FLF RENEWAL: Uncovering the drivers and consequences of changes in soil biodiversity for belowground carbon cycling in forests

Belowground biodiversity represents 59% of all species on the planet and 75% of terrestrial C stocks are in the soil. These complex and diverse soil biotic communities recycle nutrients, regulating plant nutrient availability and thus have far-reaching impacts on the capacity for trees to capture CO2. Yet, despite the importance of belowground biotic communities in regulating key ecosystem processes and supporting services vital to human wellbeing, we do not have a well-developed understanding of the drivers and consequences of changes soil biotic communities for the functioning of terrestrial systems. In particular, our understanding of the impact of changes in aboveground biotic communities for belowground foodwebs and processes is limited. This is relevant in the context of reforestation and wildlife recovery, both of which are key international strategies in mitigating the climate and biodiversity crises. As such, habitat restoration and conservation efforts mean that forest cover is expanding in Europe along with the populations and ranges of wild mammalian herbivores such as elk, and deer. Yet how herbivores influence the biotic communities that mediate tree growth and carbon storage above and belowground in forests is largely unknown, which is limiting our ability to realise the potential for natural systems to mitigate the climate emergency.

To address these gaps, the second phase of my FLF will (1) determine how changes in aboveground biotic communities impact the biggest reservoir of biodiversity on the planet: soil foodwebs; and (2) investigate how diversity in these complex foodwebs mediate the cycling and stabilisation of the largest terrestrial carbon pool: soil organic carbon.

We will continue to work with the wealth of samples collected during the first phase of my FLF (MR/T042923/1: Managing biodiversity and tropic cascades to enhance forest functioning and restoration) as well as generate new data using a powerful combination of large-scale long-term field experiments (established during the first phase), state-of-the-art molecular tools, and cutting-edge biogeochemical analysis. In doing so, we will address the following three core objectives: O1: Uncover aboveground drivers of carbon flow through belowground foodwebs. O2: Quantify how above and belowground diversity mediates the temporal stability of soil carbon in contrasting organic matter pools. O3: Disentangle the drivers of seedling regeneration and success.

In doing so, my team and I will provide a much-needed evidence-base to inform the way we manage expanding forest systems, which cover millions of hectares of the Earth’s surface. Furthermore, we will generate new knowledge of how soil biodiversity mediates natural climate solutions and thus determine the consequences of species losses for the provision of ecosystem services that underpin human well-being. The outcomes of this work will be directly relevant to landowners, conservation practitioners and policymakers, seeking to make evidence-based decisions on how to restore and project woodland systems to maximise the carbon and biodiversity benefits of their interventions.