Plant uptake of available N from different layers varies among species in an alpine meadow of permafrost regions on the Qinghai-Tibetan Plateau

Peng, F. and Sun, J. and Lai, C. and Liu, Weisong and Li, C. and Chen, X. and Chen, B. and Xue, X. and Stevens, C. (2026) Plant uptake of available N from different layers varies among species in an alpine meadow of permafrost regions on the Qinghai-Tibetan Plateau. Soil Ecology Letters, 8 (2): 260387. ISSN 2662-2297

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Abstract

The N uptake of five common species from different soil depths in alpine meadow was investigated. Plants primarily took up more than 75% from the top 15 cm. The dominant sedge species and rare forbs species could take up N from soil as deep as 70 cm. The N uptake capacity is unrelated with the relative coverage. The uptake of permafrost thaw released nitrogen (N) could benefit plant growth and change vegetation community composition in a warming climate in cold regions. However, the capacity of co-existing species to take up different forms of available N beyond the root zone remains largely unknown in permafrost areas with a deep active layer. In situ15NH4Cl, K15NO3 and C2H5NO2 (glycine) labelling were conducted up to 70 cm depth for five species. Averaged across the five species, the summed 15N recovery rate of the three tracers was 10.71% ± 10.69%, 1.69% ± 2.51%, 1.54% ± 4.16% and 0.7% ± 2.23% at 0–15, 15–30, 30–50 and 50–70 cm, respectively. Kobresia humilis had the largest N uptake diversity. The NO3−-N recovered from 30–70 cm for K. humilis and Saussurea japonica was much higher than other species, accounting for 23% and 13% of the total N recovered at 0–70 cm. Root surface area was positively related to the recovery rate of inorganic N at soil below 15 cm whereas a species’ N requirement negatively to the N recovery at 0–15 cm. The relative cover of a species in a community was negatively related to a species’ N requirement but showed no relationship with the N recovery rate or N uptake diversity. Plant communitycomposition may not be affected by vertical N uptake patterns of co-existing species. Species that can take up N from deep soil layers may gain competitive advantages, thereby altering the plant community structure in a warm climate in the future.