Cumulative effects of 20-years of livestock grazing, prescribed early fire and selective tree cutting on below ground biomass in sudanian savanna woodland, west africa

Belowground biomass is important components of terrestrial ecosystem carbon. Understanding its size and influence of disturbance on its level is essential for carbon evaluation in savanna ecosystems. We studied root biomass after twenty years (1992-2012) of application of early fire, grazing and selective tree cutting on two factorial experimental sites characterized by deep and shallow soils in Sudanian savanna-woodland ecosystems of Burkina Faso. Coring methods was used and at each sampling point, a block of soil 25×25×50 was taken and the roots (fine and coarse) were quantified used to measure root biomass. at two depths (0-20 and 20-50 cm). We found that grazing, selective tree cutting and early fire applied alone did not affect (p > 0.05) total root biomass. Nevertheless, signifcant cumulative effect was significant (P=0.001). Total dry weight of roots biomass ranged from 8.7 t.ha-1 on plots treated simultaneously with grazing, fire and wood cutting to 18.3 t.ha-1 on plots protected from grazing but subject to fire and wood cutting. Therefore, projects which aim to mitigate climate change by increasing carbon stocks in dry savanna ecosystems should pay more intention to roots biomass, taking care to avoid the co-occurence of the three disturbances factors in the same landscape.