Search

Climate change effects on forested ecosystems worldwide include increases in drought-related mortality, changes to disturbance regimes and shifts in species distributions. Such climate-induced changes will alter the outcomes of current management strategies, complicating the selection of appropriate strategies to promote forest resilience. We modelled forest growth in ponderosa pine forests that burned in Arizona's 2002 Rodeo-Chediski Fire using the Forest Vegetation Simulator Climate Extension, where initial stand structures were defined by pre-fire treatment and fire severity. Under extreme climate change, existing forests persisted for several decades, but shifted towards pinyon-juniper woodlands by 2104. Under milder scenarios, pine persisted with reduced growth. Prescribed burning at 10- and 20-year intervals resulted in basal areas within the historical range of variability (HRV) in low-severity sites that were initially dominated by smaller diameter trees; but in sites initially dominated by larger trees, the range was consistently exceeded. For high-severity sites, prescribed fire was too frequent to reach the HRV's minimum basal area. Alternatively, for all stands under milder scenarios, uneven-aged management resulted in basal areas within the HRV because of its inherent flexibility to manipulate forest structures. These results emphasise the importance of flexible approaches to management in a changing climate. [ABSTRACT FROM AUTHOR]

Increasing size and severity of wildfires have led to an interest in the effectiveness of forest fuels treatments on reducing fire severity and post-wildfire fuels. Our objective was to contrast stand structure and surface fuel loadings on treated and untreated sites within the 2002 Rodeo-Chediski Fire area. Data from 140 plots on seven paired treated-untreated sites indicated that pre-wildfire treatments reduced fire severity compared with untreated sites. In 2011, coarse woody debris loading (woody material >7.62 cm in diameter) was 257% higher and fine woody debris (woody material <7.62 cm) was 152% higher on untreated sites than on treated sites. Yet, in spite of higher levels of coarse woody debris on untreated sites, loadings did not exceed recommended ranges based on published literature and many treated sites fell below recommendations. By 2011, basal area and stand density on treated sites and stand density on untreated sites met management guidelines for ponderosa pine forests, but untreated sites had basal areas well below recommendations. Snags declined over this period and only three plots had snags that met minimum size and density requirements for wildlife habitat by 2011. The effects of pre-wildfire treatments are long-lasting and contribute to changes in both overstorey and understorey fuel complexes. Pre-wildfire thinning and fuel reduction treatments increased tree survival compared with untreated sites following the 2002 Rodeo-Chediski Fire. A decade later, treated sites have stand basal areas that fall within target ranges for increasing resiliency to future fires. Surface fuels were within acceptable levels and are unlikely to increase substantially. [ABSTRACT FROM AUTHOR]

Abstract: Land managers are routinely applying fuel reduction treatments to mitigate the risk of severe, stand-replacing fire in ponderosa pine communities of the southwestern US. When these treatments are burned by wildfire they generally reduce fire severity, but less is known about how they influence post-wildfire vegetation recovery, as compared to pre-fire untreated areas. We re-measured existing plots on the 2002 Rodeo–Chediski Fire 8years after the wildfire to track plant community and exotic species response, as well as patterns of pine regeneration. We compared areas that experienced high- and low-severity burning, and also examined how pre-fire treatment (cutting in an uneven-aged harvesting system with prescribed fire) modified vegetation response. We detected persistent differences between low- and high-severity areas for nearly all variables measured. In high-severity areas overall understory plant cover was 40.6%, nearly three times that observed in low-severity areas; shrub cover was 18.4%, four and a half times greater than that observed in low-severity areas. We also detected significantly higher exotic forb cover in high-severity areas, although overall exotic response was generally quite low (<2%). Although this represents a slight decrease in exotic cover since the initial 2004/2005 measurements, the frequency of several exotic species did increase through time (particularly Tragopogon dubius and Verbascum thapsus). Pre-fire treatment resulted in significantly higher pine regeneration frequency in treated versus untreated areas. Within low severity areas, mean pine regeneration frequency was 0.17 in pre-fire untreated areas versus 0.06 in areas that were not treated before the fire. Within high severity burned areas, mean pine regeneration frequency was 0.67 in pre-fire treated areas, but was only 0.19 in pre-fire untreated areas. This treatment effect in high-severity areas may be linked to reduction in the overall patch size of high burn severity in pre-fire treated areas, which resulted in a more heterogeneous mixture of low and moderate severity burning in the neighborhood. This pattern decreased distance to seed source, which likely facilitated the more frequent pine regeneration observed. In addition to the well-documented benefits of fuel reduction treatments in reducing subsequent fire severity, these data suggest that even where treated areas do burn severely the size of severely burned patches is limited in extent, which is likely to have important ramifications for future reforestation and retention of foundation species. [Copyright &y& Elsevier]

Recent literature suggests that natural disasters such as wildfires often have the short-term effect of 'bringing people together' while also under some circumstances generating social conflict at the local level. Conflict has been documented particularly when social relations are disembedded by nonlocal entities and there is a perceived loss of local agency. There is less agreement about longer term impacts. We present results of a re-study of a set of communities affected by the largest wildfire in Arizona history. The re-study uses structuration theory to suggest that while local recovery has been generally very successful, vestiges of both fire-related social cohesion and conflict have survived. While some sources of post-fire conflict and cohesion have remained relatively unchanged, others have evolved. We suggest that more needs to be known about the longer term effects of large wildfire events and the role that advanced preparation for such events plays in local recovery. [ABSTRACT FROM AUTHOR]

Wildfire is becoming the focus of increasing attention. It is now realized that changes in the occurrence frequency and intensity of wildfires has important significant consequences for a variety of important problems, including atmospheric change and safety in the urban-wildland interface. One important but poorly understood aspect of wildfire behavior-pyrocumulonimbus firestorm dynamics and atmospheric impact-has a curious history of theory and observation. The 'pyroCb' is a fire-started or fire-augmented thunderstorm that in its most extreme manifestation injects huge abundances of smoke and other biomass-burning emissions into the lower stratosphere. The observed hemispheric spread of smoke and other biomass-burning emissions could have important climate consequences. PyroCbs have been spawned naturally and through anthropogenesis, and they are hypothesized as being part of the theoretical 'Nuclear nuclear winter' work. However, direct attribution of the stratospheric aerosols to the pyroCb only occurred in the last decade. Such an extreme injection by thunderstorms was previously judged to be unlikely because the extratopical tropopause is considered to be a strong barrier to convection. Two recurring themes have developed as pyroCb research unfolds. First, some 'mystery layer' events-puzzling stratospheric aerosol-layer observations-and other layers reported as volcanic aerosol, can now be explained in terms of pyroconvection. Second, pyroCb events occur surprisingly frequently, and they are likely a relevant aspect of several historic wildfires. Here we show that pyroCbs offer a plausible alternate explanation for phenomena that were previously assumed to involve volcanic aerosols in 1989-1991. In addition, we survey the Canada/U.S. fire season of 2002 and identify 17 pyroCbs, some of which are associated with newsworthy fires, such as the Hayman, Rodeo/Chediski, and Biscuit Fires. Some of these pyroCbs injected smoke into the lowermost stratosphere. [ABSTRACT FROM AUTHOR]

I provide a synthesis of the papers in the Special Issue, The Conservation and Restoration of Old Growth in Frequent-fire Forests of the American West. These papers—the product of an Old Growth Writing Workshop, held at Northern Arizona University in Flagstaff, Arizona on 18-19 April 2006 #x2014;represent the ideas of 25 workshop participants who argue for a new attitude toward managing old growth in the frequent-fire forests of the American West. Unlike the lush, old-growth rainforests of the Pacific Northwest, the dry, frequent-fire forests of the western United States evolved with surface fires that disturbed the system with such regularity that young trees were almost always killed. When saplings did survive, they grew beyond the harm of frequent surface fires and, ultimately, attained the characteristics that define old growth in these systems. This system worked well, producing old-growth trees in abundance, until the onset of Euro-American settlement in the mid- to late-19th century. The arrival of these settlers put in motion an interplay of unprecedented social, political, economic, and ecological forces (e.g., removal of Native Americans and their fire-based land management systems, overgrazing of the understory, aggressive logging, establishment of federal land management agencies, implementation of a federal fire suppression policy). These activities have culminated in 1) overly dense forested ecosystems that are now on the verge of collapse because of catastrophic fires (i.e., crown fire at the landscape level; the Rodeo-Chediski Fire) and insect outbreaks, 2) the emergence of conservation-minded environmental legislation and policy, and 3) greater levels of interaction between citizens, federal agencies, and fire-prone landscapes. Recognizing the tenuous ecological situation of these forests, restoration ecologists, foresters, and others have developed ways to return historic ecological processes and lower tree densities to these forests. However, their efforts are not without challenges, including working with communities and citizens, serving as a bridge between entrenched bureaucracies (i.e., federal agencies and environmental groups), balancing both ecological and economic interests, and producing new applied technologies and science-based policy to advance conservation and restoration efforts aimed at preserving and developing old growth within a healthy forest environment. [ABSTRACT FROM AUTHOR]

Provides information on the Trees for the Rim project dedicated to restoring trees and a variety of native shrubs on residential, commercial and community lands in areas damaged by the Rodeo-Chediski forest fire along Arizona's Mongollon Rim in June 2002. Objective of the program; Importance of the project according to project manager Ron Romatzke; Information on the Rodeo-Chediski fire.