individual publications document part Long-term human and biophysical dynamics of soil degradation in the Kenyan Highlands 2006 Dynamics of poverty and soil degradation on smallholder farms in central and western Kenya 2005 Nitrogen fluxes in Soils Amended with Manure and Tithonia on a Chronosequence 2004 report The interplay between smallholder farmers and fragile tropical agroecosystems in the Kenyan highlands 2005