Source-sink relationships vary with age in Chinese pine (Pinus tabulaeformis Carr.): Analysis using the GreenLab model

Tree growth and development rely on the underlying dynamics of their source-sink balance. Given the difficulty of collecting experimental data on adult trees, models can be used as tools to disentangle the complex processes that drive biomass production and allocation. This paper investigates the variations of parameters with age driving the source-sink balance of individual trees through the functional-structural plant model GreenLab. Six Chinese pine (Pinus tabulaeformis Carr.) trees were destructively sampled and were divided into three groups based on ages: 5-year old, 10-year old and 18-year old. Firstly, the effects of age on organ dimensions and on organ relative mass were analyzed based on direct experimental measurement. Secondly, the hidden parameters of the GreenLab model were estimated using the data of total tree biomass for needle and wood compartment independently and then for the six trees in parallel. The statistical tests showed that there were significant differences between the tip attributes on first-, second-, and third-order branches of the three age stages for internode diameter, internode sink and needle sink. Preliminary fitting results showed that the sink of layers and the parameter of biomass production efficiency 1/r decrease with age.