Precipitation pulse use by an invasive woody legume: the role of soil texture and pulse size |
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Authors: | Email author" target="_blank">Alessandra?FravoliniEmail author Kevin?R?Hultine Enrico?Brugnoli Rico?Gazal Nathan?B?English David?G?Williams |
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Institution: | (1) School of Renewable Natural Resources, University of Arizona, Tucson, AZ 85721, USA;(2) Department of Biology, University of Utah, Salt Lake City, UT 84112, USA;(3) CNR-Istituto di Biologia Agroambientale e Forestale, CAP, 05010 Porano (TR), Italy;(4) Department of Aquatic, Watershed and Earth Resources, Utah State University, Logan, UT 84322-5210, USA;(5) Department of Geosciences, University of Arizona, Tucson, AZ 85721, USA;(6) Departments of Renewable Resources and Botany, University of Wyoming, Laramie, WY 82071, USA |
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Abstract: | Plant metabolic activity in arid and semi-arid environments is largely tied to episodic precipitation events or “pulses”.
The ability of plants to take up and utilize rain pulses during the growing season in these water-limited ecosystems is determined
in part by pulse timing, intensity and amount, and by hydrological properties of the soil that translate precipitation into
plant-available soil moisture. We assessed the sensitivity of an invasive woody plant, velvet mesquite (Prosopis velutina Woot.), to large (35 mm) and small (10 mm) isotopically labeled irrigation pulses on two contrasting soil textures (sandy-loam
vs. loamy-clay) in semi-desert grassland in southeastern Arizona, USA. Predawn leaf water potential (Ψpd), the isotopic abundance of deuterium in stem water (δD), the abundance of 13C in soluble leaf sugar (δ13C), and percent volumetric soil water content (θv) were measured prior to irrigation and repeatedly for 2 weeks following irrigation. Plant water potential and the percent
of pulse water present in the stem xylem indicated that although mesquite trees on both coarse- and fine-textured soils quickly
responded to the large irrigation pulse, the magnitude and duration of this response substantially differed between soil textures.
After reaching a maximum 4 days after the irrigation, the fraction of pulse water in stem xylem decreased more rapidly on
the loamy-clay soil than the sandy-loam soil. Similarly, on both soil textures mesquite significantly responded to the 10-mm
pulse. However, the magnitude of this response was substantially greater for mesquite on the sandy-loam soil compared to loamy-clay
soil. The relationship between Ψpd and δ13C of leaf-soluble carbohydrates over the pulse period did not differ between plants at the two sites, indicating that differences
in photosynthetic response of mesquite trees to the moisture pulses was a function of soil water availability within the rooting
zone rather than differences in plant biochemical or physiological constraints. Patterns of resource acquisition by mesquite
during the dynamic wetting–drying cycle following rainfall pulses is controlled by a complex interaction between pulse size
and soil hydraulic properties. A better understanding of how this interaction affects plant water availability and photosynthetic
response is needed to predict how grassland structure and function will respond to climate change. |
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Keywords: | Prosopis velutina Mesquite Soil texture Pulse water uptake Stable isotopes |
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