Abstract
The alpine páramo of Chingaza National Park, Colombia, has a highly variable cloud regime typical of many tropical alpine areas. Yet, little information is available regarding the effects of such dynamic sunlight regimes on alpine temperatures. A close association between changes in incident sunlight and corresponding air (T a) and leaf (T l) temperatures occurred in two dominant species with strongly contrasting leaf form and whole-plant architecture. Spikes in sunlight incidence of >3000 μmol m−2 s−1 occurred during cloud cover and corresponded to increases in T l of 4–5 °C in a 1-min-interval in both species. Although T l was predominately above T a, during the day, depressions below T a of over 6 °C occurred during cloudy conditions when photosynthetic photon flux density (PFDs) was <400 μmol m−2 s−1. The greatest frequency (69%) of changes in incident sunlight (PFD s; over 2-min intervals) was less than 100 μmol m−2 s−1, although changes >1000 μmol m−2 s−1 occurred for 2.4% of the day, including a maximum change of 1512 μmol m−2 s−1. These data may be valuable for predicting the ecophysiological impact of climate warming and associated changes in future cloud regimes experienced by tropical alpine species.
Published Version
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