Growth of a poplar short rotation coppice under elevated atmospheric CO2 concentrations (EUROFACE) depends on fertilization and species

Abstract

-Growth and woody biomass production of three Populus species (P. nigra L. clone Jean Pourtet, P. alba L. clone 2AS-11 and P. × euramericana clone I-214), were followed during the first growing season after coppice of a short rotation coppice culture exposed to elevated atmospheric CO 2 concentrations by means of Free-Air Carbon dioxide Enrichment (FACE), and to a nitrogen (N) fertilization treatment. FACE significantly increased the number of shoots per stool, but did not significantly increase height nor total basal area per stool. In September, FACE significantly increased the Leaf Area Index (LAI) with 5.5 to 16.4%, depending on species. FACE significantly stimulated the woody biomass production by up to 25%, but the stimulation of P. alba and P. × euramericana was restricted to the fertilized treatment. Significant differences between species were observed. We concluded that coppice diminished the FACE effect, that the positive FACE effect was restricted under lower soil fertility, and that species differed in their response to FACE.free-air carbon dioxide enrichment / N-fertilization / short rotation coppice culture / Populus / growth Résumé -La croissance de taillis de peuplier à courte rotation dans une atmosphère à concentration en CO 2 élevée dépend de la fertilisation et de l'espèce. La croissance et la production ligneuse de biomasse de trois espèces de peuplier (Pinus nigra L. clone J. Pourtet, P. alba L. clone 2AS-11 et P. × euramericana clone I-214) ont été suivies pendant la première saison de croissance après la coupe du taillis à courte rotation exposé à une concentration élevée en CO 2 , au moyen d'un système FACE et à une fertilisation azotée. Le FACE accroît significativement le nombre de pousses par pied. En septembre, le FACE a augmenté l'indice foliaire (LAI) de 5,5 à 16,4 % selon les espèces. FACE stimule significativement la production de biomasse ligneuse (25 %) mais pour P. alba et P. × euramericana cette stimulation ne concerne que le traitement fertilisé. Des différences significatives ont été observées entre les espèces. Nous concluons que le taillis amoindrit l'effet du FACE, que l'effet positif du FACE était limité pour un sol peu fertile et que les espèces diffèrent dans leur réponse au FACE. enrichissement de l'air en CO 2 / fertilisation azotée / taillis à courte rotation / Populus / croissance

Assessment of soil nitrogen and phosphorous availability under elevated CO2 and N-fertilization in a short rotation poplar plantation

“…We can argue that in soil under elevated [CO 2 ] this down regulation did not occur and the poplar uptake remained high. This hypothesis is confirmed by the findings of Liberloo et al (2004) that in the same year 2002 observed a positive effect of the interaction of elevated [CO 2 ] and N fertilization in plant production.…”

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

“…Fine root turnover is therefore considered as one of the major pathways of new carbon entering soil C pools. These findings contrast Liberloo et al (2004Liberloo et al ( , 2005; unpublished (a) and from Gielen et al (2001Gielen et al ( , 2003, and Liberloo et al (2006) with results from noncoppiced forests, such as the sweetgum stand , where fine root production of sweetgum trees almost doubled in elevated [CO 2 ], contributing to a sustained increase in NPP. A strong above-ground biomass response in the first year was replaced by an equally strong response of fine root productivity from the second year onwards.…”

“…Data represent continuous measurements of trees growing in permanent growth plots and are adapted from Calfapietra et al . (2003b), Liberloo et al . (2004, 2005); unpublished (a) and from Gielen et al .…”

“…During the first year after planting and after coppicing, relative and absolute growth rates of poplar stems were strongly stimulated by elevated [CO 2 ] (Table 1). In addition, after coppicing, poplars produced significantly more and thicker shoots in elevated [CO 2 ] than in ambient [CO 2 ] (Liberloo et al ., 2004). This initial developmental enhancement increased stem basal area by 68 and 13% during the first growing season of the first and second rotations, respectively (Fig.…”

“…By the end of the first rotation, the stimulating CO 2 effect was limited to only competitively advantaged trees (Calfapietra et al ., 2003b). During the second rotation, a significant decline in the number of shoots per tree limited CO 2 growth enhancement (Liberloo et al ., 2004).…”