Coppicing shifts CO₂ stimulation of poplar productivity to above‐ground pools: a synthesis of leaf to stand level results from the POP/EUROFACE experiment

Abstract

SummaryA poplar short rotation coppice (SRC) grown for the production of bioenergy can combine carbon (C) storage with fossil fuel substitution. Here, we summarize the responses of a poplar (Populus) plantation to 6 yr of free air CO 2 enrichment (POP/ EUROFACE consisting of two rotation cycles). We show that a poplar plantation growing in nonlimiting light, nutrient and water conditions will significantly increase its productivity in elevated CO 2 concentrations ([CO 2 ]). Increased biomass yield resulted from an early growth enhancement and photosynthesis did not acclimate to elevated [CO 2 ]. Sufficient nutrient availability, increased nitrogen use efficiency (NUE) and the large sink capacity of poplars contributed to the sustained increase in C uptake over 6 yr. Additional C taken up in high [CO 2 ] was mainly invested into woody biomass pools. Coppicing increased yield by 66% and partly shifted the extra C uptake in elevated [CO 2 ] to above-ground pools, as fine root biomass declined and its [CO 2 ] stimulation disappeared. Mineral soil C increased equally in ambient and elevated [CO 2 ] during the 6 yr experiment. However, elevated [CO 2 ] increased the stabilization of C in the mineral soil. Increased productivity of a poplar SRC in elevated [CO 2 ] may allow shorter rotation cycles, enhancing the viability of SRC for biofuel production.

Free atmospheric CO<sub>2</sub> enrichment increased above ground biomass but did not affect symbiotic N<sub>2</sub>-fixation and soil carbon dynamics in a mixed deciduous stand in Wales

“…To date, existing experiments have demonstrated that rising atmospheric [CO 2 ] results in increases in net primary production (NPP) and C storage in forest vegetation, e.g. (Calfapietra et al, 2003;DeLucia et al, 1999;Gielen et al, 2005;Hamilton et al, 2002;Handa et al, 2006;Karnosky et al, 2003;Liberloo et al, 2009;Norby et al, 2002). Norby et al (2005) analyzed the response of NPP (g C m −2 y −1 ) to elevated [CO 2 ] in four forest FACE experiments and calculated the following regression NPP elev = 1.18×NPP amb + 55.4 (r 2 = 0.97).…”

Elevated CO2 increased phosphorous loss from decomposing litter and soil organic matter at two FACE experiments with trees

“…Carbon enrichment was achieved by injecting pure CO 2 through laser-drilled holes in tubing mounted on six masts placed in an octagonal pattern with a diameter of about 22 m (Miglietta et al 2001). The elevated CO 2 concentrations, measured at 1-min intervals, were within 20 % deviation from the pre-set target concentration of 550 ppm for 91 % of the time (1999)(2000)(2001)(2002)(2003)(2004) (Liberloo et al 2009). The trees were coppiced after the first three growing seasons (1999)(2000)(2001).…”

“…At the EuroFACE experiment, total plant C had increased by 21 % after 6 years of elevated CO 2 treatment (Liberloo et al 2009). Above ground litter accumulated in forest floor litter layers (L ?…”

“…Based on the inference between nutrient uptake and loss from litter and soil and earlier results with respect to C and N cycling (Hoosbeek et al 2011;Hoosbeek and Scarascia-Mugnozza 2009;Liberloo et al 2009), the following hypothesis was evaluated: More P was taken up from decomposing litter and/or soil during non-Nlimited tree growth in elevated CO 2 .…”

Comparison of assimilation parameters of coppiced and non-coppiced sessile oaks

“…Compared with seedlings, sprouts are characterized by a faster above-ground growth during early development (Herve & Ceulemans 1996, Liberloo et al 2009, Drake et al 2012, although this does not entails a higher photosynthetic ability of sprouts. Indeed, seedlings allocate more assimilated carbon to below-ground biomass and root development than plants from coppicing (Drake et al 2009).…”