554 research outputs found
Microclimate and modeled fire behavior differ between adjacent forest types in northern Portugal
Fire severity varies with forest composition and structure, reflecting
micrometeorology and the fuel complex, but their respective influences are difficult to
untangle from observation alone. We quantify the differences in fire weather between
different forest types and the resulting differences in modeled fire behavior. Collection of
in-stand weather data proceeded during two summer periods in three adjacent stands in
northern Portugal, respectively Pinus pinaster (PP), Betula alba (BA), and Chamaecyparis
lawsoniana (CL). Air temperature, relative humidity and wind speed varied respectively as
CL < PP < BA, PP < CL < BA, and CL < BA < PP. Differences between PP and the other
types were greatest during the warmest and driest hours of the day in a sequence of 10 days
with high fire danger. Estimates of daytime moisture content of fine dead fuels and fire
behavior characteristics for this period, respectively, from Behave and BehavePlus,
indicate a CL < BA < PP gradient in fire potential. High stand density in CL and BA
ensured lower wind speed and higher fuel moisture content than in PP, limiting the
likelihood of an extreme fire environment. However, regression tree analysis revealed that
the fire behavior distinction between the three forest types was primarily a function of the
surface fuel complex, and more so during extreme fire weather conditionsinfo:eu-repo/semantics/publishedVersio
Evaluating Quaking Aspen\u27s Influence on Fire Behavior
In western North America, quaking aspen (Populus tremuloides Michx.) forests have long been described as low flammability, “fireproof” forest types that are less likely to burn or burn less intensely than coniferous forests. While this assumption has been based on limited scientific research and is largely anecdotal, there is growing interest in the western U.S. to promote aspen near human developments to reduce fire risk. I investigated the available evidence for aspen forests reducing fire occurrence, behavior, and severity, and assessed possible factors that affect flammability in aspen forests to better understand when and where aspen burn, and when they do not. In the first study (Chapter 2), I conducted an extensive literature review and a survey of professionals with expertise in aspen-fire encounters to examine our current understanding of how aspen influences fire. In the second study (Chapter 3), I investigated fuel characteristics in in 80 aspen stands in Utah, U.S. that spanned gradients of tree species composition from aspen to conifer dominance and stand development stage from early to late development. I found evidence for aspen forests reducing fire occurrence, behavior, and severity under certain conditions, and results from our field campaign indicated that pure, late development aspen forests were particularly associated with lower flammability conditions. However, I also found that the aspen-fire relationship was complex; factors such as the percentage of aspen vs. conifer trees in the overstory, type and load of surface fuels, weather, and season play important roles in determining how flammable an aspen forest is. While my research supports the claim that aspen forests promote lower flammability conditions under most conditions, aspen forests are certainly not “fireproof,” and uncertainty remains regarding the future of fire in aspen under a warming and drying climate
Forest Management in a Changing Climate: Integrating Social and Biopysical Sciences to Inform Adaptive Responses to Future Uncertainty
Forests provide numerous ecological and socio-economic benefits, yet climate change is creating novel and extreme conditions that threaten forests and disrupt traditional management practices. To address future uncertainty about how to manage forests amid a rapidly changing climate, researchers have developed adaptive management strategies that move away from using historical ecological baselines as management goals. However, despite increases in adaptive forest management frameworks, there are still concerns that private woodland owners (PWOs; also known as family forest owners or non-industrial private landowners) are not adopting beneficial practices. Additionally, since tree canopies often buffer understory microclimates (i.e., fine scale variation in temperature and moisture) from macroclimate extremes that occur outside of forests, there is growing interest in how forest management can be used to target specific microclimate conditions. Therefore, in order to improve forest management planning, we need to better understand how adaptive strategies can best be implemented with PWOs, in addition to understanding mechanistic links between forest management and understory conditions.
Private woodland owners represent the largest portion of national forest ownership; however, evidence suggests there may be disconnects between their climate change perceptions and behaviors, which can limit implementation of climate-focused management. We interviewed PWOs about their views of climate change and adaptive management practices, then developed a typological framework that highlights the importance of assessing their perceptions of climate-induced threats as well as their feelings of efficacy in addressing such threats. This framework can be used when targeting communications to PWOs regarding the overlap between climate adaptive management and traditional best management practices.
Forest management operations that alter stand structure to achieve silvicultural objectives can have profound effects on understory temperature and moisture, which can in turn shape long-term stand development by promoting regeneration of certain plant species that are well suited to the microclimate conditions at a given site. We used a combination of airborne laser scanning, field-based climate data loggers, and ground-based forest measurements to demonstrate that forest structure and composition play a major role in shaping understory microclimates across spatial scales spanning the plot, stand, and landscape levels. Therefore, considering the impacts to microclimate accompanied by changes in forest structure widens the purview of forest management planning aimed at promoting adaptation and resilience to climate change.
Some silvicultural prescriptions involving prescribed fire rely on predicting understory microclimate and dead fuel moisture within a stand, which can be difficult due to high variability in these dynamic drivers of fire behavior. In this study, we used terrestrial laser scanning, field-based climate data loggers, fuel moisture sticks, and forest inventory measurements to show that forest cover buffers microclimate and increases dead fuel moisture. This research enhances fire managers’ ability to plan and implement fuel treatments by highlighting how changes in forest stand structure affect fuel availability at fine scales.
Together, these studies highlight the inherent connections between management decisions and forest resilience by considering the social factors that affect decision making as well as the biophysical interactions that occur between forest stands and climate conditions near the ground
Assessing the effect of pruning and thinning on crown fire hazard in young Atlantic maritime pine forests
Management of fuel to minimize crown fire hazard is a key challenge in Atlantic forests, particularly for pine species. However, a better understanding of effectiveness of silvicultural treatments, especially forest pruning, for hazard reduction is required. Here we evaluate pruning and thinning as two essential silvicultural treatments for timber pine forests. Data came from a network of permanent plots of young maritime pine stands in northwestern Spain. Vertical profiles of canopy bulk density were estimated for field data and simulated scenarios of pruning and thinning using individual tree biomass equations. Analyses of variance were conducted to establish the influence of each silvicultural treatment on canopy fuel variables. Results confirm the important role of both pruning and thinning in the mitigation of crown fire hazard, and that the effectiveness of the treatments is related to their intensity. Finally, models to directly estimate the vertical profile of canopy bulk density (CBD) were fitted using the Weibull probability density function and usual stand variables as regressors. The models developed include variables sensitive to pruning and thinning interventions and provide useful information to prevent extreme fire behavior through effective silvicultureWe thank the Forest Services of the Government of the Principality of Asturias for financial support and access to the forests used in this study. Funding during data analysis was provided by projects SCALyFOR (AGL2013-46028-R), GEPRIF (RTA2014-00011-C06-04), PLURIFOR (SOE1/P4/F0112 Interreg SUDOE) and FORRISK (SOE3/P2/F523 Interreg IV B SUDOE). Andrea Hevia was financially supported during fieldwork and data analysis by the Spanish Ministry of Education and Science through the FPU scholarship program (Reference AP2006-03890)S
Forest landscapes and global change: Challenges for research and management
Climate change, urban sprawl, abandonment of agriculture, intensifi cation of forestry
and agriculture, changes in energy generation and use, expansion of infrastructure
networks, habitat destruction and degradation, and other drivers and pressures
of change are occurring at increasing rates globally. They affect ecological patterns
and processes in forest landscapes and modify ecosystem services derived from
those ecosystems. Consequently, the landscapes that are rapidly changing in
response to these pressures present many new challenges to scientists and managers.
Although it is not uncommon to encounter the terms “global change” and “landscape”
together in the ecological literature, there has been no adequate global analysis of
drivers of change in forest landscapes and their ecological consequences. Providing
such an analysis is the goal of this volume: an exploration of the state of knowledge
of global changes in forested landscapes, with an emphasis on their causes and
effects, and the challenges faced by researchers and land managers who must cope
with these changes.
This book was based on the IUFRO Landscape Ecology Working Group
International Conference that took place in Bragança, Portugal, in September 2010
under the theme “Forest Landscapes and Global Change: New Frontiers in
Management, Conservation and Restoration”. The event brought together more
than 300 landscape ecologists from almost 50 countries and 5 continents, who came
to expand their knowledge and awareness of global changes in forest landscapes.
We hope that the syntheses in this book, prepared by a diverse group of scientists
who participated in the conference, will enhance the global understanding of a
range of topics relevant to change in forest landscapes and stimulate new research
to answer the questions raised by these authors.
First, we introduce the broad topic of forest landscape ecology and global change.
This is followed by chapters that identify and describe major agents of landscape
change: climate (Iverson et al.), wildfi re (Rego and Silva), and human activities
(Farinaci et al.). The next chapters address implications of change for ecosystem
services (Marta-Pedroso et al.), carbon fl uxes (Chen et al.), and biodiversity conservation
(Saura et al.). A subsequent chapter describes methodologies for detecting
and monitoring landscape changes (Gómez-Sanz et al.) and is followed by a chapter that highlights the many challenges facing forest landscape managers amidst global
change (Coulson et al.). Finally, we present a summary and a synthesis of the main
points presented in the book (Azevedo et al.). Each chapter was inspired by the
research experience of the authors, augmented by a review and synthesis of the
global scientifi c literature on relevant topics, as well as critical input from multiple
peer reviewers.
The intended audience for this book includes graduate students, educators, and
researchers in landscape ecology, conservation biology, and forestry, as well as
land-use planners and managers. We trust that the wide range of topics, addressed
from a global perspective by a geographically diverse group of contributing authors
from Europe, North America, and South America, will make this volume attractive
to a broad readership.We gratefully acknowledge the following peer reviewers who helped improve
the content of this book: Berta Martín, Bill Hargrove, Bob Keane, Colin Beier, Don
McKenzie, Eric Gustafson, Franz Gatzweiler, Geoff Henebry, Kurt Riitters, Maria
Esther Núñez, Michael Ter-Mikaelian, Tom Nudds, and Yolanda Wiersma. As well,
we thank Geoff Hart for assistance with editing and Janet Slobodien and Zachary
Romano for assistance with publishing.
We also thank FCT (the Foundation for Science and Technology, Portugal),
CIMO (the Mountain Research Centre, Portugal), and IPB (the Polytechnic Institute
of Bragança, Portugal) for their support during the preparation of this volume.info:eu-repo/semantics/publishedVersio
Comparative effects of logging and wildfire on carbon and fire dynamics in resprouting and non-resprouting eucalypt forests
The tall (\u3e30 m) eucalypt forests of south-eastern Australia are valued for their carbon storage and sequestration. However, they may also act as a carbon source given that they are prone to large wildfires and subject to commercial logging. Logging may reduce carbon stocks, but the relative losses compared to wildfire have not been quantified in many types of these forests. There is also growing evidence that logging may make carbon stocks in affected forests less resistant to fire and increase the risk of wildfire. These dynamics may also vary between eucalypt forest types. Carbon and fire dynamics in forests dominated by eucalypt species that cannot resprout new foliage after fire may be more sensitive to antecedent disturbance than the more widespread resprouting eucalypt forests. Non-resprouting eucalypt forests are often subject to stand replacing wildfires, but such a response is inherently absent in resprouting eucalypt forests. Non-resprouting eucalypt forests are also subject to clearfell logging, while logging practices in resprouting eucalypt forests are often less intense. Hence, a thorough comparative assessment of the effects of logging, wildfire and carbon dynamics across these broad forest types is needed to inform ongoing management of tall eucalypt forests.
In this thesis, I compare how logging and wildfire affect forest carbon stocks, carbon stability (the capacity for carbon stocks to persist through, and recover after likely disturbances) and the risk of fire. The effects of logging and wildfire are compared between resprouting and non-resprouting eucalypt forests. I measured above ground carbon stocks and fuel characteristics (using a terrestrial laser scanner) along approximately 80-year chronosequences of logging and wildfire. Most sites in the resprouting forest study area were subsequently burnt by a mixed severity fire during the 2019-2020 fire season, enabling me to measure the change in carbon stock associated with wildfire and how it was affected by antecedent disturbance and fire severity. I also assessed the effects of variations in fuel characteristics on the severity of the 2019-2020 wildfires. To determine the effects of logging and wildfire on fire weather conditions, I measured fire weather conditions below the canopy across approximately 70-year chronosequences of logging and wildfire in the resprouting study area
Linking community ecology and biogeography: the role of biotic interactions and abiotic gradients in shaping the structure of ant communities.
Understanding what drives variation in species diversity in space and time and limits coexistence in local communities is a main focus of community ecology and biogeography. My doctoral work aims to document patterns of ant diversity and explore the possible ecological mechanisms leading to these patterns. Elucidating the processes by which communities assemble and species coexist might help explain spatial variation in species diversity. Using a combination of manipulative experiments, broad-scale surveys, behavioral assays and phylogenetic analyses, I examine which ecological processes account for the number of species coexisting in ant communities. Ants are found in most terrestrial habitats, where they are abundant, diverse and easy to sample (Agosti et al. 2000). Hölldobler and Wilson (1990) noted that competition was the hallmark of ant ecology, and we know that ant diversity varies along environmental gradients (Kusnezov 1957). Thus ants are an ideal taxon to examine the factors shaping the structure of ecological communities and how the determinants of community structure vary in space
Modeling ecological disturbances in the Southeastern United States
Society requires better insights into how disturbances will alter the global carbon cycle. Ecosystem models help us understand the carbon cycle and make predictions about how the terrestrial land sink will change under future climate regimes. Disturbances drive ecosystem cycling, but modeling disturbances has unique challenges, particularly in incorporating heterogeneity and parameter uncertainty. In this dissertation, I explore two questions. 1) How can we capture disturbance ecology in models?, which I explore in my first and second chapters, and 2) How can we use those models to make projections for the Southeastern US?, which I explore in my third and fourth chapters.
Both my first and second chapters point to the practical trade-offs in model structure and realism. In my first chapter, I found that representing spatially implicit contagious disturbances in terms of shape and frequency accurately captured structural changes over time and separated the disturbance regimes of different regions. Representing spatially implicit disturbances in terms of shape and frequency sacrificed the specificity of a space-based approach but may be more computationally efficient. In my second chapter, I developed a framework for calibrating models based on an iterative cycle between uncertainty analysis and literature synthesis, targeted field campaigns, and statistical constraint. I found that targeted field work and statistical constraint reduced parameter uncertainty until structural uncertainty began to dominate.
Models that capture disturbance dynamics can help us anticipate effects of global change factors like climate change and invasive species. In my third chapter, I found that elevated temperatures reduce cogongrass biomass, and that cogongrass facilitates pine dominance over oaks in a mixed pine-oak stand. This suggests that cogongrass mediates inter-species competition at an ecosystem scale. Prescribed burns are a management technique used to suppress cogongrass and has an add-on benefit of reducing tick populations. However, climate change may threaten how frequently prescribed fires can be safely deployed. In my fourth chapter, I found that tick populations are most sensitive to leaf litter and humidity, which allows for management strategies as an alternative to prescribed burns
Long-term effects of portuguese forest fires on morphology and aquatic habitat structure of lotic ecosystems
This thesis investigates long-term effects of forest fires on morphology and functioning of
Portuguese streams via burned wood. Wildfires influenced the landscape dynamics across
three regions examined, towards increases in shrublands encroaching into previously forested
areas. Large wood amounts within 27 streams were low and are expected to decline in the
future owing to wildfire. Likewise, wildfire was promoting wood lacking structural complexity,
thus likely reducing habitat heterogeneity that improves conditions for aquatic organisms. The
effect of fire providing wood with greater diameter will increase its probability for stream
functions such as pool formation. However, this functionality may not persist because most of
this wood was decayed and less stable in the channel. It is critical for aquatic communities if
fire-derived wood falls directly into the river or if it is previously conditioned for some time on the
forest floor; Efeitos a longo prazo dos fogos florestais na
morfologia e estrutura do habitat em
ecossistemas lóticos de Portugal
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Esta tese avalia os efeitos a longo prazo dos fogos florestais na morfologia e funcionamento de
rios portugueses através da madeira ardida. O fogo influenciou a dinâmica da paisagem em
três regiões estudadas, favorecendo a invasão por matos de áreas previamente florestadas. A
quantidade de pedaços de madeira em 27 rios foi baixa e prevê-se a sua diminuição futura por
influência do fogo. O fogo promoveu também a presença de madeira com menor complexidade
estrutural, reduzindo provavelmente a heterogeneidade de habitat que melhora as condições
para os organismos aquáticos. A madeira queimada tinha maior diâmetro, aumentando a
probabilidade de função no rio, como a criação de fundões. Esta funcionalidade pode não
persistir porque esta madeira estava degradada e menos estável no canal. É determinante para
as comunidades aquáticas se a madeira dos fogos cai directamente no rio ou se é previamente
condicionada durante algum tempo no solo da floresta
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