8 



BULLETIN 658, U. S. DEPARTMENT OF AGRICULTURE. 



ease an estimator wished to give a full estimate of a stand of white- 

 bark pine {Pinvs albicaulis Engelm.) growing upon a flat ridge. The 

 trees of this stand upon closer examination were found to be almost 

 universally heart-rotted with Polyporus schweinitzii'ior a distance of 

 5 to 12 feet up from the base. The trees were fairly large and if 

 sound would have made excellent stull material, the chief product 

 in the Big Hole Basin region of Montana. Giving a full estimate to 

 these trees would have meant a serious overestimation of the stand, 

 since it was finally estimated that about 40 to 50 per .cent by volume 

 was cull due to the heart-rot. Fruiting bodies of the causal fungus 



almost hidden in the de- 

 bris at the base of the 

 trees gave the determin- 

 ing clue, and soundings 

 upon the trunk followed 

 by notching completed the 

 determination. 



There has always been 

 a serious need for some 

 method by which a fairly 

 accurate estimate can be 

 made of the rate of decay 

 of a stand of timber. 



Good results as to the 

 probable cull percentage 

 to be expected from rot 

 upon a certain stand have 

 been secured by expert and 

 experienced cruisers and 

 appraisers. Timber sur- 

 veys have in most cases 

 placed the estimates of 

 sound timber within a rea- 

 sonable limit of error; but 

 evidently no attempt has ever been made to secure a more accurate 

 result in respect to the cull in a stand due to rot other than those 

 results secured by ocular estimates. Occasionally in the administra- 

 tion of ^National Forests the question arises concerning the probable 

 rate of increase in rot per annum in a certain stand of timber. The 

 resultant decision as to the time of disposal of the timber hanging 

 in the balance depends upon the amount of accurate knowledge and 

 the data at hand regarding the decay in the trees. If proper and 

 sufficient data are secured, these will furnish the total volume and 

 the total volume of rot for the stand in question. With these as a 



Fig. 



9. — Pblyporua sulphureus, sulphur 

 base of larch. 



