Reducing Fire Severity and Extent Bolsters Subalpine Forest Resilience to Global Change Through Key Demographic...

Area of Science:

• Ecology
• Forestry
• Climate Change Science

Background:

• High-elevation subalpine forests are vulnerable to climate change, disturbances, and altered wildfire regimes.
• The resilience of these forests to global change drivers remains uncertain, with mixed evidence on potential ecological transformations.

Purpose of the Study:

• To investigate how demographic responses of subalpine fir (Abies lasiocarpa) and Engelmann spruce (Picea engelmannii) to global change influence forest community resilience.
• To develop a framework for categorizing forest community trajectories based on species' demographic trends.

Main Methods:

• Utilized United States Forest Service Forest Inventory and Analysis (FIA) data to quantify population trends for subalpine fir and Engelmann spruce.
• Developed hierarchical Bayesian demographic models for mortality, regeneration, and recruitment, incorporating climate, disturbance, and structural predictors.
• Employed a multinomial classification model to link demographic rates to forest community trajectories and applied future climate/disturbance scenarios.

Main Results:

• Identified strong negative relationships between species' demography and disturbance extent/severity, with climatic responses consistent with energy-limited systems.
• Future scenario modeling indicates that reducing wildfire extent and severity significantly enhances subalpine forest resilience.
• Management intervention effectiveness varies by fire history, forest type, biophysical setting, and land tenure, with key opportunities in the northern Rocky Mountains.

Conclusions:

• Subalpine forest resilience is strongly influenced by disturbance regimes and climate.
• Targeted reductions in wildfire extent and severity are critical for bolstering forest resilience.
• Management strategies must be tailored to specific regional contexts, with notable intervention opportunities in the northern Rocky Mountains and resilience centers in the Cascades.