Effects of irregular stand structure on tree growth, crown extension and branchiness of plantation-grown Pinus patula

The practice of combining row and selective thinning in commercial pine plantation silviculture carries the risk of unwanted irregularities in tree distribution, a situation that is aggravated when tree selection during marking is poor. The potential consequences of poor tree selection are accentuated by gaps along row removal. This leads to spatially asymmetric growing space to adjacent trees. The effect of irregular stand structures on tree morphology and growth are investigated in this study, and are based on two stands of Pinus patula (Schiede ex Schltdl. et Cham.) in Langeni Plantation, South Africa. A comparison between trees grown in an all-sided and one-sided spatial competition situation is presented to assess the degree of differences between the two situations. Results of this study show significantly larger crown diameters, crown lengths, longer and thicker branches, disproportionately one-sided crown growth and a reduction in space-use efficiency in stands with irregular competitive status. These factors potentially negatively affect saw timber quality and volume production from the stands at final felling.