PLANT ASSOCIATIONS OF NORTHERN MICHIGAN 155 



in hay, in packing material, and doubtless in other ways also, and 

 are distributed through the clearing along all of the logging roads. 

 They are all common field and roadside weeds of the neighboring 

 farming region or ruderal plants of the city of Cheboygan, to 

 which the lumber is hauled. Away from the settlements their 

 distribution is restricted completely to areas more or less modified 

 by human activity, as has been described in another place." 



These species demand full sunlight for their successful growth, 

 and consequently develop rapidly during the first summer. At 

 that time the premises of the logging camp, every logging road, 

 every site of a log pile and every feeding ground are marked by an 

 assemblage of foreign species, occurring as scattered individuals 

 but greatly outnumbering the few relics of the forest. Owing 

 to the great seed production so characteristic of weeds, their 

 numbers are vastly increased during the second summer. By 

 the third summer one species, Poa pratensis, and frequently 

 another, Phleum pratense, have become so abundant that they 

 form extensive patches of sod, which occupy the camp grounds and 

 extend in narrow lines along every logging road. In short, every 

 part of the original forest which has been accessible to horses and 

 wagons is converted in three years into a blue grass meadow, 

 which forms a striking contrast to the tangle of shrubbery hem- 

 ming it in on all sides. 



Elimination of species begins with the establishment of a sod, 

 and by the third summer several species of the first year have dis- 

 appeared. Of the remainder, the majority are restricted to the 

 edge of rubbish heaps or sawdust piles, to the base of the walls of 

 buildings, or to small and dense colonies within the meadow. In 

 such places they may resist the further encroachment of the 

 meadow for many years, as evidenced below. A minority, on the 

 other hand, seem well adapted to the sod and are found widely 

 distributed over it. These species are Trifolium pratense, Tri~ 

 folium hyhridum, Trifolium repens, Agrosiis alba, and Rumex 

 acetosella. 



It is noteworthy" that these foreign species are virtually inde- 

 pendent of the local physical environment. The logging roads 



«Bull. Torr. Bot. Club 41: 511-521. 1914. 



