Abundance of microbial community genes encoding terminal proteins of the aerobic and denitrification respiratory chains as indicators of ecohydrologic gradients in a coastal temperate rainforest

The persistence of soil organic carbon (SOC) is closely linked to the capacity of the soil microbial community to catalyze oxidative degradation of organic matter. This study uses a landscape-scale metagenomics approach to examine the relative abundances of genes encoding different terminal electron acceptors used for aerobic respiration and denitrification between soil microbial communities across an ecohydrologic gradient. The perhumid zone of the North Pacific coastal temperate rainforest serves as a template to test the associations between these differing respiratory pathways, soil conditions, and tree species biomass. We used the occurrence of reads in soil metagenomes as a proxy for the relative abundance of genes across the ecohydrologic gradient and identified distinct microbial fingerprints differentiating the driest (upland forest) and wettest (palustrine scrub-shrub and palustrine emergent wetland) ecosystem types. There was little gene-based differentiation between the ecosystem types at the wettest end of the ecohydrologic gradient - scrub-shrub wetland and emergent wetlands – while forested wetlands, which occur as gradient sites between upland forests and emergent wetlands on the landscape, were characterized by substantial metagenomic variability and, consequently, overlapped in their soil metagenome with the other ecosystem classes. Hydrology, as measured by groundwater depth was a predictor of O2 and N-oxide reductase abundances. High affinity O2 reductase genes were associated with wetter topographic positions, which has not been shown at the ecosystem scale, or in soils in-situ previously. N-oxide reductase genes were more associated with plant communities found at wetland sites but were not related to soil inorganic nitrogen, suggesting that nitrate supply may be limiting to denitrifiers ubiquitously across this gradient. Two plant species, Tsuga heterophylla (TSHE) and Pinus contorta spp. contorta (PICO), were more strongly correlated with O2-reductase and N-oxide reductase genes than site hydrology, respectively. This research represents a step toward fingerprinting the ecosystem microbiome using genes coding for specific terminal electron acceptors that control the fate of SOC and their ecohydrologic controls

Atributos de solos hidromórficos no Pantanal Norte Matogrossense Attributes of the hydromorphic soils in the Pantanal of North Matogrosso

Os solos hidromórficos, comuns na Amazônia e no Pantanal, estão sujeitos à alternância natural de períodos de alagamento e secamento, que conduzem a uma formação e características diferenciadas. Estes solos guardam estreita relação com a natureza do material de origem e com os processos de deposição e sedimentação. O objetivo neste trabalho foi avaliar as características químicas, morfológicas e mineralógicas de três perfis de solos do Pantanal Norte Matogrossense (Planossolo, Plintossolo e Gleissolo), a fim de interpretar as relações entre suas propriedades e o ambiente em que foram formados. Os Planossolos e Gleissolos possuem maior fertilidade natural, evidenciada pelos valores expressivos de CTC (capacidade de troca de cátions) e saturação por bases. Os menores teores de Fe2O3 do Planossolo estão relacionados com a redução e remoção do Fe durante sua gênese A mineralogia da fração areia dos solos é constituída principalmente de quartzo, nódulos e concreções de Fe e de Mn, e em menor grau, biotita, muscovita e traços de turmalina, magnetita, ilmenita, epídoto, zircão e rutilo. Os solos apresentaram perfil mineralógico semelhante na fração argila, constituído por caulinita, esmectita, ilita e interestratificados do tipo ilita-esmectita. A mineralogia da fração argila dos solos foi compatível com as diferenças químicas constatadas entre eles, pois o Planossolo apresentou argila de maior atividade relativa às esmectitas e interestratificados ilita/esmectita, com maior soma de bases trocáveis e CTC, enquanto o Plintossolo e o Gleissolo, cujo mineral predominante foi a caulinita, apresentaram baixo teor de bases trocáveis e menor CTC.<br>The hydromorphic soils, common in the Amazon and the Pantanal, are subject to alternating periods of natural flooding and drying, leading to formation and differentiated characteristics. These soils are closely related to the nature of the sediments, a consequence of the source material and the processes of deposition and sedimentation. The objective of this study was to evaluate the chemical, mineralogical, and morphological profiles of three soils in the North Brazilian Pantanal North (Solonetz, Plinthosol and Gleysol) in order to interpret the relations between their properties and the environment in which they were formed. The Solonetz and Gleysol have higher fertility, as evidenced by the significant values of CEC (cation exchange rate) and base saturation. The lowest levels of Fe2O3 in the Solonetz are related to the reduction and removal of Fe during its genesis. The mineralogy of sand fraction consists mainly of quartz, nodules and concretions of Fe and Mn and to a lesser extent, biotite, muscovite and traces of tourmaline, magnetite, ilmenite, epidote, zircon and rutile. The soil profile was similar in clay mineralogy, consisting of kaolinite, smectite, illite and interstratified illite-smectite type. The clay mineralogy of soils was consistent with the observed chemical differences between them, as the clay Planossolo showed greater activity on smectite and interstratified illite / smectite, with greater total exchangeable bases and CEC, while the Plinthosol and Gleysol, whose predominant mineral was kaolinite, showed a low content of exchangeable bases and lower CEC