The amount and patterning of precipitation beneath vegetation is determined by throughfall and stemflow. Throughfall is the portion of precipitation that falls through, or drips from, the canopy; whereas, stemflow is the portion that drains down the stem. This chapter briefly synthesises throughfall and stemflow methods, data and major drivers of variability from all studies returned from Web of Science that reported relative annual or seasonal throughfall and stemflow (% of precipitation across the canopy) to date: 644 observations spanning broad climate (boreal, temperate, Mediterranean, subtropical and tropical) and plant types (forests, shrublands, croplands and grasslands) around the globe. Relative throughfall was greatest for forests followed by shrubs > crops > grasses; whereas, relative stemflow was greatest for grasses followed by crops > shrubs > forests. This synthesis identified challenges to integrating net precipitation into large-scale (regional-to-global) hydrologic and climate processes and estimates, including: (1) under-sampling at sites; (2) lacking data for solid and mixed precipitation events’ throughfall and stemflow; (3) very few throughfall and stemflow observations for herbaceous vegetation (compared to woody plants) despite croplands and grasslands representing 11% and 27% of the land surface, respectively, as well as understory herbaceous vegetation being present in nearly all forests; and (4) the current focus on fine-scale drivers of highly localized patterns.
Sadeghi, S. M. M., Gordon, D. A., & Van Stan, J. T. (2020). A global synthesis of throughfall and stemflow hydrometeorology. In Precipitation Partitioning by Vegetation: A Global Synthesis (pp. 48–69). Springer International Publishing. https://doi.org/10.1007/978-3-030-29702-2_4