3.1. Forest inventory
The pristine forest has a lower number of trees exceeding 6 cm diameter at 1.3 m height (839 ± 154 ha−1) than the Eucalyptus plantation (983 ± 93 ha−1). However, the Nyungwe forest has a much higher total basal area of 62.7 ± 27.2 m2 ha−1 compared to the Eucalyptus plantation (13.7 ± 2.2 m2 ha−1) because of the larger tree diameters of PE species in the Nyungwe forest (Table 2). In the Nyungwe forest, the dominant species was PE with the highest average tree number (322 ± 38 ha−1) and a basal area of 58.6 ± 2.9 m2 ha−1. The number of CP and CG trees in Nyungwe was 278 ± 79 and 239 ± 96 ha−1, respectively, with a basal area of only 2.2 ± 1.5 and 1.9 ± 1.1 m2 ha−1, respectively. In the pristine forest, the number of trees with a diameter at 1.3 m height exceeding 30 cm accounted for 27% of the total tree number. In the Eucalyptus plantation, there were no trees exceeding 30 cm at 1.3 m height. The canopy was more open in the Eucalyptus plantation than in the Nyungwe forest. Canopy openness varied from 17.9% to 39.3% in Nyungwe forest and from 38.9% to 53.1%in the Eucalyptus plantation.
3.2. Litterfall
in the pristine forest, total annual litterfall was on average 4175 kg ha−1 in the first study year and 4053 kg ha−1 in the second year. There was no significant difference in total litterfall between both years though differences occurred for the different litter fractions (Table 3).
Peaks in leaf litterfall (LLF) occurred in the major (July–August) and minor (December–January) dry seasons and at the onset of the rainy season (September–October) (data not shown). In the Eucalyptus plantation, total litterfall was only 2221 kg ha−1 year−1 and was significantly lower than in the pristine forest (Table 3).