Abstract
Fog water is generally considered to be an important water source for epiphytes in cloud forests because they cannot directly access ground-level water sources. However, the water use proportions of potential water sources and water use efficiency of epiphytes in the subtropical montane cloud forests (MCF) remain to be further explored. In this study, we investigated the water use pattern in the dry season and the intrinsic water use efficiency (WUEi) of four epiphyte groups (i.e., epiphytic lichens, epiphytic bryophytes, epiphytic ferns, and epiphytic seed plants) using stable isotope (δ2H, δ18O, and δ13C) techniques. Our results indicated that the water sources of epiphytes were significantly different among groups and species. The contribution proportions of fog water to epiphytic lichens, epiphytic bryophytes, epiphytic ferns, and epiphytic seed plants were 83.2%, 32.7%, 38.8% and 63.7%, respectively. Epiphytic lichens and epiphytic seed plants mainly depended on fog water whereas the epiphytic bryophytes and epiphytic ferns relied on both fog water and humus. This may be due to their differences in morphological and structural traits (e.g., thallus or leaves, rhizoid or roots). Additionally, the difference in WUEi was also significant among epiphyte groups and species, which could be related to their different water acquisition patterns. In conclusion, our study reveals the differentiation of water utilization in epiphytes and confirms the importance of fog water for epiphytes during the dry season.
Highlights
In the context of global climate change, the frequency, duration, and intensity of drought will increase in many regions of the world [1,2]
The mean δ2H and δ18O of fog water were above the local meteoric water line (LMWL) and global meter water line (GMWL), indicating that the fog water experienced lower evaporative enrichment than the canopy humus and rainwater
While epiphytic lichens and epiphytic seed plants mainly relied on fog water, the epiphytic bryophytes and epiphytic ferns were depending on both fog water and humus
Summary
In the context of global climate change, the frequency, duration, and intensity of drought will increase in many regions of the world [1,2]. Epiphytes, which grow on living or residual host trees, are one of the most diverse groups in the forest ecosystem. These plants play an important role in maintaining biodiversity and biomass and promoting the processes of nutrient and water cycling [4,5]. Epiphytes lack direct access to the ground soil and rely heavily on atmospheric resources (e.g., water, nutrients), which makes them exceptionally sensitive to changes in environmental conditions and good biological indicators of global climate change [6,7]. Understanding the water use strategies of different epiphytes is critical for correctly predicting the impacts of predicted changing rainfall patterns on them
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