Abstract
Background and aims
Root exudates play a vital role in driving ecosystem carbon (C) cycling; however, few studies have examined the degree to which a specific exudate component affects soil C loss. The objective was to examine the impacts of different exudate components on microbially-mediated C decomposition and their underlying mechanisms.
Methods
In a well-controlled simulated rhizosphere system, we added exudate chemicals (glucose, glycine and oxalic acid) to spruce (Picea asperata) plantation soils over a 35-day period. The total C contents, net N mineralization rates, microbial communities and extracellular enzymes were measured.
Results
The three exudate components induced different C losses by different mechanisms. Oxalic acid promoted net C loss by accelerating microbial mineralization of soil organic matter (SOM). In contrast, glucose resulted in a net C accumulation, which challenged the assumption that glucose serves as a co-metabolite in driving SOM decomposition to lose C. Glycine increased the total C content via negative priming effects.
Conclusions
Exudate-induced rhizosphere priming effects are not entirely dependent on the energy properties of root exudates. Different exudates may affect SOM decomposition differently, thus the component-specialized rhizosphere processes induced by individual exudate components on soil C dynamics should be integrated into forest C cycle-climate feedbacks under environmental changes.
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Acknowledgements
This study was supported jointly by the National Key R&D Program of China (2017YFC0505200), Frontier Science Key Research Programs of CAS (QYZDB-SSW-SMC023), the National Natural Science Foundation of China (31670449, 31500445), the Youth Innovation Promotion Association, CAS (2013242), the CAS “Light of West China” Program (Y6C2051100), Sichuan Youth Science and Technology Foundation (2016JQ0037) and the Key Laboratory of Mountain Surface Processes and Ecological Regulation of CAS. We also thank the staff in the Forestry Bureau of Western Sichuan and the Maoxian Mountain Ecosystem of CERN Research Station for their kind help with field investigations.
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Yuan, Y., Zhao, W., Xiao, J. et al. Exudate components exert different influences on microbially mediated C losses in simulated rhizosphere soils of a spruce plantation. Plant Soil 419, 127–140 (2017). https://doi.org/10.1007/s11104-017-3334-6
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DOI: https://doi.org/10.1007/s11104-017-3334-6