Climatic controls of aboveground net primary production in semi-arid grasslands along a latitudinal gradient portend low sensitivity to warming

• Published in: Oecologia Vol. 177; no. 4; pp. 959 - 969
• Main Authors: Mowll, Whitney, Blumenthal, Dana M, Cherwin, Karie, Smith, Anine, Symstad, Amy J, Vermeire, Lance T, Collins, Scott L, Smith, Melinda D, Knapp, Alan K
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01-04-2015; Springer; Springer Berlin Heidelberg; Springer Nature B.V
• Subjects: Acclimatization; Analysis; atmospheric precipitation; Biodiversity; Biomass; Biomedical and Life Sciences; Climate; Climate models; covariance; Ecology; Evaporation; Evapotranspiration; Global Warming; graminoids; Grassland; Grasslands; Growing season; Hot Temperature; Hydrology/Water Resources; Life Sciences; Plant communities; Plant growth; Plant Sciences; Plants; Poaceae; prediction; Primary production; primary productivity; Rain; regression analysis; Seasons; SPECIAL TOPIC: COORDINATED APPROACHES TO GLOBAL CHANGE RESEARCH; temperature; Water; Weather forecasting; Western United States; Climate change; Precipitation; Temperature; Evapotranspiration; Standardized precipitation evaporation index
• ISSN: 0029-8549; 1432-1939
• DOI: 10.1007/s00442-015-3232-7

Although climate models forecast warmer temperatures with a high degree of certainty, precipitation is the primary driver of aboveground net primary production (ANPP) in most grasslands. Conversely, variations in temperature seldom are related to patterns of ANPP. Thus forecasting responses to warming is a challenge, and raises the question: how sensitive will grassland ANPP be to warming? We evaluated climate and multi-year ANPP data (67 years) from eight western US grasslands arrayed along mean annual temperature (MAT; ~7–14 °C) and mean annual precipitation (MAP; ~250–500 mm) gradients. We used regression and analysis of covariance to assess relationships between ANPP and temperature, as well as precipitation (annual and growing season) to evaluate temperature sensitivity of ANPP. We also related ANPP to the standardized precipitation evaporation index (SPEI), which combines precipitation and evapotranspiration to better represent moisture available for plant growth. Regression models indicated that variation in growing season temperature was negatively related to total and graminoid ANPP, but precipitation was a stronger predictor than temperature. Growing season temperature was also a significant parameter in more complex models, but again precipitation was consistently a stronger predictor of ANPP. Surprisingly, neither annual nor growing season SPEI were as strongly related to ANPP as precipitation. We conclude that forecasted warming likely will affect ANPP in these grasslands, but that predicting temperature effects from natural climatic gradients is difficult. This is because, unlike precipitation, warming effects can be positive or negative and moderated by shifts in the C₃/C₄ratios of plant communities.