Competition in a Mixed-Species Planting With Four Contrasting Species

Background: Mixed-species systems are well-suited to smallholder and community forestry, but reliable evidence regarding and procedures to assess species performance in such systems is scarce. This study concern a field trial with a pair of clinal plots varying spacing and species composition that offered insights into competition between four species proposed for mixed-species plantings by smallholders for landscape rehabilitation in the Philippines. Results: Use of a size-distance competition index allowed an assessment of the competitive and collaborative influences between four tree species. Within the expected general trend for growth to decline with increasing competition, there were indications that Shorea palosapis is a benign competitor that may stimulate the growth of neighbouring individuals. Paraserianthes falcataria is a strong competitor that is also strongly impacted by competition, especially through antagonistic intraspecific competition. Paraserianthes falcataria appears well suited as a solitary tree in a field or village, whereas Shorea palosapis seems ideal for plantations, in both monoculture and mixed plantings. Conclusion: Pterocarpus indicus exbibits strong intraspecific, but low inter-specific competition, so appears well-suited for polyculture plantings. Of the four species, Swietenia macrophylla appears to be best-suited as a monoculture species as it exhibits the lowest intraspecific competition.