www.elsevier.com/locate/jnlabr/yjare Journal of Arid Environments Journal of Arid Environments 59 (2004) 27–39 Plant water relations and photosynthesis during and after drought in a Chihuahuan desert arroyo Amrita G. de Soyza a, * ,1 , Keith T. Killingbeck b , Walter G. Whitford c,2 a USDA-ARS Jornada Experimental Range, MSC 3JER, New Mexico State University, PO Box 30003, Las Cruces, NM 88003, USA b Department of Biological Sciences, University of Rhode Island, Kingston, RI 02881, USA c Environmental Science Division, National Exposure Research Laboratory, Office of Research and Development, US-EPA, PO Box 93478, Las Vegas, NV 89193, USA Received 28 April 2003; received in revised form 19 November 2003; accepted 14 January 2004 Abstract In order to understand the physiology and ecology of perennial shrub species occupying the banks of ephemeral streams we studied the plant water relations and gas-exchange characteristics of six perennial shrub species growing along an ephemeral stream (arroyo) in the northern Chihuahuan Desert. Two of the species are restricted to riparian habitats (Brickellia laciniata and Chilopsis linearis), three are classified as semi-riparian (Fallugia paradoxa, Prosopis glandulosa, and Rhus microphylla) and one is considered to be non-riparian (Flourensia cernua). Differences in gas-exchange patterns and water relations emerged among these six species, yet differences among obligate, semi-riparian, and non-riparian classes of species were evident, but not universal. Chilopsis and Brickellia did not develop the low plant water potentials that characterized some semi-riparian (Rhus) and non-riparian species (Flourensia) during periods of drought. Rates of photosynthesis and transpiration were highest in Prosopis throughout the study, and were relatively constant in Chilopsis during and after drought. Whether water became available as channel flow or direct rainfall appeared to play a role in the physiology of these arroyo shrubs. r 2004 Elsevier Ltd. All rights reserved. Keywords: Phreatophytic; Riparian; Gas-exchange; Channel-flow; Rainfall; Plant water potential ARTICLE IN PRESS *Corresponding author. Desert Research Institute, 755 E. Flamingo Road, Las Vegas, NV 89119, USA. Tel.: +1-702-295-7498; fax: +1-702-295-7501. E-mail address: ag desoyza@msn.com (A.G. de Soyza). 1 Current address: Nevada Desert FACE Facility, PO Box 236, Mercury, NV 89023, USA. 2 Current address: USDA-ARS Jornada Experimental Range, MSC 3JER, NMSU, PO Box 30003, Las Cruces, NM 88003, USA. 0140-1963/$-see front matter r 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.jaridenv.2004.01.011