The forest fire statistics for the period 1963 to 1997 are given in Table 1. The majority of fires burned within the central and eastern parts of the forested area. Moreover, economic activity is much higher here as compared to other parts of the region. Extreme fire seasons are induced by long droughts. Fires burn from April to July under such conditions.
Large fires occur on the background of mass fires.
In Mongolian forests, fire seasons are usually discontinuous, i.e. they have two peaks of fire danger. Intensive solar radiation removes thaw water from the topsoil by evaporation, and the remaining thaw water flows from elevated sites downhill and accumulates in depressions because it cannot penetrate deeply into frozen soils. Spring fires are thus most common in stands on these elevated dry landscape elements and in those where herbs and small shrubs form a loosely compacted living ground cover layer. The number of fires reaches its maximum in May and June which are the hottest and driest months. In summer, abundant green vegetation reduces the fire start risk considerably.