COS 42-4 - The impacts of fog and dew on plant water status in the Namib Desert

Background/Question/Methods

Fog and dew are the least studied hydrological components in most ecosystems. There are growing interests to study the role of fog and dew in ecosystem dynamics particularly in drylands. However, key knowledge gaps exist such as the mechanisms of fog and dew alleviating vegetation water stress. In this study, we used concurrent leaf and soil water potential measurements from 3 years to investigate the species-specific capacity to utilize moisture from fog and dew within the Namib Desert. Eight common plant species in the Namib Desert were selected.

Results/Conclusions

Our results showed that both fog and dew significantly increased soil water potential. Seven of the eight plant species studied responded to fog and dew events, although the magnitude of the response differed. Plants generally showed stronger responses to fog than to dew. Fog timing seemed to be an important factor determining vegetation response; for example, night fog did not affect plant water potential. We also found that Euclea pseudebenus and Faidherbia albida likely exploit fog moisture through foliar uptake. This study provides a first comprehensive assessment of the effects of fog and dew on plant water status within the Namib Desert. Furthermore, this study highlights the importance of concurrent leaf and soil water potential measurements to identify the pathways of fog and dew water use by desert vegetation. The results indicate that to better predict the ecosystem responses to climate change, especially in drylands, a better understanding and quantification of fog and dew contributions is essential.