BOOKS AND CURRENT LITERATURE 



Forest Climatology. — A comparative study of climatic condi- 

 tions in pine forest and in open natural "park" has been made by 

 Pearson 1 at Fort Valley, at an elevation of 7200 feet in northern Arizona. 

 Air and soil temperatures, humidity, evaporation, precipitation, and 

 wind were measured at a station in the forest, one on the edge of the 

 forest, and one in the park. Substantial differences in all of the climatic 

 conditions except precipitation were discovered. There was a differ- 

 ence of 6.4° between the mean minimum temperatures of forest and 

 park, the latter having the lower range. The mean maximum was 

 about 1° higher in the park than in the forest. The thermometers 

 in the park were 5§ feet from the ground; a comparative set of read- 

 ings taken 8 feet from the ground showed a mean minimum 2° higher, 

 with nearly identical maxima. A comparison of minima in the forest 

 and in a cut-over area of the same topographic situation, showed a 

 mean about 2° lower in the clearing. These results are taken to indi- 

 cate that radiation is partly responsible for the lower minima of the 

 park, and that cold air drainage is also partly responsible for the differ- 

 ence. The mean summer temperature of the soil at a depth of 2 feet 

 was about 5° higher in the park than in the forest. The mean humidity 

 of summer was about 2.5% higher in the forest, and that of the winter 

 about 4% higher in the park. The mean daily wind movement in 

 all months was about twice as great in the park as in the forest. The 

 evaporation at the edge of the forest was from 25 to 50% higher than 

 in the forest. The other data for the edge of the forest are commonly 

 midway between the values for the forest and the park. The influence 

 of the described differences of climate on the fate of seedling pines 

 was shown by planting two-year old trees in the forest and on the edge 

 of the park. In the forest 90% survived, and on the edge of the park 

 only 11% survived at the end of one month in the arid, windy season. 

 It is difficult to overestimate the importance of such work as Pear- 

 son's for the placing of silvicultural methods on a sound scientific 



1 'Pearson, G. A., A meteorological study of parks and timbered areas in the 

 western yellow pine forests of Arizona and New Mexico. Mo. Weather Rev., 

 41: 1615-1629. 1914. 



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