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Abundance of fungi and bacteria in long-term no-till (NT) and intensively tilled (IT) soils in the Northern Great Plains were measured using phospholipid fatty acid analysis (PLFA) to determine if a shift in the relative abundance of fungi and bacteria occurs as the result of conversion to NT. Four tillage trials located in four different soil zones were sampled in spring of 2005 and 2006 before the crop was seeded to evaluate the long-term effect of tillage on the microbial community. With the exception of one site-year, total, bacterial, and fungal PLFA were greater in NT than IT soils at the soil surface (0- to 5-cm depth) (p < 0.05). Increases ranged from 8 to 202% for total biomass, 26 to 58% for bacterial biomass, and 0 to 120% for fungal biomass. At one site (Ellerslie) all biomass measurements were greater in IT than NT in 2005 and bacterial biomass was also greater under IT in 2006. The influence of tillage on microbial biomass was less pronounced with depth. Fungal dominance is commonly assumed under NT; however, our results demonstrate that although biomass of both fungi and bacteria increase in NT, the abundance of fungi vs. bacteria was not consistently greater under NT in the soils studied. Further research is needed to determine if fungi may be able to exert a more functionally dominant role in NT soils without an increase in relative abundance. Abbreviations: IT, intensive-tillage; NT, no-tillage; PLFA, phospholipid fatty acid analysis; SOM, soil organic matter.

Widespread global changes, including rising atmospheric CO2 concentrations, climate warming and loss of biodiversity, are predicted for this century; all of these will affect terrestrial ecosystem processes like plant litter decomposition. Conversely, increased plant litter decomposition can have potential carbon-cycle feedbacks on atmospheric CO2 levels, climate warming and biodiversity. But predicting litter decomposition is difficult because of many interacting factors related to the chemical, physical and biological properties of soil, as well as to climate and agricultural management practices. We applied 13C-labelled plant litter to soil at ten sites spanning a 3500-km transect across the agricultural regions of Canada and measured its decomposition over five years. Despite large differences in soil type and climatic conditions, we found that the kinetics of litter decomposition were similar once the effect of temperature had been removed, indicating no measurable effect of soil properties. A two-pool exponential decay model expressing undecomposed carbon simply as a function of thermal time accurately described kinetics of decomposition. ( R2 = 0.94; RMSE = 0.0508). Soil properties such as texture, cation exchange capacity, pH and moisture, although very different among sites, had minimal discernible influence on decomposition kinetics. Using this kinetic model under different climate change scenarios, we projected that the time required to decompose 50% of the litter (i.e. the labile fractions) would be reduced by 1-4 months, whereas time required to decompose 90% of the litter (including recalcitrant fractions) would be reduced by 1 year in cooler sites to as much as 2 years in warmer sites. These findings confirm quantitatively the sensitivity of litter decomposition to temperature increases and demonstrate how climate change may constrain future soil carbon storage, an effect apparently not influenced by soil properties. [ABSTRACT FROM AUTHOR]

Soil is an important source of bacteria and fungi for the plant, but seeds can also provide microbial inocula through heritable or stochastic assembly. Seed-associated microbial communities can potentially interact with the host plant through multiple generations. Here, we assessed the impact of two different soil types on the seed microbiome assembly of seven lentil (Lens culinaris) genotypes under environmentally controlled conditions and examined the vertical transmission of bacterial communities from seed to seed across two generations. Bulk soil microbiomes and seed microbiomes were characterized using high-throughput amplicon sequencing of the bacterial 16S rRNA gene. Our results revealed that bacterial communities in the two soils differed significantly and that bacterial communities associated with seeds were significantly impacted by genotype (15%) in one of the soils. Co-occurrence of amplicon sequence variants between generations suggests that members of the genera Cutibacterium, Methylobacterium, Sphingomonas, Streptococcus and Tepidimonas are transmitted and preserved in lentil genotypes irrespective of the soil in which they were grown. Increasing our knowledge of how microbial communities carried by seeds are assembled, transmitted and preserved offers a promising way for future breeding programs to consider microbial communities when selecting for more resilient and productive cultivars., (© The Author(s) 2021. Published by Oxford University Press on behalf of FEMS.)