Thirty five-year results from seven<i>Pinus elliottii</i>(Engelman.) and<i>Pinus taeda</i>(L.) provenance trials in South Africa

Summary In 1937 a number of composite trials of Pinus elliottii var elliottii and P. taeda were established throughout South Africa, with seed of 6 P. elliottii and 11 P. taeda provenances, supplied by the Southern Forest Experiment Station, U.S.A. The trials were located at Tweefontein, Dukuduku, Kwa-Mbonambi, Border North, Border South, Kleinplaat and Lottering. The layout was a completely randomized design with a variable number of replications (1 to 4). The trials were measured regularly until 1972. The results of these trials can be summarised as follows: P.elliottii. In 1972, no significant differences were detected between the provenances at any of the trials. In most trials highly significant correlations were found between early and later growth traits. Definite assessment of the volume production was possible at age 4 years, except at two trials. Volume production tended to decline with latitude of place of origin, indicating that southern provenances are probably the best suited to South African conditions. Interaction between trial and provenance was probable for many trials. P. taeda. Significant differences between provenances were detected at most trials. More regular and stronger correlations between latitude of place of origin and all growth traits studied were found, and volume production declined with latitude. Provenances from coastal southern Texas, southern Louisiana and Florida were most suitable for South African conditions. Differences between the best and the poorest provenance were as large as 119%. P. taeda had on average a lower volume production than P. elliottii at all trials, except at Tweefontein, The growth of P. taeda at Tweefontein was outstanding with mean annual increments of the best provenances of 32 – 44 m3/ha at 35 years. Generally, it was possible to select the best provenances at age 2–3 years, or at most at age 9 years. Interaction between provenances and trials were not common and loblolly pine appeared to be a stable pine species over large environmental variation in South Africa.

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