Linking Biomass Productivity to Genotype-Specific Nutrient Cycling Strategies in Mature Hybrid Poplars Planted Along an Environmental Gradient
Fortier, J., B. Truax, D. Gagnon and F. Lambert. 2017.
Abstract
This study used three hybrid poplar (Populus × spp.) clones (13 years old) with different parentages planted in three abandoned farmland sites along a regional gradient of elevation and soil fertility in southern Québec (Canada). We evaluated the effects of plantation site and clone on nutrient concentrations in green foliage and leaf litter, on leaf litter mass remaining, on soil properties and on biomass yield. Green foliage and leaf litter nutrient concentrations, and litter decomposition, are under strong genetic and environmental control in hybrid poplars. Clone-specific correlation patterns between green foliage and leaf litter nutrient concentrations were observed, as well as between soil nutrient availability and foliage or leaf litter nutrient concentrations. Despite the wide variations in soil nutrient availability and elevation between sites, only the clone effect was significant on biomass yield. An increase in N and P resorption proficiency with declining soil NO3 and P availability, observed in all clones, could explain stable yields of each clone across sites. The most productive clones (DN × M-915508 and M × B-915311) were more proficient at resorbing N, P and K, while the least productive clone (D × N-131) had the highest N, P and K concentrations in green foliage and in litter. The ability of clone M × B-915311 to maintain high litter Ca and Mg concentrations on sites with soil characterised by lower pH, lower base saturation and lower nutrient availability (NO3, P, Ca and Mg) may also be linked to its high and stable productivity. Differences in litter quality between clones did not yield significant differences in soil properties or in litter mass remaining after 2 years. However, short-term decay trajectories varied between clones. As litter mass remaining was strongly correlated to elevation, the plantation site significantly affected leaf litter mass remaining, which ranged from 4.5 to 35.5% between sites after 2 years.
