Germination traits explain the success of direct seeding restoration in the seasonal tropics of Brazil

Abstract

Direct seeding is a major method for active restoration of tropical forests and savannas. Although seed traits such as large and rounded seeds are proxies for successful establishment, the effects of germination traits have not been investigated. The study of germination traits allows understanding how to manipulate seed and germination traits to improve the success of seedling establishment. In this study, we evaluated how germination traits are related to success of seedling emergence after direct seeding for forest and savanna trees of the Cerrado, as well as how dormancy breaking treatments modify germination traits and the success of seedling emergence. Twenty-three trees and three shrubs species from forest and savanna in the Cerrado biome were studied in the laboratory. To evaluate how dormancy breaking treatments modify germination traits, intact and pretreated seeds were sowed in a greenhouse. Data on direct seeding success of pretreated and untreated seeds were taken from the literature. Time to start imbibition had a positive effect, and seed shape (variance of seed dimensions) had a negative contribution to direct seeding success. Seed size was not significant in the presence of these variables. In the greenhouse, pretreated seeds anticipated emergence from 40 to 24 days. In field direct seeding, seedling emergence decreased from 30 % for untreated seeds to 18 % for pretreated seeds. Delayed seedling emergence is a positive strategy for direct seeding. Seed technology should target mechanisms and structures to avoid fast and synchronic emergence for direct seeding in the seasonal tropics.