Figure 5: Daily fluctuations in deadwood moisture content (grey lines), measured by pressure cushions for four deadwood pieces (CB1 – CB4), normalized between 0 and 1 (a) , compared to precipitation events (blue bars) and daily variations in vapor pressure deficit (VPD; red line) (b) . Deadwood absorbed moisture from the air during the night, when VPD was low, and evaporated moisture to the subcanopy atmosphere during the day, when VPD was high.
Water storage and retention capacity in forest floor deadwood (and spruce cones)
We assessed the water storage dynamics of 40 pieces of deadwood (divided between two sites, one under beech and the other under spruce canopies – see Figure 1b) and 20 spruce cones (only under spruce canopy) by weighing them daily for eight weeks. The temporal patterns of water retention capacity and the timescale of water storage recession were broadly similar for deadwood (at both sites) and for the spruce cones, as indicated by the boxplots in Figure 6. The median storage capacity of deadwood pieces is 1.7 times their dry weight, and for spruce cones is 1.3 times their dry weight. Overall, deadwood - even when not fully saturated - retains moisture for more than 7 days, and spruce cones retain moisture over even longer time periods, as indicated by the duration of declining water-content values in Figure 6. The mean time between the highest saturation following each precipitation event, and the time when 50 % of the moisture was lost, was approximately 2.5 to 3.5 days for deadwood and 3.5 to 4.5 days for the spruce cones.