荆江地区湿地与稻田有机碳、微生物多样性及土壤酶活性的比较

摘要

[目的]通过湖北荆江地区湿地与稻田土壤有机质、微生物多样性及土壤酶活性比较分析,研究在人为培育下水稻土有机碳与微生物特性之间的关系.[方法]在湖北荆江地区采集代表性河流湿地和稻田耕层(0-20 cm)土壤样本,用硫酸-重铬酸钾消煮法和氯仿熏蒸-硫酸钾提取法测定土壤有机碳和微生物生物量碳,用稀释平板菌落计数法和PCR-DGGE研究微生物区系数量和群落结构多样性,并配合比色法测定土壤酶活性.[结果]湿地在长期种植水稻后,土壤有机碳含量提高了55.42％,全氮和碱解氮也大幅度升高.而且,微生物生物量碳提高了180％o尽管细菌、真菌、放线菌和自生固氮菌的丰度与细菌和真菌多样性均未发生分异,但是稻田土壤蔗糖酶、脲酶和碱性磷酸酶活性比湿地分别提高了89％、70％和72％.微生物生物量碳和归一化的酶活性均与土壤有机碳呈显著正相关关系.[结论]在人为定向培育下,荆江地区水稻土有机碳含量明显提高,微生物生物量碳与酶活性也显著增强,同时,土壤微生物生物量碳和酶活性可以作为稻田土壤有机质功能变化的指示指标.%[Objective] The purpose of this study is to, by means of a comparative analysis of soil organic carbon (SOC), microbial community abundance and soil enzyme activity, look into the relationship between SOC and microbial abundance/activity after rice cultivation of wetland soil for several decades. [Method] The topsoil (0-20 cm) samples of uncultivated wetland and paddy field were collected in Jingjiang area, Hubei, China. Contents of SOC, soil microbial biomass carbon (SMB-C) and microbial community abundance were analyzed using wet digestion with potassium dichromate, chloroform fumigation-extraction, dilute plate incubation counting and PCR-DGGE assays respectively. Microbial activity was examed using soil enzyme assays as well. [Result] The results showed that the SOC content increased by 55.42%, in accordance to the increases of total N and alkali-hydrolyzable N in rice paddies compared to wetland. SMB-C was found 180% higher in rice paddies than in wetlands. There was no significant difference in abundance of a single microbial community of bacterial, fungi, actionmycetes and autotrophic azotobacter, neither in diversity of bacterial and fungi between wetlands and rice paddies. However, microbial enzyme activities of invertase, urease and alkaline phosphatase was enhanced by 89%, 70% and 72%, respectively, in rice paddy over wetlands. Statistical analysis revealed a significant correlation of SMB-C and normalized overall enzyme activity index with soil organic carbon contents, respectively. [Conclusion] These results indicate that the size of soil microbial biomass and microbial functional activity with enzymes were enhanced as SOC storage increased due to rice cultivation of wetlands for several decades. Therefore, SMB-C size and normalized enzyme activity could be used as indicators for soil functioning by SOC.