Abstract: Ponderosa pine (Pinus ponderosa) is an ecologically important tree species of the American West. Historically, wildfires in Colorado's ponderosa pine forests were commonplace. With its many fire adaptations, mature ponderosa pine could survive low-intensity fire, and the forests could remain within their historic range of variability. However, forest fuel dynamics are being altered via rapidly increasing climatic variability and the anthropogenic effects of European settlement. If fuel sources accumulate for unusually long periods of time, the risk for severe canopy wildfire is significantly increased. A key restoration focus is the mitigation and prevention of intense wildfires. Prediction of fuel loads at the forest floor is pivotal when assessing the hazard level a forest fire may present. Scientists already have much data correlating fuel characteristics to fire effects and behavior. However, links between montane climate variability and relative effects on fuel load characteristics have not been extensively explored in the Front Range and southwestern Colorado. This study system was uniquely located along a North-South monsoonal gradient and encompasses variable aspects, slopes, and elevations, providing topographic differences within the species’ range in Colorado. We aimed to 1) evaluate how coarse woody debris fuel mass changes over time within unique plots across montane regions of Colorado, 2) determine how decomposition rates are influenced during a growing season across plots 3) assess the hierarchy of local topographic drivers on microclimate within a particular site, and 4) describe how varying fuel types are influenced by these topo-climatic relationships. We resampled forest fuels in old-growth ponderosa pine forest plots initially taken in 1994. Additionally, we analyzed FIA (forest inventory and analysis) fuel type datasets, and thus used two different scales: 1) a 1994-2021 coarse woody debris resample and 2) a large-scale analysis of Colorado’s downed woody material from forest inventory and analysis (FIA) datasets. We found that coarse woody debris increased in all but one plot that experienced definite fuel management, and increases were associated with growing season precipitation. Decomposition did not significantly differ across field sites. However, decay rates appeared to be limited by precipitation and temperature. While topo-climatic associations primarily were strong and hinged on elevation, these associations were not strongly associated with fuel accumulations. Topo-climatic relationships to forest fuel deposition, decomposition and change over time are important components in wildland fuels prediction. With an ever-increasing need for accurate fuel estimation techniques, researchers should place greater importance on wildland fuel dynamics.
