冻融循环期高寒草原典型物种紫花针茅氮吸收策略

氮(N)是高山和极地生态系统重要的限制性生长因子。目前对冻土区植物N利用机制的研究主要集中于完全融化期，而冻融循环期植物N吸收策略仍存在不确定性。以高寒紫花针茅为研究对象，分别在冻结期(晚秋)和融化期(早春)采用同位素示踪技术，分析植物对(¹⁵NH₄)₂SO₄和Na¹⁵NO₃的吸收量与偏好动态变化。研究结果显示冻结期紫花针茅冠层生长已停滞，融化期冠层尚未返青，但根系和立枯均可以吸收同化¹⁵N,具备吸收养分的需求。融化期紫花针茅¹⁵N在标记21天后¹⁵N-NH⁺₄和¹⁵N-NO^-₃的总回收率分别为4.44%和6.91%,而冻结期紫花针茅在¹⁵N标记21天后¹⁵N-NH⁺₄和¹⁵...

Nitrogen absorption strategy of Stipa purpurea, a typical species in alpine grassland during freeze-thaw cycle

Nitrogen is an important limiting growth factor in alpine and polar ecosystems. At present, the research on the mechanism of plant N utilization in permafrost area mainly focuses on the complete thawing period, while the strategy of plant N absorption in the freeze-thaw cycle is still uncertain. In this study, the absorption and preference of plants for (¹⁵NH₄)₂SO₄ and Na¹⁵NO₃ were analyzed by isotope tracer technology in freezing period (late autumn) and thawing period (early spring). The results showed that the growth of Stipa purpurea canopy had stagnated in the freezing period, and its canopy had not turned green in the thawing period, but the root system and standing dry could absorb and assimilate ¹⁵N, which had the need to absorb nutrients. The total recoveries of ¹⁵N-NH₄⁺ and ¹⁵N-NO₃^- in thawing stage were 4.44% and 6.91% respectively after 21 days of ¹⁵N labeling, while the total recoveries of ¹⁵N-NH₄⁺ and ¹⁵N-NO₃^- in freezing stage were 8.65% and 3.55%, respectively. In the early stage of thawing, the overall recovery of ¹⁵N-NH₄⁺ was higher than ¹⁵N-NO₃^-, but in the later thawing stage of thawing, the recovery of ¹⁵N-NH₄⁺ and ¹⁵N-NO₃^- was not significant or ¹⁵N-NO₃^- was slightly higher. The recovery rate of ¹⁵N-NH₄⁺ was higher than that of ¹⁵N-NO₃^- in the whole freezing period. This study supplements the nutrient absorption data of plants in the non-growing season in the alpine permafrost region, and provides a scientific basis for a comprehensive understanding of plant N nutrition strategy in the permafrost region and its response to future climate change.