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Forest impacts on climate; what are the controls on greenhouse gas emissions from trees?


Project Description

Forest are well known for their globally important role in the carbon cycle. Despite this many questions remain, especially with lesser known but highly important trace gas emissions (methane and nitrous oxide) which play a critical role in forest carbon and nutrient cycling. After CO2, methane (CH4) and nitrous oxide (N2O) are the most important greenhouse gases in the atmosphere. Recent world leading research by the supervisory team has shown tree stems to be one of the most important emission pathways for these greenhouse gases from forests (Pangala et al 2017; Welch et al 2019) yet trees remain understudied components of the CH4 and N2O cycles.

While we know trace gasses can be transported through and emitted from tree stems, the spatial variability can be extremely high, between forests, between trees and across stems. For example, trace gas exchanges varying both up the tree stem and radially around it. Ecological, biogeochemical and physical variables such as bark roughness, orientation, bark moisture, cryptogamic covers, the interior pockets of rot in the stem and other morphological interior features likely control this variability. But these controls are not understood. This is essential information if we are to understand how trees exchange climate relevant gases under a range of conditions – but notably in response to infections which can devastate whole forests. Tree death will alter both local soil biogeochemistry and the inner architecture of standing trees, promoting higher trace gas emissions. This could also happen in response to fire, flood or drought.

You will employ novel techniques including sonic and x-ray tomography to peer into living and dead tree stems to view these previously hidden controls. Further, you will use the latest field portable analytical equipment to directly observe and analyse CO2 and trace gas exchange in forests within Canada, Switzerland and the BIFoR FACE site in the UK where trees are exposed to elevated CO2 concentrations. The assembled supervisory team within the Birmingham Institute of Forest Research (BIFoR) and Forest Research has access to the full range of forests and techniques (e.g. Fig 1) to enable each of these questions to be investigated.

Funding Notes

CENTA studentships are for 3.5 years and are funded by the Natural Environment Research Council (NERC). In addition to the full payment of their tuition fees, successful candidates will receive the following financial support.
• Annual stipend, set at £15,009 for 2019/20
• Research training support grant (RTSG) of £8,000

References

Welch, B., Gauci, V., and Sayer E. (2019), Tree stem bases are sources of CH¬4 and N2O in a tropical forest on upland soils during the dry to wet season transition Global Change Biology 25(1): 361-372 https://doi.org/10.1111/gcb.14498 DOI: 10.1111/gcb.14498
Pangala, S.R. Alex Enrich-Prast, Luana S. Basso, Roberta Bittencourt Peixoto, David Bastviken, Edward Hornibrook, Luciana V. Gatti, Humberto Marotta Ribeiro, Luana Silva Braucks Calazans, Cassia Mônica Sakuragui, Wanderley Rodrigues Bastos, Olaf Malm, Emanuel Gloor, John Miller, Gauci V. (2017) Large emissions from floodplain trees close the Amazon methane budget, Nature DOI 10.1038/nature24639
Popkin, G. (2019) How Much Can Forests Fight Climate Change? Nature 565, 280-282 (2019) doi: 10.1038/d41586-019-00122-z

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