| Reclamation is one of the main reasons leading to the sharp reduction of wetlandresources. The study of the impact of reclamation on the wetland soil microbialcommunity structure, soil physical and chemical properties is very important for theprotection and rational use of wetland recourses, because it can lay a foundation forthe clarification of the evolution of wetland soil eco-system, and provide the referencefor the government in the enforcement of the "farmland for lake" policy.Soil samples from nature wetland or paddy field, vegetable plot, waste-land andfishpond sediment after different years (38,48,92years) of reclamation inJiangxianglianyu Nanchang County that located in Southwest of Poyang Lake werecollected. We investigated the soil physical and chemical properties, including soilmoisture(SM),Bulk density (BD), total organic carbon (TOC), ammonia-state carbon(NH4+-N), nitrate (NO3-N) and pH values, and the activities of enzymes, includinglaccase (ABTS), beta-glucosidase enzyme (BG), glucosaminidase (NAG), xylanases(BX) and pHospHatase (PHos), in different samples. The results showed:(1) Different reclamation period has a significant impact on the soil physical andchemical properties. After reclamation, soil moisture content, total organic carbon,ammonia nitrogen content significantly increased, while bulk density, nitrate and pHdidn’t change much. Changes in the organic carbon is worth focusing on: organiccarbon content in paddy soil after38years reclamation increased significantly to16.01g/kg, while the content in natural wetland is relatively low (about3.56-9.40g/kg). The contents in paddy soil after48years and92years of reclamation were17.52g/kg and18.26g/kg, respectively. This means there might be a threshold in theincrease of organic carbon content after reclamation.(2) The soil microbial community structure and diversity were changed afterreclamation. Soil enzyme activity is an important indicator of the number of soil microbial community structure. The results of analysis in paddy soil samples after38,48and92years of reclamation showed that the activity of laccase decreased, theactivates of beta-glucosidase, xylanase, glucosaminidase and pHospHoric acidincreased after reclamation. The PCR-DGGE tests on16SrDNA in different soilbacteria and fungi showed that the number of bands in the PCR-DGGE fingerprintinggradually reduced after reclamation, indicating that the diversity of microbe reducedafter reclamation. The results of Biolog tests showed that the growth conditions of themicrobe in natural wetland were mostly better than those from the soil of reclamation.⑶Returning the farmland in lake area to lake might be the best way to restorethe wetland eco-system. The study on the soil samples from25years returnedfarmland showed：i) The soil enzyme activities of returned farmland were restored:the activities of all kind of enzymes were similar to the samples from natural wetland,but showed significant differences with the samples from the reclamation paddy field;ii) The microbial diversity were restored: The PCR-DGGE fingerprint results weresimilar to the samples from natural wetland, but showed significant differences withthe samples from the reclamation paddy field; The Biolog test showed that themicrobial growth curves were similar to the samples from natural wetland, butshowed significant differences with the samples from the reclamation paddy field.(4) Land-use patterns might change the soil microbial community structure anddiversity. The study on the samples form paddy field, vegetable plot, waste-land andfishpond sediment showed that the soil physical and chemical properties, includingsoil moisture, bulk density, total organic carbon, ammonia-state carbon, nitrate, andthe activities of enzymes, including laccase, beta-glucosidase enzyme,glucosaminidase, xylanases and phosphatase, were significantly affected by theland-use patterns. The PCR-DGGE fingerprint test also showed the microbialdiversity was also changed significantly in the four different land-use patterns. |
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