黄土高原半干旱区轮作休耕模式对土壤真菌的影响

Effects of fallow rotation modes on soil fungal communities in semi-arid area of the Loess Plateau,northwest China

通过田间试验,研究休耕(CK)、残膜覆盖、伏天深耕、施有机肥、秸秆还田和绿肥还田对土壤微生物量碳氮、酶活性及真菌群落的影响。结果表明,除过氧化氢酶外,不同处理对土壤微生物量碳氮、脲酶、碱性磷酸酶、脱氢酶、pH及有机质均有显著影响。从门水平上看,土壤真菌群落主要由子囊菌门、担子菌门和被孢霉门构成。其中伏天深耕、玉米秸秆粉碎还田+施牛羊粪+深翻耕后连续休耕3年处理的子囊菌相对丰度分别为43.23%和69.38%,显著高于CK(33.71%);从纲水平上看,座囊菌纲、粪壳菌纲、伞菌纲和被孢霉纲为优势菌纲,其中玉米秸秆粉碎还田+施牛羊粪+深翻耕后连续休耕3年处理以座囊菌纲为主(60.69%),其余处理以粪壳菌纲为主(4.11%—24.79%);真菌多样性指数施牛羊粪+深翻耕+连续3年种植豌豆(拌根瘤菌粉8.5 g/kg种子)并在盛花期翻压还田、玉米秸秆粉碎还田+施牛羊粪+深翻耕后连续休耕3年、玉米秸秆粉碎还田+施牛羊粪+深翻耕+连续3年种植箭筈豌豆并在盛花期翻压还田处理显著低于CK和其他处理,丰富度指数玉米秸秆粉碎还田+施牛羊粪+深翻耕+连续3年种植毛苕子并在盛花期翻压还田处理显著高于CK和其他处理;真菌营养类型玉米秸秆粉碎还田+施牛羊粪+深翻耕后连续休耕3年处理以腐生营养型为主(62.9%),其他处理以病理营养型和腐生营养型为主。冗余分析和Monte Carlo置换检验结果显示,土壤微生物量碳、微生物量氮、pH和有机质含量对土壤真菌群落结构影响显著(P<0.05)。与休耕(CK)、残膜覆盖、伏天深耕相比,施有机肥、秸秆还田、绿肥还田结合深耕均降低了土壤中病理营养型真菌的相对丰度,利于保持农田土壤生态系统健康。

Fallow rotation has profound significance for sustainable agriculture in China. Currently, winter fallow system such as tillage and sunning, growing winter green manure crops, and intercropping with bean crops are practiced and advocated in mono-cropping obstacle area. Planting new varieties of crops, soil amelioration, scientific irrigation, and control of crop uptake of heavy metals are carried out in heavy metal pollution area. The seasonal fallow and annual fallow are enforced in groundwater funnel area. Significant economic, social and ecological benefits have been reachieved after adoption and implementation of the rotation/fallow modes in three typical regions. A field experiment was conducted to examine the effects of fallow(CK), residual plastic film mulching, deep tillage in hot summer, organic manure application, straw retention, and planting green manure on soil microbial biomass carbon and nitrogen, enzyme activity and fungal community in major ecological degradation area of Gansu Province. Soil microbial biomass and enzyme activity were analyzed while soil microbial DNA was extracted for PCR amplification and high throughput sequencing. The results showed that different treatments had significant effects on soil microbial biomass carbon and nitrogen, urease, alkaline phosphatase, dehydrogenase, organic matter and pH value except for catalase activity. The top three most abundant phyla were Ascomycota, Basidiomycota, and Mortierellomycota. The relative abundance of Ascomycota in three consecutive years deep tillage in hot summer treatment and three consecutive years fallow after corn straw retention 7500 kg/hm2 and 30 cm deep tillage treatment were significantly higher(43.23% and 69.38%, respectively) than CK(33.71%). Dothideomycetes, Sordariomycetes, Agaricomycetes, and Mortierellomycetes were the dominant fungus, with the relative abundance of Dothideomycetes being the highest(60.69%) in three consecutive years fallow after corn straw retention 7500 kg/hm2 and 30 cm deep tillage treatment while Sordariomycetes being the highest in other treatments(4.11%—24.79%), respectively. The diversity indexes of Simpson and Shannon-wiener in returning green manure of Pisum sativum(seed dressing with rhizobia 8.5 g/kg) for 3 consecutive years after corn straw retention 7500 kg/hm2 and 30 cm deep tillage treatment, three consecutive years fallow after corn straw retention 7500 kg/hm2 and deep tillage of 30 cm treatment, returning green manure of Vicia sativa for 3 consecutive years after corn straw retention 7500 kg/hm2 and 30 cm deep tillage treatment were significantly lower than CK and other treatments. The abundance indexes of ACE and Chao1 in returning green manure of Iicia villosa for 3 consecutive years after corn straw retention 7500 kg/hm2 and 30 cm deep tillage treatment were significantly higher than CK and other treatments. Saprotroph was the main functional group of soil fungi in three consecutive years fallow after corn straw retention 7500 kg/hm2 and 30 cm deep tillage treatment(62.9%), whereas pathotroph and saprotroph were the main functional group of soil fungi in other treatments. Redundancy analysis(RDA) and the Monte Carlo permutation test showed that the soil microbial biomass carbon, soil microbial biomass nitrogen, pH value, and organic matter content showed a significant impact on the composition of the fungal community. Compared to CK, residual plastic film mulching and deep tillage in hot summer treatments, combining organic manure application, straw retention and returning green manure with deep tillage could reduce pathotroph relative abundance, which was conducive to the maintainance of the soil ecosystem health.