QUINTUS
Quinquennial (half-decadal) carbon and nutrient dynamics in temperateforests: Implications for carbon sequestration in a high carbon dioxide world
A £3.7m NERC funded research project, led by the University ofBirmingham’s Institute of Forest Research (BIFoR)October 2019 – September 2024.
The PI is Prof Rob MacKenzie (University of Birmingham) the postdoctoral research fellow is Dr Carolina Mayoral (c..mayoral@bham.ac.uk).
Atmospheric CO2 boosts photosynthesis, enhancing tree growth and forest carbon storage, a process known as 'CO2 fertilisation'. This removes 2-3 billion tonnes of carbon yearly, offsetting 25-30% of human-caused emissions. However, the continuation of this trend is uncertain due to potential nutrient shortages in soil, which could limit future forest growth and carbon absorption. This uncertainty underscores the need for reduced emissions to combat climate change effectively.
The study of mature forests is crucial for understanding potential limits on carbon absorption by terrestrial ecosystems due to nutrient availability. Mature forests stand as the primary carbon sinks on land, yet they often experience low nutrient levels because the extensive root systems have already exhausted the soil's key nutrients. Should these forests fail to sustain nutrient intake and carbon sequestration, it would significantly impact society. This would necessitate a more aggressive reduction in carbon dioxide emissions than presently anticipated to prevent the most severe effects of climate change.
Temperate forests currently absorb almost as much carbon as the emissions from all EU nations. While tropical rainforests are, of course, important, mature temperate forests are calculated to be fourfold more efficient at absorbing carbon, and so merit special attention. To be able predict how mature temperate forests will respond in the future, it is critical that we determine whether greater carbon dioxide concentrations in the atmosphere will allow mature trees in temperate forest to: 1) take up more nutrients from soils, and/or,2) increase the efficiency with which they use available nutrients to produce new plant tissue.
Manipulating CO2 for whole stands of mature forest is challenging and expensive, and until now there has been no experiment that would have allowed us to address the uncertainties. However, with BIFoR FACE, a unique whole-ecosystem, free-air carbon dioxide enrichment (FACE) experiment has been established, successfully exposing forest patches to CO2 concentrations over one third higher than current levels. Within this FACE ecosystem, the towering canopy trees have stood for at least 160 years, and the land has been forested for the past 400 years.
QUINTUS aims to carry out the detailed measurements of nutrient cycling (more than 20,000 analyses) that are required to answer the two key processes outlined above and, thus, determine how a mature temperate forest responds to rising atmospheric CO2. This new experimental understanding will then be used to develop and test the next generation of the computer models which are used to predict future rates of climate change. QUINTUS will deliver a foundational change in our understanding of future C uptake in temperate forests, and in mature forests generally.
This groundbreaking research is shedding light on how mature forests respond to elevated levels of CO2, providing invaluable insights into the future of these vital ecosystems.