PH and exchangeable aluminum are major regulators of microbial energy flow and carbon use efficiency in soil microbial communities. (November 2019)

• Record Type: Journal Article
• Authors: Jones, Davey L.; Cooledge, Emily C.; Hoyle, Frances C.; Griffiths, Robert I.; Murphy, Daniel V.
• Is Part Of: Soil biology and biochemistry. Volume 138(2019)
• Publication Date: 2019-11
• Subjects: Agroecosystem -- Carbon sequestration -- SOM dynamics -- Texture -- Tipping point; Soil biochemistry -- Periodicals; Soil biology -- Periodicals; Sols -- Biochimie -- Périodiques; Sols -- Biologie -- Périodiques; Sols -- Microbiologie -- Périodiques; Bodembiologie; Biochemie; 631.46
• DOI: 10.1016/j.soilbio.2019.107584
• Languages: English
• ISSNs: 0038-0717

Abstract

Abstract: The microbial partitioning of organic carbon (C) into either anabolic (i.e. growth) or catabolic (i.e. respiration) metabolic pathways represents a key process regulating the amount of added C that is retained in soil. The factors regulating C use efficiency (CUE) in agricultural soils, however, remain poorly understood. The aim of this study was to investigate substrate CUE from a wide range of soils ( n = 970) and geographical area (200, 000 km 2 ) to determine which soil properties most influenced C retention within the microbial community. Using a 14 C-labeling approach, we showed that the average CUE across all soils was 0.65 ± 0.003, but that the variation in CUE was relatively high within the sample population (CV 14.9%). Of the major properties measured in our soils, we found that pH and exchangeable aluminum (Al) were highly correlated with CUE. We identified a critical pH transition point at which CUE declined (pH 5.5). This coincided exactly with the point at which Al 3+ started to become soluble. In contrast, other soil factors [e.g. total C and nitrogen (N), dissolved organic C (DOC), clay content, available calcium, phosphorus (P) and sulfur (S), total base cations] showed little or no relationship with CUE. We also found no evidence to suggest that nutrient stoichiometry (C:N, C:P and C:S ratios) influenced CUE in these soils. Based on current evidence, we postulate that the decline in microbial CUE at low pH and high Al reflects a greater channeling of C into energy intensive metabolic pathways involved in overcoming H + /Al 3+ stress (e.g. cell repair and detoxification). The response may also be associated with shifts in microbial community structure, which are known to be tightly associated with soil pH. We conclude that maintaining agricultural soils above pH 5.5 maximizes microbial energy efficiency. Graphical abstract: Image 1 Highlights: Microbial carbon use efficiency (CUE) was studied in 970 agricultural soils. CUE was highly correlated with soil pH and exchangeable Al content. A critical transition point in microbial CUE occurred at pH 5.5. Other soil factors showed little, or no, relationship with CUE. A decline in CUE at low pH is due to greater use of C to overcome acid stress.