High tree diversity enhances light interception in tropical forests

We used two forest plantation experiments, the Sardinilla site in Panama (containing monocultures, 2-, 3- and 5-species mixtures in the main plantation, established in 2001, and 6-, 9- and18-species mixtures in the high-diversity plantation, established in 2003), and the Anhembi site in Brazil (established in 2006, containing 20-, 58- and 114-species mixtures), to investigate the effects of forest tree richness on the amount and distribution (horizontal, vertical and temporal) of intercepted ligh (red:far-red ratio - R:FR - for Sardinilla and intercepted photosynthetically active radiation - iPAR - for Anhembi). At the Sardinilla site, light interception was higher in 5-species mixtures than in 2- or 3-species mixtures, and all mixtures presented higher light interception than monocultures. At the Anhembi site, during the dry season, 20-, 58- and 114-species mixtures, respectively, presented increasing light interception. However, during the rainy season, 58- and 114- species mixtures did not present significant differences in light interception. Overall, the distribution of intercepted light was less variable over the (horizontal and vertical) space and time at higher richness levels (except for vertical distribution of R:FR at the Sardinilla site's high-diversity plantation).