Improved tree height estimation of secondary forests in the Brazilian Amazon

Abstract

This paper presents a novel approach for estimating the height of individual trees in secondary forests at two study sites: Manaus (central Amazon) and Santarém (eastern Amazon) in the Brazilian Amazon region. The approach consists of adjusting tree height-diameter at breast height (H:DBH) models in each study site by ecological species groups: pioneers, early secondary, and late secondary. Overall, the DBH and corresponding height (H) of 1,178 individual trees were measured during two field campaigns: August 2014 in Manaus and September 2015 in Santarém. We tested the five most commonly used log-linear and nonlinear H:DBH models, as determined by the available literature. The hyperbolic model: H = a.DBH/(b+DBH) was found to present the best fit when evaluated using validation data. Significant differences in the fitted parameters were found between pioneer and secondary species from Manaus and Santarém by F-test, meaning that site-specific and also ecological-group H:DBH models should be used to more accurately predict H as a function of DBH. This novel approach provides specific equations to estimate height of secondary forest trees for particular sites and ecological species groups. The presented set of equations will allow better biomass and carbon stock estimates in secondary forests of the Brazilian Amazon.

Retrieving Secondary Forest Aboveground Biomass from Polarimetric ALOS-2 PALSAR-2 Data in the Brazilian Amazon

“…and Casearia grandiflora Cambess, a pioneer species and early secondary species, respectively, which are virtually absent in the PFs and have a lifespan superior than 50 years [81]. Such findings have implications for modeling tree growth, as reported by Cassol et al [63], who observed a higher initial MAI of the Ht in the secondary species in relation to pioneer species at the same study site.…”

“…(Maçaranduba) and Hymanaea courbaril L. (Jatobá) with an average height of 35-40 m and a lower stratum made of sub-dominant trees (average height = 15-30 m) [60][61][62]. The SFs, however, show a unimodal distribution of tree-height with mean 14.3 m where emergent trees are rare and represented by small individuals [63]. The species density ranged between 133 and 186 sp ha −1 , and the tree density is 441 ± 43 ind ha −1 with the most prominent families being Lechytidaceae and Fabaceae [51,60,61].…”

“…where AGB is the live aboveground biomass in kg, DBH in cm, h is the total height estimated by hypsometric equations adjusted by ecological species groups by Cassol et al [63], and ρ (rho) is the wood density collected from the literature and from the Global Wood Density Database [63,68]. Palm AGB was measured with distinct equations according to Table S1, Supplementary Materials.…”

“…So, the classification of the SF in the ISS, IntSS, and AdvSS should not be only based on structural parameters or species richness and composition [12]. Pioneer species comprise 33% of the S and almost 40% of the N in the Santarém study site [63,64]. The most common species were Guatteria poeppigiana Mart.…”

Allometric models to estimate tree height in northern Amazonian ecotone forests

“…Our accuracy measures for the best model support this assertion (standard error of the estimate = ~3.3 m), because the spread of points around the predicted values from the true regression line could be considered to represent a substantial bias due to different forest types and environmental filters acting in the ecotone zone. However, this bias is very close to values obtained by other regional studies based on larger datasets, as in Cassol et al (2018), which indicated an accuracy between 2.3 and 3.0 m for different models formulated to estimate the height of trees in two secondary-forest sites in Brazilian Amazonia. This implies that our best allometric relationship expresses the shared environmental dependence within a standard of accuracy similar to other studies using larger databases.…”