Rooting depth and leaf hydraulic conductance in the xeric tree Haloxyolon ammodendron growing at sites of contrasting soil texture

Abstract

An experiment was conducted on Haloxylon ammodendron C.A. Mey, a small xeric tree. Soil water content, soil evaporation, leaf water potential, leaf transpiration rate and stomatal conductance were measured at the two sites that contrast in soil texture: sandy and heavy textured, 8 km apart on the southern periphery of Gurbantonggut Desert, Central Asia, during the 2005 and 2006 growing seasons. Leaf specific hydraulic conductance was calculated from the measurements, and root distributions of plants grown at the two sites were quantified by whole-root system excavation. In general, plants grown in sandy soil experienced better water status than in heavy textured soil. Low soil evaporation loss is not the main reason for this better plant water status at sandy site. Plants in sandy soil developed much deeper root systems, larger root surface areas and higher root: leaf surface area ratio than in heavy textured soil, which facilitated plants acquiring more water and surviving the prolonged drought period. Plants growing at light textured sites should have an advantage in acclimatising to the changed water conditions of the future. Plants at the more sandy sites have a larger buffering capacity to excessive variation in ambient conditions.