Nutrient cycling in a poplar plantation (Populus trichocarpa x Populus deltoides 'Beaupré') on former agricultural land in northern Belgium

Hydrological fluxes, atmospheric deposition, litterfall, and soil percolation of the most important nutrients were measured in an 18-year-old poplar plantation on a well-drained silt loam soil during 2 consecutive years. Downward soil water flux and transpiration are the most important factors in the water balance. Around 80% of total nitrogen input (6.6 and 6.5 kmol center dot ha(-1) in years 1 and 2, respectively) originates from litterfall. After nitrification only a negligible amount of nitrate leaches during the growing season. Yearly uptake of nitrogen by the poplar ecosystem (woody biomass, leaves, and ground vegetation) approximately equals the input, of which more than 50% is accounted for by the leaves. This indicates very efficient nitrogen cycling. Total deposition of base cations originates from two processes, dry deposition (Mg2+ and Ca2+) and canopy leaching (K+ and Ca2+). Litter input of Ca2+ represents about 83% of the total input (stand deposition + litterfall), Mg2+ about 61%, and K+ less then 50%. Percolation of base cations at 1 m depth is very limited. Rather high Ca2+ and K+ contents of the woody biomass can lead to high exports at harvest. Nutrient cycling in the poplar stand proved to be very efficient, with no significant nutrient losses

Above- and below-ground phytomass and carbon storage in a Belgian Scots pine stand

We investigated the storage of carbon (C) in the soil, litter and various phytomass compartments in a 69-year-old Scots pine (Pinus sylvestris L.) stand in the Belgian Campine region, Brasschaat, Belgium. The total amount of C stored in the stand was 248.9 t·ha-1, 47 % of which was in soil organic matter, 11 % in surface litter and 42 % in phytomass. More than 60 % of total C was stored belowground. Total phytomass C in the stand was 104 t·ha-1; most phytomass C was found in the stems (70 %). The root system was very shallow and contained only 14 % of the phytomass C, most of it in the coarse roots. Although total live fine root (< 1 mm) length was high (3.3 km·m-2), fine roots contributed only 2 % to total phytomass. (© Inra/Elsevier, Paris.)Phytomasse aérienne et souterraine et stock de carbone dans un peuplement de pin sylvestre en Belgique. Nous avons étudié le stockage du carbone dans le sol, dans la litière et dans différents compartiments de la phytomasse d'une plantation de pins sylvestre (Pinus sylvestris L.), âgés de 69 ans, localisée à Brasschaat, région de la Campine, Belgique. La quantité totale de carbone stockée au niveau de cette plantation était de 248,9 t ha -1. 47 % étaient localisés dans la matière organique du sol, 11 % dans la litière, et 42 % dans la phytomasse. Plus de 60 % de la quantité totale de carbone se trouvait dans le sous-sol. La quantité de carbone contenue dans la phytomasse était de 212 t ha-1. La plus grande partie de ce dernier a été trouvé dans les tiges (70 %). Le système racinaire était très superficiel et ne contenait que 14 % du carbone de la phytomasse, principalement localisé dans les grosses racines. Bien que la longueur des racines fines et vivantes ait été importante (3,3 km m-2), elles ne représentaient que 2 % de la phytomasse totale. (© Inra/Elsevier, Paris.

Field evaluation of willow under short rotation coppice for phytomanagement of metal-polluted agricultural soils

Short rotation coppice (SRC) of willow and poplar might be a promising phytoremediation option since it uses fast growing, high biomass producing tree species with often a sufficient metal uptake. This study evaluates growth, metal uptake and extraction potentials of eight willow clones (Belders, Belgisch Rood, Christina, Inger, Jorr, Loden, Tora and Zwarte Driebast) on a metal-contaminated agricultural soil, with total cadmium (Cd) and zinc (Zn) concentrations of 6.5 +/- 0.8 and 377 +/- 69mg kg1 soil, respectively. Although, during the first cycle, on average generally low productivity levels (3.7 ton DM (dry matter) ha1 y1) were obtained on this sandy soil, certain clones exhibited quite acceptable productivity levels (e.g. Zwarte Driebast 12.5 ton DM ha1 y1). Even at low biomass productivity levels, SRC of willow showed promising removal potentials of 72g Cd and 2.0kg Zn ha1 y1, which is much higher than e.g. energy maize or rapeseed grown on the same soil. Cd and Zn removal can be increased by 40% if leaves are harvested as well. Nevertheless, nowadays the wood price remains the most critical factor in order to implement SRC as an acceptable, economically feasible alternative crop on metal-contaminated agricultural soils