Rhizosphere priming effect increases the temperature sensitivity of soil organic matter decomposition

• Published in: Global change biology 2011-06, Vol.17 (6), p.2172-2183
• Main Authors: ZHU, BIAO, CHENG, WEIXIN
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Climate change; Decomposition; developmental stages; Fundamental and applied biological sciences. Psychology; General aspects; Geochemistry; global change; growth chambers; priming effect; Q10 value; rhizosphere; rhizosphere respiration; soil; soil heating; soil organic matter; soil respiration; soil warming; Soils; substrate availability; temperature; uncertainty analysis
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/j.1365-2486.2010.02354.x

The temperature sensitivity of soil organic matter (SOM) decomposition has been a crucial topic in global change research, yet remains highly uncertain. One of the contributing factors to this uncertainty is the lack of understanding about the role of rhizosphere priming effect (RPE) in shaping the temperature sensitivity. Using a novel continuous ¹³C-labeling method, we investigated the temperature sensitivity of RPE and its impact on the temperature sensitivity of SOM decomposition. We observed an overall positive RPE. The SOM decomposition rates in the planted treatments increased 17-163% above the unplanted treatments in three growth chamber experiments including two plant species, two growth stages, and two warming methods. More importantly, warming by 5 °C increased RPE up to threefold, hence, the overall temperature sensitivity of SOM decomposition was consistently enhanced (Q₁₀ values increased 0.3-0.9) by the presence of active rhizosphere. In addition, the proportional contribution of SOM decomposition to total soil respiration was increased by soil warming, implying a higher temperature sensitivity of SOM decomposition than that of autotrophic respiration. Our results, for the first time, clearly demonstrated that root-soil interactions play a crucial role in shaping the temperature sensitivity of SOM decomposition. Caution is required for interpretation of any previously determined temperature sensitivity of SOM decomposition that omitted rhizosphere effects using either soil incubation or field root-exclusion. More attention should be paid to RPE in future experimental and modeling studies of SOM decomposition.