Drought-hardening or not? Medium-term performance of native woody species under field experimental revegetation of arid woodlands

Abstract

Introduction: Restoring degraded drylands is a global concern. While revegetation with drought-hardened native plants is considered effective, its success varies. Objectives: We aimed to evaluate drought-hardening's impact during nursery sapling production and study the field performance of different species with potential for revegetation in the Central Monte Desert, one of South America's most arid ecosystems. Methods: We monitored plant size, survival, and general condition of Bulnesia retama, Neltuma argentina, Neltuma flexuosa, and Neltuma alpataco. These were transplanted into an experimental revegetation plot in a livestock-disturbed area of the Central Monte Desert. Before out-planting, saplings were cultivated in a glasshouse with high and low water supply. We analysed plant performance concerning to the plasticity of previously measured morphological traits. Results: Nursery drought-hardening had no detectable effect after five years on most traits. Species identity was a key determinant, with Neltuma species showing superior performance, achieving the greatest canopy size and coverage. These species also displayed remarkable allometric plasticity, particularly in leaf area and root:shoot ratio. Conversely, Bulnesia retama performed poorly. Plant growth during the first year after transplanting, with irrigation and organic amendments, was 24 times greater than in subsequent years. Conclusions: Drought-hardening of saplings did not confer any medium-term advantage in this environment. Among the species evaluated, the three Neltuma species were the most suitable and plastic. Long-term estimates suggest vegetation cover recovery may require decades, highlighting the slowness of processes in these ecosystems.