Numerical Investigation of Aggregated Fuel Spatial Pattern Impacts on Fire Behavior

Abstract

Landscape heterogeneity shapes species distributions, interactions, and fluctuations. Historically, in dry forest ecosystems, low canopy cover and heterogeneous fuel patterns often moderated disturbances like fire. Over the last century, however, increases in canopy cover and more homogeneous patterns have contributed to altered fire regimes with higher fire severity. Fire management strategies emphasize increasing within-stand heterogeneity with aggregated fuel patterns to alter potential fire behavior. Yet, little is known about how such patterns may affect fire behavior, or how sensitive fire behavior changes from fuel patterns are to winds and canopy cover. Here, we used a physics-based fire behavior model, FIRETEC, to explore the impacts of spatially aggregated fuel patterns on the mean and variability of stand-level fire behavior, and to test sensitivity of these effects to wind and canopy cover. Qualitative and quantitative approaches suggest that spatial fuel patterns can significantly affect fire behavior. Based on our results we propose three hypotheses: (1) aggregated spatial fuel patterns primarily affect fire behavior by increasing variability; (2) this variability should increase with spatial scale of aggregation; and (3) fire behavior sensitivity to spatial pattern effects should be more pronounced under moderate wind and fuel conditions.

Severe fire weather and intensive forest management increase fire severity in a multi‐ownership landscape

“…Fine‐scale spatial patterns of fuels can significantly alter fire behavior, and the effects of spatial patterns on fire behavior may increase with the spatial scale of heterogeneity (Parsons et al. ), which would likely be the case in O&C Lands due to the large scale checkerboard spatial pattern of ownership types.…”

“…In contrast, public forests were dominated by older forests that tend to have greater variability in both tree size and spatial pattern vs. plantations (Naficy et al 2010), arising from variable natural regeneration (Donato et al 2011), post-disturbance biological legacies (Seidl et al 2014), and developmental processes in later stages of stand development (Franklin et al 2002). Fine-scale spatial patterns of fuels can significantly alter fire behavior, and the effects of spatial patterns on fire behavior may increase with the spatial scale of heterogeneity (Parsons et al 2017), which would likely be the case in O&C Lands due to the large scale checkerboard spatial pattern of ownership types.…”

Re‐evaluating pattern and process to understand resilience in transitional mixed conifer forests

“…, Parsons et al. ). Analyses of GLO data have generally determined that mixed conifer forests in the Lake States were historically lower density, more open forests (Bolliger et al.…”

“…Frequent low-intensity fires in pine forests are often associated with lower tree densities, higher proportions of multi-cohort stands, and greater within-stand spatial variability including aggregated tree patterns as compared to fire-excluded forests (Drobyshev et al 2008, Larson and Churchill 2012, Knapp et al 2017. One of the most important roles of heterogeneity in forest structure is in moderating and regulating disturbances such as fire (Parsons et al 2017). Aggregated spatial patterns modify fire spread and intensity of subsequent fires, fostering variability in fire effects (Knapp and Keeley 2006, S anchez Meador et al 2009, Parsons et al 2017).…”

“…One of the most important roles of heterogeneity in forest structure is in moderating and regulating disturbances such as fire (Parsons et al 2017). Aggregated spatial patterns modify fire spread and intensity of subsequent fires, fostering variability in fire effects (Knapp and Keeley 2006, S anchez Meador et al 2009, Parsons et al 2017).…”