Piñon pine and juniper seedling regeneration persists at burned edges but remains limited two decades after large wildfires

Abstract

Pinon-juniper woodlands, a prominent ecosystem in the southwest US, are undergoing significant ecosystem changes due to drought and fire. Concerns arise over lack of resilience, especially as this ecosystem experiences hotter and drier recovery conditions. To understand vegetation trajectories and to identify risk factors that may reduce tree seedling establishment, we examined three 25 +- year-old fires in western Colorado, USA, and compared plant community recovery and tree establishment patterns in unburned, interior burned, and edge burned plots. Assessment included pinon and juniper seedling recovery and their microsite conditions, and plot structure, including percent cover of understory plant functional groups and fuel loading. We found that in burned plots, tree regeneration was highest in edge plots compared to interior plots. Seedlings were more often found under nurse objects, with more seedlings present under Gambel oak and logs compared to other nurse types. Our models indicated that pinon seedling presence was negatively associated with non-native plant cover and positively associated with the density of mature live pinon trees. Juniper seedling presence was positively associated with density of mature live juniper trees, as well as 1-h and 10-h fuels. Our findings suggest that recovery to a woodland structure may be prolonged, especially in large burned patches with limited seed sources and areas with high colonization of non-native plants.