ACCOUNTING FOR CARBON IN ARTOCARPUS ALTILIS AFFORESTATION SYSTEMS

Abstract

As the impacts of climate change accelerate, the need for climate-smart agriculture—crops and systems with a high degree of productivity that are both resilient to a changing environment and reduce greenhouse gas emissions—will only increase. Once a substantial source of calories in the Hawaiian Islands and elsewhere around the Pacific, Artocarpus altilis, or breadfruit, has been suggested as an agricultural product that meets these standards. Among its potentially climate-smart attributes, breadfruit has the potential to store carbon in its biomass, and accompanying farming practices such as co-cropping could potentially increase carbon storage within the soil. To begin to elucidate some of these attributes, this study explored the terrestrial carbon pools associated with breadfruit afforestation by 1) quantifying above-ground biomass (AGB), 2) extrapolating to landscape-scale impacts by reviewing the below-ground biomass (BGB) and creating growth curves for breadfruit, and 3) conducting a cursory exploration of dead organic matter (litter) and soil organic carbon. The study followed guidelines and methods published in the scientific literature and carbon accounting documents to develop the allometry to describe AGB and growth of A. altilis over time, and based on this estimate, employed a root-to-shoot ratio to estimate BGB. We employed a standard sampling technique to estimate litter mass and its associated carbon content and developed a sampling design to describe total and hot water extractable soil organic carbon present within a subsection of the breadfruit orchard. This thesis’ primary contribution to the body of literature is the development of a novel allometric equation that describes AGB and carbon in terms of diameter at breast height (DBH) in A. altilis AGB=-4.586+0.1635×DBH+ 0.2229×〖DBH〗^2. Applying these equations approximately 10 years into an afforestation project each breadfruit tree contains approximately 90.2 kg Carbon in above- and below- ground biomass. In comparison, the litter sampling effort arrived at an estimated .538 kg Carbon per tree in the surface layer of litter and the soil carbon sampling showed no significant changes in soil carbon over the same timeframe. The thesis concludes that breadfruit has a significantly higher potential to sequester carbon compared to other annual staples, with most of the sequestration occurring in the treesʻ biomass. In combination with existing data supporting breadfruit’s ability to adapt to various climate change scenarios, we agree with the previous assessments that prioritize A. altilis as a climate-smart commodity.