Tropical forests post-logging are a persistent net carbon source to the atmosphere

Area of Science:

• Tropical ecology
• Forest carbon cycling
• Climate change science

Background:

• Logged and degraded tropical forests are widespread.
• They are commonly assumed to be carbon sinks due to regrowth.
• This assumption overlooks carbon losses from soil and necromass.

Purpose of the Study:

• To quantify and partition net ecosystem carbon dioxide exchange in logged forests in Malaysian Borneo.
• To determine the complete carbon budget of tropical forests during logging and recovery.
• To challenge the assumption that recovering logged forests are net carbon sinks.

Main Methods:

• Utilized forest plots and an eddy covariance tower for measurements.
• Quantified net ecosystem CO2 exchange.
• Partitioned carbon fluxes between biomass, soil, and necromass.

Main Results:

• Logged forests are substantial and persistent net carbon sources.
• Woody biomass gain in logged forests is offset by larger carbon losses from soil and deadwood.
• Emissions from moderately logged plots averaged 1.75 Mg C ha-1 yr-1, and 5.23 Mg C ha-1 yr-1 in severely degraded plots, persisting for at least a decade.

Conclusions:

• The assumption that recovering logged tropical forests are net carbon sinks is incorrect.
• Tropical forest carbon sequestration estimates may be significantly overestimated.
• Understanding complete carbon budgets is crucial for accurate climate change modeling.