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Xi X.F.,Tongji University | Xi X.F.,Collaborative Innovation Center for Regional Environmental Quality | Wang L.,Tongji University | Wang L.,Collaborative Innovation Center for Regional Environmental Quality | And 13 more authors.
Journal of Environmental Sciences (China) | Year: 2014

Estuarine wetland, where freshwater mixes with salt water, comprises different regions (rivers and marine ecosystems) with significantly varying tidal salinities. Two sampling areas, ZXS and JS, were selected to investigate the effect of tidal salinity on soil respiration (SR). ZXS and JS were located in Zhongxia Shoal and Jiangyanan Shoal of Jiuduansha Wetland respectively, with similar elevation and plant species, but significantly different in salinity. The results showed that with almost identical plant biomass, the SR and soil microbial respiration (SMR) of the tidal wetland with lower salinity (JS) were significantly higher than those of the tidal wetland with higher salinity (ZXS) (p<. 0.05). However, unlike SMR and SR, the difference in the soil microbial biomass (SMB) was not significant (p>. 0.05) with the SMB of ZXS a little higher than that of JS. The higher SMR and SR of JS may be closely connected to the soil microbial community structures and amount of dominant bacteria. Abundant β- and γ-Proteobacteria and Actinobacteria in JS soil, which have strong heterotrophic metabolic capabilities, could be the main reason for higher SMR and SR, whereas a high number of ε-Proteobacteria in ZXS, some of which have carbon fixation ability, could be responsible for relatively lower carbon output. Path analysis indicated that soil salinity had the maximum negative total influencing coefficient with SMR among the various soil physical and chemical factors, suggesting that higher soil salinity, restricting highly heterotrophic bacteria, is the principle reason for lower SMR and SR in the ZXS. © 2014 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

Hu Y.,Tongji University | Hu Y.,Collaborative Innovation Center for Regional Environmental Quality | Wang L.,Tongji University | Wang L.,Collaborative Innovation Center for Regional Environmental Quality | And 9 more authors.
Science of the Total Environment | Year: 2016

Soils were collected from low tidal flats and high tidal flats of Shang shoal located upstream and Xia shoal located downstream with different tidal water qualities, in the Jiuduansha wetland of the Yangtze River estuary. Soil respiration (SR) in situ and soil abiotic and microbial characteristics were studied to clarify the respective differences in the effects of tidal water salinity and nutrient levels on SR and soil carbon sequestration in low and high tidal flats. In low tidal flats, higher total nitrogen (TN) and lower salinity in the tidal water of Shang shoal resulted in higher TN and lower salinity in its soils compared with Xia shoal. These would benefit β-Proteobacteria and Anaerolineae in Shang shoal soil, which might have higher heterotrophic microbial activities and thus soil microbial respiration and SR. In low tidal flats, where soil moisture was high and the major carbon input was active organic carbon from tidal water, increasing TN was a more important factor than salinity and obviously enhanced soil microbial heterotrophic activities, soil microbial respiration and SR. While, in high tidal flats, higher salinity in Xia shoal due to higher salinity in tidal water compared with Shang shoal benefited γ-Proteobacteria which might enhance autotrophic microbial activity, and was detrimental to β-Proteobacteria in Xia shoal soil. These might have led to lower soil microbial respiration and thus SR in Xia shoal compared with Shang shoal. In high tidal flats, where soil moisture was relatively lower and the major carbon input was plant biomass that was difficult to degrade, soil salinity was the major factor restraining microbial activities, soil microbial respiration and SR. © 2016 Elsevier B.V..

Tang Y.,Tongji University | Wang L.,Tongji University | Jia J.,Tongji University | Li Y.,Tongji University | And 3 more authors.
Ecological Engineering | Year: 2011

To clarify the effects of artifical disturbances on the soil microbial respiration (SMR) of existed tidal wetlands, the SMR of three typical areas in Chongming Dongtan and Jiuduansha of the Yangtze River Estuary, China, were evaluated. The causes of the differences in the SMR were also evaluated by analyzing the microbial activity factors and community structure, as well as the physical-chemical characteristics of the different wetland soils. The results showed that the SMR of the existed wetlands in the area of siltation promotion was significantly higher (P< 0.01) than that of the natural area. Different agricultural practices on the inner land also affected the SMR of the tidal wetlands. Overall, the results indicated that the difference in soil microbial characteristics between the artificially disturbed and natural tidal wetlands may be the primary cause of their different SMR. Path analysis indicated that the correlation between soil bacterial diversity and SMR were especially strong. Phylogenetic analysis showed that the bacterial microbial community structure in wetland soil that had been subject to artificial disturbance was changed due to the alteration of the soil physicochemical characteristics, and Pseudomonas sp., Bacillus sp., Uncultured Lactococcus sp. and Streptococcus sp., which have high heterotrophic metabolism or stress tolerance capability, became the dominant bacterial flora in the artificially disturbed wetland soil, ultimately strengthening the SMR. This may be the essential cause of the higher SMR in wetland soils that have been subjected to artificial disturbance, resulting in a low organic carbon accumulation capability. © 2011 Elsevier B.V.

Zhang Y.,Tongji University | Wang L.,Tongji University | Hu Y.,Tongji University | Xi X.,Tongji University | And 4 more authors.
PLoS ONE | Year: 2015

Undisturbed natural wetlands are important carbon sinks due to their low soil respiration. When compared with inland alpine wetlands, estuarine wetlands in densely populated areas are subjected to great pressure associated with environmental pollution. However, the effects of water pollution and eutrophication on soil respiration of estuarine and their mechanism have still not been thoroughly investigated. In this study, two representative zones of a tidal wetland located in the upstream and downstream were investigated to determine the effects of water organic pollution and eutrophication on soil respiration of estuarine wetlands and its mechanism. The results showed that eutrophication, which is a result of there being an excess of nutrients including nitrogen and phosphorus, and organic pollutants in the water near Shang shoal located upstream were higher than in downstream Xia shoal. Due to the absorption and interception function of shoals, there to be more nitrogen, phosphorus and organic matter in Shang shoal soil than in Xia shoal. Abundant nitrogen, phosphorus and organic carbon input to soil of Shang shoal promoted reproduction and growth of some highly heterotrophic metabolic microorganisms such as β-Proteobacteria, γ-Proteobacteria and Acidobacteria which is not conducive to carbon sequestration. These results imply that the performance of pollutant interception and purification function of estuarine wetlands may weaken their carbon sequestration function to some extent. © 2015 Zhang et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Hu Y.,Tongji University | Wang L.,Tongji University | Tang Y.,Tongji University | Li Y.,Tongji University | And 6 more authors.
Soil Biology and Biochemistry | Year: 2014

Wetlands are an important part of the global soil organic carbon pool and microorganisms play a pivotal role in carbon exchange between soils and atmosphere. Most wetland carbon studies have focused on boreal freshwater wetlands, especially peatlands. Less attention has been paid on the estuarine wetlands where variation in tide salinity can highly affect microbiology and carbon sequestration ability of the wetland soils. In this study, two representative estuarine wetlands in the Yangtze River estuary were chosen to determine the possible differences in microbial communities and activities between coastal (high salinity) and riparian (low salinity) zones of both wetlands. Over a 4-year period, the mean soil respiration of the coastal zones was significantly lower (P<0.05) than that of the riparian zones in each wetland. Soil respiration activities measured in laboratory as well as dehydrogenase activity were also lower in the coastal than in the riparian zones of the wetlands. The differences in the microbial activities could be a result of the differences in the microbial community structure. The riparian wetlands had e.g. more β-Proteobacteria with strong heterotrophic metabolic activity than the coastal wetlands. Soil salinity correlated negatively to the abundance of β-Proteobacteria and thus respiration. The riparian wetlands received approximately the same organic matter from plant biomass compared with the coastal wetlands but have lower soil carbon content than the coastal wetlands. This could be associated to the higher microbial decomposition capacity in soils with low salinity. © 2013 Elsevier Ltd.

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