Modelling aboveground biomass and nutrient export in South African Pinus elliottii

Muyambo, Phillip (2017-03)

Thesis (MScFor)--Stellenbosch University, 2017.

Thesis

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.

AFRIKAANSE OPSOMMING: Die doel van die studie was om ‘n allometriese model vir Pinus elliottii wat groei in die Tsitsikamma area van die Oos-Kaap provinsie in Suid Afrika, te ontwikkel. 20 bome wat destruktief getoets is, is gebruik binne ‘n krono-orde van drie ouderdoms groepe in plantasies met uniforme kenmerke. Veld data was versamel van DBH (diameter by bors hoogte) en hoogte (H). Monsters van stomp skuiwe, takke en blare was versamel van die gesaagde bome. Veranderlikes wat ingesamel is van die biomassa monsters was gebruik vir die biomassa en voedingstowwe uitvoer modelering. Die digtheid van die hout skuiwe en bas was bepaal deur water ‘n verplasing tegniek. Stam biomassa was geherkonstruktireer met behulp van Smalian’s se volume formule. Die droë massa van die biomassa monsters is met behulp van regressive gebruik om ‘n stel lineêre modelle te ontwikkel wat biomassa voorspel teen logaritmies getransformeer voorspellers wat DBH, H, en DBH2H ingesluit. Modelle is gekies deur middel van orde-van-pas analise statistieke en parsimonie. ‘n Twee-stap skaal proses was gebruik om monsters op te skaal tot boom grootte en van boom grootte tot vak grootte, met behulp van alometriese modelle. Logaritmiese (ln) veranderde DBH was gebruik as enkel voorspeller vir die op skalings proses om bo-grond biomassa van ha orde te voorspel. Die berame AGB vir die 16 (522 SPH), 28 (347 SPH) en 33 (380 SPH) jaar oue Pinus elliottii bome was 99, 254 en 205 Mg haˉ¹ onderskeidelik. Die BEF waardes vir die studie was 0.81, 0.96 en 1.37 vir ligging 1, 2 en 3. Makro-voedingstowwe uitvoer toegeneem met die stand ouderdom. Die geskatte N uitvoer as gevolg van die oes stemwood en bas alleen was 388,7 kg ha-1 in jonger bome (16 jaar) en 720,7 kg ha-1 in ouer bome (28 en 33 jaar). 'N Groter uitvoer van mikro-voedingstowwe soos Mn, Fe en Zn is potensieel deur die oes van.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/101267
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