title: Differential sensitivity to regional-scale drought in six central US grasslands.
abstract: Terrestrial ecosystems often vary dramatically in their responses to drought, but the reasons for this are unclear. With climate change forecasts for more frequent and extensive drought in the future, a more complete understanding of the mechanisms that determine differential ecosystem sensitivity to drought is needed. In 2012, the Central US experienced the fourth largest drought in a century, with a regional-scale 40% reduction in growing season precipitation affecting ecosystems ranging from desert grassland to mesic tallgrass prairie. This provided an opportunity to assess ecosystem sensitivity to a drought of common magnitude in six native grasslands. We tested the prediction that drought sensitivity is inversely related to mean annual precipitation (MAP) by quantifying reductions in aboveground net primary production (ANPP). Long-term ANPP data available for each site (mean length = 16 years) were used as a baseline for calculating reductions in ANPP, and drought sensitivity was estimated as the reduction in ANPP per millimeter reduction in precipitation. Arid grasslands were the most sensitive to drought, but drought responses and sensitivity varied by more than twofold among the six grasslands, despite all sites experiencing 40% reductions in growing season precipitation. Although drought sensitivity generally decreased with increasing MAP as predicted, there was evidence that the identity and traits of the dominant species, as well as plant functional diversity, influenced sensitivity. A more comprehensive understanding of the mechanisms leading to differences in drought sensitivity will require multi-site manipulative experiments designed to assess both biotic and abiotic determinants of ecosystem sensitivity.
authors: Graduate Degree Program in Ecology and Department of Biology, Colorado State University, Fort Collins, CO, 80523, USA, aknapp@colostate.edu.
authors: Alan K
authors: AK
authors: Knapp
authors: Charles J W
authors: CJ
authors: Carroll
authors: Elsie M
authors: EM
authors: Denton
authors: Kimberly J
authors: KJ
authors: La Pierre
authors: Scott L
authors: SL
authors: Collins
authors: Melinda D
authors: MD
authors: Smith
mesh_terms: D000222:Adaptation, Physiological; D018533:Biomass; D057231:Climate Change; D055864:Droughts; D065948:Grassland; D010944:Plants; D006109:Poaceae; D011891:Rain; D012621:Seasons; D013312:Stress, Physiological; D014481:United States
references: Oecologia. 2008 Feb;155(1):123-32
references: 17968592
references: Science. 2001 Jan 19;291(5503):481-4
references: 11161201
references: Ecology. 2013 Sep;94(9):2030-41
references: 24279274
references: Proc Natl Acad Sci U S A. 2005 Oct 18;102(42):15144-8
references: 16217022
references: Oecologia. 2007 May;152(1):131-9
references: 17180369
references: Nature. 2014 Apr 24;508(7497):521-5
references: 24531763
references: Nature. 2011 Aug 03;476(7359):202-5
references: 21814202
references: Ecology. 2009 Dec;90(12):3279-89
references: 20120798
references: Oecologia. 2012 Jul;169(3):845-52
references: 22223080
references: Proc Natl Acad Sci U S A. 2013 Jan 2;110(1):52-7
references: 23248309
references: Philos Trans R Soc Lond B Biol Sci. 2012 Nov 19;367(1606):3135-44
references: 23045711
references: Oecologia. 1992 Feb;89(2):257-264
references: 28312881
references: Oecologia. 2013 Aug;172(4):1117-27
references: 23263528
references: New Phytol. 2010 Jul;187(2):426-37
references: 20487311
references: Science. 2000 Aug 4;289(5480):762-5
references: 10926535
references: Ecology. 2010 Jun;91(6):1672-81
references: 20583709
references: Ecology. 2013 Feb;94(2):435-43
references: 23691662
references: Nature. 2004 Jun 10;429(6992):651-4
references: 15190350