Soil salinization and overgrazing are two main factors limiting animal husbandry in the Songnen Grassland. Leymus chinensis is a dominant rhizome grass, resistant to grazing as well as to-lerant to salt stress. Foliar labeled with 15N-urea was used to study the nitrogen allocation strategy and compensatory growth response to clipping under saline-alkali conditions. The results showed that the total absorbed 15N allocated to the aboveground part was more than 60%. Compared with the control treatment (no saline-alkali, no clipping), saline-alkali increased the distribution of 15N by 5.1% in root; the 15N distribution into aboveground in the moderate clipping and saline-alkali treatment was 11.6% higher than that of the control, exhibiting over-compensatory growth of aboveground biomass and total biomass, however, 15N allocated to stem base was significantly increased by 9.5% under severe clipping level and saline-alkali addition, showing under-compensatory growth of shoot, root and total biomass. These results suggested that L. chinensis adapted to mode-rate clipping by over-compensatory growth under salt-alkali stress condition. However, L. chinensis would take a relatively conservative growth strategy through the enhanced N allocation to stem base for storage under severe saline-alkali and clipping conditions.
土地盐碱化和过度放牧是制约松嫩平原畜牧业发展的两大因素,羊草是松嫩平原上的优势种,被认为具有较强的耐牧及耐盐碱能力.本文通过田间原位试验,以叶面涂抹标记15N-尿素的方法,研究了不同盐碱条件下刈割干扰对羊草的氮素分配策略及补偿生长的影响.结果表明: 总体上叶面新吸收的氮60%以上保留在地上部分.与不施盐碱无刈割处理的对照相比,单纯的盐碱胁迫使新吸收的氮在细根中的分配率显著增加了5.1%;而盐碱胁迫下,中度刈割使叶面新吸收的氮在地上部分的分配率增加了11.6%,地上及总生物量发生超补偿生长,但是重度刈割使叶面新吸收的氮在茎基部的分配率显著增加了9.5%,地上、细根及总生物量均表现为欠补偿生长.上述结果表明盐碱胁迫下,中度刈割干扰时羊草采取积极的再生策略,促进其超补偿生长,但在重度刈割时羊草会采取增加氮素在茎基部存储的相对保守的氮素分配和生长策略.
Keywords: Leymus chinensis; clipping; compensatory growth; nitrogen allocation; saline-alkali stress.