. Bulletin of the Department of Agriculture. Agriculture; Agriculture. DEFECTS IN TIMBER CAUSED BY INSE( K 37 follows iii recovering trees. In fir trees one, two, or three rings may fail to form completely around the stem, particularly at tin- base, and are represented only by partial arcs (fig. 36} ( ,' Rings of traumatic resin ducts are frequently deposited in the terminal portions of defoliate! fir trees during the firsl to third years of feeding. Complete defoliation of certain hardwood- in the early spring produces a double ring the same year. These defects resull in a great loss of
. Bulletin of the Department of Agriculture. Agriculture; Agriculture. DEFECTS IN TIMBER CAUSED BY INSE( K 37 follows iii recovering trees. In fir trees one, two, or three rings may fail to form completely around the stem, particularly at tin- base, and are represented only by partial arcs (fig. 36} ( ,' Rings of traumatic resin ducts are frequently deposited in the terminal portions of defoliate! fir trees during the firsl to third years of feeding. Complete defoliation of certain hardwood- in the early spring produces a double ring the same year. These defects resull in a great loss of increment, increasing the rotation from 3 to 1" years, and cause confusion in growth studies based on the annual rings. Similar distortions of rings are found in Douglas fir, due to de- foliation by the spruce bud worm, and in western fir, spruce, yellow pine, and particularly lodgepole pine, due to defoliation by the nee- dle Such losses and de- fects can be prevented only by the prevention of defoliation, a prob- lem of forest manage- ment. DEFECTS CLASSED AS PITCH POCKETS AND PITCHY TIMBER Pitch pockets are openings between the grain of the wood which contain more or less pitch or bark. They are graded as small, standard, and large pitch pockets. These pockets range from one-eighth inch to 2 inches in width and from 3 to 12 inches in length. Sometimes, instead of pockets, there are merely pitch streaks. These defects may be caused by insects as well as other agents. The pockets are small, usually about one-half to 1 inch in length. and about one-half inch in width, full of pitch; in pine, they parallel to the grain. Sometimes they are as large as 2 inches in diameter and contain a large quantity of pitch. This injury may be caused by unsuccessful attacks of bark beetles 31 which have failed to kill the tree and have been drowned out by the flow of pitch. (Fig. 37.) It is a sound defect which can be prevented only by con- trolling the bark beetles that attack th
Size: 1771px × 1410px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauth, bookcentury1900, bookdecade1910, booksubjectagriculture
