Canopies shape net precipitation patterns, which are spatially
heterogeneous and control soil moisture response to rainfall. The vast
majority of studies on canopy water fluxes were conducted in forests,
whereas grassland canopies are often assumed to be spatially
homogeneous, therefore likely not inducing patches of heterogeneity at
and below the soil surface. Yet, some studies on short-structured
vegetation, such as grasslands, proposed the importance of
canopy-induced heterogeneity for net precipitation, but systematic
investigations on the effects on soil wetting patterns are missing.
Therefore, in this study, we investigated soil moisture response to
rainfall in a managed temperate grassland by exploring the individual
impacts of spatially varying throughfall, vegetation height and
antecedent soil moisture status on the soil wetting patterns. We applied
linear mixed effects models to disentangle the role of grassland canopy
versus abiotic drivers. The spatial average soil water response showed
that less and less water was stored in the upper parts of the soil as
the growing season progressed and the soils dried, indicating bypass
flow. Spatial variation of grass height was a significant driver of soil
wetting patterns along with precipitation and antecedent soil moisture
status. Soil wetting was suppressed in locations with tall canopy,
although surprisingly this was not directly related to throughfall
patterns. Instead, our results suggest that seasonally drier conditions
and grassland stemflow kick off preferential flow. Ultimately, our
results confirm that spatial variation of the canopy affects soil
moisture wetting patterns not only in forests and indicate a strong
influence of preferential flow on soil water patterns.