Climate change is making droughts more intense and frequent, but some conifer forests have a trick up their sleeve to weather dry spells. A new study shows that these trees can adjust their water use to cope with drought stress.
The researchers used airplane and satellite data to measure how much water conifer forests in California and Oregon lost through evaporation and transpiration during and after a severe drought from 2012 to 2015. They found that the forests reduced their water loss by about 30 percent during the drought, mainly by closing their stomata — tiny pores on the leaves that allow gas exchange.
This strategy helped the trees conserve water and avoid wilting or dying. But it also came at a cost: less photosynthesis and growth. The researchers estimated that the forests’ productivity declined by about 15 percent during the drought.
However, the forests bounced back quickly after the drought ended. Within a year, they regained their normal water use and productivity levels. The researchers suggest that this resilience may help conifer forests survive future droughts and store more carbon in the long term.
The study also compared conifer forests with broadleaf forests, which have larger and flatter leaves. They found that broadleaf forests did not reduce their water use as much as conifer forests during the drought, but they also did not suffer as much productivity loss. The researchers say this difference may be due to the different leaf shapes and sizes, which affect how efficiently the trees use water and light.
The findings highlight the diversity of responses that different types of forests have to drought stress, and how they may cope with climate change in different ways.
