Do seeding and seedling planting result in similar restored plant communities?

Aims

Restoration practitioners often face a tradeoff between low cost but risky seeding vs expensive but more reliable seedling planting to meet revegetation goals. Knowing under what environmental and management conditions direct seeding vs seedling planting benefit different species could improve restoration practice.

Methods

We compared seed emergence to planted-seedling survival among perennial herbaceous species commonly used in restoration across eight experimental restoration sites on the Colorado Plateau, USA. We used linear models to assess relationships between emergence and survival among species, and to assess the effects of site climate and seeding pre-treatments on those relationships.

Results

We found that among species, emergence was positively correlated with survival in the cooler sites, meaning that species with high emergence also had high survival and vice versa, but had no relationship in the hottest sites. Furthermore, pre-treatments to enhance soil moisture in seeded plots, specifically microtopography (pits) and mulch, also resulted in positive relationships between emergence and survival among species, while seeding without additional soil pre-treatments did not. Seedling planting cost 14 times as much as direct seeding alone, dropping to nine times as much when pre-treatments were combined with seeding.

Conclusions

Taken together, these results suggest that investments in seedling planting at hotter dryland sites, or in creating microtopography or mulching prior to seeding across sites, are likely to promote establishment success compared to simple seeding methods in degraded dryland ecosystems. These findings also identify opportunities for hybrid seeding and planting approaches that balance tradeoffs between risk and cost, respectively.