Arctic stream resiliency and nutrient uptake dynamics across a wildfire chronosequence
Abstract
Fire return intervals in Arctic Boreal forests are shortening which can affect stream chemistry and fluxes of solutes from the landscape. Here we report results from a series of studies across a wildfire chronosequence in the Central Siberian Plateau (CSP) and assess how in-stream biogeochemical processes respond to, and recover from, wildfire disturbance. We quantified stream chemistry and rates of nutrient uptake across sites ranging between 3 to > 100 years since last burn. Wildfire in this forested and continuous permafrost landscape lead to increases in nitrate (NO3) and declines in dissolved organic carbon (DOC). NO3 concentrations remained elevated for approximately 10 years while DOC concentrations required approximately 50 years to return to pre-disturbance levels reflecting the recovery and resiliency of these watersheds after wildfire. We also conducted a series of NO3 and ammonium (NH4) nutrient pulse additions across the chronosequence. Nutrient uptake velocities were determined for each site and related to background chemistry, hydrological parameters, and DOM composition. Across sites NH4 uptake was greater than NO3 with higher rates of dissolved inorganic nitrogen (DIN) uptake with increasing DOC: DIN ratios and Q, while the response to DOM composition was variable. Variation in stream chemistry and DIN uptake across the chronosequence suggests that recently burned sites can be net exporters of DIN, intermediate burn sites have greater demand for DIN, and old burn sites demonstrate little uptake. These data will help better understand the resiliency of these watersheds in a changing world and help inform models of watershed recovery in the Arctic Boreal.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.B31F2534R
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCESDE: 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCESDE: 0475 Permafrost;
- cryosphere;
- and high-latitude processes;
- BIOGEOSCIENCESDE: 1640 Remote sensing;
- GLOBAL CHANGE