[1] Nelson Mandela African Inst Sci & Technol NM AIST, Sch Life Sci & Bioengn, Dept Sustainable Agr Biodivers & Ecosyst Manageme, POB 447, Arusha, Tanzania
[2] Tanzania Wildlife Res Inst, POB 661, Arusha, Tanzania
[3] Univ Hohenheim, Hans Ruthenberg Inst, Ecol Trop Agr Syst, D-70599 Stuttgart, Germany
[4] Stockholm Univ, Dept Phys Geog, Svante Arrhenius Vag 8, S-10691 Stockholm, Sweden