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

Soil salinization and overgrazing are two major factors restricting the development of animal husbandry in the Songnen Plain. Leymus chinensis is a dominant species in the Songnen Plain and is considered to have relatively strong tolerance to grazing and salinization. In this paper, through in-situ field experiments and by the method of applying labeled ¹⁵N - urea on the leaf surface, the effects of cutting interference on the nitrogen allocation strategy and compensatory growth of Leymus chinensis under different saline-alkali conditions were studied. The results showed that: overall, more than 60% of the newly absorbed nitrogen on the leaf surface was retained in the above-ground part. Compared with the control without saline-alkali application and no cutting treatment, the saline-alkali stress alone significantly increased the allocation rate of the newly absorbed nitrogen in the fine roots by 5.1%; under saline-alkali stress, moderate cutting increased the allocation rate of the newly absorbed nitrogen in the above-ground part by 11.6%, and the above-ground and total biomass showed over-compensatory growth. However, severe cutting significantly increased the allocation rate of the newly absorbed nitrogen at the stem base by 9.5%, and the above-ground, fine roots and total biomass all showed under-compensatory growth. The above results indicate that under saline-alkali stress, when there is moderate cutting interference, Leymus chinensis adopts an active regeneration strategy to promote its over-compensatory growth, but when there is severe cutting, Leymus chinensis will adopt a relatively conservative nitrogen allocation and growth strategy of increasing the storage of nitrogen at the stem base.

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．