ECOLOGY. 401 



the plants, the abundance of dominants and subdominants, etc., 

 are recorded, and photographs made of representative quadrats. 

 The vegetation is then removed by cutting it near the surface of the 

 soil, after which it is collected, thoroughly dried, and the production 

 determined on the basis of dry weight. 



During the present season pure stands of v/heat-grass (Agropyrum 

 glaucum) gave yields of 400, 457, and 606 grams per square meter at the 

 Burhngton, Phillipsburg, and Lincoln stations respectively. However, 

 the yield of buffalo-grass {Bulbilis dactyloides) in pure stands reached 

 the maximum in the mixed prairie at Phillipsburg (266 gms.), while 

 the true prairie ranked second (235 gms.), and the short-grass plains 

 third (207 gms.). The results thus far obtained v;ith mixtures of the 

 dominants indicate a fairly direct correlation between the chresard 

 and plant production. Final correlations will be possible, however, 

 only after the studies have been continued through the climatic cycle. 



The Relation oj Hardpan to Root Development, by J. E. Weaver and J. W. Crist. 



During the excavation of the root systems of native and crop plants 

 in the prairie and plains associations during the past five years, 

 so-called hardpan has been found in more than 30 localities. This 

 characteristic layer of soil underlies much of the area with limited 

 rainfall at depths ranging from 8 or 12 inches to 2 or 3 feet. 

 Typical samples of hardpan have been collected at several widely 

 separated stations for analysis, together with the soils lying above and 

 belov/ this layer. It is hoped that this will determine the degree to 

 which the hardpan is due to the physical structure or to carbonates 

 and other cementing substances. The chief effect of hardpan upon 

 root development lies in its reduction of water penetration, though 

 when thoroughly moist it becomes quite mellow. 



Transplant Quadrats and Areas, by F. E. Clements and J. E. V/eaver. 



The studies in experimental vegetation, which have been carried 

 on for the past three years, have been greatly extended during 1921. 

 In addition to the stations already established, a new one at Peru, 

 Nebraska, and another in the salt flats at Lincoln have been installed. 

 Reciprocal transplants of dominant grasses have been made at several 

 intervals at Lincoln, Tucson, Pike's Peak, and Berkeley. 



In general, grass sods and seedlings establish themselves in new 

 climates only when the rainfall and winter temperatures are not too 

 different in the minus direction. Thus, dominants from the true 

 prairies at Lincoln are thriving at Pike's Peak and Berkeley, while 

 dominants from the bunch-grass prairie at La Jolla and the desert 

 plains at Tucson establish themselves only occasionally at Lincoln, 

 or persist for but a portion of the season. In the few cases where 

 they have grown throughout the summer, they died during the fol- 



