三种沙生灌木叶片含氮量的季节变化及其水分响应

Seasonal variation and water response of leaf nitrogen content for three psammophytic shrub species.

沙生灌木叶片含氮量的季节变化及其对土壤水分的响应对理解植物资源利用、胁迫适应以及生态系统氮水过程耦合具有重要意义。文中研究了宁夏盐池油蒿(Artemisia ordosica),沙柳(Salix psammophila)和杨柴(Hedysarum mongolicum)叶片含氮量的季节动态及其与土壤水分的关系。结果表明:杨柴叶片含氮量显著高于油蒿和沙柳。在展叶期三种植物叶片含氮量均随时间下降;在叶变色期和落叶期叶片含氮量再次呈现下降趋势。在完全展叶期,三种植物叶片含氮量均不随时间发生趋势性变化,但随10cm土壤含水量的升高而增加,而不随深层(30,70cm)土壤含水量变化。此外,叶片含氮量对水分响应的敏感性存在种间差异,油蒿较其它两种植物更为敏感。在整个生长季,0-30cm土壤含氮量随10cm土壤含水量的升高而增加,表明土壤水分是通过改变土壤含氮量而间接影响植物叶片氮动态的。

knowledge on the seasonal variation and water response of plant leaf nitrogen （N） content in arid/ semiarid ecosystems is crucial for revealing how plants use limiting resources and cope with abiotic stresses, and helpful for understanding the coupling between nitrogen and water cycling. We conducted field investigations throughout a growing season to explore the relationships among leaf N, soil total N and soil water content （SWC） for three psammophytic shrubs, i. e. , Artemisia ordosica, Salix psammophila and Hedysarum mongolicum, in Yanchi, Ningxia. Results showed that the leaf N content of the H. mongolicum was significantly higher than that of A. ordosica and S. psammophila, reflecting the high activity of rhizobia. For all of the three species, leaf N content was the highest in the early leaf - expansion stage, and then declined with time. Leaf N content also decreased with time during the coloration and defoliation stages. Leaf N content in the full - expansion period did not show a trend with time but increased with SWC measured at 10cm depth. The sensitivity of leaf N content to soil moisture differed among species, as indicated by the largest slope for A. ordosica in the leaf N - SWC relationship as compared to that for S. psammophila and H. mongolicum. Over the entire growing season, soil total N at 0 - 30cm depth increased with 10 - cm SWC, suggesting that the influence of shallow soil water on leaf N content was mediated by its effects on soil N content.