Stable Carbon Isotope Composition of Desert Plant Leaves and Water-use Efficiency

Water is usually considered to be the key limiting factor for growth of desert plants, yet there is little information available of the water use efficiency of species within a desert community. As a reliable indicator of long-term water use efficiency in C3 plants, leaf carbon isotope ratios were often used to evaluate the adaptive degree of plants to arid environments. So, foliar δ 13 C values were measured on species occurring within two desert communities of Fukang, Xinjiang and Jinta, Gansu. The results showed that dryer condition led to higher foliar δ 13 C values. A decrease of 1 mm in annual precipitation amount would result in an increase of 0\^01‰～0\^015‰ in foliar δ 13 C values. Both in Fukang and in Jinta, foliar δ 13 C values of shrubs were significantly more positive to these of grasses, which were closely similar to those from the previous literature sources, indicating that shrubs have stronger adaptability to arid environments than grasses do. The conclusion was indirectly supported by SOD activities, SOD activities of Reaumuria soongorica and Haloxylon ammodendron were higher 1 time than those of Alhagi spasifolia and Limonium gmelinii. The further analysis showed that plants with stronger adaptability to arid environments came mainly from Chenopodiaceae and Leguminosae families and partly from Gramineae families.