Give Seeds A Chance? Opportunities and Techniques for Post-Fire Reforestation Using Tree Seeding

<p>This data package includes results of experimental seeding trials and GIS analyses describing the opportunities to use direct tree seeding in post-fire reforestation approaches throughout the Southern Rocky Mountains, USA. It includes all data, R code, and statistical model outputs from Rodman et al. (2025). The abstract of this publication is as follows:</p> <p>Altered fire regimes and post-fire tree regeneration failures have the potential to drive forest cover losses throughout western North America, but management practices such as active reforestation may help to address these challenges. Planting of nursery-grown tree seedlings currently accounts for most of the active reforestation in the western United States (US). Direct tree seeding – an alternative approach involving the dispersal of tree seeds into a project site – is rare but has the potential to supplement planting and increase the pace and scale of reforestation activities, particularly where planting is operationally challenging. In the Southern Rocky Mountains, US we used a regionwide analysis of implementation data to describe (a) the typical locations of post-fire tree planting and (b) the percentage of severely burned forests that are difficult to access using such treatments. In experimental field trials in two Colorado wildfires, we tracked nearly 40,000 seeds over a one-year period to test a range of seed enhancement techniques (seed coating, pelleting, priming) and operational factors (sowing season, microsite characteristics) that might influence direct seeding outcomes. In the Southern Rockies, nearly two thirds (63.4%) of all post-fire tree planting activities occurred in severely burned areas, near established roads, and on flatter slopes. About one third (32.2%) of all severely burned forests are challenging to access for tree planting based on current patterns of implementation. In field trials of direct seeding, first-year establishment rates averaged just 0.2% but ranged from 0 to 2.7% across treatments. Untreated seeds had 4x higher establishment rates than those receiving seed enhancement techniques. In the older (ca. 20-years-old) fire, direct seeding was most effective in sites with bare ground cover, whereas, in the more recent (ca. 1-year-old) fire, direct seeding was most effective in sites where mulch was present due to post-fire hillslope stabilization treatments. Direct seeding may help to treat vast areas that are difficult to access using tree planting activities. However, increases in seed collection and further exploration of techniques to increase tree establishment rates are needed for this technique to become operationally feasible at broad scales.</p>