A chronosequence of soil carbon and nitrogen dynamics in tropical multistrata agroforestry sytems
This thesis is an investigation of carbon and nitrogen dynamics in a 25 year chronosequence of cocoa ('Theobroma cacao' Linn.) plantations in Ghana, Africa. Three treatments, 2, 15 and 25-year-old plantations were selected as on-farm research sites. Soil carbon varied between treatments (2 years: 22.6 Mg C·ha-1; 15 years: 17.6 Mg C·ha -1; 25 years: 18.2 Mg C·ha-1) with a significant difference between 2 and both 15 and 25-year-old treatments (p < 0.05). Total soil nitrogen in the top 15cm varied between 1.09 Mg N·ha-1 and 1.25 Mg N·ha-1 but showed no significant differences between treatments. Nitrification rates, litter fall, and fine root quantity increased significantly with treatment age. However, Photosynthetically Active Radiation and soil temperature showed a significant decrease with age. No difference was found between litter decay rates at each treatment age. The effect of structural diversity on soil carbon and nitrogen was not significant in any of the measured parameters.