Soil carbon accumulation in a Populus spp. plantation supplied with high atmospheric CO2 and nitrogen fertilization

Abstract

This work was carried out in the experimental area POPFACE (Tuscania, Viterbo), where a poplar short rotation forest (SRF) was treated with 550 ppm of atmospheric CO2 for six years. The experimental plots (Control and FACE) were divided in two halves, one of which was treated with nitrogen fertilization. The general aim of this research was to quantify the impact of the two rotation cycles, the CO2 enrichment and the nitrogen fertilization on: i) soil organic matter fractions more relevant for microbial metabolism; ii) microbial C mineralization activity and iii) the ecosystem capacity to store C in the soil. On soil samples collected from 2000 to 2004, the soil Organic C (TOC), the total extractable C (TEC) and several labile C fractions (MBC, WSC, ExC) were analysed. The microbial mineralization activity was also analysed. In comparison with the previous culture crop, the plantation increased the organic C storage in soil by about 23% in the second rotation cycle. Under elevated CO2, the increase of above- and belowground productivity supported a greater accumulation of labile C in soil, favouring a microbial C immobilization process. Fertilization treatment induced short-term changes in the soil C content, without overall modifications in the second rotation cycle.

Keywords

• Populus spp
• FACE
• Nitrogen
• Soil organic carbon
• Microbial mineralization