Drivers and pathways of carbon and nitrogen in soil and streams: insights from the Sleepers River Research Watershed in Vermont
Abstract
Shifts in acid deposition and precipitation patterns impact the total and relative amounts of carbon (C) and nitrogen (N) species in streams in complex ways—making predictions of future water quality difficult. To disentangle the interacting drivers of solute loading to streams, we investigated the influence of regional environmental conditions and soil processes on stream solute concentrations using a combined "pattern to process" approach in the forested headwater catchment of Sleepers River Research Watershed in Vermont. We investigated patterns in stream solute concentrations both independent and dependent of flow by applying Seasonal-Kendall tests on long-term, flow-adjusted concentrations and identifying seasonal behavior in C-Q relationships, respectively. For process investigation we conducted experiments across seasons where we flushed intact soil cores with solutions that simulate events with past precipitation composition (high acid deposition) and present-day composition (reduced acid deposition). Our results indicate that dissolved organic carbon (DOC) and N concentrations in leachate often co-varied and that winter soils produced the highest concentrations in effluent, especially in experiments simulating present-day conditions. This pattern is consistent with long-term C-Q behavior, where organic solutes were linearly correlated with Q especially during snowmelt flushing of winter soils. This pattern is also in agreement with the general trend of increasing stream DOC concentrations over the past several decades. In contrast, dissolved inorganic N (DIN) concentrations were highest in experiments simulating past conditions of acid deposition—indicating that soil process recovery might additionally contribute to decreasing trends in stream DIN concentrations in recent decades. Together, these results point to a continued pattern of increases in stream DOC, decreases in stream DIN and overall increasing C:N ratios that might fundamentally impact aquatic productivity moving forward.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFM.H32S1157P