Green is the New Black: Outcomes of Post-Fire Tree Planting Across the Us Interior West

Abstract

Reforestation activities such as tree planting are an important tool to offset carbon emissions, restore forest ecosystem integrity, and maintain essential ecosystem services. Major financial investments and recent policy changes are expected to accelerate rates of tree planting throughout burned landscapes in the United States (US), but the impacts of such activities have not been broadly examined. We quantified the outcomes of recent (1987-2022) post-fire plantings in the western US using remotely sensed estimates of forest cover change and in-situ survival records (69,745 seedlings) spanning 302 fire events. Overall, planted areas gained forest cover 25.7% more rapidly than environmentally similar, unplanted sites in the same fires, and average planted seedling survival after was 79.8% after one growing season. Forest regrowth and planted seedling survival were typically highest in cold, wet areas and when planting was followed by suitable weather conditions. Planting season also shaped outcomes, with late summer or fall plantings performing best on warm, dry sites, and spring plantings performing best in cold, wet areas. Fire severity was positively associated with planted seedling survival, but negatively associated with forest regrowth rates, likely due to effects on patterns of natural tree regeneration. Tree planting can enhance post-fire forest recovery rates, though its effects are dependent on a range of environmental and operational factors. This information helps to inform realistic expectations of planting outcomes, an issue of global relevance as such projects expand to achieve restoration and climate mitigation goals.

Keywords: Reforestation, Wildfire, Forest Recovery, Landsat Time Series, Tree Recruitment, REPLANT Act