J. Ecol. http://doi.org/bqr5 (2016)
Increased temperatures and reduced rainfall are two of the main short-term effects predicted for anthropogenic climate change. Both can cause stress for growing trees, although temperature rises could also enhance plant growth. The two together may have effects greater than either alone. In experiments on a semi-arid woodland in New Mexico, Charlotte Grossiord, of the Los Alamos National Laboratory, and colleagues have shown that the situation may be far simpler, with physiological changes dominated by responses to water scarcity.
The researchers manipulated the temperature and rainfall of piñon pines (Pinus edulis) growing at the Los Alamos Survival-Mortality experiment. Over 3 years from 2012, the mature trees (around 50 years old) were enclosed in open-topped, transparent chambers that increased temperatures by around 4.8°C, or covered by clear, polymer troughs that reduced rainfall by 45%, or both.
The restriction of rainfall induced a number of water-saving measures in the trees, including reductions in photosynthesis, stomatal conductance, growth rate and needle length. However, trees subjected to higher temperatures showed neither adverse nor advantageous changes, whether coupled with water stress or not. Under ideal conditions, a similar rise in temperature would be predicted to increase plant growth, reducing the effects of drought. However, as this study reminds us, in natural environments it is the most limited resource that calls the tune.