Rehabilitation of degraded areas of Central Amazonia using direct sowing of forest tree seeds

Abstract

Deforestation in the Amazon Basin is still increasing, and the rehabilitation of these lands continues to be a challenge. Autoecological studies of most Amazonian species are rare, and efficient techniques for restoration of forested habitats have yet to be developed. The aim of this study was to test direct sowing as a rehabilitation technique for sites with different degrees of disturbance: bare soil, pasture, and secondary and mature forests in Central Amazonia, Brazil. At each site, we sowed seeds of 11 native tree species. Throughout the following year we evaluated germination and seedling survival. The germination differed according to the study site and species. Seedling survival in degraded sites was higher than in other areas. After 1 year in the bare soil site, 33% of the sown seeds of eight species developed seedlings; in the pasture the establishment was 23%, in secondary forest 15%, and in mature forest 12% of only four species. The only widespread survivor with more than 45% emergence in all perturbed sites was Caryocar villosum. No pioneer seedlings remained after 1 year. There was a positive correlation between seed size and survival. Large-seeded non-pioneer species seem to be more suitable for direct sowing than small-seeded species. We recommend a combination of direct sowing and planting of seedlings as an appropriate means to accelerate the rehabilitation of degraded areas in Central Amazonia.