110 FOREST PROTECTION 



III. The mineral fertility of the soil is absorbed by the 



weeds (especially the fruiting weeds) competing 

 with the trees for a food supply. 



IV. The weeds, notably those produced after fires, inter- 



fere with the natural regeneration of the best 

 species of the forest; they prevent, through dense 

 shade, the lignification of the valuable seed- 

 lings during summer. Instances are: Chinqua- 

 pin and gum in the case of yellow pine regener- 

 ation at Biltmore; witch hazel, dogwood in yel- 

 low poplar regeneration in Pisgah forest; black 

 jack oak in long leaf pine forests. 



V. Some weeds distort and oppress the seedlings and 

 saplings after climbing to their tops. Grape- 

 vine on yellow poplar; Convolvulus on many 

 tree seedlings. In tropical countries, the tree 

 climbers (sometimes parasitic) are particularly 

 troublesome, notably in felling trees. 



VI. Certain weed species (notably Ericacce) produce, 

 through their leaf fall, an unfavorable, dusty 

 humus. 



VII. Weeds harbor and hide mice and damaging insects. 



VIII. Dead weeds increase the danger of fires, especially 

 in the spring. 



IX. The dead mould spread on the ground by many weeds 

 prevents the germinating seed of valuable species 

 from sending its rootlets into the mineral soil. 



X. Certain weeds play an important part in the path- 

 ology of the trees, the weeds acting as hosts 

 for the second generation of certain fungi. 

 C. Means of Protection. 



I. Preventive measures. 



a. Maintain a complete cover overhead — 



a pions wish in the primeval forests. 



b. Underplant light demanding species with 



shade bearers at a time at which 

 the leaf canopy overhead, through 

 friction of crown against crown, be- 

 comes excessively open — another 

 pious wish under the present con- 

 ditions confronting American silvi- 

 culture. 



c. Work towards immediate reforestation 



after making a clean sweep of the 

 old crop. 



