Rock Particles Promote Dew Formation: Aiming to Explain Ambiguous Published Findings

ABSTRACT The role played by rock particles (RPs) in dew formation and their effect on nonrainfall water (NRW) is controversial. RPs may affect the amounts of NRW that accumulate on/under the RPs. While some scholars maintain that RPs increase NRW, other argue to the contrary, a conclusion that was apparently supported following measurements with microlysimeters (MLs). Hypothesizing that RPs increase NRW and that the use of MLs may lead to erroneous conclusions, a research experiment was designed in the Negev Desert. It included the use of small (2.8 × 2.3 × 2.0 cm) and large (6 × 6 × 2.5 cm) RPs having 0.1‐mm‐thick cloths attached to their tops. We compared (i) the amount of NRW, that is, dew and vapour as obtained on 7.2‐cm‐diameter and 3.8‐cm‐long MLs overlaid with three (ML‐3), two (ML‐2) and one (ML‐1) small RPs (SPRs) and MLs with no RPs (ML‐0), and (ii) the amount of NRW as obtained on large RPs (LRPs) overlying the intact soil as well as to cloths overlying the intact soil. We measured the amounts of NRW that accumulated on the cloths, and the difference in the total weight of the ML (between late afternoon and the following early morning). Our findings indicate that (i) the total amount of NRW as calculated by the change of weight of the MLs decreased with the number of SRPs, but (ii) the amount obtained by the LRPs was on average 7.8‐fold higher than that received on the intact soil. It is concluded that while ML measurements result in an apparent reduction of the NRW (following vapour blockage to the soil overlain by RPs), RPs act to increase the NRW. The ecological implications are discussed.