Reviewing the Past to Gauge the Future

63 years of environmental monitoring on the Santee Experimental Forest

 

Weather station on the Santee Experimental Forest, circa 1967. Photo by U.S. Forest Service.
Weather station on the Santee Experimental Forest, circa 1967. Photo by U.S. Forest Service.

Effects of climate variability on forest hydrology and carbon sequestration on the Santee Experimental Forest, a new general technical report published by the U.S. Forest Service Southern Research Station (SRS), describes an assessment of long-term weather and hydrology data collected on the experimental forest over a 63-year time span.

The publication is the result of collaboration between Zhaohua Dai, the lead author and research scientist at the University of New Hampshire, and Carl Trettin and Devendra Amatya, research soil scientist and research hydrologist, respectively, with the SRS Center for Forested Wetlands Research .

The Santee Experimental Forest, located about 35 miles northwest of Charleston, South Carolina, in the Francis Marion National Forest, was established in 1937 and has been the site of continuous research ever since. The 6,100-acre site is the only experimental forest in the Atlantic Coastal Plain and includes all major forest types in the region and both tidal and non-tidal streams. The new report highlights some of the major trends in air temperature, precipitation, and water balance in gauged watersheds within the forest over a 63-year period.

The average annual temperature in the area covered has increased at a rate higher than the global mean. And despite the warmer temperatures, there was no significant change in total annual precipitation. However, the data showed that there has been a 21 percent increase in the number of large (more than 2 inches of precipitation) storm events. Those changes in climatic conditions can be expected to affect forest growth as well as the amount and timing of stream flow delivered to the estuary.

Changes in temperature and precipitation can alter streamflow and water table depth. Understanding these changes is especially important in forested wetlands where hydrology is one of the most important elements influencing forest productivity, hence the amount of carbon sequestered in the vegetation and soil.

On the Santee Experimental Forest, the authors predict that the warming trend will have significant impacts on the water balance and carbon dynamics. Data suggests that a continued warming trend will decrease streamflow due to an increase in evaporation and the loss of water through plant respiration, particularly if that increase is not offset by additional precipitation.

Moreover, water table levels will fluctuate with varying amounts of precipitation and increased demand for water from the vegetation. As a result, water stress, or a limited supply of water for plant use, can reduce forest productivity which reflects lower amounts of carbon removed from the atmosphere. 

“The productivity of the estuaries and near-shore coastal zone are inextricability linked to the organic matter and nutrient inputs from the terrestrial watersheds,” states Trettin.

Understanding the implications of altered climatic conditions on forest conditions is particularly important in the lower south Atlantic Coastal Plain, where large forested areas drain into the coastal rivers and streams. Those surface waters may also serve municipal water supplies; hence, changes in forest hydrology are relevant to the rapidly urbanizing landscape along the coast.

Experimental forests provide unique places for long-term science and management studies, and places like the Santee Experimental Forest make it possible for the Forest Service to understand the long-term impacts that urbanization and changing weather patterns, for example, have on forests, watersheds, and wildlife habitat.

The findings reported in this report are fundamental to assessing the interactions of sea level rise on forest processes, a unique capability on the Santee Experimental Forest given its location on the lower coastal plain. “Long-term studies and the continuity of environmental research are critical since most changes on the landscape occur over a period of time and the relative impacts may not be completely understood immediately. What you learn over a 10-year period is so much more than in a two to three year study,” Trettin says.

For more information, email Carl Trettin at ctrettin@fs.fed.us

Read the full text of the report.

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