Modelling the seasonal nitrogen partitioning in young sycamore (Acer pseudoplatanus) trees in relation to nitrogen supply
1993
Habib, R. | Millard, P. | Proe, M.F.
A model of nitrogen partitioning during the seasonal growth of sycamore (Acer pseudoplatanus) seedlings was developed and tested against data from trees grown with two contrasting levels of nitrogen supply. The model considered each tissue type (roots, trunk, stems and leaves) as sources and sinks for nitrogen and used flow equations to simulate the dynamics of nitrogen partitioning during a growing season, with increases in tissue dry matter as driving force variables. Withdrawal of nitrogen from leaves during senescence was allocated back to other tissues assuming a linear decrease in leaf mass. The model was fitted to data from trees grown in sand culture with 6.0 molN m-3 (high N) supplied with the irrigation. Model parameters thus determined were used to predict nitrogen partitioning in trees grown with 1.0 molN m-3 (low N) in the same year, and for trees from both treatments given either high or low N during a second year. The model accurately predicted the nitrogen content of roots and leaves and gave small errors in the amount of nitrogen partitioned to stems. In contrast, the nitrogen content of the trunks were over-estimated due to a failure to simulate the decrease in nitrogen content found at the start of the growing season. The ability of the model to simulate nitrogen partitioning by changes in tissue dry matter in trees of varying size and nitrogen status is discussed and possible modifications to model partitioning of trunk nitrogen more accurately suggested.
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