Recrutamento de espécies nativas via semeadura direta no Cerrado

Abstract

The sowing of green manure plants has been recommended for restoration initiatives at the expense of conventional planting of seedlings, thus generating demand for seeds of these species. Despite this recommendation for restoration, the combination of species in an ideal arrangement may vary according to the characteristics of the environment to be restored and the goal to be achieved via direct seeding. If successful, these species will play an important role in facilitating restoration, mainly in the sense of removing invasive species from the system, such as the case of invasive exotic grasses from the Cerrado, reducing competition for light from native species introduced via seeding and consequently allowing recruitment and development of native species. However, as restoration may follow different trajectories than expected, the restorer will need to be alert and ready to intervene if the system falls back into a state of degradation, justifying experimental studies that support predictions. Hence, our objective in this study was to verify in the field, which is the best combination of seeds of facilitating species, considered green fertilizers, to be sown intercropped with native species in order to obtain greater diversity and coverage in overcoming ecological filters, e.g., competition with exotic grasses. We experimentally tested four combinations of seeds from native species with possibly facilitating species in the following treatments: 1) only native tree seeds – N, (2) seeds of green manure: pigeon pea (Cajanus cajan (L.) Huth) + native - GN, (3) seeds of native + native shrub: Lepidaploa aurea - NL, (4) pigeon pea seeds + L. aurea + native GLN, (5) exotic herbaceous green manures (Crotalaria sp. + Canavalia ensiformes) + pigeon pea seeds + native - HGN and (6) control: no sowing, only monitoring of natural regeneration - C that were established every 10 meters. The species of green manures of the legume family used in the combinations were: Pigeon pea (Cajanus cajan), Crotalaria sp. and Pig bean (Canavalia ensiformis) and a native shrub species, Amargoso (Lepidaploa aurea), an Asteraceae. We evaluated the temporal dynamics of native diversity and soil cover for 18 months. Our results showed that the combinations had no effect on native richness and did not influence the abundance of different native species sown under different combinations with green manure. Our results also highlighted the need to use seeds with greater mass as a criterion for choosing the species. In conclusion, under the conditions studied, our data indicate that the use of green manures did not facilitate the increase in the diversity of sown native trees, and its use may be unnecessary when this is the objective. However, the use of shrub and herbaceous green manure plant species together improved soil cover initially, when without the effects of environmental filters, which may be an initial benefit to be considered by ecological restoration project managers to be assessed as to the decision to invest or not in this input.