REPRODUCTION OF WESTERN YELLOW PIXE. 59 



depth of one-fourth inch in full sun at Fort Valley registered 

 1*23.8° F. at 2 p. m., whereas in the shade of a group of tall pines 

 it registered only 69.8° F. Differences of this magnitude are not 

 at all uncommon. 



A similar relationship was exhibited by the transpiration of 

 yellow pine and Douglas fir seedlings. Those exposed to the great- 

 est amount of sunlight invariably showed the highest loss of water. 

 It is reasonable to suppose that a reduction of transpiration might 

 save seedlings from death during critical periods of drought. On 

 the other hand, the probabilities are that this saving of water i- ; 

 accomplished at the expense of growth. Moreover, many of the 

 seedlings so situated as to be shaded by trees during any consider- 

 able portion of the day encounter competition for soil moisture 

 from the roots of older trees; thus they may fare worse from the 

 standpoint of moisture than seedlings exposed to full sunlight but 

 beyond the influence of tree roots. Bates's (1) investigation of 

 windbreaks throws additional light on this subject. He found that 

 for a distance equal to from one-half to the total height of a wind- 

 break, on the north side, the yield of field crops was below normal, 

 due to shading, and that sapping carried this effect to about one 

 and one-half times the height of the trees. Beyond this point the 

 yield was above that of unprotected fields for a distance equal to 

 from 4 to over 10 times the height of the windbreak. Although the 

 arrangement of trees in a cut-over stand would not give such pro- 

 nounced effects as a continuous windbreak, it seems fair to assume 

 that the same principles would apply. 



EFFECT OF CUTTING OX SOIL MOISTURE. 



AREAS OF STRONG ROOT ACTIVITY VS. AREAS OF XO ROOT ACTIVITY. 



When a tree is removed from the stand, the water loss resulting 

 from increased insolation and wind movement is in a greater or less 

 degree offset by stopping the consumption by the tree itself Whether 

 the net result is a loss or a saving of soil moisture is a matter 

 of importance. With the object of answering this question, experi- 

 ments were carried on at the Fort Valley Experiment Station in 

 1919 and 1920. 



In 1919 soil-moisture tests were made in areas occupied by the 

 roots of living trees (site 1) and in areas containing the dead roots 

 of trees felled two years previously (site 2). Excessive grazing 

 had reduced the stocking of herbaceous vegetation on both sites 

 to below normal density, and continued cropping for the most part 

 kept it from growing more than a few inches tall. Lupine became 

 luxuriant during July and August, but declined early in September 

 from the effects of a leaf disease. 



