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Microbial communities of Temperate, Artic and Tropical peatlands and their role in the response of carbon storage function to global change

Periodic Reporting for period 1 - MicroPEAT (Microbial communities of Temperate, Artic and Tropical peatlands and their role in the response of carbon storage function to global change)

Reporting period: 2016-05-01 to 2018-04-30

The study of peatlands is of great relevance in the current changing world, they are known as critical carbon reservoirs and store about one third of terrestrial carbon. Carbon storage function is linked to slow degradation of organic material (carbon) by microbes (bacteria, fungi, archaea, and protozoa), due to restricted environmental conditions (low pH and oxygen levels, and high concentration of phenols). Carbon cycle in peatlands are characterised by low carbon dioxide release and methane production, both recognised as critical greenhouse gases. Consequently, changes in the carbon metabolism in peatlands might have important consequences at global scale, releasing huge amounts of carbon dioxide to atmosphere and exporting dissolved organic carbon (DOC) to running waters and lakes. The highest extensions of peatlands are in temperate countries, where most of the research has been focused, but they are broadly distributed with significant resources in the Arctic and Tropical regions. Through the MicroPEAT project, we aimed to assessing peatlands from a global scale and shedding some lights on many aspects of peatland ecology still unresolved. Specifically, we compared peat-associated microbes and microbial metabolism from three contrasting regions: Temperate, Arctic and Tropic (Fig. 1), and tested the response of microbial metabolism, CO2 and CH4 emissions, and DOC exportation to drought disturbance in peatlands from those contrasting regions. Overall, through MicroPEAT project we got a comparative view of Arctic, Tropical and Temperate peatlands, showing so far key differences in environmental conditions, microbial metabolism and the effect of drought of moss-dominated peatlands. Our results highlight peat bogs diversity despite of having similar plant cover and restricted conditions, and contribute with critical information for peatlands management at local, European and global perspective.
In order to achieve the objectives of the project, MicroPEAT research programme involved two main components for each study region: an initial fieldwork to investigate local variability in terms of environmental conditions, microbial community structure and metabolism, and a later experiment to test drought effect on peat soil. During the first year of MicroPEAT project fieldwork in the Arctic and Wales was performed, samples from those sites were processed and drought experiment with Arctic peat cores was conducted. During the second year of the project, fieldwork in Colombia was concluded and drought experiments of Welsh and Colombian peat cores were developed together.
Requirements for field work and sample transport were checked in each study site before to make each field expedition, and corresponding administrative processes were conducted. Summarising, sampling in each region consisted of selecting six undisturbed peatlands sites dominated by mosses and, per triplicate, i) collecting peat cores of 5 x 100 cm and pore water, ii) measuring gas fluxes with static closed chambers, iii) measuring depth, temperature, pH, and conductivity. In the laboratory, an enzymatic profile, following natural layers in depth, was measured together with soil characteristics and metabolism. Soil microbial community, including Fungi, Bacteria, Archaea and Protozoa, of superficial soil layer is currently being assessed using specific primers.
Drought experiments consisted of four stages: i) an initial acclimation period, after extraction and transportation, of minimum 1 month; ii) then a pre-treatment period where all cores were kept waterlogged, around 2 months; iii) then 3 months of drought treatment; and, iv) 15 days of re-wetting. Enzyme activities and quality of pore water and gases emission were measured, as well as enzyme activities, chemistry and metabolism of peat soil. Currently, metagenomics of the microbial community from the experiments is being assessing.
MicroPEAT final results are not available yet but some general conclusions we have got so far are explained below. We have found remarkable differences in environmental characteristics (pH values, nutrients, and phenolic concentrations) among regions linked to variations in peat soil metabolism. For example, lignin degradation was particularly reduced in Wales, were lower pH value and higher phenol concentration were found, while degradation of cellulose and hemicellulose was quite constant among regions. Consequently, punctual gas emissions, measured in the field, suggest Welsh peatlands retain more carbon dioxide than Colombian and Arctic peatlands, but together with Colombian peatlands have more methane emissions (Fig. 2). Finally, preliminary analysis of the responses to drought from the three regions suggests that differential environmental and possibly microbial soil characteristics might are determining contrasting soil metabolism responses to drought. For example, lignin degradation seemed to be suppressed by drought in Colombia while not significant effect was observed in Wales and Arctic peat soil. Currently, several manuscripts are in preparation to disseminate MicroPEAT results.
Knowledge about peat bogs functioning and microbial carbon metabolism have many potential management application at global scale. This is even more relevant with the Wetland’s recent inclusion in international policy frameworks as part of climate change adaptation schemes, setting the ground for practitioners that manage carbon-balanced landscapes, to include wetland creation, restoration, and conservation in their portfolio (Villa & Bernal, 2018). In this context, MicroPEAT results have a relevant global and European impact by giving comparative data of critical information for peatlands management, such as gas emission, microbial metabolism, and responses to climate change of peatlands from contrasting regions.
Specifically for Colombia, MicroPEAT results is one of the first studies linking gas emission, peat soil metabolism, and microbial communities of peatlands from high Andes Mountains. This information contributes to the base-line on moss-dominated peatlands ecology in the Colombian Paramos, and more concretely will give critical knowledge to be used by the Sumapaz NNP employers in the natural park management.
In Wales, MicroPEAT involved collecting samples from peatlands in Welsh Water (drinking water Company in Wales) catchments and final results related to dissolved organic carbon exportation to the catchments and water quality will be supply to the company at the end of the project.
MicroPEAT results from the Arctic have especial relevance due to the rapidly change this environment is suffering related to climate change. The methane stored in polar peaty soils potentially could be released to atmosphere due to changes in temperature and precipitations, accordingly, the understanding of carbon cycle in this environment might help to mitigate the climate change impact. Additionally, MicroPEAT project was included in the Research in Svalbard Database (RiS) and final results will be also sharing through this platform.
Figure 1. Study sites of MicroPEAT project.
Figure 2. Gas emissions in peatlands from Colombia, Svalbard and Wales