Growth and water relations of Tamarix ramosissima and Populus euphratica on Taklamakan desert dunes in relation to depth to a permanent water table

Abstract

The hypothesis that water relations and growth of phreatophytic Tamarix ramosissima Ledeb. and Populus euphratica Oliv. on dunes of varying height in an extremely arid Chinese desert depend on vertical distance to a permanent water table was tested. Shoot diameter growth of P. euphratica was inversely correlated with groundwater depth (GD) of 7 to 23 m (adj. R 2 = = = = 0.69, P = = = = 0.025); growth of T. ramosissima varied independent of GD between 5 and 24 m ( P = = = = 0.385). Pre-dawn (pd) and midday (md) water potentials were lower in T. ramosissima (minimum pd − − − − 1.25 MPa, md − − − − 3.6 MPa at 24 m GD) than in P. euphratica (minimum pd − − − − 0.9 MPa, md − − − − 3.05 MPa at 23 m GD) and did not indicate physiologically significant drought stress for either species. Midday water potentials of P. euphratica closely corresponded to GD throughout the growing season, but those of T. ramosissima did not. In both species, stomatal conductance was significantly correlated with leaf water potential ( P. euphratica : adj. R 2 = = = = 0.84, P < < < < 0.0001; T. ramosissima : adj. R 2 = = = = 0.64, P = = = = 0.011) and with leaf-specific hydraulic conductance ( P. euphratica : adj. R 2 = = = = 0.79, P = = = = 0.001; T. ramosissima : adj. R 2 = = = = 0.56, P = = = = 0.019); the three variables decreased with increasing GD in P. euphratica . Stomatal conductance of P. euphratica was more strongly reduced ( > > > > 50% between − − − − 2 and − − − − 3 MPa) in response to decreasing leaf water potential than that of T. ramosissima (30% between − − − − 2 and − − − − 3 MPa). Tolerance of lower leaf water potentials due to higher concentrations of leaf osmotically active substances partially explains why leaf conductance, and probably leaf carbon gain and growth, of T. ramosissima was less severely affected by GD. Additionally, the complex below-ground structure of large clonal T. ramosissima shrub systems probably introduces variability into the assumed relationship of xylem path length with GD.

Genomic insights into salt adaptation in a desert poplar

“…Populus euphratica is an excellent candidate for the analysis of salt tolerance 22 , as it displays apoplastic sodium accumulation and develops leaf succulence after prolonged salt exposure 8 . Consequently, in the last decade it has become a model for elucidating both physiological and molecular mechanisms of salt tolerance in tree species [5][6][7][8][9][10][11] . Using a newly developed fosmid-pooling strategy 14 , we sequenced and assembled the complex genome of P. euphratica with high heterozygosity and compared it with the closely related salt-sensitive model plant, P. trichocarpa.…”

“…More than 30 wild Populus species occur across diverse habitats over a wide geographical range, thereby providing an excellent system for unravelling the genetic bases of adaptive divergence 4 . Populus euphratica Oliv., which is native to desert regions ranging from western China to North Africa, is characterized by extraordinary adaptation to salt stress [5][6][7][8] . Notably, at high salinity it maintains higher growth and photosynthetic rates than other poplar species 9,10 and can survive concentrations of NaCl in nutrient solution up to 450 mM 11 .…”

Groundwater-dependent ecosystems: recent insights from satellite and field-based studies

“…The average error in ET g was estimated to be about 12 %, which in the absence of field measurements is a very valuable estimate of rates of groundwater use. Further application of the method can be found in Groeneveld (2008).…”

Water uptake from different soil depths for halophytic shrubs grown in Northern area of Ningxia plain (China) in contrasted water regimes

“…The patterns of water uptake by woody species are summarized as either using only deep soil water or tapping both shallow and deep layers (Dodd et al 1998;Goldstein et al 2008;Guevara et al 2010;Williams & Ehleringer 2000;West et al 2007). On the basis of this finding, a terminology 'phreatophyte'(the species that extract water from aquifers or the capillary fringe above the water table) has come into being and has been widely agreed in the academic field (Busch et al 1992;Eggemeyer et al 2009;Gries et al 2003;Lite & Stromberg 2005;Lin et al 1996;Sperry & Hacke 2002). According to the extent of this dependence, phreatophytes are classified as either 'obligate' (plants that utilize only shallow alluvial groundwater) or 'facultative' (plants that have the ability to utilize sources in addition to alluvial groundwater) (Busch et al 1992;Horton et al 2003).…”

“…A large number of reports concentrating on the water source, water use strategy, and plantÁwater relations of plants using stable isotopic compositions have touched on several ecological systems: riparian areas (Dawson & Ehleringer 1991;Shafroth et al 2000;Horton et al 2003;Chimner & Cooper 2004;Lite & Stromberg 2005), desert regions (Sperry and Hacke 2002;Gries et al 2003;Xu & Li 2006), woodland (Lin et al 1996;Picon-Cochard et al 2001), and grassland (Eggemeyer et al 2009). The information about water use strategies of halophytes, Tamarix ramosissima Ledeb., Atriplex canescens (Pursh) Nutt., and Lycium barbarum L. in salinity-and alkalinity-affected regions is scarce.…”