Articles | Volume 5, issue 2
Earth Syst. Dynam., 5, 257–270, 2014
Earth Syst. Dynam., 5, 257–270, 2014

Research article 10 Jul 2014

Research article | 10 Jul 2014

Bimodality of woody cover and biomass across the precipitation gradient in West Africa

Z. Yin1, S. C. Dekker2, B. J. J. M. van den Hurk1,3, and H. A. Dijkstra1 Z. Yin et al.
  • 1Institute for Marine and Atmospheric research Utrecht, Utrecht University, Utrecht, the Netherlands
  • 2Copernicus Institute of Sustainable Development, Utrecht University, Utrecht, the Netherlands
  • 3Royal Netherlands Meteorological Institute, De Bilt, the Netherlands

Abstract. Multiple states of woody cover under similar climate conditions are found in both conceptual models and observations. Due to the limitation of the observed woody cover data set, it is unclear whether the observed bimodality is caused by the presence of multiple stable states or is due to dynamic growth processes of vegetation. In this study, we combine a woody cover data set with an aboveground biomass data set to investigate the simultaneous occurrences of savanna and forest states under the same precipitation forcing. To interpret the results we use a recently developed vegetation dynamics model (the Balanced Optimality Structure Vegetation Model), in which the effect of fires is included. Our results show that bimodality also exists in aboveground biomass and retrieved vegetation structure. In addition, the observed savanna distribution can be understood as derived from a stable state and a slightly drifting (transient) state, the latter having the potential to shift to the forest state. Finally, the results indicate that vegetation structure (horizontal vs. vertical leaf extent) is a crucial component for the existence of bimodality.

Final-revised paper