ALBERT

Description: Forest regeneration operations increase the concentration of nitrogen (N) in watercourses especially outside the growing season when traditional biological water protection methods are inefficient. Biochar adsorption-based water treatment could be a solution for nutrient retention. We studied the total nitrogen (TN) and nitrate–nitrogen (NO3−–N) adsorption–desorption properties of spruce and birch biochar. The adsorption test was performed under four different initial concentrations of TN (1, 2, 3, and 4 mg L−1) using forest runoff water collected from ditch drains of boreal harvested peatland. The results showed that the TN adsorption amount increased linearly from the lowest to the highest concentration. The maximum adsorption capacity was 2.4 and 3.2 times greater in the highest concentration (4 mg L−1) compared to the lowest concentration (1 mg L−1) in spruce and birch biochar, respectively. The NO3−–N adsorption amount of birch biochar increased linearly from 0 to 0.15 mg NO3−–N g biochar−1 when the initial concentration of NO3−–N increased from 0.2 to 1.4 mg L−1. However, in spruce biochar, the initial concentration did not affect NO3−–N adsorption amount. The results indicate that concentration significantly affects the biochar’s capacity to adsorb N from water. The desorption test was performed by adding biochar extracted from the adsorption test into the forest runoff water with low TN concentration (0.2 or 0.35 mg L−1). The desorption results showed that desorption was negligibly small, and it was dependent on the TN concentration for birch biochar. Therefore, biochar can be a complementary method supporting water purification in peatland areas.

Description: Forest fires modify soil organic carbon and suppress soil respiration for many decades after the initial disturbance. The associated changes in soil autotrophic and heterotrophic respiration from the time of the forest fire, however, are less well characterized. The FireResp model predicts soil autotrophic and heterotrophic respiration parameterized with a novel dataset across a fire chronosequence in the Yukon and Northwest Territories of Canada. The dataset consisted of soil incubation experiments and field measurements of soil respiration and soil carbon stocks. The FireResp model contains submodels that consider a Q10 (exponential) model of respiration compared to models of heterotrophic respiration using Michaelis–Menten kinetics parameterized with soil microbial carbon. For model evaluation we applied the Akaike information criterion and compared predicted patterns in components of soil respiration across the chronosequence. Parameters estimated with data from the 5 cm soil depth had better model–data comparisons than parameters estimated with data from the 10 cm soil depth. The model–data fit was improved by including parameters estimated from soil incubation experiments. Models that incorporated microbial carbon with Michaelis–Menten kinetics reproduced patterns in autotrophic and heterotrophic soil respiration components across the chronosequence. Autotrophic respiration was associated with aboveground tree biomass at more recently burned sites, but this association was less robust at older sites in the chronosequence. Our results provide support for more structured soil respiration models than standard Q10 exponential models.