The increasing importance of atmospheric demand for ecosystem water and carbon fluxes
- Novick, Kimberly A [ Indiana Univ, Sch Publ & Environm Affairs, Bloomington, IN 47405 USA ]
- Ficklin, Darren L [ Indiana Univ, Dept Geog, Bloomington, IN 47405 USA ]
- Stoy, Paul C [ Montana State University: Land Resources & Environmental Sciences ]
- Williams, Christopher A [ Clark Univ, Grad Sch Geog, Worcester, MA 01610 USA ]
- Bohrer, Gil [ Ohio State Univ, Dept Civil Environm & Geodet Engn, Columbus, OH 43210 USA ]
- Oishi, A Christopher [ US Forest Serv, USDA, Southern Res Stn, Coweeta Hydrol Lab, Otto, NC 28763 USA ]
- Papuga, Shirley A [ Univ Arizona, Sch Nat Resources & Environm, Tucson, AZ 85721 USA ]
- Blanken, Peter D [ Univ Colorado, Dept Geog, Boulder, CO 80309 USA ]
- Noormets, Asko [ North Carolina State Univ, Dept Forestry & Nat Resources, Raleigh, NC 27695 USA ]
- Sulman, Benjamin N [ Princeton Univ, Dept Geosci, Princeton, NJ 08544 USA ]
- Scott, Russell L [ USDA ARS, Southwest Watershed Res Ctr, Tucson, AZ 85719 USA ]
- Wang, Lixin [ Indiana Univ Purdue Univ, Dept Earth Sci, Indianapolis, IN 46202 USA ]
- Phillips, Richard P [ Indiana Univ, Dept Biol, Bloomington, IN 47405 USA ]
Soil moisture supply and atmospheric demand for water independently limit-and profoundly affect-vegetation productivity and water use during periods of hydrologic stress(1-4). 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(5-7). 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(8,9). 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.