Tropical forests structure and diversity: A comparison of methodological choices

Abstract

1. Large-scale data compilation is increasing steadily in tropical forest research, but the lack of standardized methods for data collection limits drawing inference from large datasets and cross-biome analyses. Different inclusion methods and minimum tree diameter threshold are among these varying factors. To tackle this issue, we evaluated how different approaches for tree sampling affects our understanding of diversity and functioning in different tropical vegetation types.2. We used a unique dataset of 44 inventory plots (43.54 ha) encompassing an aridity gradient: evergreen moist forests, semideciduous and deciduous tropical forests.Data were collected using the by-tree inclusion method, in which, all stems are measured if the equivalent diameter of the tree reaches the minimum threshold.We simulated the impact of adopting different inclusion methods (by-stem and by-tree) and different minimum diameter thresholds on the estimation of number of trees and stems, biomass and species richness. We used linear and nonlinear mixed models to investigate the effect of minimum diameter threshold and inclusion method on our different response variables. We also evaluated species chance to be sampled under different minimum inclusion criteria.3. Inclusion method and minimum diameter threshold mainly affect the estimation of number of trees and stems and species richness, especially in deciduous and semideciduous forests, where resprouting is a prevalent strategy. In these forests, many trees that have several stems do not reach the minimum size individually when adopting the by-stem method, yet they do reach the minimum size threshold when all stems are considered together. For these environments under water stress, our analysis showed that using large minimum sizes, such as the 10 cm typically used in rainforests, implies large sampling losses, especially when used jointly with the by-stem inclusion method.4. The by-tree inclusion method represents an alternative approach that offers a more reliable sampling in different vegetation types, particularly in those habitats where resprouting is a widely encountered strategy along all age classes. 2018 | Methods in Ecology and Evoluঞon de SOUZA et Al.

Flooding drives tropical dry forest tree community assembly in Southeast Brazil

“…In each plot, the circumference at breast height (1.3 m above the soil) of every living tree that met the inclusion criterion (minimum circumference: 10 cm) was recorded. For trees with multiple stems, we included those of which the square root of the sum of squares of each stem's circumference met the inclusion criterion (Scolforo and Mello 1997, Souza et al 2021a,b2021b). Tree identification was performed by a specialist in the field or by comparisons with herbarium specimens.…”

“…The Brazilian Neotropical flooded forests have been intensively studied in Amazon and Pantanal wetlands (Wittmann et al 2010, 2013, Aldana et al 2017, Souza et al 2021a,b2021b). Flooding systems may contribute uniformly spatially to main floristic units across Amazon (Oliveira‐Filho et al 2021).…”

Beyond the “resprouter versus non‐resprouter” dichotomy: On the prevalence and evolutionary fingerprint of resprouting in tropical dry forest trees

“…The choice to use equivalent diameter as a measure for sampling trees was detailed in de Souza et al (2021). The use of this method is a common practice in tropical forests in which multistemmed trees are prevalent.…”

Tallo: A global tree allometry and crown architecture database

“…D was measured at breast height (1.3 m aboveground) or otherwise just above buttress roots using either diameter tape or callipers. As is common practise, for multi‐stemmed trees a single pooled value of D was calculated by summing the diameter values of all individual stems ( D i ) using the quadratic diameter: (de Souza et al, 2021; Paul et al, 2016). While care was taken to identify records from multi‐stemmed individual, it is possible that for records compiled from existing databases a small number of multi‐stemmed trees were mistakenly treated as separate individuals.…”