It has been suggested that fog acts as a supplemental source of water and plays an important role in the water relations of plants during rainless dry periods. Epiphyte growth benefits from the interception of fog water. However, the proportional use of fog water and water uptake pathways in epiphytes remain unclear.
Researchers from Xishuangbanna Tropical Botanical Garden (XTBG) quantified fog water use in epiphytes in a tropical karst dwarf forest in Xishuangbanna. They analyzed leaf carbon isotope ratios as a measure of water use efficiency (WUE), proportions of fog, rain, and soil water use, and foliar water uptake (FWU) in species of epiphyte and their host trees during the dry season.
They found that the water use efficiency, as represented by leaf δ13C, was generally enriched in the epiphyte species compared to their host trees.
During the dry season, the proportion of fog water used by epiphytes was greater than that of the host trees, whereas the trees used greater proportions of soil water.
The foliar water uptake may relate to foliar structures, such as the presence of fungal endophytes. The distinct physiological and morphological traits of the epiphytes facilitated adaptation to the intermittent drought stress conditions associated with the canopy.
The study highlights the he importance of fog water for epiphytes during the dry season. The researchers suggest that epiphytes may be vulnerable to changes in the occurrence of fog events.