Tree species growth under a rubber (Hevea brasiliensis) plantation: native restoration via enrichment planting in southern Bahia,Brazil

Enrichment planting is a technique that is gaining recognition for its potential to restore native forests. Due to the steep economic trade-offs involved and dearth of silvicultural and ecological knowledge about native flora, however, it remains unclear whether it has promise for widespread application. Focusing on growth performance, this study explores the restoration potential of twenty-one native tree species 3 years after planting in the understory of a rubber plantation in southern Bahia, Brazil. We tested the effects of slope, aspect, successional guild and basal area of the overstory rubber trees on the enriched species’ height, root collar diameter, and diameter at breast height. Height was the growth parameter that most differentiated species, with Parkia pendula, Sloanea monosperma, and Tachigali densiflora being three of the most successful species. Pioneer species grew faster than the non-pioneer species. Overstory basal area was the most important variable influencing the performance of the planted tree seedlings, while aspect and slope were less important. For every additional unit of basal area per hectare of rubber, there was an incremental decrease in the growth rates of the enrichment species. This suggests that the tree species are likely limited by available light, and that there are distinct trade-offs between overstory rubber density and understory tree species growth that are important to consider when accelerating forest recovery by using enrichment planting techniques.