Articles containing the keyword 'pioneer species'

The occurrence of Caleopsis bifida on clear-cut and burned forest soil and its disappearance in 4–6 years after disturbance is attributed to its germination ecology. Initially the seeds are dormant 96–100% and remain dormant in nylon gaze bags in different types of forest humus layers at least 10 years. Dormancy is released in laboratory (1) by treatment of 100 ppm aqueous solution of GA₃, (2) by heating the dormant seeds to 40–55°C for 1–5 h, and (3) by 1% KNO₃ solution. It is concluded that conditions in clear-cut and burned areas favour germination of seeds in regard to temperature and content of nitrates in contrast to humus of closed vegetation where the seeds remain dormant.

The PDF includes an abstract in Finnish.

• Hintikka, E-mail: vh@mm.unknown

The tendency of successional development from young vegetation, rich in species and exposed to chance factors, towards regular plant communities, is found all around the world. Thee ecological groups of trees seem to be present in all forest regions in the world, namely the pioneer and the climax species, and a group of pre-climax species that can be ecologically either near the pioneer or the climax species. The succession of tree species in forest always leads to a climax stand, determined by climate, quality of soil and the mutual biotical strengths of the tree species in the region.

This division into ecological groups greatly facilitates choosing among different methods of treating stands and understanding the silvicultural methods of foreign regions. Stands formed by species of the same group must follow the same lines in their silvicultural treatment. For instance, mixed stand consisting of both pioneer and climax species represents a transition stage, in which the climax species strive for dominating position, and preservation of pioneer species is difficult. This indicates the broad lines for management of the stand. Also, regeneration methods of pioneer and climax species must be different. Studying the succession of natural forests can be used as a means to reach the highest possible silvicultural level. This is one reason why the preservation and study of virgin forests still in existence is indispensable.

The PDF includes a summary in Finnish.

• Kalela, E-mail: ek@mm.unknown