Provenance and family-within-provenance variation in Pinus patula, Pinus patula subspecies tecunumanii and Pinus oocarpa planted at Turbo, Kenya.

摘要

Pinus patula accounts for about 26% of all forest plantations in Kenya and is used mainly for timber, pulpwood and plywood production, whereas Pinus patula subsp. tecunumanii and Pinus oocarpa have been planted on experimental scale only. The 3 close coned pine species were studied in a field trial planted in 1985 at Turbo, Kenya, as part of an international series of trials of the species. The study investigated variation among the species, provenances and families-within-provenances. Seven families of P. patula, 5 provenances of P. patula subsp. tecunumanii comprising 10 families each, and 3 provenances of P. oocarpa were included in the trial. Results of assessments of height and diameter at breast height (DBH) made at 8 yr old showed significant differences among the species. P. patula was the best in both height and volume production whereas P. patula subsp. tecunumanii was best in DBH and volume per hectare. However, the differences between these 2 species were non-significant, despite P. patula being genetically, while P. patula subsp. tecunumanii is still in a relatively unimproved state. Furthermore, P. patula subsp. tecunumanii has also been shown to have a better form and lighter branching and may be more productive both in quantity and quality of products. P. oocarpa was poorest in all characteristics assessed. Significant differences were detected in DBH and volume production among provenances of P. oocarpa but not in height, whereas the differences in height, DBH and volume amongfamilies of P. patula were non-significant. Family heritability estimates in P. patula subsp. tecunumanii were high: 0.61, 0.69 and 0.70 for height, DBH and volume production, respectively. The results suggest that P. patula subsp. tecunumanii may have potential for planting at Turbo and in regions with similar conditions, and also in areas currently planted with P. patula. P. oocarpa may be suitable for planting in drier parts of Turbo and sub-humid lowlands.