Stable Carbon Isotope Characteristics Of The Dominant Desert Herbaceous Species In Junggar Basin

This paper presented a comprehensive investigation on dominant desert plants in Junggar Basin of Xinjiang, China with the application of stable carbon isotope technique. The stable carbon isotope ratios (δ¹³C) were measured in leaves of 50 individuals of long nutrional period plants and 36 individuals of early spring epheramals. At the same time, the physiological factors of Tulipa iliensis Regel including leaf nitrogen, phosphorus, potassium concentration, leaf water content, and the physical and chemical properties of soil such as soil water content, total nitrogen, total potassium and available phosphorus content were analyzed. The distribution characteristics of stable carbon isotope of Tulipa iliensis Regel and the correlations betweenδ¹³C values and the environmental factors and physiological factors were analyzed and discussed to elucidate the main factors affecting theδ¹³C values and the physiological adaptive mechanism. The results showed that:(1) Theδ¹³C values of desert plants had an extensive range from -7.77‰to -30.10‰in Junggar Basin. Theδ¹³C values of C3 species ranged from -23.80‰to -30.10‰and the averageδ¹³C value was -26.79‰; theδ¹³C values of C4 species ranged from -7.77‰to -14.90‰and the averageδ¹³C value was -13.04‰respectively. The averageδ¹³C values of long nutrional period plants and early spring epheramals were -21.98‰and -26.53‰respectively, which were more positive than average values(-28.74‰) reported for other desert plants in the world.(2) Most desert plants of C4 species in Junggar Basin were annual species and included in long nutritional period plants, but early spring epheramals belonged to C3 species.(3) Theδ¹³C values of shrubs were more positive than those of grasses significantly, which were closely similar to those from the previous literature sources. This indicated that shrubs had stronger adaptability to arid environments than grasses. In addition, the averageδ¹³C value of annual plants was more positive than that of perennial plants. Since a strong correlation was observed betweenδ¹³C of plants and water use efficiency, it suggested that annual species tended to be more adaptable than perennial species in this area.(4) Theδ¹³C values of same plant like Tulipa iliensis Regel were steadily in differert regions, but theδ¹³C values of different plants even in the same area had significant differences. The results suggested that theδ¹³C values of the plants in Tulipa L. could be highly affected by intermittent environmental factors, although their genetic characteristics played a significant role in determining theirδ¹³C values.(5) Theδ¹³C values of Tulipa iliensis Regel correlated negatively with leaf water content, leaf total nitrogen, and total phosphorus content.There were no significant correlations between theδ¹³C values and leaf total potassium content. We concluded that theδ¹³C values of Tulipa iliensis Regel and their water use efficiency could be highly affected by leaf water content, leaf total nitrogen content and total phosphorus content.(6) With the incresing of soil available phosphorus content, theδ¹³C values of Tulipa iliensis Regel increased significantly, which also correlated negatively with soil water content in 0.01 level. There were no significant correlations between theδ¹³C values and soil total nitrogen, potassium content. The results indicated that soil water content was one of the most important factors to theδ¹³C values of Tulipa iliensis Regel. Soil available phosphorus content might play a significant role in determining theirδ¹³C values.