Adjustment of forest ecosystem root respiration as temperature warms

Area of Science:

• Ecology
• Climate Change Biology
• Forest Science

Background:

• Soil respiration is a major component of ecosystem carbon cycling.
• Root respiration's response to warming is crucial for predicting future carbon availability.
• Previous models often assume a high temperature sensitivity (Q10) for root respiration.

Purpose of the Study:

• To investigate the relationship between forest root respiration and mean annual temperature across ecosystems.
• To compare cross-ecosystem temperature sensitivity of root respiration with short-term within-ecosystem responses.
• To assess the impact of soil warming experiments on root metabolic capacity.

Main Methods:

• Meta-analysis of 44 published annual forest root respiration values.
• Examination of specific root respiration rates and root biomass.
• Analysis of root respiration data from three soil warming experiments at Harvard Forest.

Main Results:

• Ecosystem root respiration increased with mean annual temperature, but with a lower Q10 (1.6) than short-term responses (Q10=2-3).
• Root metabolic capacity decreased with increasing mean annual temperature, showing a tradeoff with root biomass.
• Roots from heated plots in soil warming experiments exhibited reduced metabolic capacity.

Conclusions:

• Current models may overestimate root respiration's contribution to CO2 efflux under future warming.
• Underestimation of carbon availability for net primary productivity is a potential consequence.
• Root physiological acclimation or soil moisture effects may explain reduced metabolic capacity in warmer conditions.