Soil seed bank characteristics ofCanarium schweinfurthii(Engl.): implications for its natural regeneration.

Abstract

Introduction. Canarium schweinfurthii, a tree species in the rainforest of Nigeria whose fruits are intensively gathered and eaten, is seriously endangered because of poor seed ger- minability and usage. Our study examined the pattern of seed distribution of C. schweinfurthii in the soil from the stem base of the parent plant and through the soil profile, and it assessed the seed level of germinability. Materials and methods. Four stands of C. schweinfurthii were selected from a study area in Southeastern Nigeria. Soils were collected from six distances from each trunk base (1 m, 5 m, 10 m, 15 m, 20 m and 25 m) and at four soil depths (0-5 cm, 5-10 cm, 10-20 cm and 20-30 cm); then seeds of C. schweinfurthii were isolated from the cores. Moreover, the percentage of viability and germinability of the seeds collected from each distance and depth were determined. Results. The maximum number of seeds occurred at 1 m from the trunk base (82.3 seeds·30 cm -2 ), which was 55% of the total collected seeds, and no seed occurred beyond 20 m from the trunk base. The mean number of C. schweinfurthii seeds occurring at 0-5 cm soil depth was 51.3 seeds·30 cm -2 , which was the highest from any profile. No seeds occurred below 20 cm. Sixty-seven percent of the total 148 seeds collected were considered viable, with about 80% of them occurring at the 0- 5 cm soil depth. Even with the pre-sowing treatment (cutting the hard endocarp), only 30.8% of via- ble seeds collected from 0-5 cm soil depth were able to germinate, while 10% of those collected from 5-10 cm depth germinated. Conclusion. The localization of over 80% of C. schweinfurthii seeds within a 5-m radius from the stem base and 65% within 0-5 cm soil depth encourages easy fruit gathering by local sellers and leads to depletion of the seed bank. Seedling multiplication, pro- tection of stands and domestication need to be initiated to lift C. schweinfurthii out of endangered status, considering the demand for the fruit and poor seed germination due to the hard endocarp. Nigeria / Canarium schweinfurthii / seed stands / gene banks / germinability