High severity fire promotes a more flammable eucalypt forest structure

2021 ◽  
Author(s):  
James W. Barker ◽  
Owen F. Price ◽  
Meaghan E. Jenkins
Keyword(s):  
Forest Structure ◽  
High Severity ◽  
Eucalypt Forest

Is the END (emulation of natural disturbance) a new beginning? A critical analysis of the use of fire regimes as the basis of forest ecosystem management with examples from the Canadian western Cordillera

2016 ◽  
Vol 24 (3) ◽  
pp. 233-243 ◽  
Author(s):  
Chris Stockdale ◽  
Mike Flannigan ◽  
Ellen Macdonald
Keyword(s):  
Forest Management ◽  
Ecosystem Management ◽  
Forest Structure ◽  
Fire Regime ◽  
Natural Disturbance ◽  
Fire Regimes ◽  
Disturbance Regime ◽  
Ecological Processes ◽  
High Severity ◽  
Management Actions

As our view of disturbances such as wildfire has shifted from prevention to recognizing their ecological necessity, so too forest management has evolved from timber-focused even-aged management to more holistic paradigms like ecosystem-based management. Emulation of natural disturbance (END) is a variant of ecosystem management that recognizes the importance of disturbance for maintaining ecological integrity. For END to be a successful model for forest management we need to describe disturbance regimes and implement management actions that emulate them, in turn achieving our objectives for forest structure and function. We review the different components of fire regimes (cause, frequency, extent, timing, and magnitude), we describe low-, mixed-, and high-severity fire regimes, and we discuss key issues related to describing these regimes. When characterizing fire regimes, different methods and spatial and temporal extents result in wide variation of estimates for different fire regime components. Comparing studies is difficult as few measure the same components; some methods are based on the assumption of a high-severity fire regime and are not suited to detecting mixed- or low-severity regimes, which are critical to END management, as this would affect retention in harvested areas. We outline some difficulties with using fire regimes as coarse filters for forest management, including (i) not fully understanding the interactions between fire and other disturbance agents, (ii) assuming that fire is strictly an exogenous disturbance agent that exerts top-down control of forest structure while ignoring numerous endogenous and bottom-up feedbacks on fire effects, and (iii) assuming by only replicating natural disturbance patterns we preserve ecological processes and vital ecosystem components. Even with a good understanding of a fire regime, we would still be challenged with choosing the temporal and spatial scope for the disturbance regime we are trying to emulate. We cannot yet define forest conditions that will arise from variations in disturbance regime; this then limits our ability to implement management actions that will achieve those conditions. We end by highlighting some important knowledge gaps about fire regimes and how the END model could be strengthened to achieve a more sustainable form of forest management.

Stand Structure and the Influence of Overwood on Regeneration in Tropical Eucalypt Forest on Melville-Island

1992 ◽  
Vol 40 (3) ◽  
pp. 335 ◽  
Author(s):  
RJ Fensham ◽  
DMJS Bowman
Keyword(s):  
Forest Structure ◽  
Tree Species ◽  
Stand Structure ◽  
Root Systems ◽  
Ground Layer ◽  
Significant Response ◽  
Life Stages ◽  
Relative Dominance ◽  
Eucalypt Forest ◽  
Tap Root

The stand structure of tree species in tropical eucalypt forest on Melville Island reveals a mass of short woody sprouts in the ground layer and low numbers of sapling eucalypts. The growth of the woody sprouts showed no significant response in the first 2 years after release from overwood competition. However, eucalypts are released in response to overwood removal, after 2-5 years, although investigations of old clear-felled blocks indicated that this response is not consistent. The initiation of saplings may be related to the size of the lignotuber and the presence of a tap root for some species. It is suggested that the accession of saplings may be limited by the degradation of root systems by termite herbivory. Using assumptions regarding longevity of life stages, it is demonstrated that the forest structure of the study site can be perpetuated undercurrent conditions despite indications that the relative dominance of the forest eucalypt species will shift.

Fuel treatments change forest structure and spatial patterns of fire severity, Arizona, U.S.A.

2019 ◽  
Vol 49 (11) ◽  
pp. 1357-1370
Author(s):  
Morris C. Johnson ◽  
Maureen C. Kennedy ◽  
Sarah Harrison
Keyword(s):  
Forest Structure ◽  
Fire Severity ◽  
Fire Effects ◽  
Wildlife Habitat ◽  
Fuel Treatments ◽  
Treatment Unit ◽  
Fuel Treatment ◽  
Treated Area ◽  
High Severity ◽  
Management Objectives

Fuel reduction treatments are often designed to achieve multiple resource management objectives in addition to reducing potential fire hazard. In the White Mountains of Arizona State (U.S.A.), the 2014 San Juan Fire burned through several thinning prescriptions designed to achieve wildlife habitat objectives. Many studies have documented reduced fire severity for a standard set of fuel treatments, but the range of variability in fuel treatment effectiveness for alternative treatment designs is poorly understood. We used nonlinear mixed-effects modeling to estimate the distance into the treated area at which fire severity decreases and randomization tests to compare forest structure. High-severity fire effects were estimated to be reduced between 114 m and 345 m into the treated area. The range of variability in observed-distance high-severity fire effects persist into the treated area and, in conjunction with estimated relationships between posttreatment forest structure and severity, can inform the design of alternative fuel treatment prescriptions with various target prescriptions. We found that as cover was maintained in a treatment unit for wildlife habitat, the size of the fuel treatment necessary to observe a reduction in severity needs to be larger. Our study will inform decision makers on the size of treatments required to accomplish management objectives.

scholarly journals Assessing Legacy Effects of Wildfires on the Crown Structure of Fire-Tolerant Eucalypt Trees Using Airborne Lidar Data

2019 ◽  
Author(s):  
Yogendra K. Karna ◽  
Trent D. Penman ◽  
Cristina Aponte ◽  
Lauren T. Bennett
Keyword(s):  
Airborne Lidar ◽  
Lidar Data ◽  
Legacy Effects ◽  
Individual Tree ◽  
Tree Crowns ◽  
High Severity ◽  
Eucalypt Forest ◽  
Crown Width ◽  
In Fire ◽  
Airborne Lidar Data

Fire-tolerant eucalypt forests of south eastern Australia are assumed to fully recover from even the most intense fires but surprisingly very few studies have quantitatively assessed that recovery. Accurate assessment of horizontal and vertical attributes of tree crowns after fire is essential to understand the fire’s legacy effects on tree growth and on forest structure. In this study, we quantitatively assessed individual tree crowns 8.5 years after a 2009 wildfire that burnt extensive areas of eucalypt forest in temperate Australia. We used airborne lidar data validated with field measurements to estimate multiple metrics that quantified the cover, density, and vertical distribution of individual-tree crowns in 51 plots of 0.05 ha in fire-tolerant eucalypt forest across four wildfire severity types (unburnt, low, moderate, high). Significant differences in the field-assessed mean height of fire scarring as a proportion of tree height, and in the proportions of trees with epicormic (stem) resprouts were consistent with the gradation in fire severity. Linear mixed-effects models indicated persistent effects of both moderate- and high-severity wildfire on tree crown architecture. Trees at high-severity sites had significantly less crown projection area and live crown width as a proportion of total crown width than those at unburnt and low-severity sites. Significant differences in lidar-based metrics (crown cover, evenness, leaf area density profiles) indicated that tree crowns at moderate- and high-severity sites were comparatively narrow and more evenly distributed down the tree stem. These conical-shaped crowns contrasted sharply with the rounded crowns of trees at unburnt and low-severity sites, and likely influenced both tree productivity and the accuracy of biomass allometric equations for nearly a decade after the fire. Our data provide a clear example of the utility of airborne lidar data for quantifying the impacts of disturbances at the scale of individual trees. Quantified effects of contrasting fire severities on the structure of resprouter tree crowns provide a strong basis for interpreting post-fire patterns in forest canopies and vegetation profiles in lidar and other remotely-sensed data at larger scales.

Impact of high-severity fire in a Tasmanian dry eucalypt forest

2016 ◽  
Vol 64 (3) ◽  
pp. 193 ◽  
Author(s):  
Lynda D. Prior ◽  
Grant J. Williamson ◽  
David M. J. S. Bowman
Keyword(s):  
Plant Mortality ◽  
Dry Forests ◽  
Obligate Seeder ◽  
High Severity ◽  
Fuel Loads ◽  
Eucalypt Forest ◽  
Whole Plant ◽  
Eucalypt Forests ◽  
Wet Forests

Dry eucalypt forests are believed to be highly fire tolerant, but their response to fire is not well quantified. We measured the effect of high-severity fires in dry eucalypt forest in the Tasmanian Midlands, the driest region on the island. We compared stand structures and fuel loads in long-unburnt (>15 years since fire) and recently burnt (<5 years since fire) sites that had been completely defoliated. Even in unburnt plots, 37% of eucalypt stems and 56% of acacia stems ≥5 cm in diameter were dead, possibly because of antecedent drought. The density of live eucalypt stems was 37% lower overall in burnt than in unburnt plots, compared with 78% lower for acacias. Whole-plant mortality caused by fire was estimated at 25% for eucalypt trees and 33% for acacias. Fire stimulated establishment of both eucalypt and acacia seedlings, although some seedlings and saplings were present in long-unburnt plots. The present study confirmed that eucalypts in dry forests are more tolerant of fire than the obligate seeder eucalypts in wet forests. However, there were few live mature stems remaining in some burnt plots, suggesting that dry eucalypt forests could be vulnerable to increasingly frequent, severe fires.

Impacts of increased fire frequency and aridity on eucalypt forest structure, biomass and composition in southwest Australia

2009 ◽  
Vol 258 (9) ◽  
pp. 2136-2142 ◽  
Author(s):  
Burak K. Pekin ◽  
Matthias M. Boer ◽  
Craig Macfarlane ◽  
Pauline F. Grierson
Keyword(s):  
Forest Structure ◽  
Fire Frequency ◽  
Eucalypt Forest ◽  
Southwest Australia

Impact of a moderate/high-severity prescribed eucalypt forest fire on soil phosphorous stocks and partitioning

2018 ◽  
Vol 621 ◽  
pp. 1103-1114 ◽  
Author(s):  
Cristina Santín ◽  
Xose L. Otero ◽  
Stefan H. Doerr ◽  
Chris J. Chafer
Keyword(s):  
Forest Fire ◽  
High Severity ◽  
Eucalypt Forest ◽  
Soil Phosphorous

High-severity fire reduces early successional boreal larch forest aboveground productivity by shifting stand density in north-eastern China

2016 ◽  
Vol 25 (8) ◽  
pp. 861 ◽  
Author(s):  
Wen H. Cai ◽  
Jian Yang
Keyword(s):  
Carbon Storage ◽  
Forest Structure ◽  
Forest Regeneration ◽  
Fire Severity ◽  
Eastern China ◽  
Larch Forest ◽  
Understorey Vegetation ◽  
High Severity ◽  
Sapling Density ◽  
Tree Sapling

Climate warming is predicted to increase fire activity across the Eurasian boreal larch forest in the 21st century, which could have serious consequences on carbon storage. Quantifying the effects of fire disturbance on forest structure and aboveground net primary productivity (ANPP) could aid in our ability to predict future carbon storage on a regional and biome level. In this study, we examined the spatial heterogeneity of forest structure and ANPP on sites of varying fire severity and topographic position in a recently burned landscape in the Great Xing’an Mountains, China. Results indicated that after 11 years of vegetation regrowth, fire severity significantly affected forest regeneration ANPP. Spatial heterogeneities in forest regeneration ANPP were explained by both tree sapling density and understorey vegetation abundance. Although understorey vegetation productivity on average contributed 50% of total ANPP after fire, the increase in understorey productivity with fire severity could not offset the decrease in tree productivity in severely burned stands where tree sapling density was limited. Our results suggest that high-severity fire can decrease forest regeneration ANPP by altering forest structure in the early post-fire successional stage and that this shift in forest structure may influence future forest productivity trajectories over an extended period.

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