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).