. The distribution of vegetation in the United States, as related to climatic conditions. Phytogeography. CLIMATIC CONDITIONS OF THE UNITED STATES. 333 (4) Ratios of Nobmal Total Precipitation for Period of Average Frostless Season Plus preceding 30 Days, to Total Evaporation for the Same Period, July 1887 to June 1888 {ir/E). (Table 11, Plate 59.) This form of the moisture ratio is based on the idea, already men- tioned, that some of the precipitation occurring before the beginning of the frostless season is effective to supply water for plant activities in the early part of that season. The
. The distribution of vegetation in the United States, as related to climatic conditions. Phytogeography. CLIMATIC CONDITIONS OF THE UNITED STATES. 333 (4) Ratios of Nobmal Total Precipitation for Period of Average Frostless Season Plus preceding 30 Days, to Total Evaporation for the Same Period, July 1887 to June 1888 {ir/E). (Table 11, Plate 59.) This form of the moisture ratio is based on the idea, already men- tioned, that some of the precipitation occurring before the beginning of the frostless season is effective to supply water for plant activities in the early part of that season. The numerator (P) of the first form of ratio has thus been increased, in each case, by adding to it the normal total precipitation for the 30 days just preceding the beginning of the average frostless season. This increased precipitation value has been termed tt, to distinguish it from P and p, so that the form of ratio here considered becomes tt/E. The values of tt and E, and those of tt/Ej are given, for our list of stations, in table 11, the ratio values occupying the last column. The chart based on these ratios is shown as plate 59. The essentials of this chart are so nearly like those shown by plates 57 and 58 that no special comment is here needed. It may be noted, however, that the full line separating the humid from the semihumid zone is here taken as having the value instead of , as in plates 57 and 58. (5) Ratios of Normal Total Annual Precipitation to Total Annual Evaporation, July 1887 TO June 1888 {PjEa). (Table 15, Plate 60.) These annual ratios are derived by the method employed by Tran- seau. We have termed the normal total annual precipitation P^, and. Fig. 15.—Moisture zonation of the eastern l^nittxl States, acconlini: to piooipitation-evavoration ratio (annual), after Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations m
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectphytoge, bookyear1921
