disease, failure of germination and establishment of conifer seedlings, 

 alteration of the nitrogen availability in the soil, and decreased rate of 

 decomposition. 



Forest systems also absorb heavy metals from the atmosphere. Siccamma and 

 Smith (1978) found that 987© of the lead entering a forest system was retained. 

 Other metals that show increasing levels in the forest included aluminum, 

 gold, chromium, nickel, lead, antimony, and vanadium (Galloway and Likens 

 1977). While these studies were conducted in the Adirondack Mountains and in 

 New Hampshire, the same levels probably exist in Maine. The long-term effects 

 of metals and the extent to which they can continue to be accumulated are not 

 known . 



Forest systems are also affected by logging, fire, and insect and wind damage. 

 These disturbances, particularly that of logging, affect a greater amount of 

 Maine's forest land each year than does urban or suburban development. Their 

 effects are not permanent and forest systems recover from them. Wind affects 

 forests in ways similar to those of logging. These effects and those of fire 

 are discussed below. 



Effects of Logging 



The common cutting and logging practices employed in Maine are discussed in 

 chapter 19, "Commercially Important Forest Types." The two main types of 

 practices are selective cutting and clearcutting. Management of uneven-aged 

 stands employs selective cutting, which strives to simulate the conditions in 

 a steady-state forest, removing only selected, mature trees that would 

 normally be lost through natural mortality. This type of system is best for 

 regenerating tolerant tree species, because it maintains a closed canopy at 

 all times. Selective cutting usually does very little damage to forest 

 systems. The forest floor and understory vegetation is somewhat disturbed by 

 heavy machinery, road construction, and use. The forest system largely 

 remains intact and tends to function normally. 



Clearcutting simulates conditions in a forest that follow a major disturbance, 

 such as fire or wind storms (Bormann and Likens 1979) and regrowth is 

 principally intolerant species. Major destruction of a forest system alters 

 the water and nutrient cycles and interrupts the pattern of productivity and 

 biomass accumulation, decomposition, and mineralization. Quantitative data 

 concerning these effects on Maine's forests are lacking but research in 

 northern hardwood stands in New Hampshire are applicable (Bormann and Likens 

 1979). 



Removal of the forest canopy allows increased solar radiation to reach the 

 ground, causing higher soil temperatures. Removal of trees reduces the rate 

 at which water is removed from the soil by plants and transpired, thus, 

 increasing soil moisture. Higher soil temperature and moisture content 

 promotes more rapid nitrification and decomposition of litter, which releases 

 more nutrients for plant and animal use. The control that the forest 

 vegetation previously had over the flow of water through the systems is 

 partially lost, resulting in accelerated runoff and erosion and greater annual 

 extremes in high and low flow. Increased runoff causes accelerated 

 particulate matter loss and soil erosion. The decomposition of the residual 

 organic matter, such as logging slash, reduces these effects for up to 2 



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