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A 3-year field experiment was conducted to investigate the effects of different organic fertilization strategies for rice–wheat annual rotation systems on net global warming potential (net GWP) and greenhouse gas intensity (GHGI) by incorporating methane, nitrous oxide emissions, the changes in soil organic carbon (SOC) derived from the net ecosystem carbon budget (NECB), and the CO 2 equivalent emissions from manure and chemical nitrogen (N) fertilizer manufacturing. Six fertilization strategies were studied, including control (CK), N fertilizer (CF), pig manure compost + N fertilizer (MC), straw + N fertilizer (SC), straw + pig manure compost + N fertilizer (SM), and straw + straw-decomposing inoculant + N fertilizer (SI). The results indicated that the application of organic amendments did not change the seasonal pattern of GHG emissions but significantly affected their seasonal quantities. Averaged over the 3 cycles, the annual SOC sequestration rates contributed significantly to the net GWPs and were estimated to be 1.01 t C ha −1  yr −1 for the control and 1.13–1.27 t C ha −1  yr −1 for the fertilized plots. Compared to CF, the MC strategy significantly increased SOC while had similar size of net GWP and GHGI, thus deserving recommendation regarding sustainable soil productivity and GHGs mitigations. However, the other proposed organic strategies of SC, SM, and SI significantly increased net GWP and GHGI as well as SOC thus requiring further researches for GHGs mitigations. Therefore, we recommend that the application of manure substituting half chemical fertilizer be an effective strategy while straw returning in any currently studied strategies should be re-examined in the rice–wheat annual rotation system. [ABSTRACT FROM AUTHOR]

The mangrove restoration wetland project in Jinjiang Estuary, Fujian Province, was started in April 2014, and the wetland was restored using vegetation restoration technology. Prior to restoration, the area was a mix of Spartina alterniflora beaches, muddy beaches, and abandoned quarries, which were not environmentally robust. Six species of mangrove plants were used in the wetland, including Kandelia obovata , Aegiceras corniculatum , Avicennia marina , Acanthus ilicifolius , Bruguiera gymnorhiza , and Rhizophora stylosa. The plants were planted according to three mixed patterns and three planting densities. Finally, the whole wetland was divided into 27 plots, and three plant-free control areas were set up in the area close to the vegetation area. In this study, 30 topsoil samples were collected (April 2019), fraction concentrations of heavy metals (Cu, Cr, Zn, and Pb), and their bioavailability and spatial distributions were determined, and the relationships between their fractions and planting patterns were analyzed. The results showed that among the nine planting patterns, the pattern " A-K-C , 0.5×0.5 m" was the most different from the other models, and the fraction of most heavy metals obtained the lowest value of soil metal content in this model. The secondary-phase fraction (SPF) of heavy metals, including acid-soluble, reducible, and oxidizable fractions, is considered to be a direct and potentially hazardous fraction to organisms. In this study, Cu, Zn, and Pb had the greatest SPFs among all the metals (35.29, 33.45, and 51.58%, respectively). Compared with the relevant results before restoration, it was found in after five years of mangrove restoration, the SPF of Cu, Cr, Zn and Pb decreased by 41.31, 22.89, 27.06, and 22.13%, respectively, indicating that the direct and potential toxicity of these four elements to the environment decreased. The risk of heavy metal release decreased from medium and high pollution levels to low pollution levels or even no pollution levels. For most metals, the fraction distributions were controlled by clay, silt, pH, and soil organic matter. The research methods and results can provide a theoretical and scientific basis for further study of wetland vegetation, and in addition, aid in selecting feasible restoration methods for further wetland restoration. [ABSTRACT FROM AUTHOR]