间作栽培对连作马铃薯根际土壤微生物群落的影响

连作严重影响了作物的产量和品质,而土壤微生物群落结构与功能对土壤生态系统和植物健康至关重要。以连作10a土壤为基质,单作马铃薯为对照,采用磷脂脂肪酸(Phospholipid fatty acids)、BIOLOGA技术和真菌形态学鉴定方法,研究了玉米、蚕豆与马铃薯间作模式下土壤微生物群落结构、功能和丛植菌根(Arbuscular Mycorrhizal)真菌对土壤环境变化的响应。结果表明:间作调控下,马铃薯根际土壤微生物主要类群结构发生显著改变;玉米间作马铃薯,土壤微生物群落总生物量降低,但群落功能多样性提高,促进了以羧酸类、多聚化合物、芳香类化合物、氨基酸类化合物为碳源的微生物类群代谢活性增强;蚕豆间作增加了土壤微生物总生物量,仅促进了以碳水化合物为碳源的微生物类群代谢活性。间作改变了作物根际土壤AM真菌的种、属数,AM真菌多样性降低,优势种由明球囊霉、地球囊霉转变为玉米间作体系里的福摩萨球囊霉、球泡球囊霉;蚕豆间作体系里福摩萨球囊霉和疣状无梗囊霉是优势种。间作栽培下AM真菌优势种群的变化可能受植物间的共生关系、微生物结构与功能等因素的制约。间作条件下,玉米显著影响了马铃薯根际土壤微生物群落功能多样性,而蚕豆则显著改变了微生物群落结构多样性;玉米、蚕豆对马铃薯根际土壤微生物群落功能与结构变化的影响不同步;间作调控后持续的土壤微生物群落结构与功能观察才有助于解释土壤微生物结构变化引起的功能响应。

Effects of intercropping on soil microbial communities after long-term potato monoculture

Soil microorganisms are one of the main components of the soil ecosystem and play an important role in agro-ecosystem function and sustainable agricultural development. Arbuscular mycorrhizal fungi (AMF) are important components of soil microbial communities because of their symbiotic relationships with many crop species. The increase in potato production area in the south mountain region of Ningxia, China, made crop rotation difficult and long-term potato monoculture led to significant yield reductions due to pests and devastating diseases. Plant complementarity may decrease interspecific competition through resource partitioning, and facilitation may improve the availability of resources. AMF seem to play an important role in these interactions, so intercropping potatoes with a different crop species and AMF may moderate yield reductions in a long-term potato monoculture system. The objective of this study was to investigate soil microbial community composition and the changes in AMF diversity due to the transition from continuous potato monoculture to an intercropping system. We studied two different intercropping systems, maize-potato and faba bean-potato, in a field where a potato monoculture system had been applied continuously for 10 a. The composition and the functional diversity of soil microbial communities were accessed by measuring the phospholipid fatty acids contents (PLFA) and by community level physiological profiles (CLPPs) using the Eco-plate technique. Then we identified AMF by morphological characteristics and calculated their relative abundance. The results showed that soil microbial community structures changed with the transition from continuous potato monoculture to the intercropping system. In the maize-potato intercropping system, PLFA levels decreased, whereas the metabolic activity of microbial functional groups, as well as the carbon utilization of carboxylic acid, polymer compounds, aromatic compounds, and amino acids, increased. In the faba bean-potato intercropping system, only carbohydrate utilization by microorganisms increased. The total PLFA content was lower in the maize-potato intercropping system than in the faba bean-potato system. The biomasses of gram-negative bacteria, gram-positive bacteria, Pseudomonas, and AMF were lower by 35.1%, 28.0%, 24.8%, and 9.0%, respectively, in the maize-potato intercropping system than in the continuous monoculture system. Conversely, the fungal biomass was higher by 21.1% in the maize-potato intercropping system than in the continuous monoculture system. However, there was a reverse tendency in the faba bean-potato intercropping system. AMF species richness decreased in the continuous monoculture system compared to the faba bean-potato intercropping system, while the dominant species in the latter was Ganoderma formosanum. The change in AMF dominant species might be restricted by some integrated factors, including the symbiotic relationship with different crops and the diversity of soil microorganism structure and function. These results suggest that the performance of soil microbial communities is not always consistent with changes in the structure of soil microbial functional groups in intercropping systems. The maize-potato intercropping system may enhance the diversity of soil microbial functional groups, whereas in the faba bean-potato intercropping system, the diversity of soil microbial functional groups is higher. We may conclude that different microbial species have different rhizosphere effects on potato cultivation.