Seeing tropical forests through their large trees

A pantropical comparison

Foreword

This page provide history and information regarding a new global study on the importance of large trees in structuring tropical forests and above-ground biomass stocks. This study follows up with previous work of Jean-François Bastin and colleagues carried in Central African forests.

Preliminary results (Bastin et al. (2015), Nature Scientific Reports)

Large tropical trees and a few dominant species were recently identifid as the main structuring elements of tropical forests. However, such result did not translate yet into quantitative approaches which are essential to understand, predict and monitor forest functions and composition over large, often poorly accessible territories. Here we show that the above-ground biomass (AGB) of the whole forest can be predicted from a few large trees and that the relationship is proved strikingly stable in 175 1-ha plots investigated across 8 sites spanning Central Africa. We designed a generic model predicting AGB with an error of 14% when based on only 5% of the stems, which points to universality in forest structural properties. For the fist time in Africa, we identifid some dominant species that disproportionally contribute to forest AGB with 1.5% of recorded species accounting for over 50% of the stock of AGB. Thus, focusing on large and dominant species provides precise information on the whole forest stand. Consequently, focusing on large trees and dominant species provides precise information on the whole forest stand. This offers new perspectives for understanding the functioning of tropical forests and opens new doors for the development of innovative monitoring strategies.

Study’s aim and data requirement

We are willing to test the generality of the relationships found in Central Africa at global scale. To do so, we are gathering basic forest structure information across the globe. AS we are mainly interested in understanding the contribution of large trees to total biomass, consistent way of estimating individual tree biomass among plots is not crucial, as long as it is consistent within-plot. Preliminary results revealed that this relationship was not affected by the choice of a particula allometric model. Similarly, wood density allocation is often performed differently among sites and studies. To enhance consistency in our analysis, we are willing to estimate AGB using the most recent allometric model based on DBH and specific wood density (WD) developped by Chave and collaborators (2014), and the highest degree of information per plot would be an asset. Mandatory plot information are listed below in decreasing order of importance:

Additionally, tree measurement shoudl conform to generally agreed international good practicies (see RAINFOR or Walker et al. 2014), notably:

Figure 1: Adjusted R2 of prediction of AGBtot (A), minimal DBH threshold (B), residual standard error (RSE) in total AGB prediction (C) and by percentage of initial population (ranked by decreasing DBH order) sampled. Trunkated Weibull DBH density function per region (D).

Page created by Ervan Rutishauser (er.rutishauser@gmail.com); Last updated: 18 January 2016