First vs. second rotation of a poplar short rotation coppice: leaf area development, light interception and radiation use efficiency

Abstract

© iForest -Biogeosciences and Forestry IntroductionEnergy security and greenhouse gas emission reductions are major challenges to meet the global energy demand and to mitigate climate change (IPCC 2014). In the light of these global concerns bioenergy could play a crucial role to achieve the EU's energy and climate targets (European Council 2009). The cultivation of lignocellulosic biomass, mostly poplar and willow in short rotation coppice (SRC) systems, has a high potential for the production of renewable electricity and the generation of "green" heat (Fischer et al. 2010). Despite the long-term experience with the commercial production in northern Europe (Rosenqvist et al. 2000, Langeveld et al. 2012, the implementation of SRC as a renewable energy crop is limited in European agriculture (AEBIOM 2010, Dimitriou et al. 2011, Don et al. 2011.Productivity is determined by light interception and by the efficiency of converting the intercepted radiation into biomass, i.e., the radiation use efficiency (RUE), as reported for both herbaceous (Sinclair & Horie 1989) and woody (tree) species (Cannell et al. 1988, Medlyn 1998. The crop's capacity to intercept radiation is determined by its photosynthetic area, generally assessed via the leaf area index (LAI), which is linearly related to the biomass production in poplar and willow plantations (Larson & Isebrands 1972, Cannell et al. 1988, Taylor et al. 2001a. In SRC systems, faster canopy closure and increased growth rates of sprouts from an established root system result in enhanced productivity of coppiced versus noncoppiced tree stands . Substantial genotypic variation exists in aboveground woody biomass productivity (AGWB) of SRC cultures in poplar (Ceulemans & Deraedt 1999, Dillen et al. 2011, Paris et al. 2011, Benetka et al. 2014). Variation in AGWB has been explained by variation in light interception, in biomass allocation, in leaf physiological factors related to RUE or in a combination of the aforementioned (Cannell et al. 1988, Green et al. 2001, Tharakan et al. 2008, suggesting inconclusive results on the relative importance of productivity determining factors in SRC. The quantification of genetic diversity and of genetic control contributes to future tree improvement and to yield maximization efforts towards sustainable bioenergy cultivation.In the present study, we analyzed the leaf area development, light interception and RUE of 12 poplar genotypes in a high-density SRC culture, before and after the first coppice of an experimental plantation. Assessment of LAI and woody biomass productivity was performed in a single versus a multi-stem culture, to analyze the effect of coppicing. We hypothesized significant genotypic, parentage and provenance variation in LAI, in leaf area duration (LAD), in RUE, in intercepted radiation (Iint) and AGWB. The objectives of this study were: (i) to determine the main differences between the first (R1) and the second rotation (R2) in the above mentioned parameters and in their relationships, i.e., before and after coppice,...

The Evaluation of Radiation Use Efficiency and Leaf Area Index Development for the Estimation of Biomass Accumulation in Short Rotation Poplar and Annual Field Crops

“…Besides LAI development in SRC poplar and AFCs, our LAD results were similar to previous studies where the LAD range varied between 58 and 180 days in AFCs (C 3 and C 4 crops) and SRC [28,47,68,71]. Higher LAI and LAD were achieved in SRC poplar as compared to AFCs because woody crops are taller, multi stemmed, and their developed roots systems may accommodate higher canopy closure as compared to AFCs [25,26,54].…”

“…The LAI increment rate increases particularly in the first three years after coppice and reaches similar LAI development dynamics as uncoppiced canopy. The data confirm the positive effect of coppice management on the LAI development and canopy closure [28,47,63].…”

“…In our study, an increase of the LAI max from 3.6-9.5 m 2 m −2 is evident after transition to coppice management. Likewise, Broeckx et al [28] reported LAI max values from 0.49-1.68 m 2 m −2 for one-year-old (first growing season) and 0.87-4.63 m 2 m −2 for two-year-old diverse poplar clones, while in other fast growing trees like eucalyptus and willow the LAI max estimated values varied from 0.8-6.1 m 2 m −2 and from 2.4-6.7 m 2 m −2 , respectively. In poplar, the LAI development dynamics is also delayed after coppice.…”

“…The power function of the allometric equation between the AGDM and DBH [59] and the linear regression among the studied variables (LAI max , LAD, RUE, and AGDM) of SRC poplar [28] and AFCs were fitted in SigmaPlot ® version 11.0 (Systat Software, San Jose, CA, USA). Pearson's correlation coefficients were estimated using the same software for individual relationships.…”

“…The RUE also varies in different vegetation types for example in woody and herbaceous plants or management type such as coppiced and uncoppiced, as well as plant density and growth rate [26][27][28][29][30][31]. Usually, RUE values are higher in AFCs compared to fast growing woody plantations.…”