Allometric equations for estimating belowground biomass of Androstachys johnsonii Prain
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METHODOLOGY
Allometric equations for estimating belowground biomass of Androstachys johnsonii Prain Tarquinio Mateus Magalhães*
Abstract Background: The belowground component of the trees is still poorly known because it needs labour- and timeintensive in situ measurements. However, belowground biomass (BGB) constitutes a significant share of the total forest biomass. I analysed the BGB allocation patterns, fitted models for estimating root components and root system biomasses, and called attention for its possible use in predicting anchoring functions of the different root components. Results: More than half and almost one third of BGB is allocated to the lateral roots and to the root collar, respectively. More than 80% of the BGB is found at a depth range of 9.6–61.2 cm. As the tree size increased, the proportion of BGB allocated to taproots decreased and that allocated to lateral roots increased. All independent models performed almost equally, with the predictors explaining, on average, 98% of the variation in the BGB. Conclusions: It was hypothesised that BGB allocation patterns are a response of the anchoring functions of the tap and lateral roots and therefore, root component biomass models can be used as a methodology to predict anchoring functions of the different root components. Based on the fact that all models performed almost equally, the models using either diameter at breast height (DBH) exclusively as a predictor should be preferred, as tree height is difficult to measure. Models using the root collar diameter (RCD) only should be preferred when the tree is found cut down, as sometimes the RCD is affected by root buttress. Given the large sample size, the validation results, and the coverage of a wide geographical, soil and climatic range, the models fitted can be applied in all A. johnsonii stands in Mozambique. Keywords: Mecrusse, Anchorage, Additivity, Belowground biomass allocation patterns, Root components Background Androstachys johnsonii Prain (A. johnsonii) stands, known as mecrusse, are very important woodlands. Almost entirely restricted to Mozambique [1], it has an important socioeconomic value to local communities, that sell and use stakes and poles of A. johnsonii in the construction of homes, shelters, and furniture; and it is the main source of income in the Funhalouro and Mabote districts [2, 3]. On the global scale, mecrusse forests form part of the woodland belt that stretches over large portions of southern Africa and are reported to be a tipping *Correspondence: [email protected] Departamento de Engenharia Florestal, Universidade Eduardo Mondlane, Campus Universitário, Edifício no.1, 257, Maputo, Mozambique
point in regional ecological and socioeconomic development [4], hence, their importance in the mitigation of greenhouse gas emissions. Forest biomass is a key variable employed when making estimates of carbon pools in forests, and for studying other biochemical cycles [5]. In the past, only the aboveground portion of trees was the desired products from fo
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