Analysis of natural regeneration in the Congo Basin: the case of Guarea cedrata (A. Chev.) Pellegr. in the forest massifs of the central basin of Yoko and Yangambi (Tshopo, DR. Congo

The present study was conducted in the forest massifs of the central basin of the Yoko Forest Reserve and the Yangambi Biosphere Reserve respectively located in the Ubundu territory, 32 km southeast of the city of Kisangani and in the Isangi territory, 100 km west of the same city. To carry out this study, twenty plots of one hectare each were installed, ten of which were in Yoko and ten in Yangambi, where seedlings of different height classes were measured and their x, y coordinates were taken; the degree of illumination and the thickness of the litter were also taken into account. In all twenty plots, except for plot 6 in Yangambi site and 3 and 8 in Yoko site, which each contain two seedlings, the rest of the plots contain only one seedling. A total of 7440 seedlings were recorded in two sites, of which 3194 seedlings (or 319.4 stems/ha) in Yangambi and 4246 seedlings (or 424.6 stems/ha) in Yoko. The S1 height class contains more stems/ha (2511 stems/ha in Yangambi and 2951 stems/ha in Yoko) than the other classes, and their numbers decrease with increasing size of individuals. Most of the seedlings developed in the covered areas (292.5 stems/ha in Yangambi and 325.1 stems/ha in Yoko) compared to the other light levels, and the same was true for the thickness of the litter, where the highest numbers were observed in the thin litter (196.3 stems/ha in Yangambi and 398.9 stems/ha in Yoko) compared to the other two litter thicknesses. There was no clear correlation between seedling height and environmental factors, namely, light levels and litter thickness. The positions of the seedlings in relation to the seedlings were independent of each other; however, some attraction was observed at small scales of analysis in some of the plots surveyed