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Cycle 5 (2015 Deadline)

Integrating dimensions of microbial biodiversity across wetlands and land use types to understand methane greenhouse gas cycling in tropical forests

PI: Jose Mauro Moura (, Universidade Federal do Oeste do Pará
U.S. Partner: Jorge Rodrigues, University of California, Davis
Project Dates: December 2016 - November 2019

Project Overview:

Deforestation is among the most important alterations occurring in tropical systems and is responsible for unprecedented losses of plant and animal biodiversity. However, little is known about the impact of land use change and seasonal inundation of wetlands on microbial biodiversity, especially in the tropics. In previous research, Dr. Moura and his colleagues discovered that soil microbial biodiversity in Amazon rainforest soil is homogenized and reduced by forest-to-agriculture conversion. However, it remains unknown how such changes in microbial biodiversity affect ecosystem functions. This challenge is paralleled by our need to understand, and ultimately manage, the problem of global
5-589 Moura
 Project PI Jose Moura with his students (Photo courtesy of J. Moura)
climate change. This project addresses the intersection of these two questions in the context of biodiversity conservation by asking: “how does the interaction between soil microbial and forest tree biodiversity control cycling of the powerful greenhouse gas methane along gradients of land use and seasonal water inundation in Amazon forests?” To predict the future of methane as a driver of climate change in this system, the researchers will combine novel gas flux measurement instrumentation with cutting-edge molecular microbial ecology. They will address biodiversity and environmental controls on methane production from tropical regions by measuring methane fluxes from a variety of potential sources, including surfaces of tree stems and leaves, soil, and water in forested and deforested areas, as well as upland and wetland areas. Detailed inventories of biodiversity of methane-active vegetation and microbial communities will be performed in the Santarem region of Brazil.

The goals of the project are to advance biodiversity conservation science in Amazônia by (1) quantifying methane-cycling microbial diversity as a function of land use and seasonal inundation, (2) quantifying interactions between methane-cycling microbes and methane cycling, and (3) incorporating knowledge of interactions between methane-cycling microbes and plants into conservation and management plans for mitigating the climate impact of methane emissions. Collaborators from the United States will work with the Brazilian team to analyze and integrate results and ultimately create a model to predict the response of methane cycling to land-use change. This model will not only be useful to a wide community of researchers but will also inform stakeholders and local policy administrators on protecting local biodiversity. The project’s focus on microbial biodiversity as a driver of methane cycling through the twin lenses of land use change and tropical wetlands (the largest natural sources of microbially produced methane to the atmosphere in the world) links development-associated anthropogenic land use change to both biodiversity conservation and climate change feedback. The project will thus bring new knowledge from a novel field (conservation biology for microbes) to our understanding of the impacts of development. Results from this project will provide a basis to inform policy development to simultaneously address problems of biodiversity conservation and management of key economic resource for riverine communities.

Summary of Recent Activities

Dr. Moura and his colleagues continued carrying out an extensive program of field work during the first quarter of 2018, with Year 2 of their project in full swing. In January, they made an extra effort to finish their inventory of the várzea area, measuring the final two planned plots and collecting information on tree diameter at breast height (DBH) (1.30 m from the ground) and approximately 3.0 m height (above the water line during the high water phase). The team also worked to take measurements of the forest biomass increment and litter production at their upland plots. They began installing dendrometric bands on the trees of the varzea plot at the two heights mentioned above and measured greenhouse gas emissions (CH4 and CO2) at the varzea and upland forest plots. In late February, the continued taking monthly biomass increment and greenhouse gas emissions measurements and collected the litterfall from the upland forest sites. They also did maintenance on the litter traps at the varzea plots and assembled 32 litterbags for a decomposition experiment. Those litterbags were distributed equally among the varzea and the upland forest plots. Installations of dendrometric bands continued, and the researchers marked the coordinates of the corners of all plots for identification and map construction purposes. The group’s campaign in late March focused on keeping up with the monthly biomass, litter production, litter decomposition, and soil moisture measurements at the terra firme plots. Litter production and litter decomposition measurements were also taken at the varzea plots, as were greenhouse gas emission readings from both types of plots.

The biggest challenge the team faced during this reporting period was working at the flooded area in Arapixuna District. By the end of January, all the forest plots they had established at the varzea for the forest inventory and gas flux measurements were flooded, with the waterline being about 1 m above the ground. This new condition changed the way they could access the area and measure biomass increment, litter production, and gas fluxes. For example, the litter traps must float now, and floating chambers are required for the gas measurements. The researchers encountered another issue when the owner of the secondary forest site (upland forest area) decided to use it for agricultural purposes and asked them to find another place to work.

Plans for the second quarter of 2018 call for installing an eddy covariance flux tower at the varzea site in Arapixuna District, keeping up with the vegetation inventories at the high varzea, low varzea, and upland secondary forest plots, and continuing to measure the DBH increment in order determine the trees’ biomass increment. At their other sites, the team will collect soil samples in forest, pasture, and soybean fields for microcosm and mesocosm experiments at the Tapajos National Forest - FLONA TAPAJOS (two pristine primary forest areas), Sao Jorge Community (one pasture site) and Km30 (one secondary forest area and on indigenous Terra Preta).

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