Figure 6: Ten weeks of daily measurements of deadwood weights
(at two sites) and of spruce cone weights. Each boxplot shows the
statistics of 20 measurements. In the background we show the daily
precipitation sums (light blue columns).
We assessed the relationship between deadwood weight and maximum storage
capacity in laboratory measurements with 76 deadwood pieces at different
levels of decay (low – intermediate – high – Figure 7). The median
storage capacity of deadwood was around 1.7 times the dry weight, but
storage capacities were markedly higher at more advanced states of decay
(1.5 ± 0.1, 2.5 ± 0.4, and 4.4 ± 0.6 g per g dry weight for low,
intermediate, and high decay, respectively; n = 36, 30, and 10). Similar
values were reported in the HJ Andrews forest by Harmon & Sexton
(1995), with maximum storage capacities of 3.5 times the dry weight. The
influence of deadwood decay on water storage was expected because decay
separates wood fibers, decreases wood density, and consequently
increases the porosity (Sexton & Harmon, 2009; Paletto and Tosi, 2010;
Pichler et al., 2012; Błońska et al., 2018). The specific water storage
capacity (g water / g dry wood) was not related to the thickness of the
deadwood pieces, but only to their state of decay. We did not account
for differences in wood type, or bark and moss water storage, which
might also affect deadwood storage capacity (e.g., Van Stan et al.,
2016; Błońska et al., 2018; Thielen et al., 2021). We also assessed the
storage capacity of spruce cones (Figure 6c), and found that their
median storage capacity (1.30 g water /g dry weight) was lower than that
of deadwood. This result contrasts with previous studies for other
forest fruiting bodies (sweetgum, pine cones) that stored more water
(Levia et al., 2004; Van Stan et al., 2017).