长期肥料施用对华北大田玉米土壤丛枝菌根真菌群落结构的影响

Effects of long-term fertilization on arbuscular mycorrhizal fungal communities in intensive agroecosystems in North China Plain

华北平原是我国北方最重要的粮食主产区之一,过去30年间其粮食产量稳定提高的同时,肥料等生产资料的投入也大幅增加。丛枝菌根(Arbuscular mycorrhiza,AM)真菌作为一类重要的土壤功能性微生物,研究施肥措施对其群落、功能的影响,在挖掘农田有益微生物的潜在作用方面具有重要意义。本研究采用分子生物学方法测定了华北平原典型集约化农田体系中不同养分用量和投入模式对土壤AM真菌群落的影响。试验样地于2007年开始对冬小麦-夏玉米轮作体系进行施肥处理:有机肥(牛粪9 000kg/hm^2)、高量化肥(296.4kg N/hm^2、177.3kg P/hm^2、287.8kg K/hm^2,较当地常规化肥施用量上调25%)、低量化肥(74.1kg N/hm^2、44.3kg P/hm^2、71.9kg K/hm^2,较当地常规化肥施用量下调75%)和不施肥对照,每个处理3次重复,于2011年10月玉米收获季进行土壤取样。试验获得的31个OTUs主要属于Glomerales目(球囊霉目)(Glomus Group A/B)及Diversisporales目(多孢囊霉目),其中部分AM真菌类群如Glo12、Aca3、Scutellospora aurigloba(Scut.aurigloba全球盾巨孢囊霉)以及Div2仅在有机肥处理中被检测到。与其他处理相比,有机肥处理的116bp片段(Glo9/12/13/14;Fun1/2;Rhi1)相对丰度显著升高,而140bp片段(Uncultured Glomus)(球囊霉属)则主要受到化肥处理的促进。对于Diversisporales目AM真菌所对应的片段(141、142、169bp),施肥明显对其有促进作用。4年的肥料施用对土壤AM真菌物种多样性无显著影响,施肥处理0–20、20–40、40–60cm深度土壤AM真菌群落的多样性水平分别为1.14–1.78、1.61–1.84、1.23–2.07,丰富度分别为3.7–7.5、8.0–8.3、5.0–7.3。表明深层土壤是AM真菌重要的库,多样性水平并不低,对于维持土壤微生物多样性水平具有重要作用。本研究发现,p H值是影响表层土壤AM真菌群落分布的主要原因,土壤全氮、全碳、速效磷等肥力因子也是影响表层土壤AM真菌群落分布的重要因子,而深层土壤AM真菌的群落组成与固有的盐分特征(土壤电导率EC)有着较好的相关性。

The North China Plain is one of the most important regions for grain production in China. In this region, large amount of agrochemical is supplied. This study aims at understanding the community structure of arbuscular mycorrhizal fungi under long-term fertilization condition in this intensive agroecosystem. This experiment began in 2007, and the molecular biological methods were employed for comprehensively studying the effect of different fertilizer type and application strategy on AMF community. Fertilizer treatments included organic manure（9 000kg/hm^2）, high application treatment（296.4kg N/hm^2, 177.3kg P/hm^2, 287.8kg K/hm^2）, 25% increment of local chemical fertilizer application amount, and low application treatment（74.1kg N/hm^2, 44.3kg P/hm^2, 71.9kg K/hm^2）, 75% reduction of local chemical fertilizer application amount, and CK treatment. A typical maize cropped land was used as experimental plot. Three replications for each treatment were set. Soil samples were taken in maize harvest season（October 2011）. The results were that 31 OTUs were detected in this experiment and most of AM fungi belonged to Glomerales（Glomus Group A/B） and Diversisporales. Some AMF taxa（Glo12, Aca3, Scutellospora aurigloba and Div2） were stimulated by organic fertilizer application. Similar results were also obtained from T-RFLP fingerprint analysis. The relative abundance of 116bp（Glo9/12/13/14; Fun1/2; Rhi1） increased in organic fertilizer treatment and 140bp（uncultured Glomus） was mainly stimulated by chemical fertilizer. Fertilization stimulated the relative abundances of 141, 142 and 169bp（belonging to Diversisporales）. A 4-yrs fertilization had no significant effects on richness and diversity index of soil AMF community. The AMF community diversity index in each soil depth（0–20, 20–40 and 40–60cm） were 1.14–1.78, 1.61–1.84 and 1.23–2.07, and the richness index were 3.7–7.5, 8.0–8.3 and 5.0–7.3, respectively. Deep soil is an important library for AMF community in agricultural ecosystem, and the species diversity is not low. Soil p H contributed greatly to AMF community in top soil layer, and soil fertility indexes（soil TC, TN, OM, Olsen-P, etc.） also had a greater impact on the fungal community. Soil electrical conductivity played an important role in deep soil AMF community.