THE QUADRAT METHOD IN TEACHING ECOLOGY 277 



gravel, a portion of which was once removed leaving a large 

 circular depression several rods wide but only a few feet deep. 

 The bottom of this gravel pit is rather completely revegetated. 

 Wind erosion is wearing away the bank and uncovering the 

 roots of the prairie plants. As the soil rolls down it forms a 

 new area for invasion. A quadrat placed with one edge on this 

 new area extends back into fairly stabihzed vegetation, for the 

 bank is crimibling at the rate of only 1 or 2 inches a year. Quad- 

 rats in this area have been followed since 1916. Only one need 

 be used here. This is shown in figure 7. Beginning with the 

 newest portion of the vegetation we find Solidago is a successful 

 pioneer. It persisted, because of its rhizomes, during the dry 

 year of 1918, while the annual Euphorbia and the perennial 

 Physalis had entirely disappeared. Sporobolus and Stipa to- 

 gether with Eragrostis are the pioneer grasses. It is instructive 

 to note that many of these seedlings disappear after a single 

 year. In 1918, with few exceptions, only well-established clumps 

 in the less densely vegetated portion of the quadrat withstood 

 the drought. Indeed, the writer had a similar experience with 

 a large number of prairie grasses of seven different species, the 

 seedlings of which were transplanted from pots and watered 

 until well established and left on June 1 in a flourishing con- 

 dition.3 All but a few of Sporobolus succumbed. 



The more stabilized portion of the quadrat includes Sor- 

 ghastrum, Laciniaria, and Bouteloua. Some of these are slowly 

 increasing their area of occupation. The 1917 quadrat shows a 

 gain of 29 per cent in the total number of individuals over that 

 of the preceding year, but in 1918 there is even a more marked 

 decrease. Other quadrats give similar results. 



This example illustrates how a student taking ecology for only 

 a single year may apply the most fundamental method of investi- 

 gating succession, that of sequence, which consists in tracing the 

 actual development of a community in a definite spot from year 

 to year (Clements 1916:423). This is the direct study of 

 vegetation as a process. Each class passes on its results to the 



3 These plantings were made in connection with a general study of the life 

 histories of range plants, a field of ecology very much in need of investigation. 



