缙云山柑橘林土壤微生物磷脂脂肪酸(PLFAs)及酶活性的季节变化特征

Seasonal Variations of Soil Microbial PLFAs and Soil Enzyme Activity Under the Citrus Plantation in Mt. Jinyun,Chongqing

土壤微生物和土壤酶作为土壤生态环境最重要的组成成分,对环境变化敏感.本文以缙云山柑橘林为研究对象,采用磷脂脂肪酸法并结合主成分分析方法,分析季节更替对柑橘林土壤表层(0~20 cm)的土壤微生物数量、群落结构特征及酶活性等的影响.结果表明:1季节更替对土壤微生物有显著影响(P<0.05),16:0、i17:0、16:1 2OH、18:0、cy19:0ω8c、i17:1ω9c或16:0 10-methyl为4个季节共有PLFAs,含量之和分别占PLFAs的49.57%、41.63%、35.41%和38.05%.各微生物种类中,细菌PLFA比例最高,其次为真菌PLFA,放线菌PLFA比例最低,且均具有显著的季节变化特征,柑橘林土壤PLFAs总量变幅为6.868~24.085 nmol·g-1,大小顺序为春季>秋季>冬季>夏季,细菌PLFAs、G-、G+及放线菌PLFAs也呈现一致的变化规律,但真菌PLFAs则表现为秋季最高,其次是冬季和夏季,春季最低.季节更替对微生物群落多样性指数亦产生显著影响,丰富度指数(R)随季节变化依次为春>冬>秋>夏,多样性指数(H')随季节变化表现出冬>秋>春>夏,均匀度指数(J)表现为夏>秋>冬>春,优势度指数(D)则随季节表现为直线升高的变化趋势.2土壤脲酶随季节变化表现为夏季>春季>秋季>冬季;土壤蔗糖酶、土壤过氧化氢酶和酸性磷酸酶活性随季节变化均表现为秋季最高,其次是春季、夏季,冬季最低.3主成分分析结果表明细菌PLFAs、G+、G-、放线菌PLFAs和总PLFAs对土壤肥力贡献最大,其次是蔗糖酶、过氧化氢酶、酸性磷酸酶和真菌PLFAs,贡献最小为脲酶.

The soil microbial community and soil enzyme activity are important parts of soil ecosystem,and they are sensitive to the ecological environment. In this study,citrus plantation in Mt. Jinyun was chosen as the research object. The phospholipid fatty acid（ PLFAs） combined with principal component analysis method was used to study the effect of season changes on soil microbial quantity,community structure characteristics and soil enzyme activity at 0-20 cm soil layer under citrus forest. The results obtained from this study were as follows： 1 The season changes had a significant impact on soil microbes（ P〈0. 05）. Moreover,16： 0,i17： 0,16： 12 OH,18： 0,cy19： 0ω8c,i17： 1ω9c or 16： 0 10-methyl were found to be common in all four seasons,and the proportion of each phospholipid fatty acid was 49. 57%,41. 63%,35. 41% and 38. 05%,respectively. In various microbial species,the PLFAs content of bacteria was the highest,followed by fungi,and that of actinomycetes was the lowest. Our results revealed that all kinds of microorganisms showed obvious seasonal variation characteristics. The total PLFAs quantity of citrus forest ranged from 6. 868 to 24. 085nmol·g-1,which had a content order of spring 〉autumn 〉winter〉 summer. The PLFAs content of bacteria,G-,G＋and actinomycetes also showed the same variation trend. However,the PLFAs content of fungi showed a different variation trend,i. e.,autumn was the highest,followed by winter and summer,and spring was the lowest. The results suggested that season change also had a significant impact on microbial community functional diversity index. The variation trend of richness index（ R） followed the order ofspring winter autumn summer. Moreover,the variation trend of diversity index（ H＇） was winter autumn spring summer.Furthermore,the variation trend of evenness index（ J） was summer autumn winter spring. The dominance index（ D） increased with the change of season. 2 Urease showed a change with the seasons following summer spring autumn winter; Soil invertase,soil catalase and acid phosphatase activity changed obviously in autumn,followed by spring,summer,and winter. 3 The principal component analysis demonstrated that the PLFAs content of bacteria,G-,G＋,actinomycetes and total PLFAs made the greatest contribution to soil fertility followed by that of invertase,catalase,acid phosphatase and fungi. Moreover,our studies showed that the PLFAs content of urease made a minimum contribution to the soil fertility.