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Heterogeneity and Nonequilibrium Dynamics

JRN scientists discovered that variability in ecosystem responses in both time and space is more characteristic of drylands than average conditions. New research approaches provide insights into old problems, including inconsistent responses through time, persistent and variable patterns in space, and emergent behavior across scales.

Monger HC, Cole DR, Buck BJ, Gallegos RA. 2009. Scale and the isotopic record of C4 plants in pedogenic carbonate: from the biome to the rhizosphere. Ecology 90:1498-1511.
Peters DPC, Bestelmeyer BT, Herrick JE, Monger HC, Fredrickson E, Havstad KM. 2006. Disentangling complex landscapes: new insights to forecasting arid and semiarid system dynamics. BioScience 56: 491-501.
Peters DPC, Groffman PM, Nadelhoffer KJ, Grimm NB, Collins SL, Michener WK, Huston MA. 2008. Living in an increasingly connected world: a framework for continental-scale environmental science. Frontiers in Ecology and the Environment 5:229-237.
Dr. Debra P.C. Peters
Explanations for unsuccessful attempts to limit shrub expansion using various methods, including livestock removal, have emerged from JRN studies. Current dominance by creosotebush of this exclosure (right panel) built in 1920 on a site dominated by black grama grasslands (left panel) is attributed to spatial processes of redistribution of water, nutrients, and seeds across scales that overwhelmed effects of release from grazing on grass-shrub competition.
USDA ARS, Jornada Experimental Range archive
Large variability in aboveground net primary production (ANPP) through time for grassland (upland) and shrubland (mesquite) ecosystem types can be explained by positive feedbacks at plant to patch scales that emerge following a sequence of wet years. Higher ANPP than expected based on rainfall in 2006-2008 (red points) results from herbaceous plants recruited in the wet summers of 2004-05 that captured water from patch-scale overland flow in each successive wet year to increase rain use efficiency. These interactions across scales are increasingly recognized as key to understanding variability in time and space in drylands at the Jornada and globally.
D.P.C. Peters, J. Yao, O.E. Sala, and J.P. Anderson Global Change Biology (submitted).



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