PART I\ — TERRESTRIAL ECOS\ STEMS 



The Role of Fire in Forest Management and Ecology 



Wildfires destroy vegetation and 

 wildlife, may result in erosion and 

 soil damage, leave unsightly vistas, 

 are costly to suppress, and upset 

 management plans and schedules. 

 Thus, one of the most important 

 tasks of the forest manager is to 

 control wildfire, preferably by pre- 

 vention. Only if the forest is free of 

 wildfires, can management measures 

 be applied as needed to yield the 

 maximum amount of goods and serv- 

 ices the forest is capable of pro- 

 ducing. 



Prescribed fire, however, can be a 

 useful tool for achieving these ends. 

 It is often one of the measures that 

 may be appropriate' in manipulating 

 forest vegetation. But to use fire 

 properly it must be fully controlled. 



Because of the great variation in 

 climate, topography, soils, and vege- 

 tation in the United States, a compre- 

 hensive discussion of the role of fire 

 in forest management and ecology 

 would require much more space than 

 is available here. This discussion 

 will therefore be limited to the lob- 

 lolly-shortleaf pine-hardwood forest 

 type, which extends from Maryland 

 to Texas through the middle South. 

 It is the most important forest type 

 in the southern timber economy and 

 one in which the fire history encom- 

 passes both substantially wild and 

 prescribed fire. 



Ecology of Fire 



Fire was apparently the major fac- 

 tor in maintaining extensive stands 

 of pine long before the South was 

 settled by man; it can probably be 

 considered a natural ecological factor 

 in southern pines. With the advent 

 of human settlement and, later, ex- 

 tensive logging, it became a frequent, 

 almost annual occurrence over much 

 of the region. Not until the organiza- 

 tion of public forestry agencies and 



the establishment of permanent forest 

 industries was the custom of indis- 

 criminate annual woods burning 

 brought under control. However, 

 wildfire continues to be a frequent 

 occurrence. 



Loblolly pine is the most prominent 

 tree species in this type of forest. 

 It usually occurs in relatively pure 

 stands, being a serai species. On 

 drier sites, shortleaf pine is often 

 mixed with it, particularly in the 

 western part of its range in Arkansas, 

 Louisiana, and Texas. Pine is fol- 

 lowed by deciduous hardwoods in 

 the plant succession, and the pine 

 stands characteristically have an un- 

 derstory of hardwood tree and shrub 

 species which eventually displace the 

 pine unless a disturbance occurs that 

 again favors pine. 



The effect of fire in loblolly pine 

 stands is closely related to the bi- 

 ological requirements and character- 

 istics of the species and to the trend 

 toward hardwoods in the plant suc- 

 cession. The effect of fire on the 

 succession depends on the age of the 

 pine stand and on the intensity, fre- 

 quency, and season of fire occurrence. 



Effect of Fire Intensity — Crown 

 fires at any season of the year com- 

 pletely destroy the pine stand. Fires 

 of this type occur during periods of 

 exceptionally high fire hazard, so 

 that understory vegetation is also 

 killed back to the ground. A burned 

 soil surface is an excellent seedbed 

 for loblolly pine, and the proportion 

 of pine in the new stand depends 

 on the supply of pine seed in the first 

 year or two after the crown fire. Pine 

 becomes established readily in the 

 burned area, and the resulting stand 

 is made up of pine seedlings and 

 hardwood seedlings and sprouts. In 

 one study, pine reproduction equalled 

 hardwoods in basal area but not in 

 number of stems nine years after a 

 crown fire, showing that the pine 



stems were growing much faster than 

 the hardwoods and would probably 

 form the bulk of the dominant stand. 



Loblolly pine stands become fairly 

 resistant to surface fires at about 10 

 years of age. Fire usually destroys 

 younger stands completely but sur- 

 face fires damage older stands very 

 little. Furthermore during the dor- 

 mant season such fires in older pine 

 stands have very little effect on suc- 

 cession. Litter is consumed and small 

 stems are killed. The hardwood stems 

 are quickly replaced by sprouting and 

 the thin litter permits establishment 

 of pine seedlings, so that conditions 

 quickly become as they were before, 

 except that hardwood stems are prob- 

 ably more numerous. 



Effect of Season — In the loblolly 

 pine range, wildfires are most likely 

 to occur in spring, before growth 

 begins, and in autumn, after leaf- 

 fall. Winter fires are less frequent, 

 while summer fires occur only during 

 prolonged and severe dry periods. 



Fires during dry periods in the 

 growing season may be very destruc- 

 tive because initial vegetation tem- 

 peratures are higher, growing tissues 

 are more exposed to heat, and sprout- 

 ing is less vigorous than that follow- 

 ing dormant-season fires. Depending 

 on how much of the overstory is 

 killed, conditions after summer fire 

 range from something resembling 

 those after a crown fire to a reduction 

 in the smaller understory hardwoods 

 only. The succession varies accord- 

 ingly. 



Fires within the first year after har- 

 vest cutting differ in their effects, de- 

 pending on the time of the year they 

 occur in relation to pine seedfall. 

 During the dormant season they de- 

 stroy not only advance reproduction 

 but also whatever seed is present. 

 Hardwoods are highly favored be- 

 cause a whole growing season must 



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