Woody biomass production during the second rotation of a bio‐energy Populus plantation increases in a future high CO₂ world

Abstract

The quickly rising atmospheric carbon dioxide (CO 2 )-levels, justify the need to explore all carbon (C) sequestration possibilities that might mitigate the current CO 2 increase. Here, we report the likely impact of future increases in atmospheric CO 2 on woody biomass production of three poplar species (Populus alba L. clone 2AS-11, Populus nigra L. clone Jean Pourtet and Populus  euramericana clone I-214). Trees were growing in a high-density coppice plantation during the second rotation (i.e., regrowth after coppice; 2002-2004; POPFACE/EUROFACE). Six plots were studied, half of which were continuously fumigated with CO 2 (FACE; free air carbon dioxide enrichment of 550 ppm). Half of each plot was fertilized to study the interaction between CO 2 and nutrient fertilization. At the end of the second rotation, selective above-and belowground harvests were performed to estimate the productivity of this bio-energy plantation. Fertilization did not affect growth of the poplar trees, which was likely because of the high rates of fertilization during the previous agricultural land use. In contrast, elevated CO 2 enhanced biomass production by up to 29%, and this stimulation did not differ between above-and belowground parts. The increased initial stump size resulting from elevated CO 2 during the first rotation (1999)(2000)(2001) could not solely explain the observed final biomass increase. The larger leaf area index after canopy closure and the absence of any major photosynthetic acclimation after 6 years of fumigation caused the sustained CO 2 -induced biomass increase after coppice. These results suggest that, under future CO 2 concentrations, managed poplar coppice systems may exhibit higher potential for C sequestration and, thus, help mitigate climate change when used as a source of C-neutral energy.

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

“…The values of LAImax observed during the consequent growing seasons were comparable to values reported for various willow (Lindroth et al 1994, Tharakan et al 2008, Petzold et al 2010) and poplar SRC cultures , Liberloo et al 2006, Al Afas et al 2008, Fischer et al 2013. The seasonal evolution of leaf area development with a maximum near the end of the summer reflects the indeterminate deciduous growth habit of poplar and confirmed earlier reports for poplar , Howe et al 2000, Fischer et al 2013) and willow (Lindroth et al 1994, Guidi et al 2008, Tharakan et al 2008.…”

Effects of free atmospheric CO<sub>2</sub> enrichment (FACE), N fertilization and poplar genotype on the physical protection of carbon in the mineral soil of a polar plantation after five years

“…Enhanced growth due to increasing atmospheric CO 2 concentration is hypothesized to further increase this terrestrial C sink (Prentice et al, 2001). Free air CO 2 enrichment experiments in aggrading forests and plantations have demonstrated significant increases in net primary production (NPP) and C storage in forest vegetation DeLucia et al, 1999;Gielen et al, 2005;Hamilton et al, 2002;Liberloo et al, 2006;Norby et al, 2005;Norby et al, 2002). The extra C uptake may, next to forest vegetation, also be stored in forest floor litter and in forest soil.…”

Intercropping cover crops with a poplar short rotation coppice: Effects on nutrient uptake and biomass production

“…The yield gap of the LP can be related instead to the negative effect that the addition of high C:N biomass to the soil had on the activity of the telluric biocenosis reducing the nutrient availability for plants. In literature, there are studies that confirmed (Coleman et al, 2006;Stolarski et al, 2015) or denied (Liberloo et al, 2006;Ceotto et al, 2016) the effect of nutrient supply on poplar yield. These differences are presumably to put in relation to different fertility condition of the soil where the research activities have been carried out (Moscatelli et al, 2008).…”