Growth and Yield of Multi-Storeyed Stands

1990

S. 22-27

1 Abb., 2 Tab., 15 Lit. Ang.

Unselbständiges Werk

200054455

An alternative to the conventional clearfelling system with single storeyed stands is to focus the silviculture on maintaining multistoreyed stands. Multi-storeyed stands are often considered as poor yielders that are difficult and expensive to manage. However, they do offer environmental advantages and may yield timber of higher quality. To illustrate the yield effects of multi-storeyed stands, some theoretical aspects are discussed and some studies of this topic are summarized. The following conclusion are drawn: - Theoretically, on good sites a selection system is expected to yield more timber than a clear felling system, while on poorer sites it will yield significantly less. - Young two-storeyed stands, with a fast-growing light demander in the upper storey and a shade tolerant species in the lower storey, will yield more than a single storeyed stand of either species. An example of this is a shelterwood of birch with spruce generatin beneath. - In older pine stands, spruce seedlings may compete with the pines. Three studies, indicating losses in pine growth ranging from 8-18% are quoted. The gain in spruce production however appears to outweight the loss in pine production. - Shelterwood trees seem to have a positive effect on the long term yield of regenerating stands on high altitudes. The volume growth of the shelterwood trees more than compensates the delayed development of the seedlings, compared to seedlings grown in the open. - Topping, tat is cleaning of overtopping seedlings in dense pine regenerations on poor northern pine heaths, momentally decreases the average height. But an even crown layer gives the best long-term yield. - A simulation of the development of pure pine and spruce stands with small and big height variations shows that bit height variations are unfavourable for the yield, and that pine is more sensitive than spruce in this respect.