Detritus material in forested watersheds is the major terrestrial source of dissolved organic matter (DOM) and disinfection by-product (DBP) precursors in source waters. Forest fire reduces the thickness of detritus layer and changes foliar litters into pyrogenic organic matter (PyOM) on the forest floor, resulting in different quantity and quality of DOM exported from forested watersheds. Many studies have examined DBP precursors exported from forested watersheds; however, DOM leaching from PyOM, or dissolved black carbon (BC), could have different reactivity in DBP formation compared to the DOM leaching from unburned detritus layer. Using controlled laboratory burning in this study, characteristics of foliar litters before and after burn were compared. Quality and quantity of water extractable organic matter (WEOM) from raw and burned foliar litters commonly found in the southeastern United States, including baldcypress (Taxodium distichum), boxelder (Acer negundo), longleaf pine (Pinus palustris), pop ash (Fraxinus caroliniana), sweetgum (Liquidambar styraciflua), and water tupelo (Nyssa aquatica) was compared, and evaluated for their disinfection by-product yield and specific DBP formation using a uniform formation condition test. Laboratory analysis

Understanding the relationship between fire intensity and fuel mass is essential information for scientists and forest managers seeking to manage forests using prescribed fires. Peak burning temperature, duration of heating, and area under the temperature profile are fire behavior metrics obtained from thermocouple-datalogger assemblies used to characterize prescribed burns. Despite their recurrent usage in prescribed burn studies, there is no simple protocol established to guide the orientation of thermocouple installation. Our results from dormant and growing season burns in coastal longleaf pine ( Mill.) forests in South Carolina suggest that thermocouples located horizontally at the litter-soil interface record significantly higher estimates of peak burning temperature, duration of heating, and area under the temperature profile than thermocouples extending 28 cm vertically above the litter-soil interface ( < 0.01). Surprisingly, vertical and horizontal estimates of these measures did not show strong correlation with one another ( ≤ 0.14). The horizontal duration of heating values were greater in growing season burns than in dormant season burns ( < 0.01), but the vertical values did not indicate this difference ( = 0.52). Field measures of fuel mass and depth before and after fire showed promise as significant predictive variables ( ≤ 0.05) for the fire behavior metrics. However, all correlation coefficients were less than or equal to = 0.41. Given these findings, we encourage scientists, researchers, and managers to carefully consider thermocouple orientation when investigating fire behavior metrics, as orientation may affect estimates of fire intensity and the distinction of fire treatment effects, particularly in forests with litter-dominated surface fuels.

Forest detritus material is one of the major terrestrial sources of dissolved organic matter (DOM) in source waters. There is a health concern on DOM because it reacts with disinfectants to form a variety of potentially carcinogenic disinfection by-products (DBPs) during drinking water treatments. Prescribed fire is a common forest management practice in Southeastern US to reduce the risks of wildfire and beetle infestation.However, this forest management practice alters the composition and quantity of detritus materials on forest floor, changing the DOM and DBP precursors exports from those forested watersheds. In this book chapter, we discussed a prescribed fire study conducted in three 20m x 20m experimental plots in Hobcaw Barony, Georgetown, South Carolina. Litter and duff mixtures of field samples before and after prescribed fire were collected for water extraction experiments in the laboratory. In addition, water extracts were further exposed to sunlight for 15 days in order to understand the biogeochemical processes on the degradability of DOM and DBP precursors. The concentrations of water extractable organic carbon (WEOC) and water extractable total nitrogen (WETN) from unburned detritus (60.3 g-WEOC/m 2 and 1.9 g-WETN/m 2 ) were significantly greater than those from burned detritus (11.4 g-WEOC/m 2 and 0.5 g-WETN/m 2 ). Importantly, the yield of DBP was significantly reduced from 3651 mg-THM/m 2 to 484 mg-THM/m 2 after fire. There was no change in specific DBP formation in both burn and unburned samples after sunlight exposure although significant decreases in ultraviolet absorbance and fluorescence intensity were observed. This field study showed that prescribed fire could significantly decrease the production of dissolved organic carbon (DOC) and dissolved total nitrogen (DTN) per unit area in forest floor and potentially decrease the DBP formation in water supply.