Nitrogen retranslocation, allocation, and utilization in bare root Larix olgensis seedlings

Abstract

We quantified biomass accumulation and nitrogen (N) retranslocation, allocation, and utilization of Changbai larch (Larix olgensis) seedlings subjected to four fertilization treatments (24, 59, 81, 117 kg⋅ha -1 N) with an unfertilized control during summer and autumn 2009. Ammonium phosphate (18-46-0) was the fertilizer used in all treatments.On both sampling dates, the needles had greater biomass and N content than new (2009) stems and old (2008) stems, and coarse, medium and fine roots (diameters of >5, 2−5 mm, and 0−2 mm, respectively). Higher N concentration was observed in old stems and coarse roots than that in new stems and medium roots. In mid-summer, fine roots had higher N concentration than coarse roots. The treatment with 24 kg⋅ha -1 N had the greatest biomass and N content in needles and old stems, and highest net N retranslocation (NRA) and amount of N derived from soil. On September 21, no N translocation was observed, while the treatment with 24 kg⋅ha -1 N had the highest N utilization efficiency and fertilizer efficiency.Vector analysis revealed that all four fertilization treatments induced N Responsible editor: Yu Lei excess relative to the control. The treatments with 59, 81, 117 kg⋅ha -1 N induce N excess compared with treatments at 24 kg⋅ha -1 N. We conclude that the traditional local fertilizer application rates exceeded N requirements and N uptake ability for Changbai larch seedlings. The application rate of 24 kg⋅ha -1 N is recommended.

Growth and Nitrogen Retranslocation of Nutrient-Loaded Clonal Betulaalnoides Transplanted with or without Fertilization

“…On average, 79%, 50%, and 6% of stored nitrogen was retranslocated to new organs at 30, 60, and 180 days after transplanting, respectively, indicating that nitrogen retranslocation declined with time as the root system expanded, improving nitrogen uptake and reducing the reliance on nitrogen redistribution [9,27]. We found that the new growth of B. alnoides plants was dependent on internal nitrogen cycling (50-79%) in the first two months after transplanting.…”

“…High rates of nitrogen retranslocation were also reported in black walnut (Juglans nigra L.) (68-83%) in sand culture for 90 days [10] and P. tremuloides (73-80%) on two reconstructed soils during the first growing season [20]. However, only 32% of nitrogen was remobilized to new growth sinks in Q. rubra [28] over 90 days in a greenhouse, indicating tree species vary widely in terms of the contribution of nitrogen retranslocation required to meet the total sink demand [8,9,26]. As the nitrogen retranslocation capacity might be species dependent and change over time [10,13] (we only explored one B. alnoides clone for six months after transplanting), long-term field experiments on tree species should be conducted to further test the utility of nursery nutrient loading.…”

“…Nitrogen storage and remobilization is important for tree growth and stress tolerance [1,8,25]. Nutrient reserves, current growth, nutrient uptake, and nutrient supply are key variables determining tissue nutrient concentration and the extent of retranslocation of phloem-mobile nutrients, such as nitrogen [9,13]. In this study, regardless of transplant fertilization (F0, F10), the nitrogen concentrations in plant tissues remained stable or they increased in the first two months after transplanting, suggesting there are short-term benefits of nursery nutrient loading, in terms of tissue nitrogen concentration.…”

“…However, Hu et al [1] found that nutrient loading increased nitrogen retranslocation rates in P. tremuloides, but not in P. glauca seedlings, after transplantation, despite enhanced internal nitrogen reserves in both tree species. The species-specific responses of nitrogen retranslocation to nutrient loading may be related to the different leaf traits and growth strategies of trees [8,9,26].…”

“…In addition to nutrient loading, soil fertility also affects the field growth performance of seedlings [1,8,9]. However, it is a challenge to distinguish the contributions of plant nitrogen reserves and soil nitrogen to new seedling growth under field conditions unless 15 N labeling is used.…”