From natural forest to tree crops, co-domestication of forests and tree species: an overview.

The process of domestication of tree crops has only been given limited attention. This process starts with the protection of natural forests and ends with the cultivation of domesticated tree crops. In this evolutionary process three types of human-influenced forest environments may be distinguished: (1) conserved forests, (2) modified forests, and (3) transformed forests. During the process of domestication an increasing input of human energy per unit of exploited forest takes place. Accordingly three phases in the domestication of forests may be distinguished: (1) an acculturalization phase in which social measures aimed at controlling the utilization of valuable tree species or patches of forests are implemented, (2) a phase of manipulation of wild tree species in which the socially-oriented management practices are enhanced with measures aimed at enhancing the (re)productive potential of valued species, and (3) a phase of cultivation of genetically modified tree crops. As a result of the co-domestication of forests and trees various types of forests and/or tree cultivation systems can be distinguished. So far more attention has been given to understanding the characteristics of the early and end phases than to the various intermediate phases represented by indigenous forest management and agroforestry systems. These are characterized by a modification of the highly diverse natural forest ecosystems to a state in which the biodiversity has been somewhat reduced, but in which a larger proportion of useful resources are present. Such systems provide interesting examples of the wide range of options for managing forest resources with varying degrees of biodiversity and productive values