Plant water use characteristics of five dominant shrub species of the Lower Rio Grande Valley, Texas, USA: implications for shrubland restoration and conservation.

J. D. White,Arjun Adhikari

doi:10.1093/conphys/cou005

Abstract

The biogeographic distribution of plant species is inherently associated with the plasticity of physiological adaptations to environmental variation. For semi-arid shrublands with a legacy of saline soils, characterization of soil water-tolerant shrub species is necessary for habitat restoration given future projection of increased drought magnitude and persistence in these ecosystems. Five dominant native shrub species commonly found in the Lower Rio Grande Valley, TX, USA, were studied, namely Acacia farnesiana, Celtis ehrenbergiana, Forestiera angustifolia, Parkinsonia aculeata and Prosopis glandulosa. To simulate drought conditions, we suspended watering of healthy, greenhouse-grown plants for 4 weeks. Effects of soil salinity were also studied by dosing plants with 10% NaCl solution with suspended watering. For soil water deficit treatment, the soil water potential of P. glandulosa was the highest (-1.20 MPa), followed by A. farnesiana (-4.69 MPa), P. aculeata (-5.39 MPa), F. angustifolia (-6.20 MPa) and C. ehrenbergiana (-10.02 MPa). For the soil salinity treatment, P. glandulosa also had the highest soil water potential value (-1.60 MPa), followed by C. ehrenbergiana (-1.70 MPa), A. farnesiana (-1.84 MPa), P. aculeata (-2.04 MPa) and F. angustifolia (-6.99 MPa). Within the species, only C. ehrenbergiana and F. angustifolia for soil water deficit treatment and A. farnesiana for the salinity treatment had significantly lower soil water potential after 4 weeks of treatment (P < 0.05). We found that soil water potential, stomatal conductance and net photosynthesis of the species significantly reduced over time for both treatments (P < 0.05). We conclude that while all species exhibited capacities to withstand current water availability, some species demonstrated limited tolerance for extreme water stress that may be important for management of future shrub diversity in Lower Rio Grande Valley.

Highlights

Continued climate change, including increased temperature and decreased precipitation, may have rapid, widespread and long-lasting impacts on species composition and distribution in shrublands (Condit et al, 1995; McDowell et al, 2008; White et al, 2008)
The specific objectives of this study were as follows: (i) to compare the shrub species for their adaptation and tolerance to prolonged soil water stress imposed by soil water deficit and increased soil salinity; and (ii) to assess the conservation of water related to assimilation of carbon as a potential measure of water stress adaptation
We found that A. farnesiana (P = 0.001), F. angustifolia (P = 0.018) and P. aculeata (P = 0.003) had significantly lower photosynthetic rate (Pn) values at week 4 compared with the control plants (Fig. 2b)

Summary

Introduction

Continued climate change, including increased temperature and decreased precipitation, may have rapid, widespread and long-lasting impacts on species composition and distribution in shrublands (Condit et al, 1995; McDowell et al, 2008; White et al, 2008). Conservation Physiology Volume 2 2014 survival and distribution of shrub species in these ecosystems (Grime, 1977; Archer, 1989; González-Rodríguez et al, 2004; Otieno et al, 2005; Gebrekirstos et al, 2006; Morgan et al, 2011). The suitability of shrub species for restoration and conservation of shrublands is related to water stress physiology of target plant species (Gebrekirstos et al, 2006). Excessive salt in soils affects the water available to plants by decreasing the osmotic potential of the soil water. A high salt concentration in the soil negatively affects plant water uptake and maintenance of turgor (Maas and Hoffman, 1977)

Objectives

Methods

Results

Discussion

Conclusion