Toward extension of a single tree functional–structural model of Scots pine to stand level: effect of the canopy of randomly distributed, identical trees on development of tree structure

Functional–structural plant growth models (FSPMs) combine the description of the structure of plants and the resource acquisition and partitioning at a detailed architectural level. They offer ameans to study tree and stand development on the basis of a structurally accurate description that combines resource capture at the same level of detail.We describe here how a ‘shoot-based’ individual tree model, LIGNUM of Scots pine (Pinus sylvestris L.) has been applied to a group of identical trees (forest). Themodel has been applied to isolated trees and saplings growing in forest gaps. First, we present the LIGNUM model and the changes necessary for simulation of a forest instead of individual trees. LIGNUM derives tree growth on the basis of a process-basedmodel of tree carbon balance and the architectural development of the 3-D tree crown. The time step is 1year.We realised the forest as consistingof individualScots pine trees onaplot 17 17m,but simplified the stand description by simulating the growth of only one tree in the middle of the plot and assumed that the other trees were identical to it at all times. Themodel produced results that are comparablewith observationsmade in real Scots pine trees and tree stands in Finland. The simulations with variable values of the parameters controlling the foliage–sapwood relationship, amount of sapwood required belowapoint in a branchor a stem, and the senescence of sapwood showedhowgrowthdeclines when the sapwood requirement in the branches and stem was high. In this case, the proportion of resources allocated to the needles became small and the needle mass was low. Additional keywords: forest, Pinus sylvestris L.