Abstract
Abstract. Throughfall heterogeneity induced by the redistribution
of precipitation in vegetation canopies has repeatedly been hypothesized to
affect the variation in the soil water content and runoff behavior, especially
in forests. However, observational studies relating the spatial variation in the
soil water content directly to net precipitation are rare, and few confirm
modeling hypotheses. Here, we investigate whether throughfall patterns
affect the spatial heterogeneity in the soil water response in the main rooting
zone. We assessed rainfall, throughfall and soil water content (at two depths,
7.5 and 27.5 cm) on a 1 ha temperate mixed-beech forest plot in Germany
during the 2015 and 2016 growing seasons using independent, high-resolution,
stratified, random designs. Because the throughfall and soil water content cannot
be measured at the same location, we used kriging to derive the throughfall
values at the locations where the soil water content was measured. We first
explored the spatial variation and temporal stability of throughfall and soil
water patterns and subsequently evaluated the effects of input (throughfall), soil
properties (field capacity and macroporosity), and vegetation parameters
(canopy cover and distance to the next tree) on the soil water content and
dynamics. Throughfall spatial patterns were related to canopy density. Although
spatial autocorrelation decreased with increasing event sizes, temporally
stable throughfall patterns emerged, leading to reoccurring higher- and lower-input locations across precipitation events. Linear mixed-effects model
analysis showed that soil water content patterns were poorly related to
spatial patterns of throughfall and that they were more influenced by unidentified,
but time constant, factors. Instead of the soil water content itself, the patterns of its increase after
rainfall corresponded more closely to throughfall patterns: more
water was stored in the soil in areas where throughfall was elevated. Furthermore, soil moisture patterns themselves affected the local soil water response, probably by mediating fast drainage and runoff. Locations with a low
topsoil water content tended to store less of the input water, indicating
preferential flow. In contrast, locations with a high water content
stored less water in the subsoil. Moreover, the distance to the next tree and macroporosity
modified how much water was retained in soil storage. Overall, throughfall
patterns imprinted less on the soil water content and more on the soil water
dynamics shortly after rainfall events; therefore, percolation rather than the
soil water content may depend on the small-scale spatial heterogeneity in canopy
input patterns.
Funder
Deutsche Forschungsgemeinschaft
Subject
General Earth and Planetary Sciences,General Engineering,General Environmental Science
Cited by
3 articles.
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