Hydrochemical and ecosystem responses of the Loch Vale Watershed, Colorado to climate change: A modeling approach using PnET-BGC

Background/Question/Methods

A biogeochemical model (PnET-BGC) is used in this study to evaluate effects of potential future changes in temperature, precipitation, solar radiation and atmospheric CO₂ concentration on the biogeochemistry and ecosystem productivity of the Long-Term Ecological Research (LTER) site of Loch Vale Watershed in Colorado. Future climate projections from coupled atmosphere-ocean general circulation models (AOGCMs) used in this study are derived from the latest World Climate Research Programme’s fifth Coupled Model Intercomparison Project (CMIP5) models under two Representative Concentration Pathway (RCP) emission scenarios from the latest report of the Intergovernmental Panel on Climate Change (IPCC) AR5.

Results/Conclusions

PnET-BGC model simulation shows a decrease in average snow water equivalent with a shift in hydrology characterized by later snow development and earlier snow melt. Our results suggest that net primary productivity (NPP) of alpine tundra will increase as a result of increasing temperature, extended growing season and a higher atmospheric CO₂ concentration. Model results also show an increase in NO₃^- leaching due to increased net mineralization and nitrification. The watershed response to climate change in other major elements in surface water such as SO₄^2- and Ca²⁺ varies depending on the climate projection model selected.