Geography

The increasing importance of atmospheric demand for ecosystem water and carbon fluxes

Document Type

Article

Abstract

Soil moisture supply and atmospheric demand for water independently limit - and profoundly affect - vegetation productivity and water use during periods of hydrologic stress. Disentangling the impact of these two drivers on ecosystem carbon and water cycling is difficult because they are often correlated, and experimental tools for manipulating atmospheric demand in the field are lacking. Consequently, the role of atmospheric demand is often not adequately factored into experiments or represented in models. Here we show that atmospheric demand limits surface conductance and evapotranspiration to a greater extent than soil moisture in many biomes, including mesic forests that are of particular importance to the terrestrial carbon sink. Further, using projections from ten general circulation models, we show that climate change will increase the importance of atmospheric constraints to carbon and water fluxes in all ecosystems. Consequently, atmospheric demand will become increasingly important for vegetation function, accounting for >70% of growing season limitation to surface conductance in mesic temperate forests. Our results suggest that failure to consider the limiting role of atmospheric demand in experimental designs, simulation models and land management strategies will lead to incorrect projections of ecosystem responses to future climate conditions.

Publication Title

Nature Climate Change

Publication Date

2016

Volume

6

Issue

11

First Page

1023

Last Page

1027

ISSN

1758-678X

DOI

10.1038/nclimate3114

Keywords

atmosphere-biosphere interaction, carbon flux, carbon sink, climate change, ecosystem response, evapotranspiration, forest ecosystem, hydrological change, soil moisture, stomatal conductance, water budget, water exchange

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