Browsing by Author "Marcia L Gumpertz, Committee Member"

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    Environmental Constraints on Growth Phenology, Leaf Area Display, and Above and Belowground Biomass Accumulation of Pinus radiata (D. Don) in Chile
    (2005-12-06) Rubilar, Rafael Alejandro; Phillip M Dougherty, Committee Member; Marcia L Gumpertz, Committee Member; H. Lee Allen, Committee Chair; Thomas R Wentworth, Committee Member; Bill Arthur Hoffmann, Committee Member
    Environmental site-specific constraints on shoot, branch, and leaf area growth and phenology were investigated during the third and fourth growing seasons in two-year-old radiata pine plantations established under a factorial combination of soil preparation, fertilization, and weed control at three contrasting textural and climatic soil-site conditions in the Central Valley of Chile. During October 2002 and June 2005, biweekly measurements of foliage accretion, branch, and stem growth were obtained together with periodical evaluations of foliage senescence. At each site, tree growth, aboveground biomass, belowground biomass, total biomass, aboveground:belowground biomass ratio, and leaf area index increased mainly by weed control (WC). The large gradient of tree growth and biomass accumulation among sites, and within sites varying in response to WC, was mainly attributed to large differences in soil water availability and possibly atmospheric water demand differences within sites. A linear relationship was established between LAI and stand growth across sites. The slope of the relationship (stemwood growth efficiency, GE) varied from 2.9 m3ha-1year-1 to 6.8 m3ha-1year-1 per unit of leaf area, with lower growth efficiencies found on sites with the greater water constraints. Phenology of growth was little affected by site or silvicultural treatments. Seasonal differences in the patterns of growth were mainly observed among sites for diameter, with longer growing seasons at sites with lower water limitations. In contrast, strong site and silvicultural treatments effects were observed on tree morphology. Trees where water limitations were more severe exhibited fewer and shorter flushes of height growth. The negative effects of soil water limitations, were at least partially ameliorated by silvicultural treatments that had been applied three years previously. Resource availability constraints during the mid to late growing season affected diameter growth more than height growth. Phenology of fascicle elongation indicated that sites with water and nutritional constraints ended fascicle elongation earlier during a growing season. Phenology of fascicle senescence indicated that maximum needlefall occurred during the summer and autumn seasons. No differences in silvicultural treatments were observed in foliage accretion or senescence patterns. Foliage longevity increased for sites with water and nutrient limitations.