RESULTS 



DISCUSSION 



Means and associated standard deviations are shown in 

 table 1 for all phloem contents evaluated in this study. Numbers 

 of sample trees varied from 79 to 86 depending on date of 

 sample and phloem component analyzed. 



Means for July 1 and 31 were consistently lower than those 

 of June 6 for dry matter, soluble reducing sugars, nitrogen, and 

 monoterpenes. Differences were significant (Pr < 0.05) for the 

 first three components and less so for the monoterpenes (0.10 

 « Pr =s 0.05). Starches and other sugars showed increases 

 from June 6 (Pr < 0.05). 



We found monoterpene percentage of the phloem dry weight 

 to be extremely small (0.238) and, of this, individual 

 monoterpenes were distributed in about the same proportion as 

 found by Smith (1964) in "pure" oleoresin (table 3). And, in 

 either case, p-phellandrene is by far the largest monoterpene 

 component, followed by the 3-terpene group and a-pinene, 

 respectively. Note that the averages are greater in larger trees 

 with thicker phloem (and vice versa) according to the interactive 

 hypothesis (fig. 1). Too, the expected trend over the d.b.h.- 

 phloem trace (fig. 2) increases to a peak at about 1 3 inches (33 

 cm) d.b.h., decreasing thereafter to a low at 20 inches (51 cm) 

 comparable to that at about 9 inches (23 cm). 



Note that the percentages of phloem dry weight reported in 

 table 1 and in figures 1 through 3 are based on the 

 monoterpenes measured in this study only. A small reduction in 

 percentages for components could be expected with upward 

 adjustment of the monoterpene sum by 6 percent, to achieve 

 comparability to Smith's (1964) percentages (table 3). 



Table 3. — Proportional distribution of monoterpenes: "pure'' 

 oleoresin versus phloem dry matter 



Monoterpenes 



In "pure" 

 oleoresin 

 (Smith 1964) 



In phloem 

 dry matter 

 this study, 



7/31/75^ 



a-pinene 



p-pheilandrene 



3-terpenes 

 (3-carene + 

 myrcene + 

 a-pinene) 



— Percent by weight 



6.4 11.9 



69.4 

 18.5 



57.0 

 25.4 



The inference limitations in this study are rather servere 

 because the sample trees involved are from a single, infinitely 

 small stand relative to the whole. But in the absence of stronger 

 information on lodgepole pine phloem, our findings provide a 

 data-base opportunity to develop hypotheses for more exten- 

 sive study. 



Table 1 contains mean percentages and standard deviations 

 for a variety of phloem components, all of which are likely to 

 have some impact on MPB population dynamics. The data on 

 sugars, starch, and nitrogen are simply documented here for 

 general interest. We note, however, that most sugars and 

 starch are at low levels in the spring and that soluble reducing 

 sugars, nitrogen, and monoterpenes are relatively high. These 

 trends follow expectations based on seasonal tree physiology, 

 but because all but monoterpene relations to tree characteris- 

 tics appeared to be extremely weak (table 2), we did not attempt 

 to develop such information further. 



Respective (but very low) concentrations of monoterpenes in 

 the phloem are parallel in proportions of the monoterpene sum 

 to those found by Smith (1964) in pure oleoresin produced in 

 lodgepole pine (table 3). Beta-phellandrene in both studies 

 proved to be, by far, the largest component of the monoter- 

 penes, and so might easily have the greatest impact on MPB 

 activities. We note that while a-pinene has been found to be an 

 effective pheromone in western white pine, it is not for lodgepole 

 (Moeck 1980). 



But whether it is (B-phellandrene or some lesser component of 

 the monoterpenes, concentrations in the phloem appear from 

 the hypothesis developed (fig. 2), to increase with tree vigor and 

 size, up to an optimum d.b.h, of about 13 inches (33 cm). 



It has been established from past research that threshold 

 diameters in lodgepole pine for successful MPB reproduction 

 are generally in the 8-inch (20-cm) to 9-inch (23-cm) range. And 

 reproduction success is known to be high in larger, more vigo- 

 rous trees. This information, together with the coincidence of 

 relatively high monoterpene content for larger trees (9-inches 

 [23-cm] to 20-inches [51cm] d.b.h.; see fig. 3), is perhaps sug- 

 gestive of an attractant role for any one or all of the monoter- 

 penes. It would also appear that monoterpene toxicity levels 

 studies by Smith (1 965) are apparently not being reached in the 

 phloem, based on the level of MPB success in larger trees. 



The hypothesis developed in this study (fig. 1-3 and appen- 

 dix) should help to identify points of future study emphasis and 

 may be rescaled (as a unit) and evaluated for performance on 

 new data sets (Jensen 1979). 



Others 

 (camphene -i- 

 limonene + 

 sabinene -i- 

 a-phellandrene) 



5.7 



(5.7) 



Total 



100.0 



100.0 



'Original percentage adjusted for 5.7 percent of "others" not evaluated. 



6 



