scholarly journals Forest Structure Drives Fuel Moisture Response across Alternative Forest States

Fire ◽  
2021 ◽  
Vol 4 (3) ◽  
pp. 48
Author(s):  
Tegan P. Brown ◽  
Assaf Inbar ◽  
Thomas J. Duff ◽  
Jamie Burton ◽  
Philip J. Noske ◽  
...  
Keyword(s):  
Climate Warming ◽  
Forest Structure ◽  
Forest Type ◽  
Fire Frequency ◽  
Substantial Improvement ◽  
Fuel Moisture ◽  
Alternative States ◽  
High Productivity ◽  
Vegetation Feedbacks ◽  
Fire Feedbacks

Climate warming is expected to increase fire frequency in many productive obligate seeder forests, where repeated high-intensity fire can initiate stand conversion to alternative states with contrasting structure. These vegetation–fire interactions may modify the direct effects of climate warming on the microclimatic conditions that control dead fuel moisture content (FMC), which regulates fire activity in these high-productivity systems. However, despite the well-established role of forest canopies in buffering microclimate, the interaction of FMC, alternative forest states and their role in vegetation–fire feedbacks remain poorly understood. We tested the hypothesis that FMC dynamics across alternative states would vary to an extent meaningful for fire and that FMC differences would be attributable to forest structural variability, with important implications for fire-vegetation feedbacks. FMC was monitored at seven alternative state forested sites that were similar in all aspects except forest type and structure, and two proximate open-weather stations across the Central Highlands in Victoria, Australia. We developed two generalised additive mixed models (GAMMs) using daily independent and autoregressive (i.e., lagged) input data to test the importance of site properties, including lidar-derived forest structure, in predicting FMC from open weather. There were distinct differences in fuel availability (days when FMC < 16%, dry enough to sustain fire) leading to positive and negative fire–vegetation feedbacks across alternative forest states. Both the independent (r2 = 0.551) and autoregressive (r2 = 0.936) models ably predicted FMC from open weather. However, substantial improvement between models when lagged inputs were included demonstrates nonindependence of the automated fuel sticks at the daily level and that understanding the effects of temporal buffering in wet forests is critical to estimating FMC. We observed significant random effects (an analogue for forest structure effects) in both models (p < 0.001), which correlated with forest density metrics such as light penetration index (LPI). This study demonstrates the importance of forest structure in estimating FMC and that across alternative forest states, differences in fuel availability drive vegetation–fire feedbacks with important implications for forest flammability.

Wildfires in the southern Canadian Rocky Mountains and their relationship to mid-tropospheric anomalies

1993 ◽  
Vol 23 (6) ◽  
pp. 1213-1222 ◽  
Author(s):  
E.A. Johnson ◽  
D.R. Wowchuk
Keyword(s):  
North America ◽  
Rocky Mountains ◽  
Large Scale ◽  
Fire Frequency ◽  
Fuel Moisture ◽  
Large Fire ◽  
Canadian Rocky Mountains ◽  
Area Burned ◽  
Upper Level ◽  
Moisture Conditions

In this paper we present evidence for a large-scale (synoptic-scale) meteorological mechanism controlling the fire frequency in the southern Canadian Rocky Mountains. This large-scale control may explain the similarity in average fire frequencies and timing of change in average fire frequencies for the southern Canadian Rocky Mountains. Over the last 86 years the size distribution of fires (annual area burned) in the southern Canadian Rockies was distinctly bimodal, with a separation between small- and large-fire years at approximately 10–25 ha annual area burned. During the last 35 years, large-fire years had significantly lower fuel moisture conditions and many mid-tropospheric surface-blocking events (high-pressure upper level ridges) during July and August (the period of greatest fire activity). Small-fire years in this period exhibited significantly higher fuel moisture conditions and fewer persistent mid-tropospheric surface-blocking events during July and August. Mid-tropospheric surface-blocking events during large-fire years were teleconnected (spatially and temporally correlated in 50 kPa heights) to upper level troughs in the North Pacific and eastern North America. This relationship takes the form of the positive mode of the Pacific North America pattern.

A dendrochronological analysis of a disturbance–succession model for oak–pine forests of the Appalachian Mountains, USA

2010 ◽  
Vol 40 (7) ◽  
pp. 1373-1385 ◽  
Author(s):  
Patrick H. Brose ◽  
Thomas A. Waldrop
Keyword(s):  
Forest Type ◽  
Fire Suppression ◽  
Appalachian Mountains ◽  
Fire Frequency ◽  
Pine Forests ◽  
Ice Storms ◽  
Pine Regeneration ◽  
Fire Disturbances ◽  
Pinus Spp ◽  
Succession Model

Disturbance–succession models describe the relationship between the disturbance regime and the dominant tree species of a forest type. Such models are useful tools in ecosystem management and restoration, provided they are accurate. We tested a disturbance–succession model for the oak–pine ( Quercus spp. – Pinus spp.) forests of the Appalachian Mountains region using dendrochronological techniques. In this model, fire promotes pines, while fire suppression, bark beetle outbreaks, and ice storms encourage oaks. We analyzed nine Appalachian oak–pine stands for species establishment dates and the occurrence of fires and canopy disturbances. We found no evidence that fire preferentially promoted the establishment of pine more than oak, nor did we find any evidence that canopy disturbances or periods of no disturbance facilitated the establishment of oak more than pine. Rather, we found that both species groups originated primarily after combined canopy and fire disturbances, and reduction of fire frequency and scope coincided with the cessation of successful oak and pine regeneration. Currently, heath shrubs are slowly dominating these stands, so we present a revised disturbance–succession model for land managers struggling to manage or restore oak–pine forests containing a dense ericaceous understory.

scholarly journals Vascular Epiphytic Diversity in a Neotropical Transition Zone Is Driven by Environmental and Structural Heterogeneity

2019 ◽  
Vol 12 ◽  
pp. 194008291988220 ◽  
Author(s):  
Edilia de la Rosa-Manzano ◽  
Glenda Mendieta-Leiva ◽  
Antonio Guerra-Pérez ◽  
Karla María Aguilar-Dorantes ◽  
Leonardo Uriel Arellano-Méndez ◽  
...  
Keyword(s):  
Species Richness ◽  
Transition Zone ◽  
Forest Structure ◽  
Forest Type ◽  
Species Turnover ◽  
Cloud Forest ◽  
Size Variation ◽  
Alpha Diversity ◽  
Forest Types ◽  
Semideciduous Forest

Vascular epiphytes contribute significantly to tropical diversity. Research on the factors that determine vascular epiphytic diversity and composition in tropical areas is flourishing. However, these factors are entirely unknown in tropical-temperate transition zones, which represent the distribution limit of several epiphytic species. We assessed the degree to which climatic and structural variables determine the diversity of vascular epiphytic assemblages (VEAs) in a transition zone in Mexico: the El Cielo Biosphere Reserve. We found 12,103 epiphytic individuals belonging to 30 species and 15 genera along a climatic gradient from 300 to 2,000 m a.s.l. Bromeliaceae and Orchidaceae were the most species-rich families. Forests along the windward slope of the Sierra Madre Oriental (semideciduous forest and tropical montane cloud forest) had higher species richness than forests along the leeward slope (pine-oak forest and submontane scrub). Species richness was largely determined by seasonality and, to a lesser degree, by forest structure, whereas abundance was mainly determined by host tree size. Variation in VEAs composition was largely explained by climatic variables, whereas forest structure was not as important. VEAs differed among forest types and slopes in terms of taxonomic and functional composition. For example, certain bromeliad indicator species reflected differences between slopes. Although within-tree epiphytic species richness (alpha diversity) was low in this transition zone relative to other habitats, species turnover among forest types (beta diversity) was high. These findings suggest that each forest type makes a unique and important contribution to epiphytic diversity in this transition zone.

scholarly journals Dispersal limitation and fire feedbacks maintain mesic savannas in Madagascar

2020 ◽  
Author(s):  
Nikunj Goel ◽  
Erik Van Vleck ◽  
Julie C. Aleman ◽  
A. Carla Staver
Keyword(s):  
Dispersal Limitation ◽  
Central Plateau ◽  
Forest Expansion ◽  
Phylogeographic Analysis ◽  
Vegetation Feedbacks ◽  
Wide Range ◽  
Limited Dispersal ◽  
Lowland Forests ◽  
Forest Boundary ◽  
Fire Feedbacks

AbstractMadagascar is regarded by some as one of the most degraded landscapes on Earth, with estimates suggesting that 90% of forests have been lost to indigenous Tavy farming. However, the extent of this degradation has been challenged: paleoecological data, phylogeographic analysis, and species diversity maps indicate that pyrogenic savannas in Central Madagascar pre-date human arrival, even though rainfall is sufficient to allow forest expansion into Central Madagascar. These observations raise a question—if savannas in Madagascar are not anthropogenic, how then are they maintained in regions where the climate can support forest? Observation reveals that the savanna-forest boundary coincides with a dispersal barrier—the escarpment of the Central Plateau. Using a stepping-stone model, we show that in a limited dispersal landscape, a stable savanna-forest boundary can form due to fire-vegetation feedbacks. This novel phenomenon, referred to as range pinning, could explain why eastern lowland forests have not expanded into the mesic savannas of the Central Highlands. This work challenges the view that highland savannas in Madagascar are derived by human-lit fires and, more importantly, suggests that partial dispersal barriers and strong non-linear feedbacks can pin biogeographical boundaries over a wide range of environmental conditions, providing a temporary buffer against climate change.

scholarly journals Evaluating Model Predictions of Fire Induced Tree Mortality Using Wildfire-Affected Forest Inventory Measurements

Forests ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 958 ◽  
Author(s):  
Jason S. Barker ◽  
Jeremy S. Fried ◽  
Andrew N. Gray
Keyword(s):  
Wind Speed ◽  
Forest Inventory ◽  
Tree Mortality ◽  
Forest Type ◽  
Flame Length ◽  
Weather Data ◽  
Fuel Moisture ◽  
Forest Types ◽  
Mean Error ◽  
Wide Range

Forest land managers rely on predictions of tree mortality generated from fire behavior models to identify stands for post-fire salvage and to design fuel reduction treatments that reduce mortality. A key challenge in improving the accuracy of these predictions is selecting appropriate wind and fuel moisture inputs. Our objective was to evaluate postfire mortality predictions using the Forest Vegetation Simulator Fire and Fuels Extension (FVS-FFE) to determine if using representative fire-weather data would improve prediction accuracy over two default weather scenarios. We used pre- and post-fire measurements from 342 stands on forest inventory plots, representing a wide range of vegetation types affected by wildfire in California, Oregon, and Washington. Our representative weather scenarios were created by using data from local weather stations for the time each stand was believed to have burned. The accuracy of predicted mortality (percent basal area) with different weather scenarios was evaluated for all stands, by forest type group, and by major tree species using mean error, mean absolute error (MAE), and root mean square error (RMSE). One of the representative weather scenarios, Mean Wind, had the lowest mean error (4%) in predicted mortality, but performed poorly in some forest types, which contributed to a relatively high RMSE of 48% across all stands. Driven in large part by over-prediction of modelled flame length on steeper slopes, the greatest over-prediction mortality errors arose in the scenarios with higher winds and lower fuel moisture. Our results also indicated that fuel moisture was a stronger influence on post-fire mortality than wind speed. Our results suggest that using representative weather can improve accuracy of mortality predictions when attempting to model over a wide range of forest types. Focusing simulations exclusively on extreme conditions, especially with regard to wind speed, may lead to over-prediction of tree mortality from fire.

Occurrence of wildfire in the northern Great Lakes Region: Effects of land cover and land ownership assessed at multiple scales

2001 ◽  
Vol 10 (2) ◽  
pp. 145 ◽  
Author(s):  
Jeffrey A. Cardille ◽  
Stephen J. Ventura
Keyword(s):  
Land Cover ◽  
Multiple Scales ◽  
Forest Type ◽  
Spatial Scales ◽  
Fire Frequency ◽  
Usda Forest Service ◽  
Data Set ◽  
Spatially Explicit Data ◽  
In Fire ◽  
Relationship Of

Risk of wildfire has become a major concern for forest managers, particularly where humans live in close proximity to forests. To date, there has been no comprehensive analysis of contemporary wildfire patterns or the influence of landscape-level factors in the northern, largely forested parts of Minnesota, Wisconsin and Michigan, USA. Using electronic archives from the USDA Forest Service and from the Departments of Natural Resources of Minnesota, Wisconsin, and Michigan, we created and analysed a new, spatially explicit data set: the Lake States Fire Database. Most of the 18 514 fires during 1985—1995 were smaller than 4 ha, although there were 746 fires larger than 41 ha. Most fires were caused by debris burning and incendiary activity. There was considerable interannual variability in fire counts; over 80% of fires occurred in March, April, or May. We analysed the relationship of land cover and ownership to fires at two different fire size thresholds across four gridded spatial scales. Fires were more likely on non-forest than within forests; this was also true if considering only fires larger than 41 ha. An area of National or State Forest was less likely to have experienced a fire during the study period than was a forest of equal size outside National or State Forest boundaries. Large fires were less likely in State Forests, although they were neither more nor less likely to have occurred on National Forests. Fire frequency also varied significantly by forest type. All results were extremely consistent across analysis resolutions, indicating robust relationships.

A process-based model of fine fuel moisture

2006 ◽  
Vol 15 (2) ◽  
pp. 155 ◽  
Author(s):  
Stuart Matthews
Keyword(s):  
Forest Type ◽  
Model Parameters ◽  
Fuel Moisture ◽  
Litter Layer ◽  
Wetting And Drying ◽  
Rainy Period ◽  
Dry Conditions ◽  
Fuel Moisture Content ◽  
Complete Process ◽  
Made In

This paper presents the first complete process-based model for fuel moisture in the litter layer. The model predicts fuel moisture by modelling the energy and water budgets of the litter, intercepted precipitation, and air spaces in the litter. The model was tested against measurements of fuel moisture from two sets of field observations, one made in Eucalyptus mallee-heath under dry conditions and the other during a rainy period in Eucalyptus obliqua forest. The model correctly predicted minimum and maximum fuel moisture content and the timing of minima and maxima in the mallee-heath. Under wet conditions, wetting and drying of the litter profile were correctly predicted but wetting of the surface litter was over-predicted. The structure of the model and the dependence of predictions on model parameters were examined using sensitivity and parameter estimation studies. The results indicated that it should be possible to adapt the model to any forest type by specifying a limited number of parameters. A need for further experimental research on the wetting of litter during rain was also identified.

scholarly journals A meta-analysis on the impacts of partial cutting on forest structure and carbon storage

2013 ◽  
Vol 10 (1) ◽  
pp. 787-813 ◽  
Author(s):  
D. Zhou ◽  
S. Q. Zhao ◽  
S. Liu ◽  
J. Oeding
Keyword(s):  
Forest Structure ◽  
Forest Floor ◽  
Management Practices ◽  
Forest Type ◽  
Meta Analysis ◽  
Mineral Soil ◽  
Basal Area ◽  
Partial Cutting ◽  
Soil C ◽  
C Storage

Abstract. Partial cutting, which removes some individual trees from a forest, is one of the major and widespread forest management practices that can significantly alter both forest structure and carbon (C) storage. Using 746 observations from 82 publications, we synthesized the impacts of partial cutting on three variables associated with forest structure (i.e. mean annual growth of diameter at breast height (DBH), basal area (BA), and volume) and four variables related to various C stock components (i.e. aboveground biomass C (AGBC), understory C, forest floor C, and mineral soil C). Results shows that the growth of DBH elevated by 112% after partial cutting, compared to the uncut control, while stand BA and volume reduced immediately by 34% and 29%, respectively. On average, partial cutting reduced AGBC by 43%, increased understory C storage by 392%, but did not show significant effects on C storages on forest floor and in mineral soil. All the effects on DBH growth, stand BA, volume, and AGBC intensified linearly with cutting intensity (CI) and decreased linearly with the number of recovery years (RY). In addition to the strong impacts of CI and RY, other factors such as climate zone and forest type also affected forest responses to partial cutting. The data assembled in this synthesis were not sufficient to determine how long it would take for a complete recovery after cutting because long-term experiments were rare. Future efforts should be tailored to increase the duration of the experiments and balance geographic locations of field studies.

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