Propagation of keystone-woody species as a first step in restoration of an overgrazed seasonal dry forest

Abstract

In degraded forest ecosystems, reintroduction of keystone-woody species is an important step for restoration because it provides regeneration niches. However, lack of information on how to propagate species restricts the use of native species; specially in tropical dry forests where seed germination is seasonal and is synchronized with the onset of the wet season. We evaluated the dormancy-breaking and germination requirements of nine keystone-woody species from Dry Chaco Forest. Most fresh viable seeds of the keystone species are nondormant, but viability decreases during dry-cold storage restricting the use of some species. Seeds of three keystone species germinated to higher percentages in light than darkness and those of five species germinated equally well in light and darkness; seeds of Castela coccinea germinated to higher percentages in darkness than in light. Alternating vs. constant temperatures had no effect on germination in seven species. Seeds of Anisocapparis speciosa and Cynophalla retusa were nondormant and remained viable for only 1 month during cold-dry storage; and 62–95% of the seeds of the other seven species were nondormant. Dormancy-break was studied in five of the seven species; seeds of four species had physiological dormancy and one had physical dormancy. Dormancy-breaking was promoted by environmental conditions in the habitat, i.e. warm stratification, after seed dispersal. Castela coccinea, Achatocarpus praecox, Mimosa detinens, and Capparicordis tweedieana are the most suitable keystone species for the restoration of overgrazed areas in the Dry Chaco Forest because their seeds germinate to a high percentage and retain viability during dry storage at low temperatures. Seeds of Mimosa detinens and Capparicordis tweedieana required mechanical scarification and 6-weeks of warm stratification, respectively, for dormancy-break.