Long-term effects of elevated CO2 on carbon and nitrogen functional capacity of microbial communities in three contrasting soils

Abstract

Elevated atmospheric CO 2 (eCO 2) affects soil-plant systems by stimulating plant growth, rhizosphere processes and altering the amount and quality of organic matter inputs. This study examined whether these plant-mediated processes indirectly influence the structure and function of soil microbial communities and soil carbon (C) and nitrogen (N) cycling. Surface soils (0-5 and 5-10 cm) of Calcarosol, Chromosol and Vertosol were sampled after 5 years' exposure to either ambient CO 2 (aCO 2 ; 390 ppm) or eCO 2 (550 ppm) using free-air CO 2 enrichment (SoilFACE). Changes in microbial community structure were not detected using automated ribosomal intergenic spacer analyses (ARISA). However, quantitative PCR of targeted organic C decomposition (cu, cbh), N mineralisation (apr, npr), nitrification (amoB, amoA, norA) and denitrification (nirK, narG, nosZ) genes showed that eCO 2 reduced the abundance of half of the functional genes in the Chromosol and Vertosol and their abundance was tightly coupled with total C and N pools. In the Chromosol, total N and C of soil (<2 mm particles) was reduced by up to 20% and was associated with enhanced microbial activity (soil respiration). Soil C was also reduced in the Vertosol (15%, 5-10 cm); however greater laccase, reduced cellulase and lower microbial activity indicated that organic matter decomposition was currently limited by N. The loss of soil organic N and C under eCO 2 was likely driven by greater N demand. This study highlighted that the indirect effects of eCO 2 on functional capacity of soil microbial communities in dryland agricultural system depended on the soil type.

Elevated CO2 and nitrogen addition have minimal influence on the rhizospheric effects of Bothriochloa ischaemum

“…Previous studies have reported that elevated CO 2 or N addition increased, decreased, or had no significant impact on community structure 7, 15, 16, 26, 28, 52 . These contradictory results could be due to differences of microbial substrate availability under different scenarios of climate change.…”

Bacterial and fungal communities are differentially modified by melatonin in agricultural soils under abiotic stress

“…Soils were air dried overnight and sieved to remove particles larger than 2 mm. A single soil sample was generated for each site by pooling all four collected soils from the subsite plots (Aye et al, 2016, Butterly et al, 2016). The collected stock soils were separately stored at ambient room temperature (21°C) in airtight plastic containers for four months, followed by subsampling (representing the first sampling timepoint; labelled as ‘T0’ in the analysis) for immediate treatments as described below.…”

“…Singletons and low abundance amplicons (<1% relative abundance) were disregarded (Fisher and Triplett, 1999). Data were normalized in the statistical software R version 3.3.2 (The R Foundation for Statistical Computing, Boston, USA), with bin sizes of 3 and 4 selected for bacteria and fungi respectively (Ramette, 2009, Butterly et al, 2016). The following analyses were conducted in Primer-E v6 (Quest Research Ltd., Auckland, New Zealand), with treatments considered as fixed factors and microbial responses analysed for each soil separately (Chow et al, 2013, Wood et al, 2016): 1) Bray-Curtis similarity for microbial communities; 2) SIMPER analysis to identify the contribution of individual Operational Taxonomic Units (OTUs) to (dis)similarity between replicates or different treatments; 3) DIVERSE to determine Shannon diversity index (H’) for sample data; 4) Permutational multivariate analysis of variance (PERMANOVA) to determine treatment effect (melatonin, stressors: cadmium and Salt) on microbial assemblages for each soil at various concentrations (High, Low and Zero).…”

Response of the rhizosphere prokaryotic community of barley (Hordeum vulgare L.) to elevated atmospheric CO2 concentration in open‐top chambers

“…These effects may alter the activity and composition of the rhizosphere inhabiting microbial community which in turn can greatly affect plant growth and health (Rogers, Runion, & Krupa, ). Recent studies investigating the effect of elevated [CO 2 ] on the soil or root‐associated prokaryotic diversity or community composition however, reported contradictory results showing either significant (Deng et al., ; He et al., ; Gschwendtner et al., ; Okubo et al., ) or no effects (Butterly et al., ; Hayden et al., ; Ren et al., ). It seems that the response of the soil prokaryotic community is characteristic to ecosystems and plant species (Dunbar et al., ).…”

“…Recent studies investigating the effect of increased [CO 2 ] on the composition of the soil microbial community relied on methods with relatively low resolution, like 16S rRNA gene clone libraries (Dunbar et al., ), fingerprinting techniques (Butterly et al., ; Gschwendtner et al., ), PhyloChip (Hayden et al., ; He et al., ), and 454 pyrosequencing of 16S rRNA gene amplicons with shallow sequencing depths (Deng et al., (1698–3299 sequences/sample); Ren et al., (2,000 sequences/sample); Okubo et al., (2523–14395 sequences/sample)). However, considering that rare taxa may be more responsive to climate factors, methods with higher resolutions should be applied (Dunbar et al., ).…”