File:Adaptive variation in Pinus ponderosa from Intermountain Regions. II, Middle Columbia River system (1986) (16772737045).jpg

Title: Adaptive variation in Pinus ponderosa from Intermountain Regions. II, Middle Columbia River system
Identifier: adaptivevariatio373rehf (find matches)
Year: 1986 (1980s)
Authors: Rehfeldt, G. E; Intermountain Research Station (Ogden, Utah)
Subjects: Ponderosa pine
Publisher: Ogden, Utah : Intermountain Research Station
Contributing Library: U.S. Department of Agriculture, National Agricultural Library
Digitizing Sponsor: U.S. Department of Agriculture, National Agricultural Library

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Figure 1—Geographic distribution of ponderosa pine (siiading) within the major drainages of the middle Columbia River system and location of sampled populations. Letters A to G locate the elevational dines presented in figure 2. 5. Drought mortality, the proportion of trees within each plot that died from drought under xeric conditions. Analyses of variance were performed on each variable according to a model in which the effects of populations, planting sites, and blocks within sites were considered as random variates. A harmonic mean of 7.31 reflected the number of seedlings in each block. Periodicity of Shoot Elongation Seedlings from 98 of the populations were grown for 2 years in plastic containers (740 cm^) in a shadehouse at Moscow. Each population was represented by nine seed- lings in each of three blocks. In mid-March of the second growing season, seedlings were moved into a greenhouse before shoot elongation had begun. Greenhouses were maintained under natural photoperiods and light inten- sities. Temperatures were held at about 24 ±3 °C during the day and were allowed to cool to a minimum 13 °C at night. All seedlings were measured three times each week until elongation was well under way. Thereafter, measure- ments were made twice each week until elongation of the preformed shoot had ceased. As described by Rehfeldt and Wykoff (1981), shoot elongation of individual trees was expressed by a modified logistic function with a hyperbolic time term: where Y is the proportion of total increment attained by day X; b, r, and c are regression coefficients; and e is the base for natural logarithms. Regression statistics allowed calculation of the following variables for describing the periodicity of shoot elongation of individual seedlings: (1) initiation of elongation: the day on which 2 mm of growth had occurred; (2) cessation of elongation: the day on which all but 2 mm of growth had occurred; (3) duration of elongation: the number of days between initiation and cessation; (4) rate of elongation: elongation (millimeters) per day during the period of max- imum elongation; and (5) total elongation (millimeters). Population differentiation was assessed according to an analysis of variance in which the effects of populations and blocks were considered to be random. A harmonic mean of 8.83 reflected the number of seedlings from each popula- tion in each block. 2

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