Biology subjects

Fonseca de Souza, L.

Publications and source records attributed to Fonseca de Souza, L..

4 recordsLinked to original sources

bioRxiv2024

Liming pasture soils in the Amazon region promotes low-affinity methane oxidation by type I and II methanotrophs

In the Amazon Forest region, cattle pastures are the main land use subsequent to deforestation. This land-use change affects the soil microbial community and methane fluxes, shifting the soil from a methane sink to a source. Soil physical and chemical attributes are changed due to slash-and-burn processes, including an increased soil pH after forest-to-pasture conversion. Without amendments, the pasture soils can become acidic again resulting in many cases in soil degradation. Liming is a standard management practice to increase soil pH while decreasing Al3+ availability. Liming is important to recover these degraded lands and increase soil fertility, but its impact on soil methane cycling in tropical soils is unknown. Here we investigated the role of soil pH on methane uptake under high concentrations of the gas. The top layer of forest (pH 4.1) and adjacent pasture soils (pH 4.8) from the Eastern Amazon were subjected to liming treatment (final pH 5.8) and incubated with [~]10,000 ppm of 13CH4 for 24 days to label DNA with 13C. Soil DNA was evaluated with Stable Isotopic Probing (SIP-DNA), methanotrophic abundance was quantified (pmoA gene), and high throughput sequencing of 16S rRNA was performed. Liming increased the methane uptake in both forest ([~]10%) and pasture ([~]25%) soils. Methanotrophs Methylocaldum sp. (type I) and Beijerinckaceae (type II) were identified to actively incorporate carbon from methane in limed pasture soils. In limed forest soils, Nitrososphaeraceae, Lysobacter sp., and Acidothermus sp. were identified as 13C-enriched taxa. The enrichment of the archaeal family Nitrososphaeraceae, known as ammonia oxidizers, is correlated with an increase of ammonia monooxygenase genes, which code for an enzyme complex with wide substrate specificity that can also perform methane oxidation. In conclusion, liming Amazonian pasture soils not only contributes to the fertility and recovery of degraded areas but also has the potential to improve the oxidation of methane at high concentrations of this gas.

ecology↗

bioRxiv2022

Dynamics of methane cycling microbiome during methane flux hot moments from riparian buffer systems

Riparian buffer systems (RBS) are a common agroforestry practice that consists of keeping a forested boundary adjacent to water bodies in agricultural landscapes, thus helping to protect aquatic ecosystems from adverse impacts. Nevertheless, despite the multiple benefits they provide, RBSs can be hotspots of methane emissions since abundant organic carbon and high-water tables are often found in these soils. In southern Ontario, Canada, the rehabilitation of Washington Creeks streambank occurred in 1985. In a recent study, methane (CH4) fluxes were measured biweekly for two years (2017-2018) in four different vegetative riparian areas alongside Washington creek: a rehabilitated tree buffer (RH), a grassed buffer (GRB), an undisturbed deciduous forest (UNF), an undisturbed coniferous forest (CF), and an adjacent agricultural field (AGR) for comparison. Based on methane fluxes in 2018 and hot moments identified, we selected two dates from summer (July 04 and August 15) and use soil sampling from those days to assess the CH4 cycling microbial communities in these RBS. We used qPCR and high-throughput sequencing from both DNA and cDNA to measure the diversity and activity of the methanogen and methanotroph communities. Methanogens were abundant in all riparian soils, including the archaeal genera Methanosaeta, Methanosarcina, Methanomassiliicoccus Methanoreggula, but they were mostly active in UNF soils. Among methanotrophs, Methylocystis was the most abundant taxon in all the riparian sites, except for AGR soils where the methanotrophs community mostly comprised members of rice paddy clusters (RPCs and RPC-1) and upland soil clusters (TUSC and USC). In summary, these results indicate that differences in CH4 fluxes between RBS at Washington creek are influenced by differences in the presence and activity of methanogens, which were higher in the deciduous forest (UNF) soils during hot moments CH4 flux, likely due to high water content in that soils. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=171 SRC="FIGDIR/small/517857v1_ufig1.gif" ALT="Figure 1"> View larger version (64K): org.highwire.dtl.DTLVardef@1dcde21org.highwire.dtl.DTLVardef@17b59e5org.highwire.dtl.DTLVardef@14adfb0org.highwire.dtl.DTLVardef@a3b411_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2020

Belowground changes to community structure alter methane-cycling dynamics in Amazonia

Amazonian rainforest is undergoing increasing rates of deforestation, driven primarily by cattle pasture expansion. Forest-to-pasture conversion has been associated with changes to ecosystem processes, including substantial increases in soil methane (CH4) emission. The drivers of this change in CH4 flux are not well understood. To address this knowledge gap, we measured soil CH4 flux, environmental conditions, and belowground microbial community attributes across a land use change gradient (old growth primary forest, cattle pasture, and secondary forest regrowth) in two Amazon Basin regions. Primary forest soils exhibited CH4 uptake at modest rates, while pasture soils exhibited CH4 emission at high but variable rates. Secondary forest soils exhibited low rates of CH4 uptake, suggesting that forest regrowth following pasture abandonment could reverse the CH4 sink-to-source trend. While few environmental variables were significantly associated with CH4 flux, we identified numerous microbial community attributes in the surface soil that explained substantial variation in CH4 flux with land use change. Among the strongest predictors were the relative abundance and diversity of methanogens, which both increased in pasture relative to forests. We further identified individual taxa that were associated with CH4 fluxes and which collectively explained ~50% of flux variance. These taxa included methanogens and methanotrophs, as well as taxa that may indirectly influence CH4 flux through acetate production, iron reduction, and nitrogen transformations. Each land type had a unique subset of taxa associated with CH4 fluxes, suggesting that land use change alters CH4 cycling through shifts in microbial community composition. Taken together, our results suggest that changes in CH4 flux from agricultural conversion could be driven by microbial responses to land use change in the surface soil, with both direct and indirect effects on CH4 cycling. This demonstrates the central role of microorganisms in mediating ecosystem responses to land use change in the Amazon Basin.

ecology↗

bioRxiv2020

Rainforest-to-pasture conversion stimulates soil methanogenesis across the Brazilian Amazon

The Amazon rainforest is a biodiversity hotspot and large terrestrial carbon sink that is threatened by agricultural conversion. Rainforest-to-pasture conversion leads to the release of a potent greenhouse gas by converting soil from a methane sink into a source. The biotic methane cycle is driven by microorganisms; therefore, this study focused on active methane-cycling microorganisms and their functions across land-use types. We collected intact soil cores from three land use types (primary rainforest, pasture, and secondary rainforest) of two geographically distinct areas of the Brazilian Amazon (Santarem, Para and Ariquemes, Rondonia) and performed DNA stable-isotope probing coupled with metagenomics to identify the active methanotrophs and methanogens. At both locations, we observed a significant change in the composition of the isotope-labeled methane-cycling microbial community across land use types, specifically an increase in the abundance and diversity of active methanogens in pastures. We conclude that a significant increase in the abundance and activity of methanogens in pasture soils could explain the greater methane flux. Furthermore, we found that secondary rainforests recovered as methane sinks, indicating the potential for reforestation to offset greenhouse gas emissions in the tropics. These findings are critical for informing land management practices and global tropical rainforest conservation.

microbiology↗