantly decreased under different inundation depths during the growing season, especially from 5 to 40 cm inundation depth in 2019. NEE was the largest contributor to the seasonal GWP, which indicates that the inundated wetlands are a net sink of C and have a cooling climate effect in the Yellow River Delta. Conclusions Inundation depth substantially affects the magnitude of CH 4 fluxes, R eco and NEE, which were correlated with altered plant traits in wetland ecosystems. Inundation depth could mitigate greenhouse gas emissions in the P. australis wetlands during the growing season. Inundation depth-induced ecosystem C exchange should be considered when estimating C sequestration capacity of wetlands due to climate change and water management activities, which will assist to accurately predict the impact of hydrological regimes on C cycles in future climate change scenarios.

Aims Climate change (extreme rainfall) and water management activities have led to variation in hydrological regimes, especially inundation, which may alter the function and structure of wetlands as well as wetland-atmosphere carbon (C) exchange. However, the degree to which different inundation depths (standing water depth above the soil surface) affect ecosystem CH.sub.4 fluxes, ecosystem respiration (R.sub.eco) and net ecosystem CO.sub.2 exchange (NEE) remains uncertain in wetland ecosystems. Methods We conducted a field inundation depth manipulation experiment (no inundation, i.e. only natural precipitation; 0, water-saturated; 5, 10, 20, 30 and 40 cm inundation depth) in a freshwater wetland of the Yellow River Delta, China. The CH.sub.4 fluxes, R.sub.eco and NEE were measured with a static chamber technique during the growing seasons (May-October) of 2018 and 2019. Results Inundation depth significantly increased plant shoot density, above-water level leaf area index (WLAI), above-water level plant shoot height (WHeight), aboveground and belowground biomass of the dominant grass Phragmites australis in both years. Meanwhile, inundation depth increased the CH.sub.4 fluxes, R.sub.eco (except for 0 cm) and NEE compared to no inundation, which could be attributed partly to the increased plant productivity (shoot density, WLAI, WHeight, biomass). Additionally, the CH.sub.4 fluxes, R.sub.eco or NEE exhibited parabolic responses to inundation depth. Furthermore, global warming potential (GWP) was significantly decreased under different inundation depths during the growing season, especially from 5 to 40 cm inundation depth in 2019. NEE was the largest contributor to the seasonal GWP, which indicates that the inundated wetlands are a net sink of C and have a cooling climate effect in the Yellow River Delta. Conclusions Inundation depth substantially affects the magnitude of CH.sub.4 fluxes, R.sub.eco and NEE, which were correlated with altered plant traits in wetland ecosystems. Inundation depth could mitigate greenhouse gas emissions in the P. australis wetlands during the growing season. Inundation depth-induced ecosystem C exchange should be considered when estimating C sequestration capacity of wetlands due to climate change and water management activities, which will assist to accurately predict the impact of hydrological regimes on C cycles in future climate change scenarios.

The ability of cells to maintain a constant level of cytoskeletal tension in response to external and internal disturbances is referred to as tensional homeostasis. It is essential for the normal physiological function of cells and tissues, and for protection against disease progression, including atherosclerosis and cancer. In previous studies, we defined tensional homeostasis as the ability of cells to maintain a consistent level of cytoskeletal tension with low temporal fluctuations. In those studies, we measured temporal fluctuations of cell-substrate traction forces in clusters of endothelial cells and of fibroblasts. We observed those temporal fluctuations to decrease with increasing cluster size in endothelial cells, but not in fibroblasts. We quantified temporal fluctuation, and thus homeostasis, through the coefficient of variation (CV) of the traction field; the lower the value of CV, the closer the cell is to the state of tensional homeostasis. This metric depends on correlation between individual traction forces. In this study, we analyzed the contribution of correlation between traction forces on traction field CV in clusters of endothelial cells and fibroblasts using experimental data that we had obtained previously. Results of our analysis showed that positive correlation between traction forces was detrimental to homeostasis, and that it was cell type-dependent.

Various types of mammalian cells exhibit the remarkable ability to adapt to external applied mechanical stresses and strains. This ability allows cells to maintain a stable endogenous mechanical tension at a preferred (homeostatic) level, which is of great importance for normal physiological function of cells and tissues, and for a protection from various diseases, including atherosclerosis and cancer. Previous studies have shown that the cell ability to maintain tensional homeostasis is cell type-dependent. For example, isolated endothelial cell cannot maintain tensional homeostasis, whereas clusters of endothelial cells can, more so the greater the size of the cluster is. On the other hand, cell clustering does not affect tensional homeostasis of fibroblasts and vascular smooth muscle cells. Underlying mechanisms for these behaviors of different cell types are largely unknown. In this study, we combined theoretical analysis and mathematical modeling to investigate several biophysical factors, including cluster shape and size, magnitude and dynamics of cellular traction forces, and applied shear forces that may influence tensional homeostasis in cells and clusters. We developed two-dimensional models of cells clusters of different shapes and sizes. To simulate temporal fluctuations of cell-extracellular matrix traction forces, we used a Monte Carlo approach. We also applied physical forces obtained from previous experimental measurements to the models. Results of the analysis and modeling revealed that cluster size, magnitude and dynamics of focal adhesion traction forces have a major influence on traction field variability, whereas the influence of cluster shape appears to be minor. The dynamics of traction forces seems to be related to cell types and it can explain why in certain cell types, such as endothelial cells, cell clustering promotes tensional homeostasis, whereas in other cell types, such as fibroblasts, clustering has virtually no effect on homeostasis. To further investigate mechanisms that may affect tensional homeostasis, we investigated the effect of applied steady shear stress on the traction field dynamics of endothelial cells and clusters. We applied steady shear stress to our two-dimensional model of cell clusters and then computed ensuing changes in the traction force variability. These simulations mimicked the effect of flow-induced shear stress on tensional homeostasis of endothelial cells and clusters. We found that under steady shear stress, temporal fluctuations of the traction field of endothelial cells became attenuated. This result agrees with the viewpoint that steady shear flow promotes tensional homeostasis in the endothelium. Together, results of this study advance our understanding of biophysical mechanisms that contribute to the cell ability to maintain tensional homeostasis. Furthermore, these results will help us to modify our current experimental procedures, as well as to design new experiments for our investigation of tensional homeostasis.

The ability of cells to maintain a constant level of their cytoskeletal tension in response to external and internal disturbances is referred to as tensional homeostasis. It is essential for the normal physiological function of cells and tissues, and for protection against disease progression, including atherosclerosis and cancer. It has been shown recently that some cell types, such as endothelial cells, can maintain tensional homeostasis only when they form multicellular clusters, whereas other cell types, such as fibroblasts, do not require clustering for tensional homeostasis. For example, measurements of cell-extracellular matrix traction forces have shown that temporal fluctuations of the traction field in clusters of endothelial cells become progressively attenuated with increasing number of cells in the cluster, whereas in fibroblasts cell clustering does not influence traction field variability. Mechanisms that are responsible for these observations are largely unknown. In this study, a theoretical analysis and mathematical modeling have been applied to analyze experimental data obtained previously from traction microscopy measurements in order to investigate possible physical mechanisms that influence temporal variability of the traction field in multicellular forms. The focus of the analysis is on the contribution of dynamics and distribution of focal adhesion traction forces in conjunction with geometrical shape and size of multicellular clusters. Results of the analysis revealed that cluster size, magnitude and temporal fluctuations of focal adhesion traction forces have a major influence on traction field variability, whereas the influence of cluster shape appears to be minor.

HighlightsThe PEDOT:PSS flexible electrodes with a unique CF3SO3H treatment exhibited high electrical characteristics and stability.An energy level tuning effect was induced to create a suitable work function.Flexible organic solar cells yielded a record-high efficiency of 16.61%, a high flexibility, and a good thermal stability.Nonfullerene organic solar cells (OSCs) have achieved breakthrough with pushing the efficiency exceeding 17%. While this shed light on OSC commercialization, high-performance flexible OSCs should be pursued through solution manufacturing. Herein, we report a solution-processed flexible OSC based on a transparent conducting PEDOT:PSS anode doped with trifluoromethanesulfonic acid (CF3SO3H). Through a low-concentration and low-temperature CF3SO3H doping, the conducting polymer anodes exhibited a main sheet resistance of 35 Ω sq−1 (minimum value: 32 Ω sq−1), a raised work function (≈ 5.0 eV), a superior wettability, and a high electrical stability. The high work function minimized the energy level mismatch among the anodes, hole-transporting layers and electron-donors of the active layers, thereby leading to an enhanced carrier extraction. The solution-processed flexible OSCs yielded a record-high efficiency of 16.41% (maximum value: 16.61%). Besides, the flexible OSCs afforded the 1000 cyclic bending tests at the radius of 1.5 mm and the long-time thermal treatments at 85 °C, demonstrating a high flexibility and a good thermal stability.

Flexible transparent electrodes (FTEs) with robust mechanical stability are crucial for the industrial application of flexible organic solar cells (OSCs). However, their production remains challenging owing to the difficulty in balancing the conductivity, transmittance, and adhesion of FTEs to substrates. Herein, we present the so-called “reinforced concrete” strategy which fine-tunes the structure of silver nanowires (AgNWs)-based FTEs with polydopamine (PDA) possessing good adhesion properties and moderate reducibility. The PDA reduces Ag + to form silver nanoparticles (AgNPs) which grow like “rivets” at the AgNW junction sites; PDA stabilizes the AgNW skeleton and improves the adhesion between the AgNWs and polyethylene ter-ephthalate (PET) substrate and interface layer. The obtained AgNW:PDA:AgNP FTE exhibits excellent optoelectronic properties and high mechanical stability. The resulting flexible OSCs exhibit 17.07% efficiency, high flexibility during 10,000 bending test cycles, and robust peeling stability. In addition, this “reinforced concrete”-like FTE provides great advantages for the production of large-area flexible OSCs, thereby paving a new way toward their commercial application.