Abstract
South Africa is a water scarce country with minimal natural forests. Plantation forest species such as the Mexican tropical hard pine, Pinus patula Schiede & Deppe ex Schltdl. & Cham., was introduced into the country to satisfy local fibre demand. Today, the majority of pine plantations in South Africa are found in the Mpumalanga province. The province has diverse growing conditions in relation to climate and soil properties. Sample plots were established in even-aged P. patula plantations and stratified according to soil parent material and altitude. Growing conditions of each sample plot were characterised according to climate and soil properties. A total of 540 sample trees were measured for height, diameter, density, and latewood content. The sample trees were harvested to produce 2690 logs. The logs were milled, and the resultant lumber was graded according to density, dynamic modulus of elasticity, and modulus of rupture. Annual maximum temperature had the most significant impact on tree growth, while rainfall correlated with wood density and latewood content of standing trees. However, annual maximum temperature and tree height had a negative relationship with the recovered lumber properties and dimensional stability. Spring rainfall appeared to be the most important factor influencing lumber twist and this was possibly due to the associated larger juvenile core present in the trees.
Funding source: York Timbers Inc
Acknowledgments
We would like to thank all of the York Timbers staff who assisted in the forests and at the Sabie processing facilities, to ensure the samples were collected, processed, and analysed. We would also like to thank the late Chief Executive Officer of York Timbers, Mr. Piet van Zyl for allocating funding to this project and believing in the power of science. This publication is dedicated to him.
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Research ethics: Ethical approval was not required to conduct the research presented in this manuscript.
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Author contributions: Jaco-Pierre van der Merwe collected the data, completed the modelling, and wrote the manuscript. Stavros Avramidis and Simon Ellis, Charlie Clarke, Julie Cool, and Shawn Mansfield aided with project conceptualisation, and reviewed and edited the manuscript. Sechaba Madiope assisted in processing and measurement of disc core samples. Oscar Tait, Hilton Kuisis, Jaco Potgieter, and Olwethu Spogter supervised the debarking and milling of sample logs, including automated log form measurements and log batching. Martin Bacher processed the machine grading measurements. Robert Ngomane and Thandekile Ncongwane assisted in the verification of machine grading values, by manual measurements.
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Competing interests: The authors declare that they have no conflicts of interest regarding this article.
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Research funding: Funding for this project was provided by York Timbers, South Africa, as well as sampling and the allocation of company resources.
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Data availability: The raw data can be obtained on request from the corresponding author.
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