Growth of four pine species at high altitude sites in the Eastern Cape Province.

Abstract

The growth of four pine species Pinus patula, P. greggii, P. elliottii and P. taeda was investigated on first rotation high altitude sites in the north-eastern region of the Eastern Cape Province. The study area encompass a broad range of sites in terms of soils (texture, drainage, depth) and climate (temperature and precipitation). Afforestation across the study area proved challenging and there is a need to better understand survival, tree growth and site variables that contribute to the unique forestry environment. Enumeration data of 539 compartments totalling 11 380 ha with an age-class distribution from 4 to 13 years were analysed using statistical analyses techniques, interpretation based on other research results and personal field experience. The dataset represents the first commercial scale growth information for the four species in the study area. The research was designed to study the survival of the four pine species and to analyse if there were any seasonal impacts on the latter. Furthermore, the tree growth, expressed as a site index at age 10 years (Sl (10)) and basal area at age 10 years (BA (10), was analysed to investigate the performance of the four pine species. Lastly, the relationship between tree growth expressed in site index (Sl (10) and basal area (BA (10) and site characteristics was investigated. On average the best survival species were P. elliottii and P. greggii yielding 69% and 68% respectively, with P. patula yielding a 56% survival. There was no statistically significant difference in the survival between the planting months for all species combined, however, P. patula showed significant differences between planting months. In addition there are statistically significant differences between the species in terms of Site Index and Basal Area and there is a relationship between growth and site variables. Evidence leading to the following conclusions is provided: i) P. patula is the worst species planted in North East Cape Forests (NECF) in terms of survival; ii) August is the best and November the worst planting month for P. patula; iii) the importance of species selection and site matching; iv) the successful introduction of P. greggii; v) tree performance can be explained with site variables, especially those derived from climatic information.