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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Invasive Species and Pollinator Health » Research » Publications at this Location » Publication #429469
Research Project: Biological Control of Invasive Pests in Agroecosystems and Wetland, Forest and Rangeland Ecosystems in the Far Western U.S.

Location: Invasive Species and Pollinator Health

Title: Drought stress increases total C released from roots

Author
item ULRICH, DANIELLE - Montana State University
item FLATHERS, KELSEU - Montana State University
item GOEMANN, HANNAH - Montana State University
item Mueller, Rebecca
item PEYTON, BRENT - Montana State University

Submitted to: Annals of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/6/2026
Publication Date: 1/8/2026
Citation: Ulrich, D.E., Flathers, K., Goemann, H.M., Mueller, R.C., Peyton, B.M. 2026. Drought stress increases total C released from roots. Annals of Botany. 137(5):1156-1168. https://doi.org/10.1093/aob/mcag007.
DOI: https://doi.org/10.1093/aob/mcag007

Interpretive Summary: Drought alters the physiology of plants, but the effects belowground through root exudates and rhizodeposits are still being explored. In addition to being a route for plant adaptation to stress induced by water deficits, inputs of nutrients through root exudates and rhizodeposits have strong effects on belowground microbial communities, with likely feedbacks to plant performance, nutrient cycling and ecosystem functions. Here, we synthesized studies of the response of belowground inputs by plants to drought stresses, incorporating a wide range of plant functional groups and species. We found that carbon inputs increased with drought stress, with smaller effects of drought intensity. Compound classes with the strongest effects included carbohydrates and organic acids. This analysis revealed a general pattern of plant response to drought and identified knowledge gaps that require further study in order to best predict the long-term effects of increased and widespread drought on landscapes.

Technical Abstract: Root exudation and rhizodeposition represent critical pathways for plant C allocation to soil, influencing soil organic carbon stability and ecosystem functioning under changing climates. However, the effects of drought and heat stress on these belowground processes remain poorly understood. We conducted a meta-analysis of 29 studies examining drought stress and 6 studies examining heat stress to quantify how stress intensity affects the direction and magnitude of changes in C allocation to root exudation and rhizodeposition. Our primary analysis included 29 studies and 79 data points spanning diverse functional types, ecosystems, sampling methods and experimental conditions. We observed that total C released as root exudates and rhizodeposition significantly increased under drought stress and marginally increased with drought intensity. Among compound classes, carbohydrates and organic acids exhibited significant increases under drought stress, suggesting these compound classes may underlie total C responses in root exudation and rhizodeposition. To direct future research, our analysis revealed knowledge gaps, particularly the need for studies examining heat stress, trees and shrubs, field-based research, broader drought intensity ranges, and total C, compound classes, and specific compounds when possible. Improving our understanding of root-derived C responses to stress is crucial for predicting terrestrial C cycling dynamics and ecosystem resilience under increased drought frequency and intensity.