Doctoral Degrees (Forest and Wood Science)

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Browsing Doctoral Degrees (Forest and Wood Science) by Subject "Branching (Botany)"

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    Estimation of tree biomass, measurement uncertainties, and morphological topology of Androstachys Johnsonii prain
    (Stellenbosch : Stellenbosch University, 2016-03) Magalhaes, Tarquinio Mateus; Seifert, Thomas; Stellenbosch University. Faculty of Agrisciences. Dept. of Forest and Wood Science.
    ENGLISH ABSTRACT: This research was aimed at estimating biomass stocks separated in above- and belowground tree components, and studying the topology of the shoot and root systems of Androstachys johnsonnii Prain in woodlands in Mozambique. A two-phase sampling design was used to determine above- and belowground biomass. In the first phase 3574 trees were measured in 23 randomly located circular plots (20-m radius). In the second phase, 93 trees were randomly selected as a subsample from the first phase sample for destructive measurement of biomass and stem volume, along with the variables of the first phase and for topological analysis of the shoot and root systems. Estimates of biomass stocks and quantification of the errors associated with those estimates were obtained using Phase-1 data and regression models. Additionally, biomass expansion factors (BEFs) were fitted based on the 93 trees harvested in the second phase. The estimated total tree forest biomass was 167.05 Mg ha–1 using biomass models and 150.74 Mg ha–1 using BEFs. The percent error resulting from plot selection and biomass regression equations for whole tree biomass stock was 4.55% and 1.53%, respectively, yielding a total error of 4.80%. Among individual variables in the first sampling phase, diameter at breast height (DBH) measurement was the largest source of error. Tree-height estimates contributed substantially to the error as well. For the second sampling phase, DBH measurements were the largest source of error, followed by height measurements and stem-wood density estimates. Of the total error (total variance) of the sampling process, 90% was attributed to plot selection and 10% to the biomass model. The BEF values of tree components were unrelated or weakly related to tree size, and root-to-shoot ratio (R/S) was independent of tree size; therefore, for A. johnsonii, constant component BEF and R/S values can be applied within the interval of sampled tree sizes. Visual analysis indicated herringbone-like branching pattern for both the root and shoot systems. However, the topological index (TI) and topological trend (TT) suggested otherwise. This discrepancy was attributed to the fact that A. johnsonii has multiple laterals per stem/taproot node, suggesting that the topological indexes (TI and TT) might yield biased conclusions regarding the branching pattern when the main axis has multiple laterals per node. Hence, a modified topological index (TIM) was developed that could be applied in the cases of multiple laterals per node while conserving the values of TI for cases with one lateral per node; the modified index was more efficient and realistic than TI. The area preserving branching was confirmed for each stem node confirming the self-similar branching. For the root system, the area-preserving branching was only confirmed for the first node; therefore, self-similarity was not confirmed.