Experimental burn plot trial in the Kruger National Park: history, experimental design and suggestions for data analysis

The experimental burn plot (EBP) trial initiated in 1954 is one of few ongoing long-termfire ecology research projects in Africa. The trial aims to assess the impacts of differentfire regimes in the Kruger National Park. Recent studies on the EBPs have raised questions as to the experimental design of the trial, and the appropriate model specificationwhen analysing data. Archival documentation reveals that the original design was modified on several occasions, related to changes in the park's fire policy. These modifications include the addition of extra plots, subdivision of plots and changes in treatmentsover time, and have resulted in a design which is only partially randomised. The representativity of the trial plots has been questioned on account of their relatively small size,the concentration of herbivores on especially the frequently burnt plots, and soil variation between plots. It is suggested that these factors be included as covariates inexplanatory models or that certain plots be excluded from data analysis based on resultsof independent studies of these factors. Suggestions are provided for the specificationof the experimental design when analysing data using Analysis of Variance. It is concluded that there is no practical alternative to treating the trial as a fully randomisedcomplete block design.