Root growth dynamics in a temperate pasture exhibits influence of phenology and sensitivity to daily soil moisture fluctuations (“Hydromatching”)

Abstract Background and aims “Hydromatching” is a phenomenon consisting of short-term adaptive acceleration of root growth in newly wetted soil layers and/or deceleration of root growth in drier layers. This phenomenon was previously observed on individual plants under controlled conditions. This study assessed whether hydromatching also occurs under natural settings at the scale of a European temperate pasture plant community. We also identified the environmental drivers of root growth and monitored seasonal shifts in vertical root distribution. Methods Using twelve minirhizotrons, root growth was imaged from May 2022 until August 2023 to estimate root length and growth rates. We focused on the responses to major rain events as changes in root abundance between top- and subsoil and between spring and summer. Main environmental drivers of root growth were identified based on regression analyses. Results Soil moisture was the strongest predictor of root growth. Following rain events, root growth shifted from deep to shallow soil layers within 1–3 days, suggesting hydromatching at the level of entire plant communities. Root growth shifted from topsoil to subsoil between spring and summer. Conclusions Root growth at the daily and seasonal scale dominates where soil moisture is available while halting where it is scarce, following dynamics in soil moisture and involving phenological responses at the plant community level.