内生真菌感染对禾草宿主生境土壤特性和微生物群落的影响

以羊草(Leymus chinensis)-内生真菌共生体为研究对象, 分别在野外样地和室内盆栽两种实验条件下研究了内生真菌感染对土壤特性和微生物群落结构的影响。结果显示：在处理时间较长并伴随有枯落物分解的羊草样地中, 内生真菌感染促进了土壤氮(N)的积累, 提高了30天培养时间内土壤初始碳(C)矿化速率和前3天土壤矿化量和土壤矿化总量; 而在处理时间较短且没有地上枯落物分解的盆栽羊草中, 内生真菌感染对土壤的C、N含量及C矿化均无显著影响。无论是野外样地还是室内盆栽实验, 内生真菌感染均未引起土壤微生物磷脂脂肪酸种类的变化, 但内生真菌感染均有提高土壤微生物生物量的趋势, 内生真菌显著增加了盆栽羊草土壤中细菌、革兰氏阴性细菌、真菌磷脂脂肪酸含量和磷脂脂肪酸总量, 增加了羊草样地土壤中革兰氏阳性细菌和放线菌的磷脂脂肪酸含量。总体看来, 内生真菌感染能够改变土壤N积累和C矿化率, 并且改变土壤中微生物群落的结构, 这有助于进一步认识内生真菌与羊草之间的共生关系及其在生态系统C、N循环中所起的作用。

Effects of fungal endophyte infection on soil properties and microbial communities in the host grass habitat

Aims Leymus chinensis is a dominant grass native to the mid-eastern Inner Mongolia Steppe. The plants of this species are sometimes heavily infected with fungal endophytes that produce alkaloids, which in turn affect insect herbivory, plant production, and litter decomposition. Our objective was to investigate the effects of the L. chinensis-endophyte association on soil properties and soil microbial communities in field and pot experiments.
Methods We concurrently conducted a field and a pot experiment. The soil total carbon (C) and nitrogen (N) were analyzed with an Elemental Analyzer, and C mineralization was determined by using a soil incubation test over a 30-day period. Soil microbial biomass and community composition were assayed by using phospholipid fatty acid (PLFA) technique.
Important findings In the field experiment, where L. chinensis plants had grown for longer time and there was litter decomposition, fungal endophyte infection significantly increased soil N content, the initial C mineralization rate, the C mineralization during the first three days, and the accumulative C mineralization during the 30-day soil incubation. In the pot experiment, where L. chinensis plants had grown for shorter time and there was no litter decomposition, the soil total C and N contents and the C mineralization did not differ between the endophyte-infected (E+) and endophyte-free (E–) treatments. We found no significant difference in the types of PLFAs between the E+ and the E– treatments in both field and pot experiment, but endophyte infection tended to increase the soil microbial biomass. The PLFA contents of bacteria, gram-negative bacteria (G–), fungi, and total PLFA were significantly higher in the E+ treatment than in the E– treatment in the pot experiment; whereas in the field experiment, the PLFA contents of gram-positive bacteria (G+) and actinomycetes were significantly higher in the E+ treatment than in the E– treatment. This study suggests that endophyte infection may change the soil N accumulation and the rate of C mineralization, and alter soil microbial community structure. Our findings can help with understanding the relationship between fungal endophytes and L. chinensis and its role in ecosystem C and N cycling.