2004), and Georgia’s Okefenokee Swamp fire (Florida Times-Union 2012). These combustion reactions can continue in deep organic soils for many days, or even months in cases such as the Kalimantan peat fires in Indonesia in 1997 (Page et al. In Regime II, char oxidation occurs, reducing the pyrolyzed fuel to ash (Hadden et al. In Regime I, pyrolysis and partial oxidation of the fuel takes place, resulting in dehydration and charring. In these fuels, combustion occurs as two sets of chemical reactions, known as Regimes I and II. In desiccated mucks and peats, smoldering can occur under surprisingly high soil-moisture contents, depending less on parent material than on mineral content (Frandsen 1997, Benscoter 2011, Watts 2013). In addition to occurring to some extent in woody fuels, smoldering is chiefly the type of combustion found in duff (e.g., Varner 2005), peat, and muck, and characterizes fires found in ecosystems in which these soils or fuel types dominate during dry conditions. This form of combustion typically takes place at much lower temperatures than flaming combustion (500 ☌ to 700 ☌ versus 1500 ☌ to 1800 ☌ Rein et al. In contrast to flaming combustion, which typically lasts a fraction of an hour at a given location, smoldering is a flameless form of combustion that occurs when oxygen reacts with the surface of solid fuels (Ohlemiller 1995). Different in many ways from the dramatic conflagrations often pictured in the news, these slow-motion wildfires pose unique challenges and hazards that make them worthy of special consideration. They typically occur rarely, but produce substantial ecological effects and hazards for human health and safety. Such fires, variously called ground fires, peat fires, or muck fires, are the result of smoldering combustion in organic soils. However, during prolonged drought conditions, the organic soils found in many wetlands may dry sufficiently to ignite and burn (de Groot 2012). In the southeastern USA, pine flatwoods adjacent to marshes or swamps can contribute ignition sources that result in fires as frequently as every decade (Wade et al. Where frequently burned uplands commonly occur adjacent to wetlands, fires can occur in wetlands with surprising frequency. We suggest that despite the well-recognized negative aspects of ground fires, there may exist under-recognized ecological benefits that should be further studied and weighed against known hazards posed by these events.įires in wetlands frequently occur in the form of smoldering fires in the deep organic soils that accumulate in these ecosystems. This synthesis describes some aspects of smoldering combustion, and discusses some of the particular ecological aspects of ground fires, focusing on examples from the southeastern United States. Additionally, ecological effects of smoldering ground fires are generally perceived to be negative, particularly where their historical frequencies are thought to be low. Smoldering fires represent hazards to human health and safety locally, and global ecological concerns due to their potential for carbon release. Increasing occurrence and size of these events from the Arctic to the tropics has been matched by increasing research interest, yet our understanding of smoldering lags behind that of flame-based combustion. A common feature of fires in wetlands is smoldering combustion in organic soils, such as peat and muck. Although fires in wetlands would seem to be rare or impossible by definition, these ecosystems do occasionally experience fire.
0 Comments
Leave a Reply. |