Assessment of Canopy Structure, Light Interception, and Light-use Efficiency of First Year Regrowth of Shrub Willow ( Sa
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Assessment of Canopy Structure, Light Interception, and Light-use Efficiency of First Year Regrowth of Shrub Willow (Salix sp.) Pradeep J. Tharakan & Timothy A. Volk & Christopher A. Nowak & Godfrey J. Ofezu
Published online: 25 October 2008 # Springer Science + Business Media, LLC. 2008
Abstract According to the light-use efficiency model, differential biomass production among willow varieties may be attributed either to differences in the amount of light intercepted, the efficiency with which the intercepted light is converted to aboveground biomass, or both. In this study, variation in aboveground biomass production (AGBP) was analyzed in relation to fraction of incoming radiation intercepted (IPARF) and light-use efficiency (LUE) for five willow varieties. The plants were grown in a short-rotation woody crop (SRWC) system and were in their first year of regrowth on a 5 year old root system. The study was conducted during a two-month period (June 15th–August 15th, 2001) when growing conditions were deemed most favorable. The objectives were: (1) to assess the relative importance of IPARF in explaining variation in AGBP, and (2) to identify the key drivers of variation in LUE from a suite of measured leaf and canopy-level traits. Aboveground biomass production varied nearly three-fold among genotypes (3.55–10.02 Mg ha−1), while LUE spanned a two-fold range (1.21–2.52 g MJ−1). At peak leaf area index (LAI), IPARF ranged from 66%–92%. NonetheP. J. Tharakan International Resources Group, 701 Connecticut Avenue, Washington DC 20036, USA e-mail: [email protected] T. A. Volk : C. A. Nowak : G. J. Ofezu Dept. of Forest and Natural Resources Management, State University of New York, College of Environmental Science and Forestry (SUNY-ESF), Syracuse, NY 13210, USA T. A. Volk (*) Dept. of Forest and Natural Resources Management, SUNY-ESF, 346 Illick Hall, Syracuse, NY 13210, USA e-mail: [email protected]
less, both IPARF and LUE contributed to AGBP. An additive model combining photosynthesis on leaf area basis (Aarea), leaf mass per unit area (LMA), and light extinction coefficient (k) produced the most compelling predictors of LUE. In a post-coppice willow crop, the ability to maximize IPARF and LUE early in the growing season is advantageous for maximizing biomass production. Keywords Aboveground biomass . Canopy structure . Light interception . Light-use efficiency . Willow (Salix sp.) Abbreviation Aarea Light-saturated photosynthesis per unit leaf area μmol m−2 s−1 AGBP Aboveground biomass production Mg ha−1 Amass Light-saturated photosynthesis per unit leaf mass nmol g−1 s−1 Ic Leaf compensation irradiance IPARF Fraction of incoming photosynthetically active radiation intercepted IPART Total incoming photosynthetically active radiation intercepted MJ m−2 IRGA Infrared gas analyzer k Light extinction coefficient for Beer’s law LAI Leaf area index LMA Leaf mass per unit area g m−2 LUE Light-use efficiency g MJ−1 Narea Leaf nitrogen concentration expressed on a per unit area g m−2 Nmass Leaf nitrogen concentration expre
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