Litter interception and water storage
To upscale the effect of litter interception across our study site, we
sampled three randomly selected 1 m2 plots of
broadleaf and needle litter, obtaining oven-dried litter weights of
about 400 +/- 120 g m-2 for broadleaf litter and 1230
+/- 152 g m-2 for needle litter. Previous studies have
reported litter weights of 785 g m-2 (Li et al., 2013)
and 1090 g m-2 (Zagyvai-Kiss et al., 2019) for
broadleaf litter and 115 g m-2 (Van Stan et al., 2017)
to 1890 g m-2 (Zagyvai-Kiss et al., 2019) for needle
litter in temperate mixed forests. Scaling our litter weights by the
median specific storage capacities (g water per g dry weight) reported
in section 3.1 yields a potential total water storage of 1.9 mm for
beech litter and 3.1 mm for spruce litter. However, these figures are
derived from laboratory experiments in which the litter was fully
saturated by being submerged in water. Assuming that the litter layer
actual storage capacities are 70% of these laboratory values (resulting
in specific storage capacities of 3.4 and 1.8 times the dry weight for
broadleaf and needle litter, respectively), we estimate the storage
capacity of the broadleaf and needle litter layers to be 1.3 mm and 2.2
mm respectively (Table 1).
Table 1: To estimate the mean storage potential of the
forest-floor litter layer at our field site, we combine laboratory and
field measurements (in bold) with assumptions on the typical saturation
reached during precipitation events (in italics) as summarized below.