LIGNUM has been implemented with C++ and currently it runs on several UNIX platforms (SGI, Sun, HP). The visualization is implemented with OpenGL graphics library. We give here some examples of trees that have been produced by LIGNUM. All the simulations are for Scots pine.
4.1 The Effect of Light
LIGNUM allows us also to study various effects of light. On the left the parameter values have been adjusted so that the tree can be said to have adapted to grow in a shade; each tree segment can utilize even a small amount of light. The result is a tree that has an outlook that resembles a Norway spruce. The form of the tree follows its function.
In the middle the parameter values are adjusted so that the tree segments are sensitive to shade. Notice how the lower branches are dying due to the shading of the crown as a result of this property. The result is a tree that mimics a sapling in a Scots pine stand. Again, the form follows function.
The rightmost tree simulates a tree growing beside an obstacle. The effect of the obstacle can be achieved by blocking the solar radiation from one side of the hemisphere.
Strong branching produces clearly a bushier tree than the tree with somewhat "artificial" parameter values that allow all the tree segments to have equal growth potential regarding the branch order effect.
Also, the photosynthetic rates of the two trees are the same. Comparing the two trees one could state that the photosynthetic rate and growth does not necessarily correlate. Stronger branching may prevent the higher growth potential the faster photosynthetic rate may give.
4.3 The Sapwood Senescence
The sapwood is a major cost for a tree and it is important to study how the turnover from sapwood to heartwood affects the growth of the tree. LIGNUM allows us to study this without making simplifying assumptions of the structure of the tree.
Our premilinary studies show that the large sapwood senescense produces somewhat shorter trees than the trees with small sapwood senescence.