Separating autotrophic respiration due to roots from soil heterotrophic respiration in an agroforestry parkland system in Saponé, Burkina Faso

Abstract

Soil respiration is the largest component of ecosystem respiration but little is known about it and its components in parkland systems. We therefore conducted an experiment to estimate the amount of CO₂ respired and to partition it into soil, tree root and crop root contributions in parkland systems in Burkina Faso. Three factors effects were estimated: pruning, species and presence of tree canopy. Pruning showed no significant effect on soil respiration. The soil respiration was significantly higher under Parkia biglobosa (1.54 g CO₂ m^-2 h^-1 against 0.93 in the open area) than under Vitellaria paradoxa (0.98 g CO₂ m^-2 h^-1 against 0.52 in the open area). The autotrophic respiration associated with the P. biglobosa system due to sorghum roots was 0.37 g CO₂ m^-2 h^-1 and due to tree roots was 0.61. For the V. paradoxa system, the figures were 0.13 g CO₂ m^-2 h^-1 for sorghum roots and 0.46 for tree roots. We observed higher CO₂ emissions from under trees crowns than in open areas owing to higher tree-root respiratory activities, and higher water and organic matter contents. However, further studies are needed to discover if these low values of soil CO₂ fluxes from parklands translate into higher amounts of carbon fixed than emitted taking into consideration the seasonal variations.

Keywords: Carbon balance, CO2 flux, carbon-sink, carbon-source.