BLM 



Figure 10. — Alaska's first commercial oil well. 



WATERSHEDS 



Wherever located, an undamaged water- 

 shed performs the same useful function: it catches 

 rain or snow and allows the water to percolate 

 into the soil; thus, it controls streamflow in an 

 orderly fashion. A good watershed slows the 

 flow of water into streams during the spring and 

 early summer. It also acts as a storage basin and 

 allows water to flow into streams slowly during 

 the season when precipitation is low. 



Many effects of fire on characteristics of 

 soils and watersheds and on species distribution 

 are similar to what is expected in more southerly 

 States. Interior Alaskan soils are generally shal- 

 low. Fine-textured soils become poorly aerated 

 and cooled; organic matter tends to remain unin- 

 corporated in the mineral soil and to rest on the 

 soil as a mantle. The moss and lichen cover is 

 a good insulator in the summer,- its removal 

 causes a lowering of the permafrost level. 

 Though fire may not alter soil texture and struc- 

 ture, it does reduce the infiltration rate and in- 

 crease overland flow. 



Not all ecological effects of uncontrolled 

 fire are detrimental to the environment. Thermal 

 effects on soil temperature are generally favor- 

 able, as are the chemical changes. Nutrients that 



are normally locked up on the cold forest floor 

 are liberated for assimilation by new plant 

 growth. 



Interior Alaska has one watershed feature 

 that exists nowhere else in the United States: 

 permafrost. Changes in permafrost resulting 

 from forest fires are discussed further in chapter 

 3. Briefly, fire destroys the moss insulation and 

 permits warm air and solar radiation to melt the 

 permafrost. The earth on slopes often moves or 

 sags, trees fall over, and the water table drops. 

 Evaporation excessively dries the soil surface 

 after the permafrost level has been lowered; this 

 in turn defeats efforts at revegetation. 



USFS 



Figure 11. — This accelerated erosion started after surface 

 vegetation was burned; near Fairbanks. 



USFS 



Figure 12. — Irrigated farmlands depend on productive 



watersheds; near Fairbanks. 



16 



