丛枝菌根真菌对玉米秸秆降解的影响及其作用机制

为了比较菌根、菌丝、植物根系对玉米秸秆降解的影响,采用4室分根装置即土壤室(S)、根室(R)、菌根室(M)和菌丝室(H),分室间用400目尼龙网和有机板分隔,尼龙网袋包埋玉米秸秆于不同分室内,以玉米为宿主植物,接种丛枝菌根(AM)真菌Glomus mosseae。试验分别在移栽后第20、30、40、50、60天时取样,通过测定接种AM真菌后玉米秸秆的碳、氮释放,土壤中3种常见酶活性、微生物量碳和氮及土壤呼吸的动态变化,探讨AM真菌降解玉米秸秆可能的作用机制。研究结果表明:经60 d的培养后,与未接种S室相比,接种AM真菌的M室和H室玉米秸秆降解量提高了27.72%和8.07%;另外,M室玉米秸秆碳素释放显著增加,而氮素的释放减少,致使碳氮比显著低于其他3室,较初始值降幅达8.72%,有利于秸秆进一步降解。在试验条件下,M室中土壤酸性磷酸酶、蛋白酶、过氧化氢酶活性较其他3室都有显著提高,并增加了微生物量碳、氮和土壤呼吸作用,形成了明显有别于根际的微生物区系。这一系列影响都反映出AM直接或间接作用于玉米秸秆的降解过程,是导致玉米秸秆降解加快的重要原因。

Compare different effect of arbuscular mycorrhizal colonization on maize straw degradation

The decomposition of plant residues plays an important role in the substance circulation, especial carbon-nitrogen cycle, which is influenced by many microorganism that acts the role of the consumer and decomposer could directly and indirectly accelerated the degradation process. As a member of microorganism, mycorrhizas are recognized as being of special importance as it has an especial microhabitat. Arbuscular mycorrhizal (AM) fungi form mutualistic symbiosis with more than 80% of the higher plant species. The contribution of AM to plant residues' degradation process varied at different hierarchical levels: plant root, mycorrhizas and the soil mycelium, of course the accompanying bacteria should be mentioned. In previous studies, most experiments were carried out with pot or other single compartment devices, this made it difficult to clarify different effects of mycorhiza symbiosis on plant residues degradation. In present study, the split-root device with four compartments was used to quantitatively compare the change of degradation process in rhizosphere, mycorrhizosphere and hyphaesphere. We choose maize straw as the representative of plant residue, AM fungus, Glomus mosseae (G. m) was inoculated. Harvested samples respectively in 20, 30, 40, 50 and 60 days, and then analysed the effects of soil enzymatic activity, soil microbial biomass carbon and nitrogen, soil respiration, discuss mechanism of mycorrhizal inoculation accelerate maize straw degradation. The results showed that inoculation with G. m, the maize straw degradation mass and degradation coefficient in mycorrhizal compartment were higher than that in root compartment at all stages, Mycorrhizal inoculation enhanced C release but prejudiced N release, and then reduced the C/N ratio, and so as to facilitate its further degradation. For the soil biological performance, we found that the catalase, protease, acid phosphatase, microbial biomass carbon and soil respiration have been enhanced in mycorrhizal compartment compared with root compartment, and the same as hyphae compartment with soil compartment, formed the active microbial community further. The increase of these indexes involved in the degradation process, and become the important reasons for mycorrhizal speed up the degradation. More AM fungal species and soil types will be considered in our following studies.