Determinants of the seeds germination of Mukulungu- Autranella congolensis (De Wild.) A.Chev. in nursery

Abstract

Subject description. Autranella congolensis is one of the most exploited species in the Congo Basin and generally suffers from a regeneration deficit. To guarantee its renewal and sustainability, silvicultural interventions based on planting or enrichment techniques from seedlings produced in nurseries should be encouraged.
Objective. This study aims to evaluate the germination determinants of A. congolensis seeds in nursery.
Methods. The seeds were collected from 87 samples of A. congolensis seed plants chosen in a range of dbh from 20 to 155 cm in North Congo, in the Celtis forest in a plot of 400 ha on argilo- soils to sandy clay. A completely randomized two-block device was set up in a greenhouse at the National Forest Research Institute (IRF) of the Scientific City of Brazzaville, at an average temperature of 24 ° C. A batch of seeds (200 seeds) was divided into eight treatments to test the modalities for breaking dormancy, at a rate of 25 seeds per treatment. The seeds were individually and immediately sown after pretreatment, on a substrate previously sterilized and composed of 25 % sawdust and 75 % humified earth in 0.5 phytocells.
Results. Results show that the trees density was 0.22 stem/ha, and population structure showed a Gaussian distribution according the diameter class, indicating that this species generally suffers from a regeneration deficit. Average germination observed under treatments combination was 25 % of total sown seeds. Indeed, germination rate was respectively 33 %, 31 %, 25 % and 23 %, for the treatments T1, T8, T2 and T6, with germination deadlines of 51 days for T1, 62 days for T2, 74 days for T6 and T8.
Conclusion. The pretreatments applied showed a relatively significant effect on the germination rate. Subsequent studies on the germination of Autranella congolensis seeds on other substrates under controlled conditions.