Scale-dependent lake characteristics determine ecological sensitivity to atmospheric nutrient deposition in alpine regions
Abstract
Over the past century, enhanced atmospheric nitrogen (N) deposition has increased algal biomass and productivity and decreased water clarity of North American and European alpine lakes. Alpine lakes are sensitive to atmospheric N deposition due to high elevation, low acid neutralizing capacity, poorly developed catchment soils, sparse catchment vegetation, exposed bedrock, and low nutrient status. Predictors of ecological sensitivity vary among mountain lakes, however. Here, we evaluate controls of sensitivity of western North American and European alpine and subalpine lakes. Lake data were contributed by the Alpine Lake Sensitivity Working Group. Lake algal biomass and dissolved inorganic N (DIN) concentration were selected as key response variables to N deposition. We identified important controls of ecological sensitivity at global and regional scales using regression tree, random forest, and generalized additive model (GAM) analyses. Globally, GAMs indicate N deposition rate and lake elevation are the best predictors for lake DIN concentration (R2 = 0.24, n = 169). Lake DIN and total phosphorus (TP) are the best predictors of lake algal biomass (R2 = 0.56, n = 74). When evaluated regionally, the best predictors for North American lake DIN and algal biomass were N deposition rate and elevation (R2 = 0.14, n = 153) and N deposition rate, elevation, and nutrient limitation status (R2 = 0.36, n = 22), respectively. In Europe, the best predictors for DIN and algal biomass were N deposition rate, lake depth, unvegetated catchment area, and elevation (R2 = 0.77, n = 8) and elevation and TP (R2 = 0.79, n = 20), respectively. Based on these preliminary results, we expect further distinction of predictor variables of lake sensitivity for individual mountain ranges within North America and Europe. This study serves to identify lakes that are highly vulnerable to atmospheric N deposition and is thus an important precursor to empirically-based management strategies.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B13N2521B
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0426 Biosphere/atmosphere interactions;
- BIOGEOSCIENCES;
- 0469 Nitrogen cycling;
- BIOGEOSCIENCES;
- 0478 Pollution: urban;
- regional and global;
- BIOGEOSCIENCES