Adaptation of soil microbial growth to temperature: Using a tropical elevation gradient to predict future changes

Area of Science:

• Microbial Ecology
• Climate Change Science
• Biogeochemistry

Background:

• Terrestrial biogeochemical cycles crucial for climate regulation are influenced by soil microbial temperature responses.
• Tropical forests, as highly productive ecosystems, significantly impact global climate.
• Understanding microbial adaptation to temperature is vital for predicting climate feedbacks.

Purpose of the Study:

• To investigate whether soil bacterial and fungal communities exhibit long-term adaptation to temperature variations.
• To quantify the temperature response of microbial growth across a natural tropical forest gradient.

Main Methods:

• Utilized an Andean elevation gradient (20°C MAT range) to simulate natural temperature differences.
• Assessed soil bacterial and fungal growth temperature dependency using leucine- and acetate-incorporation methods.
• Determined key growth indices: Q10 (temperature sensitivity) and Tmin (minimum growth temperature).

Main Results:

• Increased mean annual temperature (MAT) correlated with higher Q10 and Tmin for both bacterial and fungal communities.
• Across a 6°C to 26°C MAT range, bacterial Q10-20 ranged from 2.4 to 3.5 and Tmin from -8°C to -1.5°C.
• Fungal Q10-20 ranged from 2.6 to 3.6 and Tmin from -6°C to -1°C, with no significant differences between bacteria and fungi.
• Each 1°C MAT increase led to ~0.3°C rise in Tmin and 0.05 rise in Q10-20, indicating microbial adaptation.
• Projected 2°C warming could increase microbial activity by 15-28%, with adaptation further boosting it.

Conclusions:

• Soil microbial communities in tropical forests demonstrate long-term adaptation to temperature gradients.
• Temperature adaptation significantly influences the magnitude of microbial activity response to warming.
• Warming impacts on microbial activity and soil carbon cycling are more pronounced in cooler regions.
• Findings aid in predicting microbial activity and carbon cycle responses to future climate change.