Post-logging recovery of timber stocks in Amazon managed forests
A primer analysis through TmFO
Core-team: Ervan Rutishauser, Lucas Mazzei, Marcus d’Oliveira, Cintia Suza, Bruno Hérault, Camille Piponot-Laroche and Plinio Sist
March-June 2016
Introduction
A preliminary study carried across 10 sites scattered across the Amazon Basin revealed a consistent and uniform relationship between logging intensity (i.e. the percentage of initial biomass loss) and the time to recover intial biomass stocks (Rutishauser et al. 2015). We now aim at understandgin how do timber volume recover after logging and what are the main drivers. Several research questions and a general framework were set up among TmFO partners during a 3 days workshop held in Belem in March 2016.
Research questions and methods
Timber is broadly defined as the volume of trunk of trees >= 50 cm. This volume (cubic meter) was estimated using site-specific volumetric equations. Summing all timber at plot scale provide the timber volume (TV), expressed in m3/ha. TV was further divided into three groups:
- timber species harvested in the plot
- total or potential timber stock (i.e. all timber)
- a list of commercial species harvested regionally (common to all plots)
The main research questions are:
How long does it take to recover harvested timber volumes (3 levels of analysis, see below)?
- split into trees DBH > 50 cm present before logging(“old”) and “new” trees DBH > 50 cm recruited post-logging
What are the main drivers of TV recovery post-logging?
Plots selection & descritption
Only plots that were logged (i.e. no control) or were free from major fire disturbances were selected. On 215 plots, 144 were chosen. Harvest intensity ranged from 1.79 and 102.58 m3 ha-1.
Figure 1: TV at each plot and census. Red dot=year of logging & red line = linear regression of which the slope gives the TV recovery rate.
Defining logging intensity & TV recovery
A straightforward definition of logging intensity is to sum all trees harvested within a plot. Plots that experienced post-logging treatments at Paracou, Tapajos and Ecosilva were discarded. For sake of comparison, logging intensity is expressed as a fraction of initial timber volume present before logging (%). Timbre volume (TV) recovery rates (m3 ha-1 y-1) are further computed as linear functions between TV stocks and time since logging.
Figure 2: Volume harvested by initial timber volume per plot