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Browsing by Author "Johnsen, Kurt H."

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    Comparative water use in short-rotation Eucalyptus benthamii and Pinus taeda trees in the Southern United States
    Maier, Christopher A.; Albaugh, Timothy J.; Cook, Rachel I.; Hall, Kevin; McInnis, Daniel; Johnsen, Kurt H.; Johnson, John; Rubilar, Rafael A.; Vose, James M. (2017-08-01)
    Short rotation Eucalyptus plantations offer great potential for increasing wood-fiber production in the southern United States. Eucalyptus plantations can be highly productive (>35 m(3) ha(-1) year but they may use more water than intensively managed pine (primarily Pinus taeda L) plantations. This has raised concern about how expansion of Eucalyptus plantations will affect water resources. We compared tree water use, stem growth, and WUE (kg wood per m(3) water transpired) in adjacent nine-year-old Eucalyptus benthamii and P. taeda plantations with similar stand density and leaf area. Sap flux (F-d, g cm(-2) s(-1)) was measured continuously over one year using thermal dissipation probes. Stem biomass, stem growth, tree water use (E-t, L day(-1)), canopy transpiration per unit leaf area (E-1, mmol m(-2) s(-1)), and canopy stomatal conductance (G(s), mmol m(2) s(-1)) were quantified. Eucalyptus had higher daily Fd (196.6 g cm(-2) day(-1)) and mean daily E-t (24.6 L day(-1)) than pine (105.8 g cm(-2) day(-1), 15.2 L day(-1)). Eucalyptus exhibited a seasonally bimodal pattern in daily E-t that did not occur in pine. Monthly E-t was23-51% higher in Eucalyptus and differences between species were greatest in the spring and fall. Annual E-t was 32% higher in Eucalyptus (9.13 m(3) H2O year(-1)) than pine (5.79 m(3) H2O year(-1)). Annual stem biomass increment was greater in Eucalyptus (Eucalyptus: 22.9; pine: 11.8 kg tree(-1) year(-1)), and Eucalyptus had greater WUE (Eucalyptus: 2.86; pine 1.72 kg biomass m(-3) H2O year(-1)). Pine exhibited a lower seasonal minimum and higher seasonal maximum leaf area index (LAI). At low LAI, there was no significant difference between species in E-l or G(s); however, at maximum LAI, pine E-l and G(s) were 46 and 43%, respectively of rates observed in Eucalyptus. The species differed in G(5) response to vapor pressure deficit (D). At a similar reference G(s) (G(s),(ref) at D =1 kPa), pine exhibited greater stomatal sensitivity to D. These results suggest that (1) Eucalyptus trees had higher sap flux and total water use than pine, (2) Eucalyptus had greater stem growth and WUE, and (3) species differences in water use were driven primarily by differences in E-l and G(s). Published by Elsevier B.V.
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    Root growth potential and bud dormancy of three northern pines with emphasis on eastern white pine
    Johnsen, Kurt H. (Virginia Polytechnic Institute and State University, 1985)
    A two year study examined Root Growth Potential (RGP) in a hydroponic system and Dormancy Release Index (DRI) in one-year-old (1-0) and two-year-old (2-0) eastern white pine (Pinus strobus L.), red pine (Pinus resinosa Ait.), and Scotch pine (Pinus sylvestris L.) seedlings with emphasis on eastern white pine. During 1985-86 all three species of 2-0 stock displayed a similar pattern of RGP with high levels of RGP limited to mid-March. Only 2-0 eastern white pine had a statistically significant relationship between RGP and DRI; however, this relationship was not consistent in 1986-87. The RGP/DRI relationship in 2-0 eastern white pine was strong over both years within a DRI range of 0.22 to 1.00. One-year-old and 2-0 eastern white pine stock had very different patterns of RGP over both years with 1-0 stock maintaining much wider "lifting windows" for high RGP. Cold storage (2C) of 2-0 eastern white pine resulted in variable effects on RGP although it typically progressed dormancy release. There were no strong RGP trends between northern and southern provenances of 1-0 eastern white pine and heritability values indicate that RGP is under minimal genetic control in 1-0 eastern white pine seedlings. Northern and southern provenances did display clear differences in seedling morphology and seasonal patterns of shoot activity. Results of a field outplanting study show that RGP does show promise as a measure of 2-0 eastern white pine seedling quality. The predictive ability of RGP was increased on non-irrigated versus irrigated seedlings. A comparison of greenhouse versus growthroorn RGP testing demonstrated the validity of using greenhouse RGP testing of 2-0 eastern white pine.