Effects of cumulus clouds on microclimate and shoot-level photosynthetic gas exchange in Picea engelmannii and Abies lasiocarpa at treeline, Medicine Bow Mountains, Wyoming, USA

- This study characterized the effects of cumulus clouds on conifer physiology at treeline.
- Cumulus cloud-shade reduced photosynthesis, leaf temperatures, LAVD, and transpiration.
- Cloud-gaps were brighter than clear-sky conditions, due to additional diffuse light.
- This did not increase or decrease (photoinhibition) photosynthesis relative to clear conditions.
- Cumulus clouds appear to reduce instantaneous carbon gain, while curtailing water loss.