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ARS Home » Plains Area » Temple, Texas » Grassland Soil and Water Research Laboratory » Research » Publications at this Location » Publication #348321
Title: Co-occurring woody species have diverse hydraulic strategies and mortality rates during an extreme drought

Author
item JOHNSON, DANIEL - University Of Idaho
item DOMEC, JEAN-CHRISTOPHE - Bordeaux Agro Sciences
item BERRY, Z - University Of Idaho
item SCHWANTES, AMANDA - Duke University
item MCCULLOH, KATHERINE - Us Forest Service (FS)
item WOODRUFF, DAVID - University Of Wisconsin
item Polley, Herbert
item WORTEMANN, REMI - Institut National De La Recherche Agronomique (INRA)
item SWENSON, JENNIFER - Duke University
item MACKAY, D - State University Of New York (SUNY)
item MCDOWELL, NATE - Pacific Northwest National Laboratory
item JACKSON, ROBERT - Stanford University

Submitted to: Plant, Cell & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2017
Publication Date: 1/4/2018
Publication URL: http://handle.nal.usda.gov/10113/5892714
Citation: Johnson, D.M., Domec, J., Berry, Z.C., Schwantes, A.M., McCulloh, K.A., Woodruff, D.R., Polley, H.W., Wortemann, R., Swenson, J.J., Mackay, D.S., McDowell, N.G., Jackson, R.B. 2018. Co-occurring woody species have diverse hydraulic strategies and mortality rates during an extreme drought. Plant, Cell & Environment. 41(3):576-588. https://doi.org/10.1111/pce.13121.
DOI: https://doi.org/10.1111/pce.13121

Interpretive Summary: Droughts are killing an increasing number of trees worldwide. The global trend of rising mean temperature is anticipated to further increase the frequency or severity of mortality-causing droughts. A variety of mechanisms have been proposed to explain species differences in drought vulnerability, but few have proven to be consistently predictive of drought-caused mortality. We quantified mortality and studied mechanisms thought to promote drought tolerance for four woody species, Ashe juniper, live oak, mesquite, and Texas persimmon, that co-occur in central Texas. Field studies were conducted during and shortly following the historic drought of 2011-2013. We also used a mathematical model that links soil-plant-atmosphere processes to predict mechanisms proposed to affect drought mortality. The four tree species we studied differed substantially in drought-tolerance mechanisms and mortality rate. Most of the plant mechanisms that have been proposed to promote drought tolerance failed to explain species differences in mortality. Mechanisms that failed to account for species differences in mortality include the degree to which plants regulate water loss in order to maintain similar water status during wet and dry periods, leaf carbon uptake rates, the extent to which plant carbohydrate reserves are depleted, and the size of the ‘safety’ margin in water transport that plants maintain. Rather, high mortality was associated with loss of tree-level capacity to transport water from roots to leaves, but primarily through roots, combined with shallow rooting depths. Our results indicate that incorporating information about water transport capacity and rooting depth into drought response models will improve the capacity of land managers to select drought tolerant tree species and plan for drought effects on woody densities.

Technical Abstract: From 2011 to 2013, Texas experienced its worst drought in recorded history. This event provided a unique natural experiment to assess species-specific responses to extreme drought and mortality of four co-occurring woody species: Quercus fusiformis, Diospyros texana, Prosopis glandulosa and Juniperus ashei. We examined hypothesized mechanisms that could promote these species’ diverse mortality patterns using post-drought measurements on surviving trees coupled to retrospective process modeling. The species exhibited a wide range of gas exchange responses, hydraulic strategies, and mortality rates. Multiple proposed indices of mortality mechanisms were inconsistent with the observed mortality patterns across species, including measures of the degree of iso/anisohydry, photosynthesis, carbohydrate depletion, and hydraulic safety margins. Large losses of spring and summer whole-tree conductance (driven by belowground losses of conductance), and shallower rooting depths, were associated with species that exhibited greater mortality. Based on this retrospective analysis, we suggest that species more vulnerable to drought were more likely to have succumbed to hydraulic failure belowground.