6 MASS. EXPERIMENT STATION BULLETIN 397 



Similar injury^ was observed on foliage exposed to sulphur dioxide fumes from a 

 defective electric refrigerator. 



Fire. The huge losses resulting annually from forest fires are already known 

 to most persons, but the knowledge of how a fire injures individual trees is ap- 

 parently not so well understood. Extensive injury to the trunk and branches of 

 shade and ornamental trees often results from the burning of rubbish nearby, and 

 scorching of the bark is sometimes the prelude to invasion by fungi. 



Injury from Illuminating Gas. Many trees have been killed from the effects 

 of illuminating gas in the soil. Usually by the time the gas injury shows in a 

 tree, no remedial treatment is practical. In recent years considerable progress 

 has been made in detecting gas leaks by means of surveys conducted by gas 

 companies, and tree casualties have been reduced and human lives saved by the 

 prompt repair of leaks. 



Site. Tree troubles maj' originate at the site in which the tree is growing. The 

 basic nature of a possible site may be such as to make the planting of a particular 

 type or individual tree unwarranted. After the selection of a suitable species or 

 specimen, planting should be done in such a way as to avoid air pockets in the 

 soil, which often prove a source of trouble later. Careful planting in a well- 

 chosen site is the best insurance for the future growth of the tree. Sometimes 

 after an area has been planted, new buildings or other factors may necessitate 

 the removal or transplanting of the trees. Turf grading operations which fail to 

 piovidc a needed brick- or rock-lined wall around trees are a common .'•ource of 

 trouble. The installation of curbing, hard-surfaced roads, and sidewalks may 

 result in root injury. Erosion of soil during these operations and under a variety 

 of other conditions may dangerously undermine trees. Weakening of anchorage 

 should be guarded against in all locations. 



Narrow Tree Belts. In most communities, public shade trees are ordinarily 

 planted in the space between the hard surface road and the sidewalk. In some 

 instances this area is extremely narrow, but widening is often precluded by exist- 

 ing conditions. Trees restricted in this way are under a severe handicap and in 

 most cases have been observed to do better than one would reasonably expect. 

 Extended periods of drought or other tests of vigor, however, sometimes take a 

 heavy toll of weak trees in narrow planting belts. 



Storm Damage. Ice storms, lightning, high winds, hail, hea\'>- rain, and snow- 

 result annually in severe damage, and btorm injuries accumulated o\er any 

 extended period of time may result m trees becoming serious hazards in the 

 community. Injury initiated by the hurr'cane of 1938 has served as a basis for 

 subsequent extensive damage and, in some cases, ultimate death of trees. 



Girdling Roots. In planting a tree, if care is not taken to provide a hole of 

 adequate size in which to spread the roots, there is danger that they may become 

 wrapped around the trunk in such a manner as to choke the normal growth (Fig. 

 4). The ill-advibed application of a fertilizer close to the base of trees may cause 

 excessive root development and girdling about the trunks. Girdling roots are 

 not necessarily harmful, particularly if root grafting results. When a girdling 

 root above or below ground is detected as the cause for tree weakening, it ma}' be 

 severed and the constriction of the trunk somewhat relieved. 



^ McKenzie, M. A. and L. H. Jones. Injury to trees from sulphur dioxide fumes of electric 

 refrigerators. Science 91:239-240. 1940. 



