2

We developed the first explicit and dynamic implementation of microclimate temperature buffering in a forest landscape model and investigated effects on simulated forest dynamics and outcomes. Microclimate effects on forests scaled nonlinearly from stand to landscape and days to millennia, underlining the utility of complex simulation models for dynamic upscaling in space and time. Microclimate temperature buffering can alter forest dynamics at landscape scales.

Mountain forests are biodiversity hotspots with competing hypotheses proposed to explain elevational trends in habitat specialization …

Forest ecosystems are changing rapidly, and landscape-level processes such as disturbance and dispersal are key drivers of change. …

Climate change has profound impacts on forest ecosystem dynamics and could lead to the emergence of novel ecosystems via changes in …

Understanding the impacts of changing climate and disturbance regimes on forest ecosystems is greatly aided by the use of process-based …

Tree regeneration is a key process in forest dynamics, particularly in the context of forest resilience and climate change. Models are …

We jointly assessed the effects of both climate and forest change using the process-based simulation model iLand, asking: How do understory plant communities respond to 21st-century change in a topographically complex mountain landscape, representing a hotspot of plant species richness? Nearly all species persisted in the landscape in 2050, but on average 8% of the species pool was lost by the end of the century. By 2100, landscape mean species richness and understory cover declined (−13% and −8%, respectively), warm-adapted species increasingly dominated plant communities (i.e., thermophilization, +12%), and plot-level turnover was high (62%). Subalpine forests experienced the greatest richness declines (−16%), most thermophilization (+17%), and highest turnover (67%), resulting in plant community homogenization across elevation zones. Climate rather than forest change was the dominant driver of understory responses. The magnitude of unabated 21st-century change is likely to erode plant diversity in a species richness hotspot, calling for stronger conservation and climate mitigation efforts.

Highlights: (1) Social-ecological context is critical for fire management decisions. (2) Commanders chose full suppression for nearly half the fires in the region. (3) Full suppression less likely on federal land, later in year, and for local teams. (4) Full suppression more likely with higher housing density and larger fires. (5) Changes would incentivize less-than-full-suppression to reduce future fire risk.

Species capable of growing in drier conditions and in lower vegetation zones became more abundant and regional differences in plant communities declined following short-interval fire. Dissimilarity between plot pairs increased in mesic settings and decreased with time since fire and postfire winter snowfall. Reduced postfire tree density following short-interval fire rather than FRI per se affected the occurrence of most plant species. Anomalously short FRIs altered understory plant communities in space and time, with some indications of community thermophilization and regional homogenization. These and other shifts in understory plant communities may continue with ongoing changes in climate and fire across temperate forests.

Following short-interval versus long-interval fires, live tree stem density was an order of magnitude lower, density of aspen increased, dead woody biomass was reduced by half, and recovery of live biomass and canopy fuels was delayed for at least 30 years. Our results suggest differences in tree regeneration following short-interval versus long-interval fires will be especially pronounced where serotiny was high historically. Propagule limitation will also interact with short-interval fires to diminish tree regeneration but lessen subsequent burn severity. Amplifying driver interactions are likely to threaten forest resilience under expected trajectories of future fire.