Moderate water stress does not inhibit nitrogen remobilization allowing high growth in high nitrogen content Quercus variabilis seedlings under drought conditions

Abstract

Remobilization of stored nitrogen (N) plays an important role in the early growth of deciduous trees in spring. Several environmentalfactors can modulate N remobilization, but whether water stress is one such factors is unknown. This study analyzes howthe size of N storage in Quercus variabilis Blume seedlings interacts with water stress to affect N remobilization, uptake and newgrowth. This information is important for improving success of forest tree plantations under dry spring conditions. During the firstgrowing season, we produced seedlings with distinct N content by applying two fall N fertilization rates (12 or 24 mg N per seedling)using 15N-enriched fertilizer. At the beginning of the second growing season, a new experiment was started where seedlingswere transplanted into larger pots and subjected to two watering levels (85 or 40% of field capacity). The plants were sampled at4 weeks (T1), 8 weeks (T2) and 12 weeks (T3) after transplanting. Low watering reduced the growth of high and low N seedlings,but high N seedlings showed greater growth than low N seedlings. During bud burst and initial shoot elongation (T1), restrictedwatering, which induced a moderate water stress, did not affect the amount of N remobilized from roots, the major source ofstored N source at this growth stage