per acre. Other timber survey statistics can be developed by varying; the 

 procedure. 



In this study, four contiguous ten-acre tracts were cruised by the var- 

 iable plot method using the three critical angles : 52.09', 104.18', and 208.38'. 

 A complete tally of all trees was then made of the same area for comparison. 



From the standpoint of efficiency based on both accuracy and required 

 time, the 208.38' critical angle proved best. The basal area determination 

 for the 40 acres was only 4.6 percent low and the boardfoot volume estimate 

 was 7.6 percent low. There were slightly greater deviations for the indi- 

 vidual 10-acre tracts. The results of the estimates with the 52.09' critical 

 angle were much more inaccurate. For the 40 acres the basal area deter- 

 mination was 47.8 percent low and the volume estimate was 47.5 percent 

 low. Again, somewhat greater deviations were found for the individual 10- 

 acre tracts. Using this angle, the number of estimating points that can be 

 used on an area are limited and many trees which should be counted are 

 missed because of adverse sighting conditions. The estimates with the 

 104.18' critical angle gave basal area and volume figures intermediate be- 

 tween those found for the other two angles. In addition, it required the 

 greatest length of time. 



It would appear that the method of variable plot cruising works best 

 with a wide critical angle used at the maximum number of estimating points. 



B. HuscH 



OTHER ACTIVE PROJECTS 



Reproduction Studies in White Pine 



C. L. Stevens 



Home Economics 



Human Nutrition Research 



This past year, twelve male students from the University voluntarily 

 participated in a nutritional research project to investigate the rate of 

 phosphorus supplement as it might effect the utilization of thiamine, one of 

 the B complex vitamins, and carbohydrate. 



The young men, ranging in age from 18 to 24 years, were fed a con- 

 stant basal diet for a period of 10 weeks. All food for this experiment was 

 weighed, prepared, and served in the Food and Nutrition Laboratory in the 

 Department of Home Economics. The subjects were required to eat all the 

 food served to them and no additional foods were permitted. They lived 

 together as a unit at one of the men's dormitories. 



The basal diet contained 2500 calories, 0.8 grams of phosphorus, and 

 was adequate in all other nutrients for the age group, according to the Rec- 

 ommended Allowances of the Food and Nutrition Committee of the Nat- 

 ional Research Council. Since the men differed in age, height, weight, and 

 activity, each individual's energy needs above the basal diet were provided 

 for by the addition of purified carbohydrate and fat. All subjects remained 

 on this regime for 5 weeks, after which time half of the students were given 

 additional phosphorus. None of the men knew who was receiving the ad- 

 ditional phosphorus as it was incorporated in the diet. The quantity of 

 phosphorus was increased at ten day intervals until they were eating four 

 times the quantity in the basal diet. Six of them remained on the basal diet 



30 



