Increased Peatland Nutrient Availability Following the Fort McMurray Horse River Wildfire

Abstract

Northern peatlands are experiencing increased wildfire disturbance, threatening peatland biogeochemical function and ability to remain major stores of carbon (C) and macronutrients (nitrogen—N, and phosphorus—P). The impacts of climate change-driven drying on peatland nutrient dynamics have been explored previously; however, the impacts of wildfire on nutrient dynamics have not been examined when comparing burned and unburned areas in a post-fire fen. This study assessed the impact of wildfire on N and P bioavailability, change in CNP stoichiometric balance and feedback on plant nutrient limitation patterns in a fen peatland, one-year post-wildfire, by comparing Burned and Unburned areas. Water extractable P increased up to 200 times in shallow leachate, 125 times in groundwater and 5 times in peat. Surface ash leachate had increased concentrations in Ammonium (NH4+) and Nitrate (NO3−), and through groundwater mobility, increased extractable N concentrations were observed in peat throughout the entire fen. The net mineralization of N and P were minimal at the Burned areas relative to Unburned areas. Fire affected plant nutrient limitation patterns, switching from dominantly N-limited to NP co-limited and P-limitation in moss and vascular species respectively. The top 20 cm of the Burned area C concentrations was higher relative to the Unburned area, with increased CN and CP ratios also being found in the Burned area. These findings suggest that the long-term effects of elevated C, N, and P concentrations on plant productivity and decomposition must be re-evaluated for fire disturbance to understand the resiliency of peatland biogeochemistry post-wildfire.

Deeper burning in a boreal fen peatland 1‐year post‐wildfire accelerates recovery trajectory of carbon dioxide uptake

“…In general, nutrient availability varied temporally over the growing season, although trends for NO 3 − , NH 4 + and P all differed (see also van Beest et al, 2019, for in‐depth examination of temporal nutrient dynamics between burned and unburned sites). Generally, NO 3 − availability was lowest in the Mid growing season, NH 4 + availability was highest during the Late growing season.…”

“…In peatland reclamation, P fertilizer is often applied to promote bryophyte recolonization (Sottocornola, Boudreau, & Rochefort, 2007). This technique may mimic the natural increase in available P that is found in the burned plots coincident with peat burning (van Beest et al, 2019). The extent of enhanced P availability increases with deeper burning, along with the recolonization of mosses, whereas vascular plant regrowth is lowest in the deepest burned areas, therefore indicating that, combined with changes in N availability, moss recolonization may be able to out‐compete vascular plants for the increase in available P (Figure 3).…”

“…Moisture content for each core was determined from an additional subsample within a drying oven for 24 h at 80°C, so that extractable nutrient pools could be expressed in per unit dry mass (Macrae, Devito, Strack, & Waddington, 2013). Further detail on nutrient analyses at this study site are available in van Beest et al (2019).…”

“…Ecohydrological and edaphic conditions present in post‐fire peatlands may determine the magnitude and direction of modification to C cycling in these sites. For instance, the limited fluctuation in water table and increased availability of nutrients following the loss of upper peat layers (Certini, 2005; Galang, Markewitz, & Morris, 2010) in post‐fire peatlands supports the quick initiation of secondary succession (Depante et al, 2018; van Beest, Petrone, Nwaishi, Waddington, & Macrae, 2019). Given that nutrient dynamics in peatlands play an important role in determining plant productivity and decomposition rates (Wood et al, 2016), the response of post‐fire vegetation to increased nutrient and moisture availability could be a key determinant of C cycling and storage rates.…”

Burned peatlands within the Volyn region: state, dynamics, threats, ways of further use

“…Such studies were conducted for province of Alberta (Canada) and measured the differences in waterproof and hydrophysical capabilities of burned and unburned organic soils (Elmes et al, 2019). For Canada, an attempt was also made to quantitatively assess the changes in the main aspects of migration of nutrients in the system soil-plant-water during first years after fires (van Beest et al, 2019) and assess the sensitivity of peatlands to climate warming (Tarnocai, 2006). This researcher determined that around 60% of the total area of Canadian peatlands and 51% of mass of organic carbon in all Canadian peatlands, as expected, will be heavily or severely affected by climate change.…”