Browsing by Author "Muyambo, Phillip"
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- ItemModelling aboveground biomass and nutrient export in South African Pinus elliottii(2017-03) Muyambo, Phillip; Drew, David M.; Du Toit, Ben; Dovey, Steven; Stellenbosch University. Faculty of AgriSciences. Forest and Wood Science.ENGLISH ABSTRACT: The objective of this study was to develop an allometric model for Pinus elliottii grown in the Tsitsikamma region of the Eastern Cape province in South Africa. 20 trees were destructively sampled were within a chronosequence of three ages in plantations with uniform attributes. In-field data were collected of DBH (diameter at breast height) and height (H). Samples of discs, branches and foliage were collected from the felled trees. Variables collected from the biomass samples were used for biomass and nutrient export modeling. Density of the wood discs and bark was determined by a water displacement technique. Stem biomass was reconstructed using Smalian’s volume formula. To develop a set of linear models for biomass prediction, dry mass of the sampled biomass components was regressed against logarithmically transformed predictors that included DBH, H, and DBH2H. Models were chosen based on goodness-of-fit assessment statistics and parsimony. A two-step process was used to upscale samples to tree level and from tree to stand level using the allometric models. For additivity purposes, logarithmic transformed (ln) DBH was used as a single predictor to determine the aboveground biomass (AGB) at stand level. The estimated AGB for the 16 (522 SPH), 28 (347 SPH) and 33 (380 SPH) years old P. elliottii trees were 99, 254 and 205 Mg haˉ¹ respectively. The BEF values of this study which were 0.81, 0.96 and 1.37 for Site 1, 2 and 3. Macro-nutrients export increased with stand age. The estimated N export due to harvesting stemwood and bark alone was 388.7 kg ha-1 in younger trees (16 years) and 720.7 kg ha-1 in older trees (28 and 33 years). A larger export of micro-nutrients such as Mn, Fe and Zn is potentially through harvesting of needles.