REGENERATION CAPACITY AND PRODUCTIVITY OF NATURAL FOREST IN BURKINA-FASO

In 1983 trials were established at four sites in Burkina Faso to study, through annual inventories, the potential regeneration capacity and productivity of natural forest in a coppice exploitation. The trials, planned for a period of 20 years, are in the Sudano-Sahelian zone (Yabo), North-Sudanian zone (Bissiga and Sa triple-overdot) and South-Sudanian zone (Toumousseni). After 5 years, good regeneration was found at all sites. The original felled population showed a mortality varying from 11.1% (Sa triple-overdot) to 17.6% (Yabo), and the average dominant height varied from 2.12 m (Yabo) to 3.07 m (Sa triple-overdot). The strong initial increase of the dominant height fell back sharply after 2 years for Yabo and Bissiga and after 3 years for Sa triple-overdot. Toumousseni showed poor initial height growth but good growth for the following 3 years. In 1988 the trials were partially felled to establish volume equations. Estimated average productivity over a period of 5 years in m3 ha-1 year-1 was 0.61 (Yabo), 0.80 (Bissiga), 1.04 (Sa triple-overdot) and 0.93 (Toumousseni). It is provisionally expected that the maximum average productivity will be reached in the seventh or eighth year for Yabo and Bissiga, and a few years after that for Sa triple-overdot. The regeneration at Toumousseni sustained a major setback during the first years due to dense grass development after the felling, but it has recovered well and its average productivity will soon surpass that at Sa triple-overdot. As a separate part of the trial a number of plots were felled on four different dates, of which three were felled after the first rainy season of the main trial had passed. It was found that these younger plots showed, for two investigated years, the same irregular height growth pattern as the older plots. A relation with rainfall figures was not found.