Background: Planting tree seedlings may help promote forest recovery after extensive high-severity wildfire. We evaluated the influence of growing environment characteristics on the performance of seedlings planted in the 2016 Cold Springs Fire, Colorado, USA. In 2021, four growing seasons after planting, we measured survival, height, and 2021 height growth for 300 ponderosa pine, limber pine, and Douglas-fir seedlings permanently marked along “stake rows.” For each seedling, we also recorded one site-level growing environment characteristic, aspect, and two microsite-level characteristics, the presence of coarse wood or other shade object and the presence of water-capturing microtopographic depressions. To examine a potential mechanism through which these growing environment characteristics could influence seedling responses, we also measured summer soil moisture at each ponderosa pine seedling. We used generalized linear mixed models to examine the influence of aspect, shade object presence, and depression presence on seedling survival, height, and height growth, and on soil moisture. Results: The growing environment had a clear influence on tree seedlings. We found greater seedling survival on more northerly aspects, in shade, and in depressions. Across all species, seedlings on north aspects had 37% greater survival than those on south aspects (76% vs. 39%, respectively). Seedlings planted in shaded microsites had 20% greater survival, and seedlings planted in depression microsites had 14% greater survival relative to microsites without shading or depressions, respectively. Seedling height was greater on more northerly aspects and in shade. Likewise, seedling height growth was generally greater on north aspects and in shade, although the influence of aspect and shade depended on species. Soil moisture was greater in depressions. Conclusions: The findings of this opportunistic study demonstrate how positioning seedlings to take advantage of cooler, wetter growing environments can increase their performance in what are often climatically stressful post-fire landscapes. Overall, planting seedlings on north-facing aspects, in shaded microsites, and in depression microsites, practices commonly employed by land managers, were effective at promoting survival and growth, thereby facilitating planting success. These practices will likely become ever more relevant as the pace and scale of post-fire planting increases and as planting conditions become more stressful due to ongoing climate change.

Forests of the western United States are undergoing substantial stress from fire exclusion and increasing effects of climate change, altering ecosystem functions and processes. Changes in broad‐scale drivers of forest community composition become apparent in their effect on survivorship and regeneration, driving demographic shifts. Here we take a community functional approach to forest demography, by investigating mean drought or shade functional tolerance in community assemblages. We created the Community Mean Tolerance Index (CMTI), a response metric utilizing drought/shade tolerance trade‐offs to identify communities undergoing demographic change from a functional trait perspective. We applied the CMTI to Forest Inventory and Analysis data to investigate demographic trends in drought and shade tolerance across the southern Rocky Mountains. To find the major drivers of change in community tolerance within and across forest types, we compared index trends to climate and fire‐exclusion‐driven disturbance, and identified areas where demographic change was most pronounced. We predicted that greater shifts in drought tolerance would occur at lower forest type ecotones where climate stress is limiting and that shifts in shade tolerance would correspond to excursions from the historic fire regime leading to greater changes in forest types adapted to frequent, low‐intensity fire. The CMTI was applied spatially to identify sites likely to transition to oak shrubfield, where disturbance history combined with a species‐driven demographic shift toward drought tolerance. Within forest types, lower elevations are trending toward increased drought tolerance, while higher elevations are trending toward increased shade tolerance. Across forest types, CMTI difference peaked in mid‐elevation ponderosa pine and mixed‐conifer forests, where fire exclusion and autecology drive demographic changes. Peak CMTI difference was associated with fire exclusion in forest types adapted to frequent fire. At higher elevations, site‐level stand dynamics appear to be influencing demographic tolerance trends more than broad climate drivers. Through a community demographic approach to functional traits, the CMTI highlights areas and forest types where ecosystem function is in the process of changing, before persistent vegetation type change occurs. Applied to regional plot networks, the CMTI provides an early warning of shifts in community functional processes as climate change pressures continue.

The potential for species distribution shifts in response to changing climate and altered fire regimes is a pressing concern across ecosystems. Species responses to climate and disturbance are expressed demographically as changes in survivorship and recruitment across gradients. We examined tree recruitment and radial growth response to climate along a biophysical gradient in a mixed-conifer forest in northern New Mexico, USA, in a watershed spanning from near the lower to upper elevation range for ponderosa pine (Pinus ponderosa var. scopulorum Engelm.) and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco). We compared growth responses with climate variables and stand demographic patterns of the six major tree species present, to track shifts in species community composition and dominance. We found significant changes in species composition between mature trees and seedlings and saplings across Elevation–Aspect groups in several species, indicating incipient community change. Drought stress drove patterns of tree growth and species composition shifts at low elevations, while at higher elevations increased stand density following fire exclusion led to success of shade-tolerant species. Altered growth and demographic trends driven by drought and fire exclusion can serve as the mechanism for changing species distributions and community reorganization across landscape climatic gradients.