Coarse and fine root respiration in aspen (Populus tremuloides)

Area of Science:

• Plant physiology
• Forest ecology
• Biogeochemistry

Background:

• Root respiration is a key component of ecosystem carbon cycling.
• Understanding the differences between fine and coarse root respiration is crucial for accurate carbon flux estimations.
• Aspen (Populus tremuloides Michx.) is a dominant tree species in many boreal and temperate forests.

Purpose of the Study:

• To quantify and compare coarse and fine root respiration rates in aspen.
• To investigate the influence of temperature and season on root respiration.
• To differentiate between maintenance and growth respiration in aspen roots.

Main Methods:

• Root respiration was measured across a temperature gradient (5, 15, 25°C).
• Measurements were conducted during growing and dormant periods to distinguish respiration types.
• Total nonstructural carbohydrate (TNC) concentrations were analyzed alongside respiration rates.

Main Results:

• Fine roots exhibited substantially higher respiration rates than coarse roots.
• Fine root respiration showed a nonlinear temperature response (Q10 values of 3.90 and 2.19).
• Coarse root respiration was elevated in late fall, correlating with decreased TNC, suggesting growth respiration.

Conclusions:

• Fine roots are more metabolically active than coarse roots in aspen.
• Seasonal variations in coarse root respiration indicate a role in recent radial growth rather than solely resource storage for spring growth.
• Nitrogen concentration positively correlates with root respiration across both root types.