长期不同土地利用方式下土土壤微生物特性的变化

【目的】土壤微生物是土壤生态系统的重要组成部分,研究长期不同土地利用方式对其产生的影响可为该地区选择适宜的土地利用方式,实现培肥土壤和高产高效农业生产提供理论支撑。【方法】以位于陕西杨凌的"国家黄土肥力与肥料效益监测基地"的长期定位试验为基础,利用Biolog分析结合常规分析,研究了4种长期不同土地利用方式不施肥农田(CK),长期施氮、磷、钾化肥农田(NPK),长期绝对休闲(FL)和撂荒(AL)]对土土壤微生物量、呼吸强度和微生物功能多样性的影响。【结果】AL和NPK处理的土壤微生物量碳(SMBC)和微生物量氮(SMBN)均显著高于CK和FL处理,其中AL和NPK处理之间差异不显著,CK和FL处理之间差异不显著。NPK处理的SMBC/SMBN值最高,而CK和FL处理最低,两组间差异显著,而AL处理居中但与两组之间均差异不显著。不同土地利用方式下土壤基础呼吸强度的变化趋势是ALFLNPKCK,累积呼吸量的变化趋势为ALNPKFLCK,表明AL处理的土壤微生物活性最高,其次是NPK处理,再者是FL处理,而CK处理的土壤微生物活性最低。Biolog分析的结果显示,AL、NPK和CK处理的平均颜色变化率(AWCD)在开始的24 h变化不大,此后随培养时间的延长而快速升高;而FL处理在72 h之后才快速升高。培养结束时,NPK和AL处理的AWCD最大,其次是CK处理,FL处理最低。NPK和AL处理的Shannon-Wiener物种丰富度指数H、碳源利用丰富度指数S和Simpson指数D均最高,CK其次,FL最低。各处理的Shannon-Wiener均匀度指数E没有明显差异。相比CK、NPK和AL处理能提高土土壤微生物群落的功能多样性,FL处理则会降低土土壤微生物群落的功能多样性。主成分分析共提取了5个主成分,累计贡献率达87.7%,其中第1主成分(PC1)的方差贡献率为52.0%,第2主成分(PC2)为11.6%。NPK处理和AL处理的碳源利用特征相类似,与CK和FL处理存在显著差异,表明不同土地利用方式下土壤微生物群落的结构和功能出现了显著分异。糖类、羧酸类和氨基酸类等三类碳源是区分各处理的主要碳源。【结论】撂荒和合理施肥的农田均可以提高土壤微生物量、土壤呼吸作用和土壤微生物群落结构和功能的多样性,长期的绝对休闲则不利于土壤微生物功能多样性的维持。合理施肥的农田并不会造成土壤微生物量的下降以及土壤微生物结构和功能多样性的退化,相反,合理施肥对于维持农田土壤微生物量以及微生物结构和功能多样性具有显著的积极作用。

Changes of soil microbial characteristics under long-term different land use patterns on an anthropogenic loess soil

【Objective】 As an important part of soil ecosystem, soil microbes could be influenced profoundly by different long-term land use patterns. 【Methods】 This research was based on the long-term trial of National Monitoring Base of Soil Fertility and Fertilizer Efficiency on Loess Soil in Yangling City, Shaanxi Province. Four treatments were chosen: farmland without fertilization(CK), farmland with N, P and K chemical fertilizer(NPK), abandoned land(AL) and fallow land(FL). The effects of long-term different land use patterns on soil microbial characteristics were studied by Biolog and routine analyses for the choice of rational landuse patterns and soil sustainable utilization in loess area, such as soil microbial biomass, soil respiration and soil microbial community functional diversity. 【Results】 The soil microbial biomass carbon(SMBC) and soil microbial biomass nitrogen(SMBN) in NPK and AL were higher than those in CK and FL significantly; There was no significant difference between NPK and AL in SMBC and SMBN, neither between the CK and FL. The highest ratio of SMBC to SMBN(SMBC/SMBN) was in NPK, and the lowest both in CK and FL; That was middle in AL, but no significant lower than NPK, neither not significant higher than CK and FL. The soil base respiration rate was in order of ALFLNPKCK, and the cumulative respiration was in order of ALNPKFLCK, which indicated that the soil microbial activity was the highest in AL, secondly in NPK, then in FL, and the lowest in CK. The results of Biolog analysis showed that the average well color development(AWCD) did no change significantly in AL, NPK and CK at the beginning of 24 h, then went up rapidly, while that in FL went up rapidly after 72 h. AWCD was the greatest in NPK and AL, then in CK, and the lowest in FL at the end of incubation. Shannon-Wiener richness index(H), carbon source utilization richness index(S) and Simpson index(Ds) were all the highest in NPK and AL, then in CK, and the lowest in FL. There was no difference in Shannon-Wiener evenness index(E) between treatments. Compared with CK, NPK and AL could significantly improve soil microbial structural and functional diversity, while FL had a negative impact on it. Five principal components were extracted from the principal component analysis, and their cumulative contribution of variance accounted for 87.7%, in which the variance contribution rates of the first principal component(PC1) and the second principal component(PC2) were 52.0% and 11.6%, respectively. NPK and AL were similar in carbon source utilization character by soil microbial communities, but significantly different with CK and FL, which means there was a significant differentiation on soil microbial community structure and function under different land use patterns. The carbon sources mostly used by soil microbes were carbohydrates, carboxylic acids and amino acids, which were the main carbon sources to distinguish different treatments. 【Conclusions】 Both abandoned land and farmland with rational fertilization could improve soil microbial biomass, soil respiration and soil microbial structural and functional diversity, while long-term absolute fallow land(No fertilizer, same tillage with farmland, weed control, and almost no vegetation) had a negative impact on soil microbial structural and functional diversity. Farmland with rational fertilization didnt cause the decline of soil microbial biomass and the deterioration of soil microbial structural and functional diversity. On the contrary, it had a positive effect to maintain soil microbial biomass and soil microbial structural and functional diversity.