骆驼刺幼苗氮素特征对不同灌溉量的响应

氮素在植物所有必需营养元素中是限制生长的首要元素。氮素的来源和分配不但影响氮素利用效率,而且与氮素的周转和内循环有密切关系。为了解极端干旱区深根系植物的氮素特征(生物固氮、氮素分配、氮素利用效率),在塔克拉玛干沙漠南缘的策勒绿洲,依托策勒荒漠草地生态系统国家野外科学观测研究站,以骆驼刺幼苗为研究对象,采用15N稳定同位素法和分层分段挖根法,对3种灌溉量(CK、0.1、0.2m3/m2)下骆驼刺幼苗的氮素特征进行了1个生长季内的动态研究。结果表明:⑴灌溉提高生物固氮,但是灌溉量过多抑制生物固氮。在生长季末,3个灌溉量下的生物固氮比例分别为30.0%、42.8%、11.3%;生物固氮质量分别为0.4、0.8、0.2g/株。(2)灌溉使得分配到骆驼刺幼苗茎、叶中的氮素比例、氮素质量增加,根中氮素质量增加,在生长季初,分配到叶的氮素质量最大,分配到根中的氮素质量最小,在生长季末,3种灌溉量下根中氮素比例高达49.2%、44.5%、55.0%;灌溉有利于增加氮素利用效率,但是,灌溉量过多会降低氮素利用效率。在生长季末,3种灌溉量(CK、0.1、0.2m3/m2)下氮素利用效率分别是:77.9、104.3、84.5。(3)试验中,通过比较不同灌溉量对骆驼刺幼苗氮素特征的影响,发现0.1m3/m2灌溉量为较佳灌溉量。

Effect of irrigation on nitrogen characteristics of Alhagi sparsifolia seedlings

We investigated the effect of different irrigation levels on nitrogen characteristics of Alhagi sparsifolia Shap. seedlings to study the ecological adaptation strategy of the eremophytes in Qira oasis in the extremely arid southern margin of the Taklamakan desert. We used stable isotope 15N labeling and stratified root excavation methods to investigate the biological fixation of nitrogen, nitrogen allocation and nitrogen use efficiency of a month old A. sparsifolia seedlings under three different irrigation regimes (CK, 0.1 m3/m2, 0.2 m3/m2) during the growing season (March-October) in 2008. The results indicate that irrigation influenced all studied nitrogen characteristics of A. sparsifolia seedings. (1) Irrigation promoted biological fixation of nitrogen compared to control, but decreased at higher irrigation rates (0.2m3/m2). The biological fixation of nitrogen was greatest under 0.1m3/m2 irrigation with 0.8g per plant or 42.8% and lowest under control (0.2 g per plant, 11.3%). Intermediate nitrogen fixation rates were observed under the greatest irrigation rates (0.4 g per plant, 30%). (2) Irrigation initially increased the nitrogen allocation in the stem, leaves, and the quantity of nitrogen in the surface layer of root system (0-60cm). In the beginning of the growing season, leaves had the largest proportion of nitrogen and roots had the smallest. At the end of the growing season, the proportion of nitrogen in root system under the three different irrigation regimes were 49.2% (control), 44.5% (0.1 m3/m2), and 55.0% (0.2 m3/m2). Over the course of the entire growing season, irrigation promoted the nitrogen use efficiency compared to control, but decreased under large amounts of irrigation. At the end of growing season we observed a nitrogen use efficiency of 77.9 for the control, 104.3 for the 0.1 m3/m2 irrigation and 84.5 for the 0.1 m3/m2 irrigation. (3) In this experiment, we compared the influence of different irrigation on the characteristic of nitrogen of Alhagi sparsifolia Shap. Seedlings. The result indicate that the irrigation of 0.1m3/m2 is the better. In summary, irrigation of 0.1m3/m2 had the most stimulating effect on A. sparsifolia seedlings. The plants had the greatest biological nitrogen fixation, greatest nitrogen use efficiency and allocated most of the nitrogen to the root system.