chapter 3, "Human Impacts on the Ecosystem", as well as the overall effects of 

 these on aquatic systems. 



OLDFIELDS 



Oldfields do not occupy a large area of land in coastal Maine but they are 

 ecologically important. The amount of oldfield habitat in Maine is difficult 

 to determine, partly because its regrowth superficially resembles the regrowth 

 on recently logged or burned areas. On the other hand, for the first few 

 years after abandonment oldfields resemble pasture land or idle farmland and 

 may be classified as such. The only data available on oldfield habitat are 

 for region 6, in which 18% of the farmland is brush land, or waste land. This 

 amounts to less than 1% of the total land area in Washington County. 



The amount of oldfield habitat present at any one time depends not only on the 

 rate at which farmland is abandoned but also on the rate at which formerly 

 abandoned farmland is reclaimed for agriculture or development. Neither of 

 these rates in Maine are known but until 1969 the amount of farm land was 

 decreasing, and oldfields were increasing. Presently the two about balance. 



The ecological value of oldfields stems from their importance as wildlife 

 habitat and their role in rehabilitation of disturbed ecosystems. A high 

 diversity of plant life is present during succession from farmland to forests. 

 This provides abundant food and cover for many species of insects and 

 invertebrates, birds, mammals, and some reptiles and amphibians. Usually the 

 growth of plants (density and composition) is not uniform and cover types are 

 patchily distributed. The mosaic of habitats and edges is conducive to 

 wildlife. Many important game species, such as hares, grouse, and deer, are 

 sometimes abundant in oldfields. Through the process of succession in 

 oldfields plant biomass and soil organic matter accumulate and soil structure 

 is slowly restored. This process serves to rehabilitate disturbed ecosystems. 



Succession 



The process of succession from active farmland to forest involves a series of 

 changes in plant communities. The first stage consists of annual grasses, 

 such as fescue, panic grass, Agrostis spp . , orchard grass, witch grass, and 

 bluegrass. The second stage is perennial herbs, such as goldenrod, hawkweeds, 

 asters, and ragweed. The third stage is woody shrubs that gain a foothold and 

 spread from isolated clumps. Common shrubs in Maine oldfields are dogwood, 

 spirea, willow, alder, wild apple, and juneberry. The fourth stage is trees, 

 usually the more intolerant species of aspen, birch, pine, white cedar, and 

 cherry. The invasion of trees is relatively slow but when the overstory or 

 canopy finally closes the area once more becomes a forest. 



Succession on oldfields is slow because cultivation and the application of 

 herbicides has destroyed most remnants of native vegetation and altered the 

 soil structure. In addition, the grasses develop a cover of sod that later 

 hampers the establishment of woody plants. Even after trees begin to invade 

 they 't so in isolated clumps and it may be many years before a complete cover 

 of trees is established. A study of oldfield ecology in Michigan indicated 

 that after 50 or 60 years large areas of grasses and only isolated clumps of 

 trees and shrubs were present (Weigert and Evans 1964). The sequence of 

 changes in plant communities was documented on a series of oldfields in New 



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