508 



CORRELATION OF DISTRIBUTIONAL FEATURES. 



Cape Disappointment are far exceeded by the still more moist condi- 

 tions of Cape Flattery. In short, the difference between the values of 

 the moisture ratios in moderately moist localities in the Northwestern 

 Forest and in the most moist localities is as great as the differences 

 which have already been seen to play such an important role in deter- 

 mining the distribution of the vegetation in the remainder of the 

 United States. 



It is unfortunate that the inadequacy of the climatological data gives 

 this region the appearance of being exceeded in the normal mean 

 relative humidity of the frostless season by the western section of the 

 Northern Mesophytic Evergreen Forest, an appearance that is prob- 

 ably misleading. The sunshine conditions are also imperfectly known 

 for this area. 



The moisture-temperature index for the frostless season has already 

 been shown to be closely similar in values and in amplitude for this 

 most hygrophytic of the vegetations of the United States and for the 

 Desert. In forming the product by which this compound condition 

 has been secured, the high temperature summation of the desert, 

 together with the low moisture indices, and the low temperature sum- 

 mations of the Hygrophytic Forest, together with its high moisture 

 indices, have given results which are closely identical. 



Southeastern Mesophytic Evergreen Forest (fig. 33). — In viewing the 

 entire series of blocks drawn to represent the chief climatic conditions 

 of this region, it will be noted that there is, in general, a wide ampli- 

 tude of nearly all conditions, including those of temperature and 

 precipitation, and excepting only the imperfectly exhibited mean 

 annual precipitation and the relative humidity. The ampUtude of the 

 moisture ratios is no greater than in the case of the Deciduous Forest 



tcmkkatuxc 

 Days in Normal Fhostless Scason T. S.) 

 Hot Days. F. S. 

 Cold Days. F. S. 

 PHYSiOLOCfCAL Summation. F. S. 

 Normal Daily Mcan. coldest 14 days or Year 

 Normal Daily Mean. Year 



Precipitation 

 Normal Daily Mean, F. S. 

 Days in longest Normal Rainy Period. F. S. 

 Oats in loncest Normal Dry Period. F. S. 

 Mean Total. Year 



Evaporation 

 Daily Mean. 1687-6, F. S. 



Moisture Ratios 

 Normal P/E, F. S. 

 Normal n/Z, F. S. 

 Normal P/E, Year 



Humidity 

 Normal Mean. F. S. 



Sunshine 

 Normal Daily Duration. F. S. 



Moisture-Temperature Indices 

 NaRMAi. P/E « T. r. S., Physiological Method 



Fig. 33. Climatic extremes for Southeastern Evergreen Forest. 



