INVESTIGATION OF SOIL CHEMISTRY ONE YEAR AFTER THE 16 MILE FIRE, DELAWARE STATE FOREST, PA

The 16 Mile Fire began on April 20, 2016 and burned a total of 7,949 acres in the Delaware State Forest, PA. The high intensity and behavior of the fire was not typical for forests of this region and as such the long-term implications on the soil are not well understood. The fire intensity was attributed to a warmer than average winter leading to little snow pack and lack of fuel compaction, 3 years of gypsy moth defoliation, and an extreme drying due to a drier spring. It is the intent of this study to investigate the chemical properties of the soil one year after the fire to determine if the signature of the fire is still evident. Soil was collected from 16 sites and represent stony, loamy, inceptisols. Soil was sampled from the surface to depths of 12-15 inches and represent O, A, E, B, and C horizons.

An investigation of the surface soil 8 months after the fire yielded fire-related signatures which included increased pH, concentrations of available Ca, Mg, and K, and percentage of organic content in burned soils. Soil pH of burned sites were shown to approach pre-fire conditions, while pH of scorched soils, evidenced by white ash, decreased with time but remained well above pre-fire conditions. Available Mg and K showed a decreasing trend with time, while available Ca and percentage organic content continued to increase. Soil surface thickness increased in burned areas by up to 4cm. Soil color (dry) for burned surface horizons ranged from 2.5Y 3/1 (very dark gray) to 10YR 2/1 (black) to 10YR 4/2 (dark grayish brown). Ash color ranged from 2Y 2.5/1 (black) to 10YR 5/1 (gray). We anticipate similar trends in soil pH, Ca, Mg, K, and organic content of soil collected 1-year post-fire. We expect surface horizon depth to stabilize with time. Bulk density of the soil surface will be compared to percentage of organic content. We anticipate a difference in burned soil bulk density as compared to un-burned soil.

Forest productivity and succession is in part dependent on soil chemistry. Long-term alterations of a soil’s chemical condition as a result of atypical high intensity forest fire may influence the future structure of some northeastern forests. The results of this study will begin to address the lasting influence of high intensity fire in forests of the northeast as changing climatic conditions may begin to influence their fire regimes.