苹果园生草对土壤微生物多样性、酶活性及碳组分的影响

  【目的】  果园种植生草能够改善土壤肥力与土壤结构。研究种植不同生草对果园土壤微生物多样性和土壤生物学性状的影响，为果园高效绿色管理提供理论依据。  【方法】  于2017年山东省泰安市马庄试验基地多年生苹果行间进行生草试验，供试草种为白三叶草(Trifolium pratense)、垂穗草(Bouteloua gracilis)、沙画眉草(Eragrostis trichodes)、弯叶画眉草(Eragrostis curvula)和加拿大披碱草(Elymus canadensis)，以清耕自然生草为对照(A_CK)，研究不同生草处理在连续3年内对果园土壤环境的影响。  【结果】  1) 从6个土壤样品中共得到31459个细菌操作分类单元和5021个真菌操作分类单元，6个土壤样品中共有1019个相同细菌群落(OTUs)和108个相同真菌群落(OTUs)。Alpha 多样性分析可知，弯叶画眉草处理后的土壤中细菌的Shannon、Simpson和Chao1指数高于Ack处理，比Ack分别增加了4.61%、7.01%和27.44%，尤其加拿大披碱草处理后土壤真菌的Chao1指数是对照的1.31倍(P<0.05)。在门分类水平变形菌门(Proteobacteria)、酸杆菌门(Acidobacteria)、放线菌门(Actinobacteria)、芽单胞菌门(Gemmatimonadetes)、浮霉菌门(Planctomycetes)、绿弯菌门(Chloroflexi)、拟杆菌门(Bacteroidetes)和疣微菌门(Verrucomicrobia)是优势细菌，这8个细菌门在各自处理中占比超过95%，子囊菌门(Ascomycota)、担子菌门(Basidiomycota)、球囊菌门(Glomeromycota)、接合菌门(Zygomycota)是优势真菌，这4个优势真菌门在各自处理中占比超过80%。弯叶画眉草处理可提高土壤中细菌丰富度和多样性，沙画眉草处理土壤中的细菌芽单胞菌门、浮霉菌门、绿弯菌门相对丰度降低；5个生草处理提高了土壤中真菌群落担子菌门的相对丰度，垂穗草子囊菌门相对丰度降低明显，垂穗草、弯叶画眉草和加拿大披碱草提高了土壤中的球囊菌门相对丰度。2)果园生草提高了土壤中微生物的数量，且随着生草时间的延长微生物数量增加明显，2020年9月份的弯叶画眉草处理土壤微生物数量高于清耕处理。3) 生草提高了果园土壤总有机碳和可溶性有机碳含量，弯叶画眉草、加拿大披碱草和沙画眉草处理效果显著好于清耕，弯叶画眉草的效果尤为突出，而三叶草的效果不显著。相应地，沙画眉草、弯叶画眉草和加拿大披碱草土壤脲酶、磷酸酶和过氧化氢酶活性显著高于清耕处理。4)相关性分析结果表明，果园生草处理土壤的碳组分(除DOC外)、酶活性与微生物数量之间存在极显著或显著正相关。  【结论】  种植沙画眉草、弯叶画眉草和加拿大披碱草均可显著增加土壤中总有机碳和可溶性有机碳含量，随着生草年限的增加，提高幅度也在增加，进而显著增加了土壤中微生物数量，并不同程度地改变了细菌和真菌的丰富度和多样性。弯叶画眉草和加拿大披碱草对土壤影响效应优良，极具推广价值。

Effects of grass planting in apple orchard on soil microbial diversity,enzyme activities and carbon components

  【Objectives】  Planting grasses in orchard improve soil fertility and structure. Hence, we studied soil biological properties and microbial structures as affected by grass species in orchard.  【Methods】  The field experiment was conducted at the Mazhuang experimental base in Tai'an City, Shandong Province, China. The test grass species were White clover (Trifolium pratense), Pith grass (Bouteloua gracilis), Brucella (Eragrostis trichodes), Curving thrush (Eragrostis curvula) and Canadian Elymus (Elymus canadensis). The five grass species were seeded in 2017 between the apple rows while no grass planting was taking as control. The microbial community and enzyme activities in soil were determined in three consecutive years.  【Results】  1) A total of 31459 bacterial operating taxa (or 1019 OTUs) and 5021 fungal operating taxa (or 108 OTUs) were obtained from all the soil samples. The average Shannon, Simpson and Chao1 indices of bacteria diversity in the grass planting soils were 4.61%, 7.01% and 27.44% respectively higher than that of control. At the phylum classification level, Proteobacteria, Acidobacteria, Actinobacteria, Gemmatimonadetes, Planctomycetes, Chloroflexi, Bacteroidetes and Verrucomicrobia were the dominant bacteria, accounting for more than 95% of the respective treatment. Ascomycota, Basidiomycota, Glomeromycota and Zygomycota were the dominant fungi, with their relative abundance accounting for over 80% of the respective treatment. Curving thrush increased soil bacteria abundance and diversity, but Brucella decreased the relative abundance of germ cell phylum, Phytophthora phylum and Curvulariaviridis. All the five grasses increased the relative abundance of Basidiomycota; Pith grass decreased the relative abundance of Ascomycota. Pith grass, Curving thrush and Canadian elymus increased the relative abundance of glomus. 2) The soil microbial population showed increasing trend with increase in years of the planted grasses, and the microbial population in three-year-old thrush soil was significantly higher than that in CK. 3) The activities of soil urease, phosphatase and catalase in the three years were all significantly higher than those of CK. Thrush, Canadian elymus and Curving thrush increased the soil organic carbon and soluble organic carbon contents. 4) The results of correlation analysis showed that the soil total organic carbon and enzyme activities were positively (P<0.05) correlated with the number of microorganisms.  【Conclusions】  Curving thrush and Canadian elymus planting significantly increased the soil total and soluble organic carbon contents, soil enzyme activities, microbial populations, and changed the community of bacteria and fungi composition to different extents as the grass growing year increased. The other three grasses did not show such good effect. So, Curving thrush and Canadian elymus have great promotion value.