种植模式对土壤酶活性和真菌群落的影响

Influence of cropping system on enzyme activities and fungal communities in soil

试验选择黔北具有代表性的灰岩黄壤,在实施秸秆还田的基础上,设置烤烟-小麦（T-W）和烤烟-油菜（T-C）连作,以及烤烟-小麦-玉米（T-W-M）和烤烟-油菜-玉米（T-C-M）轮作处理。利用常规分析和454-高通量测序,连续种植10年后研究了不同种植模式对土壤酶和真菌的影响。结果表明,轮作使土壤有机质比起始时增加11.23%~16.06%,微生物量碳、微生物量氮含量提高,土壤脱氢酶活性增强,有益于保持土壤肥力和生产力。轮作显著提高真菌的18SrDNA序列数、种类（OTUs）和多样性指数,优势度指数和前20种优势菌株的丰富度之和降低,说明轮作改善了土壤生态环境,使之适合多种真菌的繁殖生长,种群数量增加。多种真菌共同存在,互相制约,可防止病原真菌过度繁殖,抑制病害的发生。而在连作土壤中,真菌种群数相对减少,优势种群突出,导致作物真菌病害的发生几率增加。此外,在土壤真菌中,子囊菌超过75%。实施不同种植模式10年之后,前20种优势菌株中仍有8株共同存在于各处理的土壤中;在T-C处理的土壤中,这些优势真菌均可在其他3种种植模式之一的土壤中出现。说明土壤环境与真菌种群结构密切相关,但又因作物种植而变化。

The influence of different cropping systems on enzyme activities and fungal communities in represent- ative yellow limestone soils in north Guizhou was studied over a period of 10 years in a field experiment. There were 4 cropping systems including flue-cured tobacco （Nicotiana tabacum）-wheat （Triticum aestivum ） without rotation （T-W）, flue-cured tobacco-canola （Brassica napus） without rotation （T-C）, flue-cured tobacco-wheat- maize （Zea ,nays） rotation （T-W-M） and flue-cured tobacco-canola-maize rotation （T-C-M）. Organic matter, microbial carbon and nitrogen, and dehydrogenase activity were increased significantly in the soil of the rotation systems, with resulting benefits to soil fertility and crop productivity. Rotation also greatly increased the num- ber of 18S rDNA sequence, fungal phylotypes （operational taxonomic units）, and the diversity index of the fungal community and reduced dominance index and the sum abundance of the top 20 predominant fungal phylotypes which suggests that rotation improved soil ecosystems. Higher diversity of fungi in soil ecosystemsshould prevent over reproduction of any single fungal taxon and so inhibit disease spread on a large scale. Conversely, compared with rotation, there were fewer fungal populations and a greater tendency for predominant phylotypes in soils continuously cropped under one system, which could increase the incidence of crop disease. Taxonomically, 75% of soil fungi could be assigned to Ascomycota and eight of 20 predominant fungi were commonly observed in all studied soils. Fungi in soil in the T-C system could be observed in the soils of the other three cropping systems after 10 years of the respective cropping regimes which suggests presence of those fungi is more influenced by soil environment than cropping system.