Forest swamp ecosystems play an important role in the global carbon cycle, yet they are often overlooked. With global climate warming, it is inevitable that it will impact the relationship between soil microorganisms and organic matter. Dissolved organic matter (DOM) in the soil environment is extremely sensitive to environmental changes. Understanding the effects of climate change on DOM and microorganisms is crucial for assessing the stability of carbon (C) in forest swamp soils. Therefore, we conducted a 142-day laboratory warming incubation experiment (control: 10 °C, and warming: 20 °C) to investigate the response of forest swamp soil microbial and DOM properties to warming. Excitation-emission matrix (EEM) fluorescence spectroscopy was used to explore the changes in different material compositions of DOM over time at different incubation temperatures, and high-throughput sequencing was used to investigate the changes in soil bacteria. The DOM content (dissolved organic C, DOC) and the degree of humification index (HIX) increased with an increase in incubation time under warming conditions (p < 0.05). In contrast, microbial humic substances (C3) decreased with increasing time. Long-term warming has separated bacterial communities and gradually tightened the degree of connectivity between bacterial networks. The degree of soil humification (Mantel test r = 0.58, p < 0.01) and DOC (r = 0.21, p < 0.05) were the most critical indicators that changed the diversity of the bacterial community. Our findings suggest a degree of interaction between changes in forest swamp soil microbial communities and DOM under warming conditions. The results of this study contribute to our understanding of changes in DOM fluorescence indices in forest swamp soils under the influence of climate change and their associated microbial mechanisms.
The treatment of polluted water and sediment often costs too much and has little benefit. In this study, we proposed a novel design using dredged sediment, shrub willow (Salix spp.) and recirculating hand pumps for the restoration of polluted river water in Changchun city, China. Sediment was filled as a matrix for plant growth, shrub willow was transplanted for the absorption of nutrients, and ten hand-pumped water wells were built for recycling the polluted water. During the 5-month experimental period, the shrub willow growth and nutrient contents, sediment nutrient concentration and water quality were measured. The results showed that this pond system could effectively decrease the sediment pollutant levels, and its removal efficiencies of organic matter (OM), total nitrogen (TN) and total phosphorus (TP) could respectively reach as high as 11%, 10% and 26%. The dissolved oxygen (DO) content increased by more than 90% in August, and the chemical oxygen demand (COD) and total nitrogen (TN) content decreased by 44.93% and 19.82%, respectively. This means that the treatment pond could efficiently work toward the purification of polluted river water. The benefits and feasibility of this system application were also analyzed, and we found that it could be widely used for the treatment of polluted water and sediment in urban areas.
Understanding what controls wetland vegetation community composition is vital to conservation and biodiversity management. This study investigates the factors that affect wetland plant communities and distribution in the Tumen River Basin, Northeast China, an internationally important wetland for biodiversity conservation. We recorded floristic composition of herbaceous plants, soil properties, and microclimatic variables in 177, 1 × 1 m2 quadrats at 45 sites, located upstream (26), midstream (12), and downstream (7) of the Basin. We used TWINSPAN to define vegetation communities and canonical correspondence analysis (CCA) to examine the relationships between environmental and biological factors within the wetland plant communities. We recorded 100 plant species from 93 genera and 40 families in the upstream, 100 plant species from 57 genera and 31 families in the midstream, and 85 plant species from 76 genera and 38 families in the downstream. Higher species richness was recorded upstream of the River Basin. The plant communities and distribution were influenced by elevation, soil properties (total potassium, pH, and available phosphorus), and microclimate variables (surface temperature, precipitation, average temperature, sunshine hours, and relative humidity). More than any other factor, according to our results, elevation strongly influenced the structure of wetland plant communities. These findings support prevailing models describing the distribution of wetland plants along environmental gradients. The determination of the relationship between soil and plants is a useful way to better understand the ecosystem condition and can help manage the wetland ecosystem.
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