Foliar uptake of dew in the sandy ecosystem of the Mongolia Plateau: A life-sustaining and carbon accumulation strategy shared differently by C-3 and C-4 grasses

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 C-3 plants, and 3-18% and 5-109% for C-4 plants. Dew produced more root and total biomass (15-81% and 24-82%) in C-4 species than in C-3 species (3-28% and 5-25%). Regular dew events on five or more consecutive nights in seven days can sustain C-3 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. C-4 species and drought resistant C-3 species displayed higher efficiency for dew utilization than the moderately drought resistant C-3 species. This may affect the plant community's dynamic and ecological interactions in response to future climate change