Edaphic and environmental properties influencing microbial community structure.

<p>Edaphic and environmental properties influencing microbial community structure.</p

Effect of land use and soil organic matter quality on the structure and function of microbial communities in pastoral soils: Implications for disease suppression - Fig 1

<p><b>Influence of soil type and land use on microbial community structure: metric MDS ordination plots of mean total bacterial (A and B) and <i>Pseudomonas</i> (C and D) communities.</b> The structures of the total bacterial and <i>Pseudomonas</i> communities were assessed based on the relative abundance of terminal restriction fragments (TRFs) and denaturing gradient gel electrophoresis (DGGE) banding patterns, respectively. Mean communities (individual points) for each land use and soil type were derived from 150 bootstrap averages. For land uses and soil types with sufficient replication, 95% region estimates for the mean communities (clouds) represent the spread of the bootstrap averages. Points and/or 95% region estimates in closer proximity represent groups that share increasing similarity in microbial community structure. Observations are statistically supported by PERMANOVA testing of Bray-Curtis dissimilarity data (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0196581#pone.0196581.s004" target="_blank">S4 Table</a>). Underlying OTU data for T-RFLP and DGGE analysis is available in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0196581#pone.0196581.s005" target="_blank">S5</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0196581#pone.0196581.s006" target="_blank">S6</a> Tables, respectively.</p

Effect of land use and soil organic matter quality on the structure and function of microbial communities in pastoral soils: Implications for disease suppression - Fig 2

<p><b>Influence of land use and soil type on (A) the abundance of the total bacterial community and (B) the relative abundance of the <i>Pseudomonas</i> community (mean ± SEM).</b> The size of the total bacterial and <i>Pseudomonas</i> communities were determined by quantitative PCR. The effects of land use and soil type were formally tested by REML analysis (Genstat). Samples were characterized by land use as either high intensity ‘dairy’ systems or ‘other’, relatively lower intensity pasture systems, e.g. sheep and beef grazing systems.</p

Effect of land use and soil organic matter quality on the structure and function of microbial communities in pastoral soils: Implications for disease suppression - Fig 3

<p><b>Network plots of disease suppressive functional gene abundance in (A) dairy (high intensity) and (B) other (low intensity) pasture soil.</b> Nodes represent each individual gene, rather than gene categories, with a putative role in disease suppression. Edges (blue lines) correspond to associations between genes; bold lines reflect Pearson correlations ≥ 0.9, and fine lines correlations between 0.8 and 0.9. Sid_fun, Sid_arc and Sid_bac represent fungal, archaeal and bacterial siderophore production genes, respectively. (C) Measures of average connectivity and density were higher for other (low intensity) systems than for dairy (high intensity) systems.</p

Edaphic and environmental properties influencing microbial community abundance.

<p>Edaphic and environmental properties influencing microbial community abundance.</p

Influence of soil type, land use and abiotic properties on the composition of disease suppressive genes.

<p>Influence of soil type, land use and abiotic properties on the composition of disease suppressive genes.</p

The variation in disease suppressive gene abundance accounted for by a reduced linear model.

<p>The variation in disease suppressive gene abundance accounted for by a reduced linear model.</p

High spatial variation in population size and symbiotic performance of <i>Rhizobium leguminosarum</i> bv. <i>trifolii</i> with white clover in New Zealand pasture soils

<div><p>Biological nitrogen fixation through the legume-rhizobia symbiosis is important for sustainable pastoral production. In New Zealand, the most widespread and valuable symbiosis occurs between white clover (<i>Trifolium repens</i> L.) and <i>Rhizobium leguminosarum</i> bv. <i>trifolii</i> (<i>Rlt</i>). As variation in the population size (determined by most probable number assays; MPN) and effectiveness of N-fixation (symbiotic potential; SP) of <i>Rlt</i> in soils may affect white clover performance, the extent in variation in these properties was examined at three different spatial scales: (1) From 26 sites across New Zealand, (2) at farm-wide scale, and (3) within single fields. Overall, <i>Rlt</i> populations ranged from 95 to >1 x 10⁸ per g soil, with variation similar at the three spatial scales assessed. For almost all samples, there was no relationship between rhizobia population size and ability of the population to fix N during legume symbiosis (SP). When compared with the commercial inoculant strain, the SP of soils ranged between 14 to 143% efficacy. The N-fixing ability of rhizobia populations varied more between samples collected from within a single hill country field (0.8 ha) than between 26 samples collected from diverse locations across New Zealand. Correlations between SP and calcium and aluminium content were found in all sites, except within a dairy farm field. Given the general lack of association between SP and MPN, and high spatial variability of SP at single field scale, provision of advice for treating legume seed with rhizobia based on field-average MPN counts needs to be carefully considered.</p></div

Relationship between the <i>R</i>. <i>leguminosarum bv</i>. <i>trifolii</i> population size and symbiotic potential of the legume-rhizobia symbiosis in 50 samples of soils collected from within a single field at Pouawa (hill country sheep and beef farm).

<p>Solid line is the linear regression model fit; dashed lines are the 95% confidence intervals.</p

High spatial variation in population size and symbiotic performance of <i>Rhizobium leguminosarum</i> bv. <i>trifolii</i> with white clover in New Zealand pasture soils - Fig 2

<p>(A) <i>Rhizobium leguminosarum</i> bv. <i>trifolii</i> population size and (B) nitrogen fixing effectiveness (symbiotic potential relative to commercial <i>Rlt</i> strain TA1) in soils across different spatial scales. Boxes show median values and extend to the 25th to 75th percentiles. For 2B, the dashed line at 100% symbiotic potential = white clover growth when inoculated with the commercial rhizobia inoculant strain TA1. Treatments sharing the same lettering (<i>a</i> or <i>b</i>) have similar treatment means (Bonferroni comparison of means; α = 0.05).</p