Assistant professor, Department of Rangeland and Watershed Management, Faculty of Water and Soil, University of Zabol. Zabol city, Iran
Objective: Ecosystems with mixed species compared to the ones with pure compositions provide a broader range of options in the fields of biodiversity, conservation, protection and restoration. Nearly all forest plantations are established as monocultures, but research has shown that there are potential advantages to be gained by using carefully designed species mixtures in place of monocultures. This paper reviews recent studies that compare stand development and productivity of mixed and pure plantations. Results: Higher stand-level productivity in mixtures has been found with species interactions. These mixtures can also improve economic return through greater individual-tree growth rates and provision of multiple commercial or subsistence products. More complex plantation mixtures of several species have been used for ecological restoration of degraded lands; these large numbers of species of different successional stages are combined to reduce the need for a series of sequential plantings. Future research needs to examine many more tree species across a wider range of sites.