Shifts in tree allometry in a tropical dry forest: implications for above-ground biomass estimation

Abstract

<p><strong>Background:</strong> Accurate estimations of aboveground biomass (AGB) based on allometric models are needed to implement climate-change mitigation strategies. However, allometry can change with tree size.</p><p><strong>Questions:</strong> Does allometry in a tropical dry forest change with tree size? Does combining different allometric equations provide better AGB estimates than using a single equation?</p><p><strong>Study site and dates:</strong> San Agustín Ejido, Yucatán, México, 2016.</p><p><strong>Methods:</strong> Forty-seven trees of 18 species with 2.5 to 41.5 cm in diameter at breast height (DBH) were sampled. Stems and branches were sectioned, and samples were dried and weighed to estimate tree AGB. Segmented linear regression was used to evaluate changes in allometry between DBH, height and AGB. Different equations were tested for each size category identified, and the best models and model-combinations selected.</p><p><strong>Results:</strong> A shift in the AGB-height relationship was found, defining two tree-size categories (2.5-9.9 cm and ≥ 10 cm in DBH), with the inflection point corresponding to the average canopy height (12.2 m). The best models were AGB = exp(-2.769+0.937ln(D<sup>2</sup>HPw)) for trees < 10 cm DBH and AGB = exp(-9.171+1.591lnD+3.902lnH+0.496lnPw) for trees ≥ 10 cm DBH (<em>R</em><sup>2</sup> = 0.85 and <em>R</em><sup>2</sup> = 0.92, respectively). The combination of these models produced more accurate AGB estimates than a single model or combinations involving regional models with larger sample sizes.</p><p><strong>Conclusions</strong>: These results highlight the importance of locally-developed models and suggest changes in allometry and resource allocation: towards height growth for small trees, thereby reducing the risk of suppression, <em>versus</em> towards AGB growth for larger trees, thereby maximizing stability and resource acquisition.</p>

A Generalized Model of Complex Allometry I: Formal Setup, Identification Procedures and Applications to Non-Destructive Estimation of Plant Biomass Units

“…However, a concurrent plot of κ(x) index (Figure 1b) exhibits noticeable deviations from the line y = 1 for small values of the covariate. Similarly marked deviations of the κ(x) from the line y = 1 are shown in the biphasic fit to the Ramirez-Ramirez et al [6] data (Figure 8d). Comparable effects are displayed for small eelgrass leaves (Figure 12d).…”

“…The length times width proxy provided estimations of leaf area. A second data set composing 47 measurements of aboveground tree biomass (ABG) and height (H) was taken from Ramirez-Ramirez et al [6]. by electronic scanning methods.…”

“…This notation convention will be maintained throughout. Generally, the efficiency of analytical methods in geometrical space centers on suitability of the retransformation step entailed by Equation (6). For instance, Mascaro et al [88] asserted that biased results that Packard [66] blamed on a TAMA fit can be explained by a missing CF.…”

“…Carbon fixation by plant biomass units promotes reduction of concentration of greenhouse gases in the atmosphere, thereby lessening global warming [1][2][3][4][5][6]. Therefore, the assessment of the flux and storage of carbon in plant biomass is of great interest.…”

Peer Review #1 of "Assessment of a Takagi–Sugeno-Kang fuzzy model assembly for examination of polyphasic loglinear allometry (v0.1)"

“…Packard 2012a resources to increase height. Then, beyond a threshold height at which suppression risk is at a minimum resource may be assigned to horizontal growth parameters like diameter, crown and root cover (Weiner, 2004;Ramírez-Ramírez et al 2019). Thus, since the aim of allometric examination is comprehending the biological processes that bring about covariance among traits, analytical methods entailing break point identification must be preferred over conventional As it is demonstrated by the steps in the derivation of equation 23, an imbedding of the TSK-PLA in the original theoretical perspective of allometry makes MPCA in arithmetical scale its logical consequence.…”