Landscape dynamics in crown fire ecosystems

Abstract

Crown fires create broad-scale patterns in vegetation by producing a patch mosaic of stand age classes, but the spread and behavior of crown fires also may be constrained by spatial patterns in terrain and fuels across the landscape. In this review, we address the implications of landscape heterogeneity for crown fire behavior and the ecological effects of crown fires over large areas. We suggest that fine-scale mechanisms of fire spread can be extrapolated to make broad-scale predictions of landscape pattern by coupling the knowledge obtained from mechanistic and empirical fire behavior models with spatially-explicit probabilistic models of fire spread. Climatic conditions exert a dominant control over crown fire behavior and spread, but topographic and physiographic features in the landscape and the spatial arrangement and types of fuels have a strong influence on fire spread, especially when burning conditions (e.g., fuel moisture and wind) are not extreme.General trends in crown fire regimes and stand age class distributions can be observed across continental, latitudinal, and elevational gradients. Crown fires are more frequent in regions having more frequent and/or severe droughts, and younger stands tend to dominate these landscapes. Landscapes dominated by crown fires appear tobe nonequilibrium systems. This nonequilibrium condition presents a significant challenge to land managers, particularly when the implications of potential changes in the global climate are considered. Potential changes in the global climate may alter not only the frequency of crown fires but also their severity. Crown fires rarely consume the entire forest, and the spatial heterogeneity of burn severity patterns creates a wide range of local effects and is likely to influence plant reestablishment as well as many other ecological processes. Increased knowledge of ecological processes at regional scales and the effects of landscape pattern on fire dynamics should provide insight into our understanding of the behavior and consequences of crown fires.

Topography affected landscape fire history patterns in southern Arizona, USA

“…Landscapes are heterogeneous areas composed of multiple stands and flammability varies from stand to stand across the landscape. As a result, landscape fire spread is usually restricted to interconnected flammable stands, meaning fires do not usually spread to areas isolated by non-flammable fuels, i.e., ''fire barriers'' (Turner and Romme, 1994;Taylor, 2000). Hence, within a landscape, fire spread and extent are a function of the proportion and arrangement of flammable fuel (Turner et al, 1989).…”

Wildfires, complexity, and highly optimized tolerance

“…However, this type of extrapolation is not appropriate using power law fits to the noncumulative probability density, as some have suggested (27,28,41). Very different factors can drive smaller versus larger wildfires (25,40,42,43), resulting in exponent variations in the power law statistics of wildfire catalogs (44,45). A large size cutoff (i.e., L in Eq.…”

Inorganic nitrogen availability after severe stand-replacing fire in the Greater Yellowstone ecosystem

“…Natural stand-replacing fire regimes (infrequent, high-severity fires that kill the canopy trees) dominate the extensive boreal forests of North America, Fennoscandia, and Asia and many coniferous forests of the Northern Rocky Mountains (6). Fire return intervals are long, ranging from Ϸ60 yr in jack pine (Pinus banksiana) to several centuries in some spruce-fir (Picea-Abies) communities.…”