Soil nitrogen dynamics in canola agroecosystems of eastern Canada

Canola (Brassica napus L.) is a nitrogen (N)-demanding crop, so tissue N analysis should be related to soil N supply. We evaluated canola N uptake in relation to soil N pools in plots receiving 0, 50, 100 and 150 kg N ha-1 from urea at three sites in eastern Canada in 2012. Soil N pools varied significantly at the rosette, flowering, pod filling and maturity stages, but responded less predictably to urea. Canola N uptake was inconsistently related to soil N pools and urea input. This confirms the importance of site-specific N fertilizer management when growing canola in eastern Canada.

Plant diversity patterns and soil nitrogen dynamics after controlled burnings applied to restore mountain grasslands and create resilient landscapes

This PhD thesis encompasses three scientific works that focus on the effects of the decoupling regimes of fire and herbivory disturbances on the soils and on the dynamics of the vegetation. Altogether, the results of this doctoral dissertation highlight the risk associated to the decoupling of the burning and grazing practices and their consequences to the N terrestrial cycle and the maintenance of the community biodiversity. Eventually, the promotion of a targeted herbivory after burnings with the purpose of exerting enough control on particular troublesome species is recommended: it delays the application of controlled burnings in mountain grasslands, which recurrence and intensity may imply undesired effects in the soils, the vegetation and the N cycle. Given the current global change scenario (climate change and changing land-uses), it is necessary to understand traditional management regimes that preserve biodiversity in cultural landscapes of mountain areas, and to apply suitable emulating practices that maintain mechanisms and processes that constitute the basis of the resilient landscapes.