Resorption-Related Nitrogen Changes In The Leaves And Roots Of Larix Kaempferi Seedlings Under Nutrient-Sufficient And Nutrientstarvation Conditions

AimsLarch is the dominant timber species in Northeast China. However, compared with the adjacent secondary forests, soil available nitrogen (N) significantly declined in similar to 40-year-old larch plantations. Thus, it is of great importance to determine how N use strategies in larch change in response to declining soil N availability.MethodsWe investigated the changes in N concentration and N-15 natural abundance (delta N-15) from 18 August to 25 October in the leaves, stems, branches and roots of 1-year-old Larix kaempferi seedlings under nutrient-sufficient (NSu) and nutrient-starvation (NSt) conditions with a pot experiment in Northeast China.Important FindingsStem and branch N concentrations exhibited upward trends, and leaf N concentration exhibited a downward trend. Root N concentration exhibited an upward trend under NSu conditions, but a downward trend under NSt conditions. These results suggested that stems and branches were served as N storage organs, but roots shifted from storage to resorption organs when switched from NSu to NSt. Leaf nutrient resorption was intensely occurred on 11 October, as indicated by the sharply decreased leaf N concentration and increased stem, root and branch N concentrations. The delta N-15 of roots, branches and leaves overlapped between NSu and NSt approximately on 11 October, which may be regulated by isotope discrimination during N resorption. Leaf N resorption efficiency under NSt (76.33%) was significantly higher than that of NSu (56.76%), indicating that nutrient stress stimulates leaf N resorption. Taken together, larch seedlings enhance leaf nutrient resorption and shift roots from nutrient storage to nutrient resorption to adapt to NSt conditions. These changes might relieve the adverse effects of declining soil nutrient availability on seedling survival and regeneration.