From seed germination to established seedlings: a comparative evaluation in five shrub species and implications for seed-based restoration in arid lands

Abstract

In a context of global desertification, direct seeding of native species is emerging as a hopeful technique to achieve large-scale arid land restoration. Although low percentages of establishment have been reported for direct seeding in arid lands, it has been more cost-effective than outplantings for some species. Therefore, in order to determine the most suitable species for direct seeding we evaluated potential germination in laboratory trials (ex situ), and seedling emergence and establishment in the field (in situ) for five shrub species from the most arid region of Argentina called “Monte.” Direct seeding was performed in three alternative environmental conditions: (1) abandoned oil-drilling platforms, (2) bare soil patches, and (3) under the canopy of shrubs patches in cattle ranching areas. In the three cases, four soil treatments were applied: hydrogel, soil enrichment with arbuscular mycorrhizal fungi, and clay pot irrigation. Seedling emergence and establishment after the first period of extreme weather conditions (summer) were higher in severely degraded sites (oil-drilling platforms). In this particular condition, seedling emergence and establishment presented the highest values for Ephedra ochreata (64.8–82.8% and 26.8–46.4%, respectively) and the lowest values for Larrea divaricata (6.78–24.8% and 2.8–6.4%, respectively). These results show that direct seeding offers potential possibilities to restart processes of assisted succession in arid lands and that species selection is a key stage/phase in direct seeding success.