Dynamics of Soil Bacterial Communities Over a Vegetation Season Relate to Both Soil Nutrient Status and Plant Growth Phenology

Abstract

Soil microorganisms regulate element cycling and plant nutrition, mediate co-existence of neighbors, and stabilize plant communities. Many of these effects are dependent upon environmental conditions and, in particular, on nutrient quality and availability in soils. In this context, we set up a pot experiment in order to examine the combined effects of soil nutrient availability and microbial communities on plant-soil interactions and to investigate assemblage rules for soil bacterial communities under changed nutrient conditions. Four gamma-sterilized soils, strongly differing in their nutrient contents, were obtained from different fertilization treatments of a centenary field experiment and used to grow communities of grassland plants. The sterilized soils were either self- or cross-inoculated with microbial consortia from the same four soils. Molecular fingerprinting analyses were carried out at several time points in order to identify drivers and underlying processes of microbial community assemblage. We observed that the bacterial communities that developed in the inoculated sterilized soils differed from those in the original soils, displaying dynamic shifts over time. These shifts were illustrated by the appearance of numerous OTUs that had not been detected in the original soils. The community patterns observed in the inoculated treatments suggested that bacterial community assembly was determined by both niche-mediated and stochastic-neutral processes, whereby the relative impacts of these processes changed over the course of the vegetation season. Moreover, our experimental approach allowed us not only to evaluate the effects of soil nutrients on plant performance but also to recognize a negative effect of the microbial community present in the soil that had not been fertilized for more than 100 years on plant biomass. Our findings demonstrate that soil inoculation-based approaches are valid for investigating plant-soil-microbe interactions and for examining rules that shape soil microbial community assemblages under variable ecological conditions.

Unraveling spatiotemporal variability of arbuscular mycorrhizal fungi in a temperate grassland plot

“…It is possible that DNA measures either detected defective and dead cells (Carini et al ., ), or dormant AMF stages, such as spores from the previous year, which impacted the observed AMF community at the beginning of the vegetation period. This effect was lost during the summer, which suggests that either legacy effects due to the cyclic character of seasons in temperate regions (Bahram et al ., ) or the appearance of priority effects (Viana et al ., ) shaped AMF community composition, as has been shown for soil bacteria (Francioli et al ., , ). The plant‐AMF interaction may have been set back to zero during winter, resulting in a random start of plant growth and fungal infections during spring.…”

Differential biodiversity responses between kingdoms (plants, fungi, bacteria and metazoa) along an Alpine succession gradient

“…Also, while alpine plant communities show little change in species composition during a single growth season, changes in bacterial communities are potentially more rapid. Indeed, various studies demonstrate that seasonal changes, particularly in soil chemical characteristics, have extensive impacts on rhizosphere bacterial communities (Francioli, Schulz, Buscot, & Reitz, ; Lauber, Ramirez, Aanderud, Lennon, & Fierer, ; Regan et al., ). While the present study represents a “snapshot” of the communities at one point during the season (the first 2 weeks of July), we would argue that the alpine bioclimatic zone includes an inherently short growth season and that sampling in summer, the most active time of the year including the flowering peak of the plant community, is likely to provide a useful comparison of diversity across kingdoms.…”

“…At the other extreme, bacteria are individually short lived and extensively dispersed, which appears to be evident from the number of ubiquitous OTUs (Figure 2b). Alternatively, the wide dispersal of bacteria could be due to the restricted and acid soil ties (Francioli, Schulz, Buscot, & Reitz, 2018;Lauber, Ramirez, Aanderud, Lennon, & Fierer, 2013;Regan et al, 2014). While the present study represents a "snapshot" of the communities at one point during the season (the first 2 weeks of July), we would argue that the alpine bioclimatic zone includes an inherently short growth season and that sampling in summer, the most active time of the year including the flowering peak of the plant community, is likely to provide a useful comparison of diversity across kingdoms.…”

Shifts Between and Among Populations of Wheat Rhizosphere Pseudomonas, Streptomyces and Phyllobacterium Suggest Consistent Phosphate Mobilization at Different Wheat Growth Stages Under Abiotic Stress

“…Changes in the structure and identity of Pseudomonas species at different wheat growth stages indicate that upon a change in the environmental conditions, the culture derived Pseudomonas community is dynamic. Concurrent changes in community structure and composition according to plants growth stages are widely observed in ecology (Dunfield and Germida, 2003;Wolsing and Priemé, 2004;Francioli et al, 2018). As we found moderate to high average P solubilization potentials of taxa classified to the genera Pseudomonas and Phyllobacterium at the two growth stages studied, the observed shifts plead for functional redundancy (Allison and Martiny, 2008) between and among genera at different wheat growth stages.…”

“…Seasonal shifts in rhizosphere microbiomes related to plant growth stages are well documented for canola and grasses (Dunfield and Germida, 2003;Wolsing and Priemé, 2004;Francioli et al, 2018). The changes are mainly caused by variations in the quantity and quality of carbon-derived rhizodeposits serving as energy sources for soil microbes (reviewed in Bais et al, 2006).…”