论文摘要：

Dew is an important source of available water in arid or semi-arid areas and considerable attention has focused upon whether foliar dew uptake occurs. Nonetheless, its occurrence and effects on plant growth in the sand-based ecosystems of the Mongolia Plateau are largely unknown. We performed laboratory experiments and conducted a three-year field investigation of dew in the Hunshandak sandland, northern China. Dew yield was determined by a weighing method. The ecological significance of dew was evaluated by measuring isotopes in the field, leaf water content, photosynthesis and the biomass of drought-stressed plants exposed to dew. Nights producing dew comprised 53% of those between June and October when the atmospheric relative humidity was higher than 80% and wind speed was lower than 4.0 m s^-1. Dew yield averaged 0.15 mm night^-1 and its maximum value was 0.30 mm night^-1. When exposed to dew, drought-stressed plants increased leaf relative water content and net photosynthetic rate (P_n) between 5-76% and 5-240% for C₃ plants, and 3–18% and 5–109% for C₄ plants. Dew produced more root and total biomass (15–81% and 24–82%) in C₄ species than in C₃ species (3–28% and 5–25%). Regular dew events on five or more consecutive nights in seven days can sustain C₃ species, while C₄ species accumulate more carbon resources. This study found that the high dew yield in arenicolous ecosystems was due to the soil matrix and environmental differences in the neighboring steppe ecosystem. C₄ species and drought resistant C₃ species displayed higher efficiency for dew utilization than the moderately drought resistant C₃ species. This may affect the plant community's dynamic and ecological interactions in response to future climate change.