| The effects of mangrove ecological restoration on the seclected soil physical-chemicalproperties and the community structures of bacteria were investigated in the coastalwetlands of Fucheng of Leizhou, Guangdong province in this study. Especially, Thevariations in restoration effects from constructing vegetations was compared betweenexotic species Sonneratia apetala communities and native species Kandelia candelcommunities. The results were outlined as followed:1Mangrove restoration have more or less influence on soil physic-chemical properties:①Soil texture of NF2and Sa18were sandy soil and soil texture of NF1, Kc5, Kc18,Sa5and Sa11were loamy soil.②The soil Eh varied from-186mV to+212mV, and mean value was-42mV. In total,the Eh of surface soil was significantly higher than middle and bottom soil(p＜0.05). Eh inmangrove areas were significantly higher than mudflats(p＜0.05). The recovery ofvegetation increased significantly soil Eh. The pH of soil varied from5.90to7.80, with themean value6.86. The recovery of mangrove vegetation had obvious effect on soilacidification. As the increasing time of the mangrove restoration, Sonneratia apetalashowed significantly higher soil acidification than Kandelia candel(p＜0.05). The salinityof soil changed from6.60to27.5, with the average value15.87. As a result, mangroverecovery caused clear salt deposition. With the increasing restoration time, the soil salinityof Sonneratia apetala increased slowly while the salt deposition of Kandelia candelincreased rapidly.③The content of soil sulfide in all sampling sites ranged from0.01mg/kg to279.96mg/kg, the average values being36.59mg/kg. Soil sulfide in the forests was significantlyhigher than the corresponding mudflat (p<0.05). The concentration of soil organic carbonin all sampling sites changed from2.87g/kg to16.99g/kg, with the average of6.88g/kg.The soil organic carbon is significantly higher in the forests than non-vegetatedflats(p<0.05), The data viewed that the concentration of the soil organic carbon had aconsistent tendency among three layers in all the sampling stations: surface layer＞middlelayer＞bottom layer, a long period of vegetation restoration increased soil organic carbon contend of middle and bottom layer.④The concentration of ammonium (NH4+-N), nitrate (NO3--N) and nitrite (NO2--N)ranged from6.75mg/L to37.08mg/L, from0.84mg/L to37.72mg/L and from0.04mg/Lto0.19mg/L with the average of17.22mg/L,10.01mg/L,0.09mg/L, respectively. Thecontent of phosphate(PO33--P) changed from7.10mg/kg to12.63mg/kg, with the averageof9.07mg/L. Total phosphorus (TP) and total nitrogen (TN) ran from0.011%to0.032%,from0.044%to0.690%. with a mean of0.018%,0.100%, respectively. The content ofinorganic nitrogenous nutrients and TN in the restoration of mangrove were significantlyhigher than the corresponding mudflat (p<0.05), while the content of TP had no significantdifference(p>0.05).⑤The content of soil petroleum in all sampling sites ranged from0.162mg/kg to1.688mg/kg, the average values being0.500mg/kg. Compared to the controls(average of0.177mg/kg), The recovery of vegetation in Sonneratia apetala(average of0.580mg/kg)and Kandelia candel(average of0.712mg/kg) increased the soil content of petroleum(p<0.05).2The recovery of vegetation increased the abundance of soil bacteria andsulfate-reducing bacteria, and had a certain effect on the community structures of bacteria①Bacteria abundance was detected by fluorescence microscopy ranging from5.2×107ind./g·dw to32.9×107ind./g·dw, and the mean value is10.8×107ind./g·dw. All sitesshowed vertical distribution, soil bacteria abundance in the surface was significantly higherthan the middle and bottom, and soil bacteria in the middle presented significantly higherabundance than the bottom(p<0.05), and soil bacteria in mangrove areas higher thanmudflats(p<0.05). The bacteria abundance in Sonneratia apetala restoration forest wassignificantly lower than Kandelia candel(p<0.05).②We used the fluorescent quantitative PCR to detect the abundance of soilsulfate-reducing bacteria belonging to3genus in mangrove restoration. The averageabundance of Desulfobulbus sp. was6.07×109copies/g·dw. The average abundance ofDesulfobacterium sp. was2.46×1010copies/g·dw, and the desulfovibrio sp. was8.20×109copies/g·dw. The3genus had a consistent rule. The abundance of sulfate-reducing bacteriain surficial soils(0~10cm) was substantially higher than the middle(10~20cm) and thebottom(20~30cm) soils, and the bacteria abundance in middle soil was substantially higherthan the bottom soil(p＜0.05). Mangrove restoration significantly increased the abundanceof sulfate-reducing bacteria.③Soil bacterial richness(S) and shannon diversity index (H) in the Sa11and Sa18was significantly higher than mudflat and Sa5(p＜0.05), but Kc18were significantly lower than mudflat and Sa5(p＜0.05). Which indicated that a long period of vegetationrestoration increased soil bacterial community diversity in Sonneratia apetala, but therecovery of Kandelia candel resulted to the opposite result.④Among all the sequences, the maximum genus was Proteobacteria owning9OUT’swith a high frequency of62.86%. There were two OUT’s belong to Actinobacteria whichaccounted for12.93%, one OUT’s belonging to Bacteroidetes accounting for only6.09%,and one OUT’s belonging to Deferribacteres for10.23%. The dominant bacteria(band4) inthe soil of restored mangrove in Fucheng belonged to uncultured gamma proteobacterium,the abundance of which declined in the restored Kandelia candel forests. Moreover, theabundance of Caldithrix (band19) declined in the restored mangrove forests. However, therestoration of Kandelia candel increased the abundance of Vibrio (band10). And theabundance of Sulfurovum (band20) and Desulfovibrio (band17) increased in the restoredSonneratia apetala forests. All in all, mangrove vegetation restoration changed benthicbacterial diversity and abundance of advantage bacterium group.From the above results, Mangrove restoration not only changed the forest soilphysical and chemical properties, also had obvious changes in soil microbial communities.Research of this paper can offer the restoration of mangrove ecosystem trackingassessment of soil physical and chemical properties and bacteria community ecosystemtheory basis. |
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