Changes in root-exudate-induced respiration reveal a novel mechanism through which drought affects ecosystem carbon cycling

• Published in: The New phytologist Vol. 224; no. 1; pp. 132 - 145
• Main Authors: de Vries, Franciska T., Williams, Alex, Stringer, Fiona, Willcocks, Robert, McEwing, Rosie, Langridge, Holly, Straathof, Angela L.
• Format: Journal Article
• Language: English
• Published: England Wiley 01.10.2019; Wiley Subscription Services, Inc; John Wiley and Sons Inc
• Subjects: Biological activity; Biomass; carbon; Carbon - metabolism; Carbon Cycle; Cell Respiration; Climate change; Drought; Droughts; Ecosystem; Ecosystems; Exudates; Exudation; forbs; grasses; Grasslands; Holcus - microbiology; Holcus - physiology; Holcus lanatus; Microbial activity; Microorganisms; Nitrogen - metabolism; Organic Chemicals - metabolism; Plant Exudates - metabolism; Plant Roots - cytology; Plant Roots - physiology; Plant Shoots - physiology; plant–soil interactions; Regrowth; Respiration; root exudate; root exudates; root systems; root traits; Roots; Rumex - microbiology; Rumex - physiology; Rumex acetosa; Soil; soil bacteria; soil fungi; Soil Microbiology; soil respiration; Soil treatment; Soils; Species Specificity; root traits; plant-soil interactions; drought; soil fungi; carbon; root exudate; soil bacteria; climate change
• ISSN: 0028-646X; 1469-8137; 1469-8137
• DOI: 10.1111/nph.16001

Root exudates play an important role in ecosystem response to climate change, but the functional consequences of drought-induced changes in the quality of root exudates are unknown. Here, we addressed this knowledge gap in a unique experimental approach. We subjected two common grassland species that differ widely in their growth strategies and root systems, the grass Holcus lanatus and the forb Rumex acetosa, to 2 wk of drought. We collected root exudates and soils at the end of the drought and after 2 wk of recovery and readded all root exudates to all soils in a fully reciprocal set-up to measure root-exudate-induced respiration. We found that soil treatment was unimportant for determining root-exudate-induced respiration. By contrast, root exudates collected from plants that had experienced drought clearly triggered more soil respiration than exudates from undroughted plants. Importantly, this increased respiration compensated for the lower rates of root exudation in droughted plants. Our findings reveal a novel mechanism through which drought can continue to affect ecosystem carbon cycling, and a potential plant strategy to facilitate regrowth through stimulating microbial activity. These findings have important implications for understanding plant and ecosystem response to drought.