Determination of the most stable period for sampling Patula pine foliage in the summer rainfall region of South Africa

Abstract A study of Patula pine foliar nutrient concentrations showed that the levels varied seasonally. Highest concentrations were found in winter when the trees are dormant. The onset of the growing season caused a marked drop in foliar concentration. The trends noticed were the same at two sites approximately 25 km apart, and a study of two clones on one site showed the trends to be the same between clones. The most stable period was winter (June/July) and the most unstable, summer (January/February). Foliar levels and concentrations were correlated to climatic variables measured at the site but it was not possible to model the onset of the growing season from the data. Using stability of concentrations as our main criterion, we recommend winter sampling (June/July) as being the best for accurately estimating foliar concentration of a stand in the summer rainfall region. This recommendation is also likely to apply to other pine species planted in the area

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