intensity of sunshine are practically the same at 

 all elevations. 



Costello and Price (1939) published results 

 of much more elaborate studies that had ex- 

 tended over a longer time (1925-1934). The 

 purpose of their Bulletin was to give detailed 

 guidance in solving certain problems in range 

 management — specifically to answer the per- 

 sistent question: When is range ready for early 

 season grazing? Costello and Price's study con- 

 firmed several of Sampson's main conclusions; 

 namely, that: 



1. Rate of maturity of plants decreases di- 

 rectly as heat units decrease at successively 

 higher elevations. 



2. Amount of water required to produce 

 any unit of dry matter is greatest in the oak- 

 brush zone, lowest in the aspen-fir zone, and 

 intermediate in the spruce-fir zone; these rela- 

 tions coincide with the intensities of evapora- 

 tion in the respective zones. 



3. Total and average length of leaves and 

 total dry weight produced are greatest in the 

 aspen-fir zone and less in the other two zones. 



4. Stem elongation is greatest in the oak- 

 brush zone, intermediate in aspen-fir, and least 

 in spruce-fir; this appears to be determined 

 largely by temperature. 



5. Production of dry matter appears to vary 

 inversely with evaporation, but temperature 

 also appears to be important. 



One interesting and significant result of the 

 Costello-Price study was discovery of the im- 

 portance of the date of snowmelt in the spring. 

 This date varies considerably from year to year, 

 depending on depth of snow accumulation dur- 

 ing the winter, temperatures during the melting 

 period, and elevation. Progress of the entire 

 growing season appears to be so closely related 

 to this date that, given a 10-year average date 

 for snow disappearance and the current year's 

 deviation from that date, one can predict with 

 surprising accuracy the dates when plant 

 growth will start, when flower stalks will ap- 

 pear, when flowers will bloom, and when seeds 

 will ripen. This is extremely useful, since the 

 date when flower stalks appear indicates when 

 a range area will be ready for grazing, and the 

 "seed ripe" date is useful in determining when 

 deferred grazing may begin. Seasons that begin 

 early, late, or normal tend to remain so. Of 



course, during early growth a plant may be 

 thrown off schedule by some extreme variation 

 of weather from the normal. 



Costello and Price's system for predicting 

 dates of successive stages of plant growth was 

 based on regression equations, which in tum 

 were developed from data recorded for indi- 

 vidual species at different elevations through a 

 series of years. They checked reliability in 1935 

 by observation of development of individual 

 plants at 50 staked locations over a large area at 

 the head of Ephraim Canyon at elevations be- 

 tween 9,000 and 10,000 feet. They found that 

 rate of plant development varied within and 

 between classes of vegetation and that variation 

 between stages of development of forbs and 

 browse was much greater than for grasses. 

 Costello and Price also confirmed the observa- 

 tions of Sampson and Malmsten that for each 

 1,000-foot increase in elevation the date of veg- 

 etational readiness is delayed about 18 days on 

 south exposures and about 11 days on north 

 exposures; at high elevations this variation is 

 reduced. 



Even though subject to considerable error, 

 the methods for estimating range readiness for 

 spring grazing devised by Sampson, Malmsten, 

 Costello, and Price were a great improvement 

 over rule-of-thumb estimates that had been 

 used previously. 



■ Plant Nutrition 

 Studies 



During part of the same time that Price, 

 Evans, Costello, and others were studying the 

 influences of climate on plant development, 

 Price and Edward C. McCarty 9 were studying 

 processes of growth and food storage for moun- 

 tain brome, sticky geranium (Geranium vis- 

 cosissimum), coneflower (Rudbeckia occiden- 



9 McCarty was head of the Botany Department of 

 Riverside Junior College in Riverside, California. Dur- 

 ing summer months of 1932-1936, Intermountain 

 Station employed him as Associate Forest Ecologist 

 to carry out growth studies on several mountain range 

 forage plants. 



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