New Study Finds Lower Elevation Forests More Affected by Drought

Climate change could affect drinking water supplies in the Southeast

Fall view of part of the Coweeta watershed in North Carolina. Photo courtesy of Coweeta LTER.
Fall view of part of the Coweeta watershed in North Carolina. Photo courtesy of Coweeta LTER.

Recently published research by scientists from the University of North Carolina at Chapel Hill (UNC), the  U.S. Forest Service Southern Research Station (SRS), and two other universities shows how the effects of drought on lower elevation forest watersheds in the Southeast could affect drinking water supplies as the region’s climate continue to change.

 Taehee Hwang, UNC Institute for the Environment postdoctoral researcher, led the research team and was lead author of the study, which was recently published in the journal Global Change Biology.

The study showed that forests at low elevations in the southern Appalachians respond differently to drought than those at higher elevations. The findings indicate that lower precipitation and higher temperatures, a scenario that is likely for the region under global climate change projections, could make low-elevation forests more vulnerable to frequent drought than those at higher elevations and lead to more dependence on higher elevation forests for high quality water supply.

Using satellite data, researchers studied patterns in autumnal leaf color change and senescence at various elevations at the SRS Coweeta Hydrologic Laboratory, a Long-Term Ecological Research site located near the North Carolina-Georgia border.  In the southern Appalachians, spring greenup seems to move up the mountains as the days lengthen, reflecting the dominant control of temperature on the process, and many field studies have documented earlier leaf development in relation to the higher temperatures under climate change. In contrast, the senescence of leaves in autumn shows inconsistent patterns in relation to elevation and temperature.  

This new study ties differences in leaf-fall in relation to elevation to water availability. “Specifically, a drier late growing season leads to leaves turning and falling earlier at lower elevations than at middle and higher elevations,” said Chelcy Miniat, SRS project leader and co-author of the study. “This shows that forest growing season length is affected by water availability as well as temperature, and that lower elevation forests may be more vulnerable to changes in water availability.”

If lower elevation forests become increasingly stressed by drought patterns tied to climate change, then this may shift high-quality freshwater sources to remaining high-elevation forest sites. The results of the study also have implications for the ecosystem services that these forests provide.

“Water quality and quantity are two ecosystem services that are derived from these forests, as well as carbon sequestration, which is affected by growing season length,” said Miniat. “Using satellite data coupled with long-term records of precipitation and streamflow, we now have the ability to look at patterns such as leaf-fall over very wide areas and use what we find to examine vulnerability of different forested watersheds to climate change.”

 Adapted from University of North Carolina-Chapel Hill news release.

 Read the full text of the article.

For more information email Chelcy Miniat at cfminiat@fs.fed.us.

 Access the latest publications by SRS scientists.

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