Carbon sequestration in young temperate food forests
A case study analysis on a chronosequence of the transition from grassland to food forests
B.A.G. Wendel (TU Delft - Technology, Policy and Management)
M.J.J. Schrama – Mentor (Universiteit Leiden)
Laura Scherer – Mentor (TU Delft - Energy and Industry)
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Abstract
The food sector plays a crucial role in exceeding several planetary boundaries. Currently, humanity has the challenge to stay between these boundaries. Food forests are an approach for improving ecosystems in soil quality, sequestering carbon and enhancing biodiversity while providing food. However, this concept is yet nearly unstudied in temperate regions. Accordingly, this study attempted to investigate aboveground and belowground storage, carbon fluxes, and the build-up rate in the transition from grassland to a food forest through an in-depth case study in a temperate region. In order to analyse all key carbon pools, a plotless method was applied for the coppice, hedgerows, fruit and nut-bearing trees, and a plot-based method for the grass, herbs, litter and soil organic carbon (SOC).
Overall, the results showed exponential growth in aboveground carbon in the living biomass, though remarkably different patterns for SOC over the first 5.5 years. The ground layer (e.g. grass, herbs, and litter) is a significant source of aboveground carbon in young food forests (95% in year 3.5 to 36% in year 5.5). The trees compartments showed an exponential increase, and the total stored carbon biomass in the food forests at the age of 5.5 is 6.0 t C ha-1 yr-1. The SOC differed over the years, which is 115 t C ha-1 in the grassland and depicts 78 to 136 t C ha-1in year 5.5. Finally, the food forest has the potential to sequester around 4.4 t C ha-1 yr-1 in above and belowground biomass, functioning as active carbon sinks already within the first five years of the case study. Coppice and hedgerows have proven to be vital in sequestering carbon in living biomass. Further research should investigate older food forests in temperate regions while bearing in mind the potential of coppices and hedgerows. In addition, a better understanding of belowground carbon is essential for assessing the net carbon impact of carbon farming initiatives, as the soil stores most of the carbon.