Interaction between nematode and bacterial communities and their relationship with greenhouse gas emissions in integrated agricultural systems in Brazil
Agriculture and livestock are responsible for 2.3% of carbon dioxide (CO2) emissions and 87.1% of nitrous oxide (N2O) emissions into the atmosphere by Brazil. In this context, the expansion of areas with Integrated Agricultural Systems (IASs) is among the main climate change mitigation actions for the agricultural sector, which aims to reduce emissions of these greenhouse gases (GHGs). Currently, little is known about the effect of IASs on soil biota and their relationship to GHG emissions. Bacteria and nematodes are important components of edaphic biota and can be used to assess the impact of agricultural management practices on soil health. Nevertheless, there is a lack of research assessing bacterial and nematode communities in the context of IASs. Recent research indicates that the implementation of IASs can reduce the abundance of plant-parasitic nematodes and increase the predominance of predator nematodes. The activity of predator nematodes regulates the population of microbivore nematodes, and this may result in the mitigation of GHG emissions, mainly N2O. N2O is produced mainly by microbial processes of N transformation (nitrification and denitrification) in soils. However, there is a gap in knowledge about the relationship between GHGs emissions and the interactions between nematode and bacterial communities in the soil micro-food web. This project aims to elucidate the effects of the interactions between different trophic components of the soil nematode community and the soil bacterial community on CO2 and N2O emissions from IASs in Brazil. To achieve this object, the project is strategically designed in two stages. In stage I, the project will evaluate three experimental areas in the Amazon-Cerrado (Sinop, state of Mato Grosso), Atlantic Forest (Itambe, state of Pernambuco), and Caatinga (Sobral, state of Ceara) biomes, as well as two crop production fields with IASs in the Atlantic Forest (Jardim Olinda, state of Parana) and Cerrado (Bandeirantes, state of Mato Grosso do Sul) biomes. In stage II, three experiments under controlled conditions using the soils from the preselected experiments and production fields will be conducted. The total nematode and bacterial community will be characterized by amplicon sequencing of 18S rRNA and 16S rRNA genes, respectively. In parallel, plant-parasitic nematodes will be characterized by optical light microscopy. The greenhouse gases CO2 and N2O will be collected using the static chamber method and quantified by gas chromatography. Sequencing results and microscope counts will be related to CO2 and N2O emissions by correlation and multiple linear regression analysis. With the results of the study, it will be possible to guide or improve management practices in IASs to promote multitrophic interactions of soil biological communities capable of mitigating GHG emissions.