Modeling mid-elevation Scots pine growth on a volcanic substrate

2000

S. 223-237

9 Abb., 4 Tab, 37 Lit. Ang.

Unselbständiges Werk

200063382

The aim of this study was to set up a deterministic and individual-based growth model of natural Scots pine (Pinus sylvestris L.) forests on a volcanic mountain located in the French Massif Central. In order to take the trees' competitive status into account, isolated trees were first distinguished from trees within a stand. Then trees within stands were assignet to one of the three categories of competitive status: trees characterized by a maximum competitive advantage to their neighbors (dominant trees), trees with a maximum competitive disadvantage (suppressed trees), and trees undergoing an intermediate level of competition (co-dominant trees). The modeling was achieved in three steps: (i) Trees from the different categories were first measured and cores collected and analyzed in order to establish growth models of trunk-circumference, height, and crown-width. Radial growth curves for trees within a stand showed a similar pattern for the three competition categories, with a maximum growth value reached at age three. Growth values appeared to be strongly dependent on the tree's competitive status. Circumference curves were computed on the basis of radial increment values. Models predicting circumference and height with time were computed using a Von Bertalanffy-Chapman-Richard's model. Isolated tree-height and crown-width models were established using circumference as predictor. (ii) Competition was measured on four stands ranging from young and dense to old and sparse. Each tree of the stands was mapped by its X, Y coordinates and its dimensions were recorded. Eleven distance-dependent competition indexes based on vertical or horizontal angel sums were computed and their correlation to tree dimensions was analyzed for the four stands. (iii) Two competition indexes were selected and related to growth model parameters to produce a model predicting height and circumference from the age and the competition indexes.