Seedlings grow amid remains of a burned log.
For the first time, scientists were able to directly measure the effects of a hot wildfire on forest soils. The 2002 Biscuit Fire burned about half of twenty-seven 15-acre study plots east of Gold Beach, Oregon, established before the fire.
The fire burned at temperatures over 1,300 ºF, as evidenced by the melting of aluminum tags across the research plots—this is more than twice as hot as typical prescribed fires. Loss of topsoil and combustion of organic material were higher than most previous estimates. More than 10 tons per acre of carbon and 450 to 620 pounds per acre of nitrogen were lost, and nearly 60 percent of this came from the mineral topsoil below the organic layer.
The loss of topsoil and soil carbon can negatively affect a range of processes, including nutrient retention and water infiltration. To replace the documented amount of lost nitrogen would require nitrogen-fixing plants to dominate the forest for decades.
This study illustrates the dramatic effects of intense wildfire on soil nutrients and resulting site productivity. Understanding how fire can alter the available nutrients and thus change the productivity of a site is essential when undertaking reforestation efforts and projecting future stand development. Also, a forest that grows slower after an intense wildfire than it did before will have reduced rates of carbon sequestration.