The intensifying effects of climate change are increasing the pressure on forest ecosystems, particularly on seedling survival after reforestation. Drought resilience has become a key factor for success, especially in mountainous regions where environmental conditions are highly variable and often challenging. In response, our project investigated the effectiveness of soil amendments, specifically hydrogels and fertilizers, as preventive technical measures to reduce early seedling mortality.
We monitored the survival and growth of over 40,000 seedlings across 24 reforestation sites in Austria, ranging from dry continental lowlands to high-elevation mountain forests. The experiment included three widely planted tree species (oak, larch, spruce), two planting seasons (spring and autumn), various planting methods (manual and mechanized), and both bare-root and container-grown nursery stock. We applied two types of hydrogels and two types of fertilizer in different dosages during planting.
Our results from the first and second year after planting show that while seedling survival varied substantially by species, planting method, and nursery type, soil amendments had no consistent beneficial effect on reducing drought-induced mortality. In some cases, they were even detrimental. These findings indicate that under real-world operational field conditions, soil amendments are not a universally reliable strategy to enhance seedling survival. Instead, outcomes are strongly shaped by the interaction of multiple factors, including site conditions, application method, planting timing, and stock quality. It is suggested that adaptive, context-sensitive strategies that integrate these variables are more likely to have a positive effect than single technical fixes.