. The distribution of vegetation in the United States, as related to climatic conditions. Phytogeography. CLIMATIC CONDITIONS OF THE UNITED STATES. 323 which these profiles pass are indicated at proper distances along the horizontal axis. As ordinates, extending upward at the points so marked, are represented the mean weekly losses from the porous-cup atmometer, as given in table 17, these numerical data being placed upon the profiles. Below each profile are conventionally indicated the vegetational types traversed and their approximate boundary lines, these boundaries having been obtained fro
. The distribution of vegetation in the United States, as related to climatic conditions. Phytogeography. CLIMATIC CONDITIONS OF THE UNITED STATES. 323 which these profiles pass are indicated at proper distances along the horizontal axis. As ordinates, extending upward at the points so marked, are represented the mean weekly losses from the porous-cup atmometer, as given in table 17, these numerical data being placed upon the profiles. Below each profile are conventionally indicated the vegetational types traversed and their approximate boundary lines, these boundaries having been obtained from the generalized vegetation chart (plate 2). We need not digress here to discuss the relations brought out between vegetation and summer evaporation intensity as here indicated; these matters will receive attention in their own place. The northern west-east profile (lowest in figure 13) shows little variation in the intensity of evaporation throughout its extent. The southern west-east profile, on the other hand, shows a very great variation in evaporation values, the maximum being at Dalhart and the minimum at Pisgah Forest. The north-south profiles bring out the relatively high summer evaporation values obtained at Dickinson, at East on, and at Gainesville and Oxford. (4) Conclusions from the Study of Evaporation Conditions. All the evaporation charts agree in their main features, especially the charts derived from Russell's observations. The four evaporation provinces are represented in figure 14, based on plate 53, and may be 129° 127° 125° 123° 12f 110° 117° 116° 113° 111° 10<J° 107° 106° 103° 101° Sif 97° 96° 93° 91° 89° 87° 85° 8^ 81° 79° 77° 75° 73° 7f' 69° «J° &i' \. 119° 117° 118° US' lir 1(W lOr 105° lOr US' 07° US' SJ" 89" 87* S4* SJ* 81° TT TJ" :!• Fig. 14.—Moisture zonation, according to evaporation indices (1887-88") for period of frostlesa season. Evaporation provinces: Humid, less than
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectphytoge, bookyear1921
