Temporal variations in phosphorus fractions and phosphatase activities in rhizosphere and bulk soil during the development ofLarix olgensisplantations

Abstract Background Despite their widespread distribution and ecological importance, protists remain one of the least understood components of the soil and rhizosphere microbiome. Knowledge of the roles that protists play in stimulating organic matter decomposition and shaping microbiome dynamics continues to grow, but there remains a need to understand the extent to which biological and environmental factors mediate protist community assembly and dynamics. We hypothesize that protists communities are filtered by the influence of plants on their rhizosphere biological and physicochemical environment, resulting in patterns of protist diversity and composition that mirror previously observed diversity and successional dynamics in rhizosphere bacterial communities. Results We analyzed protist communities associated with the rhizosphere and bulk soil of switchgrass (SG) plants (Panicum virgatum) at different phenological stages, grown in two marginal soils as part of a large-scale field experiment. Our results reveal that the diversity of protists is lower in rhizosphere than bulk soils, and that temporal variations depend on soil properties but are less pronounced in rhizosphere soil. Patterns of significantly prevalent protists groups in the rhizosphere suggest that most protists play varied ecological roles across plant growth stages and that some plant pathogenic protists and protists with omnivorous diets reoccur over time in the rhizosphere. We found that protist co-occurrence network dynamics are more complex in the rhizosphere compared to bulk soil. A phylogenetic bin-based null model analysis showed that protists’ community assembly in our study sites is mainly controlled by homogenous selection and dispersal limitation, with stronger selection in rhizosphere than bulk soil as SG grew and senesced. Conclusions We demonstrate that environmental filtering is a dominant determinant of overall protist community properties and that at the rhizosphere level, plant control on the physical and biological environment is a critical driver of protist community composition and dynamics. Since protists are key contributors to plant nutrient availability and bacterial community composition and abundance, mapping and understanding their patterns in rhizosphere soil is foundational to understanding the ecology of the root-microbe-soil system.

Download Full-text

Temporal variations of rhizosphere and bulk soil chemistry in a Douglas fir stand

Geoderma ◽

10.1016/j.geoderma.2006.10.005 ◽

2007 ◽

Vol 137 (3-4) ◽

pp. 490-496 ◽

Cited By ~ 55

Author(s):

M.-P. Turpault ◽

G.R. Gobran ◽

P. Bonnaud

Keyword(s):

Soil Chemistry ◽

Temporal Variations ◽

Douglas Fir ◽

Bulk Soil

Download Full-text

Litter Quality and Microbes Explain Aggregation Differences in a Tropical Sandy Soil

Journal of soil science and plant nutrition ◽

10.1007/s42729-021-00696-6 ◽

2021 ◽

Author(s):

Moritz Laub ◽

Samuel Schlichenmeier ◽

Patma Vityakon ◽

Georg Cadisch

Keyword(s):

Sandy Soil ◽

Litter Quality ◽

Soil Aggregates ◽

Temporal Variations ◽

Bulk Soil ◽

Seasonal Development ◽

Aggregate Formation ◽

Soil C ◽

Aggregate Fraction ◽

Medium Quality

AbstractSoil aggregates store most soil organic carbon (SOC), but how does litter quality influence their formation? We hypothesized varying litter quality to facilitate differences in aggregate formation by altering the seasonal development of microbial biomass (MB) C and N, with MB driving aggregate development in a tropical sandy soil in Thailand. Aggregate development was studied in a long-term fallow experiment, receiving 10 Mg ha−1 annual applications of rice (Oryza sativa) straw (low N and polyphenols (PP)), groundnut (Arachis hypogaea) stover (high N, low PP), tamarind (Tamarindus indica) litter (medium N and PP), or dipterocarp (Dipterocarpus tuberculatus) leaf litter (low N, high PP) compared to a control. N-rich litter from groundnut and tamarind led to significantly higher MB, bulk soil C and aggregate C than dipterocarp, rice straw, and the control. Bulk soil C and small macroaggregates C of N-rich litter treatments increased about 7% in 30 weeks. Increasing MB N explained increasing small macroaggregate C and both, MB C or N were important covariates explaining temporal variations of C stored in the microaggregates, in silt and clay. MB also explained temporal variations of aggregate fraction weights. With time, SMA C only increased in the N-rich groundnut and tamarind treatments, but decreased in other treatments. Connections of MB to aggregate C and weight substantiated the importance of microbial activity for aggregate formation and carbon sequestration. By promoting MB for longest time spans, medium-quality tamarind could best facilitate aggregate formation, and increase silt and clay C.

Download Full-text