wildlife species that are important to humanity and to ecosystem functions. 

 They also provide valuable food and cover, and when compared with uniform 

 stands of softwoods support more numerous and diverse wildlife populations. 

 In addition, the long-term toxic effects of herbicides on plants and animals 

 is uncertain. The effects of logging on birds and mammals are discussed 

 further in chapters 16 and 17, "Terrestrial Birds," and "Terrestrial Mammals" 

 respectively. Briefly, some species are benefitted by habitat changes after 

 logging, while others are adversely affected. 



Pesticides are used in forest systems to control insect defoliators, primarily 

 the spruce budworm. The chemicals currently used, such as Sevin, are 

 relatively short-lived and break down rapidly. Consequently, they are not 

 concentrated in animal or plant tissue as were some of the pesticides (e.g., 

 DDT) that were used in the past. On the other hand, nontarget insects may be 

 killed by spray and reduce the abundance of insects as food for most birds and 

 small mammals. 



During clearcut logging, slash is often piled and sometimes burned. This is 

 done because slash inhibits the growth of tree seedlings. However, slash has 

 been shown to be important during the immediate postcutting period. Slash can 

 reduce the effects of rainfall and erosion, shade the ground, reduce soil 

 temperatures, and release nutrients as it decomposes (Bormann and Likens 

 1979). Excessive disturbance of the forest floor when slash is piled also can 

 result in increased decomposition and leaching of nutrients. 



Roads are necessary for access to forest stands. In New Hampshire roads 

 occupied between 1% and 107© of the forests being cut (Bormann and Likens 

 1979). Roads reduce productivity, because of disturbance and compaction of 

 the soil, removal of organic matter, and the directing of the flow of water by 

 drainage ditches associated with roads. 



Effects of Fire 



The severity of a fire largely determines its effects on forest systems. 

 Light surface fires destroy only the surface litter and ground vegetation, 

 whereas severe surface and crown fires may kill all the vegetation and destroy 

 the organic matter. As a result, the modifying influence of the forest canopy 

 over the forest environment is lost and changes occur in the water and 

 nutrient cycles, and the plant and animal life. Many of these effects are 

 similar to those following logging and are discussed above. Other aspects 

 unique to disturbance during or after a fire are discussed below. 



The amount of humus is reduced after fire because humus burns and because the 

 rate of decomposition increases after fire. Decomposition is increased by 

 higher soil temperatures and increased ash (alkaline) from burned plant 

 materials (see "Decomposition" above). 



Soil nutrients increase immediately after fires because nutrients in dead and 

 living plant material are released by burning. Initially these nutrients may 

 be leached from the soil but vegetation (especially grasses or herbs) quickly 

 recolonize the burned area and absorb the available nutrients. Since these 

 plants are short-lived, the nutrients are rapidly released again. 



9-32 



