The coefficient, c 1, increased linearly with increasing 'growing space', but c 2 was not correlated with 'growing space', nominal initial stand density, nominal post-thinning stand density, or the difference between nominal initial and post-thinning stand densities.
The models developed were then used to evaluate the influence of initial and post-thinning stand density on branch diameter in un-pruned Douglas-fir at two sites in New Zealand, one in the North Island and one in the South Island.
Fig. 7 Predicted values of whole-log average density for (a) stands grown at three contrasting sites, (b) under different silvicultural regimes (combinations of initial and post-thinning stand density), (c) for four different rotation lengths, and (d) at different heights up the stem (5-m height classes).
The objectives of this study were: (a) to develop site-specific models to predict branch diameter variation with position on the stem; and (b) to use the models to evaluate the influence of initial and post-thinning stand density on branch diameter in unpruned stands of Douglas-fir (Pseudotsuga menziesii (Mirb).
Fig. 9 Predicted values of whole-log average density a for stands grown at four contrasting sites, b under different silvicultural regimes (combinations of initial and post-thinning stand density), c for three different rotation lengths, and d at different heights up the stem (5-m height classes).
The predicted branch diameter profile for a tree of average DBH in a stand with an initial density of 1666 stems ha−1 and post-thinning stand densities of 250, 500, 750 and 1666 stem ha−1 using Model 4 (Table 9) is shown in Fig. 4b.
This is consistent with the observation that the reduction in total stand carbon stock may not change the net ecosystem exchange between pre- and post-thinning [28].
This is consistent with the observation that the reduction in total stand carbon stock may not change the net ecosystem exchange between pre- and post-thinning [ 28].
The two PSPs selected were ones where the stand density remained close to the prescribed initial or post-thinning stand density.
This study indicates the importance of considering initial stand density, post-thinning stand density and timing of thinning when designing a silviculture regime that aims to control branch diameter.
