Effects of changes in climate on the functioning of arid and semiarid ecosystems
LTER, several other networks and now NEON measure net primary production, plant species composition and precipitation for decades in arid and semiarid ecosystems. However, scientists cannot predict the future functioning of these ecosystems under climate change because it is impossible to extrapolate patterns emerging from observations and correlations beyond their original range. Only experimentation allows us to establish cause-effect relationships that can be used to predict the future functioning of arid ecosystems under novel climatic conditions. In addition, it is now clear to scientists that is impossible to predict responses to long-term directional changes based on short-term trends. In deserts of the American Southwest, as in many arid-semiarid regions globally, precipitation amount and its variability are expected to change as a result of climate change.
The objectives of this long-term study are: (1) to assess the effects of directional and prolonged changes in precipitation amount and variability on population, community and ecosystem processes; (2) to elucidate the mechanisms behind those changes, and finally (3) to predict the future state of drylands functioning under novel climate conditions.
To address these objectives, we build upon two extant experiments located in a Desert Grassland at the Jornada LTER (NM): (a) manipulation of rainfall amount (80% reduced PPT, ambient, 80% increased), and (b) manipulation of rainfall variability (control, enhanced variability by 50% and 80%). Long-term manipulations of precipitation amount will be accomplished using rainout shelters coupled with irrigation systems. Manipulations of precipitation variability is conducted by flipping drought and irrigation treatments from year to year in the same plots. Response variables monitored during the last 10 years will continue to be measured; aboveground net primary production by species, plant species cover, richness, diversity, composition and belowground productivity are measured annually to disentangle endogenous mechanisms at population, community and ecosystem levels.
Fig. 2 (from Gherardi et al. 2015. PNAS). Effects of inter-annual precipitation coefficient of variation on aboveground net primary production (ANPP). Six-year mean ANPP as a function of precipitation coefficient of variation for the six-year period for (a) total, (b) dominant grass, (c) shrub and (d) rare species ANPP. Points indicate mean values (+/- SE) for each treatment (N=10). Black: control, red: +/-50%, blue: +/-80%.
National Science Foundation
Gherardi, L., and O.E. Sala. 2015. Enhanced interannual precipitation variability increases plant functional diversity that in turn ameliorates negative impact on productivity. Ecology Letters 18: 1293-1300. PDF
Gherardi, L., and O.E. Sala. 2015. Enhanced precipitation variability decreases grass- and increases shrub-productivity. Proceedings of National Academy of Sciences 112 (41): 12735-12740. doi: 10.1073/pnas.1506433112 PDF
Sala, O. E., L. Gherardi, and D. P. C. Peters. 2015. Enhanced Precipitation Variability Effects on Water Losses and Ecosystem Functioning: Differential Response of Arid and Mesic Regions. Climatic Change (2015) 131:213–227. doi: 10.1007/s10584-015-1389-z. PDF
Reichmann, L. G. and O. E. Sala. 2014. Differential sensitivities of grassland structural components to changes in precipitation mediate productivity response in a desert ecosystem. Functional Ecology doi: 10.1111/1365-2435. PDF
Osvaldo Sala, The effect of climate change on arid and semi-arid ecosystems, Distinguish ecologist program, Colorado State University, Fort Collins, CO, March 2016
Osvaldo Sala, Climate change in arid lands: prediction, mitigation and communication. Grantham Institute, Imperial College, London, April 2016
Osvaldo Sala, Novel climate-novel ecosystems: Directional changes in precipitation amount and variability. Harvard University, Cambridge, MA, April 2016
Osvaldo Sala, The effect of climate change on ecosystem functioning, University of Puerto Rico, April 2016
Osvaldo Sala, Laureano Gherardi, Deb Peters and Lara Reichmann, Can we predict responses to directional climate change based on our understanding of pulse responses? Annual meeting of the Ecological Society of America, Fort Lauderdale, FL. August 2016
Osvaldo Sala. The Effects of climate change on ecosystem functioning. Purdue University, August 2016
Osvaldo Sala, Effects of Climate Change on Drylands, Institute of Ecology, Xalapa, Mexico. October 2016
Osvaldo Sala, Laureano Gherardi, Debra Peters, Lara Reichmann, Grasslands Response to Precipitation Extremes, American Geophysical Union, December 2016
Osvaldo Sala, Laureano Gherardi, José Anadón, Changes of the Shrub-Grass Balance under Climate Change, American Geophysical Union, December 2016