不同树叶凋落物对人参土壤理化性质及微生物群落结构的影响

树种选择是林下山参护育成败的关键,研究树叶凋落物对人参土壤养分、微生物群落结构组成的影响,旨在为林下山参护育选择适宜林地及农田栽参土壤改良提供科学依据和理论指导。通过盆栽试验,研究添加5.0 g色木槭Acer mono.Maxim.var.mono(A)、赤松Pinus densiflora Sieb.et Zucc.(B)、胡桃楸Juglans mandshurica Maxim.(C)、紫椴Tilia amurensis Rupr.(D)、蒙古栎Quercus mongolica Fisch.ex Ledeb.(E)树叶凋落物到土壤中,种植人参(Panax ginseng C.A.meyer)后研究土壤理化性质以及微生物群落结构的变化。结果表明:添加不同树叶处理后人参土壤性质发生改变,土壤p H值显著高于对照土壤5.91(P0.05),土壤全氮、速效氮磷、微生物碳氮在所有树叶处理中显著增加(P0.05),而土壤容重、速效钾和C/N在添加树叶处理中降低。18个土壤样品基因组,经16S和ITS1测序分别得到6064和1900个OUTs。其中细菌涵盖了42门、117纲、170目、213科、225属,真菌涵盖了24门、98纲、196目、330科、435属。不同树叶处理人参土壤细菌和真菌地位发生改变,细菌Proteobacteria是树叶分解的关键微生物,添加树叶后其多样性显著高于对照(P0.05)。而细菌Bacteroidetes和真菌Basidiomycota可能是区别阔叶林和针叶林树种的关键微生物,针叶林中含量显著低于阔叶林(P0.05),而真菌Ascomycota是针叶林分解的关键微生物。进一步从不同分类水平上得到特定树叶凋落物的特异细菌和真菌。典型相关分析(CDA)表明细菌Bacteroidetes、Chloroflexi、Actinobacteria及真菌Basidiomycota、Zygomycota、Chytridiomycota及Ascomycota的位置及多样性的改变均与土壤因子SMBN、TN、AP、SOC、AK、C/N、p H有关。综上所述,添加不同树叶后不仅提高土壤微生物量碳氮、改善土壤理化性质,同时改变微生物群落结构组成,不同树叶处理土壤理化性质不同导致人参土壤微生物组成的差异,本结果对于林下参选地和农田栽参土壤微生物改良具有理论指导作用。

Effects of different leaf litters on the physicochemical properties and soil microbial communities in Panax ginseng-growing soil

It is very critical for Panax ginseng to choose suitable sites in a forest environment. Leaf litters play a very significant role in determining soil physicochemical properties and shaping soil microbial communities in forest ecosystems, but their effects on the soil of understory wild ginseng and cultivated ginseng are unknown. In order to study that, leaf litters from five tree species(A) Acer mono Maxim. var. mono, (B) Pinus densiflora Sieb. et Zucc., (C) Juglans mandshurica Maxim., (D) Tilia amurensis Rupr., and (E) Quercus mongolica Fisch. ex Ledeb] were added to Panax ginseng-growing soil. MiSeq high-throughput sequencing was used to analyze and compare the bacterial and fungal diversity and community composition of soil samples from different tree litter treatments, and 6064 and 1900 OTUs were obtained from eighteen samples based on high-throughput sequencing of the V4 regions of the 16S and ITS1 rDNA gene respectively. Bacterial species detected in these samples covered 42 phyla, 117 classes, 170 orders, 213 families, and 225 genera, and fungal species detected in these samples covered 24 phyla, 98 classes, 196 orders, 330 families, and 435 genera. Our results indicated that the physicochemical properties of soil were significantly affected by all leaf litter treatments. Soil total nitrogen, available NPK, and soil microbial biomass (carbon and nitrogen) were significantly (P < 0.05) affected across all treatments. In addition, we found that the soil bulk density and C/N ratio were lower following all treatments than in the control (no addition of leaf litter). Significant changes in the bacterial and fungal community composition could be identified in all soils; specifically, the relative abundance of Proteobacteria was higher in treatments than in the control. In addition, the bacterial communities of Bacteroidetes and the fungal communities of Basidiomycota were smaller in treatments with coniferous leaf litter than those with broad leaf litter (P < 0.05), and the fungal communities of Ascomycota might be the key microbes for decomposition of coniferous leaf litter. LEfSeLine Discriminant Analysis (LDA) Effect Size] revealed that the overexpressed bacterial and fungal genes were obtained from the kingdom, phylum, class, order, family, genus, and species levels, in that order, based on relative abundance. These include the bacterial communities of Sphingomonas at the genus level in treatments of D, the fungal communities of Exophiala equina and Podospora glutinans at the species level in treatments of B. Canonical discriminant analysis (CDA) ascertained that the shift in the microbial community (the bacteria of Bacteroidetes, Chloroflexi, and Actinobacteria and the fungi of Basidiomycota, Zygomycota, Chytridiomycota, and Ascomycota) composition and diversity were closely related to the changes in soil microbial biomass nitrogen, total nitrogen, available phosphorus, soil organic carbon, available potassium, C/N, and pH in all treatment soils. The results of our experiment suggest that addition of leaf litter has a significant effect on soil bacterial community development, and it can lead to higher soil nutrients and soil microbial biomass as well as a different bacterial community composition. The resultant soil bacterial communities affect leaf litter decomposition and wild understory ginseng management.