Removing atmospheric carbon (C) and storing it in the terrestrial biosphere is one of the low-cost options to compensate for ever-increasing CO2 emissions into the atmosphere. Agroforestry systems have unique functional attributes that facilitate the restoration of nutrient stocks and soil fertility through the increase in soil carbon and nutrients. In University of Guelph Agroforestry Research Station, Canada, short-rotation coppice plantations were established as Willow-monocultures and tree-based intercropping (TBI) of Willow-Maple and Willow-Locust. In the present study, a range of published and unpublished data sets on biomass carbon, litterfall, decay rate, and soil respiration from the same experimental plot were analysed and designed to develop the process-based model. The carbon source and sink potentialities of Willow-Maple TBI, Willow-Locust TBI and Willow-monoculture were studied through the derived model. The questions addressed in this study were: (i) What are the above and below-ground biomass carbon production patterns in Willow TBI and monoculture at first 3rd year cycle of harvesting? (ii) Which systems are carbon neutral and carbon negative? (iii) What are the comparable pathways for the produced biomass, partitioned between in situ decomposition and harvesting? and (iv) How does the harvesting of willow on the first 3rd-year cycle impact the carbon budget of TBI and monoculture?
Results/Conclusions
The process-based model revealed that the management regimes influenced the carbon budgets. The ground biomass carbon production was recorded the highest under Willow-Maple TBI (14.30 Mg C ha-1 y-1) followed by Willow-Locust TBI (12.62 Mg C ha-1 y-1), and Willow-monoculture (7.63 Mg C ha-1 y-1). Total annual soil respiration was the highest under Willow-Locust TBI (18.35 Mg C ha-1 y-1) followed by Willow-Maple TBI (16.01 Mg C ha-1 y-1) and Willow-monoculture (12.47 Mg C ha-1y-1). Harvesting at the first 3rd-year cycle shows that 7.84 Mg C ha-1 were removed in both the TBI’s in comparison to 6.33 Mg C ha-1 in Willow-monoculture. The present study supports the following conclusions: (i) The Net Ecosystem Production follows the trend: Willow-Maple> Willow-Locust> Willow monoculture, (ii) The soil respiration was the highest under Willow-Locust TBI, (iii) Heterotrophic respiration was the major pathway for missing carbon in all the three systems, (iv) Willow-Maple and Willow-Locust were the major C-sink at pre-harvesting, but Willow-monoculture was the minor C-sink system and (v) Future studies should identify the best management systems for transforming monoculture plantations into systems that support biodiversity and enhances provision of ecosystem services such as carbon storage.