No. 1, Joly, 1920] ECOLOC.Y, PLANT GEOGRAPHY 57 



temperatures in the vicinity of Abilene, Tex i , aboul I bree months before planl ing can begin, 

 with a resulting indicated large accumulation of effective temperature in-fore any growth is 

 possible. — Spring wheal seeding begins with a lower mean temperature than any other major 

 spring crop, for example, in t he Dakotas and in Nebraska when t he normal daily temperature 

 rises to 37°F. and in Minnesota and Wisconsin when 40 1 . is reached. Next m thermal order 

 come spring oats, the seeding of which usually begins when the normal daily temperature rises 

 to 43 F. Early potato planting begins as a rule when the normal daily temperature rises to 

 45 F. and com when 55 F. is readied. The dates on which the Latter is reached correspond 

 closely to the average dates of the last killing frost in the spring. Cotton planting usually 

 does not begin until the normal daily temperature rises to about 62 F. The dates on which 

 this temperature is reached correspond closely to the latest dates for a killing frost. — Cotton 

 and corn are warm-weather crops and 1 he areas in which these can be successful productions on 

 a commercial scale are limited principally by general temperature conditions and the temper- 

 ature at which planting may be accomplished. These limits are defined by an available 

 thermal constant of about 1600 F. for corn and about 2000 F. for cotton, computed from 

 the normal temperature when planting usually begins. If cotton could be planted with as 

 low temperatures as corn, the cotton area would be materially increased. — Owing to the rela- 

 tively large thermal requirements of corn and cotton, a comparatively warm spring is neces- 

 sary for the best results in germination and early growth. — Joseph B. Kincer. 



379. McLean, Form an T. The importance of climatology to tropical agriculture. Phil- 

 ippine Agric. 7: 191-194. 1919. — A brief discussion of the relation of the climate (temperature, 

 evaporation, wind, sunlight, rainfall, etc.) to Philippine agricultural crops, with a plea that 

 adequate investigations be instituted as a basis for instruction in climatology at the College 

 of Agriculture. — S. F. Trelease. 



3S0. Sampson, Arthur W. Plant succession in relation to range management. U. S. 

 Dept. Agric. Bull. 791: 76 p. 26 fig. 1919. — A study of plant succession in the vicinity of the 

 Great Basin Experiment Station in Utah with especial reference to the use of plant consocia- 

 tions as determiners of factors necessary to the improvement of grazing ranges. Four plant 

 consociations are discussed, namely, the wheat-grass, the porcupine-grass-yellow-brush, the 

 foxglove-sweet-sage-yarrow and the ruderal-earlyweed consociations. The nature of each 

 of these plant succession groups is illustrated in detail by a treatment of such factors as con- 

 ditions of growth and reproduction, soil water content, effect of disturbing factors, palata- 

 bility and forage production. The most ideal conditions of soil fertility, and moisture for 

 optimum forage production on a given range are indicated by plants of the wheat-grass groups 

 and the least ideal conditions by plants of the last named group in the order above enumerated. 

 The prevalence of plants of any one of these consociations thus becomes an indicator of whether 

 or not destructive factors may be at work. Overgrazing by removing the original ground 

 cover facilitates soil erosion which in turn reduces the fertility and humus content. This re- 

 duction in turn results in the introduction of the plant consociation next lower in the scale . 

 Protection of the depleted range may be accomplished in part by grazing only after seed pro- 

 duction rather than grazing before seed production. There is included a list of the most com- 

 mon species found in each consociation which may be used as an indicator of the condition 

 of the range. — E. V. Hardenburg. 



381. Sampson, Arthur W., and L. H. Weyl. Range preservation and its relation to ero- 

 sion control on western grazing lands. U. S. Dept. Agric. Bull. 675. 85 p. 1918. — In the 

 Manti National Forest of Utah the destruction of the vegetation carpet by overgrazing, es- 

 pecially by sheep, has resulted in serious damage by erosion. The peak of this destruction 

 is in the spruce-fir basins, where the slopes are steep, the trees sparse, and the summer grazing 

 conditions good. On eroded areas new successional stages are seen, and the reestablishment 

 of the more desirable species for grazing means good range management extended over a term 

 of years. Deferred and rotation grazing and stock control are necessary. Damage resulting 

 from long-continued erosion can best be overcome by terracing, planting, and the construc- 

 tion of dams. See Bot. Absts. 2, Entry 18; Exp. Sta. Rec. 39: 439-440; also rev. by: Toumey 

 in Jour. Foresty 16: 814-817.— if. C. Cowles. 



