Flammable Vegetation Research Articles

Continental-scale prediction of live fuel moisture content using soil moisture information

Live fuel moisture content (LFMC) is a key factor that determines the flammability of vegetation in ecosystems. Soil moisture (SM) is one of the variables that is known to influence plant water use. The present study analyses the LFMC-SM relationship over Australia using gridded, remote sensing-based LFMC and land surface model-based SM products. A lag-correlation analysis conducted over 60 selected sites shows that the strength of the relationship between LFMC and SM varies from site to site and, in general, is moderately strong (median lag-correlation of ~0.5). However, the strength of the relationship changes with vegetation type and also with soil profile depth. At all the sites, SM is found to be a leading indicator of LFMC. The lag also varies with the location and is found to range from days to months. Based on the location-based correlation analysis, we identify the 0-35 cm SM profile (SM0-35cm) to be the best predictor of LFMC. We developed a simple model to predict daily LFMC, where it is hypothesised that daily variations in LFMC from its annual cycle can be predicted using daily deviations from the annual cycle in SM0-35cm. The annual cycles of LFMC and SM0-35cm are modelled using Fourier cosine series. The averaged (over 60 sites) correlation obtained for the validation period is 0.74 when a time-lag of 14 days is assumed at all locations. When the model is applied nationally at a 5 km grid, the normalised root mean squared error for the validation period is found to be less than 25% in general. The results from the present study highlight a modelling strategy that can be used to address a critical gap in the forecast of spatially and temporally continuous LFMC at regional scales in advance for operational fire management applications.

Streamlined wildland-urban interface fire tracing (SWUIFT): Modeling wildfire spread in communities

The wildland-urban interface (WUI) is defined as a geographic area where human developments and flammable vegetation merge in a wildfire-prone environment. Losses due to wildfire have been rising in the past decade, attributed to changes in vegetation growth, fuel availability, and increased land developments in WUI. This paper studies the process of wildfire spread inside WUI communities. The fire spread rate within WUI communities is determined for nine wildfires that were ranked among the most destructive wildfires in North America. An improved quasi-empirical model that considers radiation and fire spotting as modes of fire spread inside a community is proposed. The new model is validated using the documented spread rates during the 2007 Witch and Guejito fires and the 2017 Tubbs fire. The proposed model is computationally efficient and can be used to quantify fire spread rate and the number of affected structures inside a community during a wildfire event.

What shapes fire size and spread in African savannahs?

AbstractFires play an important role in savannah ecosystems, shaping among other things vegetation structure and altering species composition. As direct and indirect anthropogenic pressures on these ecosystems increase, fire dynamics in savannahs are expected to change in the coming decades, with potential impacts on ecosystem functioning. Although the ecological impacts of fires are relatively well‐known, the factors that shape fire dynamics in these ecosystems have received less research attention. Using Pendjari National Park (Benin) as a case study, we assessed the importance of different biotic and abiotic factors in shaping fire size and spread in the region. Our results show that fires spread faster (1) in the middle of the dry season compared to the early or late dry season, (2) in areas that are far away from natural and anthropogenic firebreaks, and (3) in areas that are covered with highly flammable vegetation. By contrast, most vegetation types had little influence on fire size, which seems to depend instead on rainfall. Our approach and results highlight new avenues for satellite data to improve our understanding of fire dynamics in large, remote savannah ecosystems and to improve our ability to predict how fires spread, a key variable for wildlife management in the face of rapidly changing environmental conditions.

Historical and future global burned area with changing climate and human demography

Summary Wildfires influence terrestrial carbon cycling and represent a safety risk, and yet a process-based understanding of their frequency and spatial distributions remains elusive. We combine satellite-based observations with an enhanced dynamic global vegetation model to make regionally resolved global assessments of burned area (BA) responses to changing climate, derived from 34 Earth system models and human demographics for 1860–2100. Limited by climate and socioeconomics, recent BA has decreased, especially in central South America and mesic African savannas. However, future simulations predict increasing BA due to changing climate, rapid population density growth, and urbanization. BA increases are especially notable at high latitudes, due to accelerated warming, and over the tropics and subtropics, due to drying and human ignitions. Conversely, rapid urbanization also limits BA via enhanced fire suppression in the immediate vicinity of settlements, offsetting the potential for dramatic future increases, depending on warming extent. Our analysis provides further insight into regional and global BA trends, highlighting the importance of including human demographic change in models for wildfire under changing climate.

Land use change towards forests and wooded land correlates with large and frequent wildfires in Italy

It is commonly believed that wildfires in southern Europe have been favored by the encroachment of flammable vegetation on cultivated and grazed areas no longer managed as a consequence of deep socio-economic changes in rural areas. Using the whole of Italy as study case, this paper explores the hypothesis that wildfires selectively burn areas with specific land use changes (LUC) characteristic of agricultural land abandonment, especially in large (> 500 ha) and recurrent burnt areas. Additionally, we examined LUC within 200 m buffer areas around perimeters of large fires to explore if active land management may hamper the growth of large fires. To investigate the study hypotheses, pre-fire LUC were compared within six different geographic domains defined according to the burnt areas from 2007 to 2017 across Italy. Estimates of LUC between 1990 and 2008 came from the Italian Land Use Inventory (IUTI), which is based on photointerpretation of 1,206,198 sample points on high-resolution aerial images. The analyses reveal that LUC in all geographical domains reflect typical trends of agricultural land abandonment in southern Europe during the last decades: expansion of forests, shrubland and new settlements at the expense of agricultural land, grasslands and pastures. However, results show higher rates of pre-fire LUC in burnt areas than in the rest of territory considered available for burning. We found that higher rates of forest expansion and shrub encroachment on abandoned grasslands and pastures are related to a higher incidence of large and recurrent fires, respectively. Furthermore, areas surrounding large fires were less affected by pre-fire land abandonment than burnt areas and show higher increases in vineyards and orchards. Our findings suggest that land abandonment have probably increased fire proneness at national scale by expanding shrub and tree encroachment, and thus increasing fuel connectivity and fuel build-up. Therefore, we urge for a greater integration between fire management and rural development policies.

Increased fire severity triggers positive feedbacks of greater vegetation flammability and favors plant community‐type conversions

AbstractQuestionsIncreased wildfire activity is resulting in plant community‐type conversions worldwide. In some regions, fire‐sensitive forests are being replaced by flammable fire‐resilient communities, increasing the likelihood of reburning due to positive fire feedbacks. Here we evaluated whether fire severity affects post‐fire plant community flammability attributes that lead to community‐type conversions and changes in the likelihood of reburning. Specifically, we assessed how fire severity, the dominant pre‐fire vegetation, and distance to unburned remnant forest may shape post‐fire community properties and flammability trajectories in northwestern Patagonia.LocationNorthwestern Patagonia, Argentina.MethodsWe repeated sampling of Nothofagus pumilio, Nothofagus dombeyi, and Austrocedrus chilensis forests and native shrublands (composed of multiple shrub species) two and 18 years after fires that burned at low‐ to very high‐severity levels, and measured community structure and flammability attributes.ResultsEighteen years after fire, forests that burned at moderate to very high severity were unable to recover and were replaced by more flammable shrublands and grasslands. Following low‐severity fire, fine‐fuel density was lower and forest recovery was enhanced by greater survival of remnant seed trees. Burnt shrublands increased in abundance across all severity classes but attained highest fine‐fuel production after moderate‐ to very high‐severity fire.ConclusionsLow fire severity, by enabling regeneration of forests that are less flammable than shrublands, diminishes the likelihood of reburning, thus establishing a negative feedback favorable to forest perpetuation. Conversely, moderate to very high fire severity leads to a positive feedback by promoting conversion to shrublands and greater fine‐fuel accumulation. This increases the likelihood of reburning, reinforcing the persistence of pyrophytic communities and favoring landscape‐scale loss of fire‐sensitive forests. This fire severity‐mediated positive feedback may in many regions worldwide further amplify warming‐related wildfire activity increases, posing serious threats to the persistence of fire‐sensitive ecosystems.

In the Line of Fire: Consequences of Human-Ignited Wildfires to Homes in the U.S. (1992–2015)

With climate-driven increases in wildfires in the western U.S., it is imperative to understand how the risk to homes is also changing nationwide. Here, we quantify the number of homes threatened, suppression costs, and ignition sources for 1.6 million wildfires in the United States (U.S.; 1992–2015). Human-caused wildfires accounted for 97% of the residential homes threatened (within 1 km of a wildfire) and nearly a third of suppression costs. This study illustrates how the wildland-urban interface (WUI), which accounts for only a small portion of U.S. land area (10%), acts as a major source of fires, almost exclusively human-started. Cumulatively (1992–2015), just over one million homes were within human-caused wildfire perimeters in the WUI, where communities are built within flammable vegetation. An additional 58.8 million homes were within one kilometer across the 24-year record. On an annual basis in the WUI (1999–2014), an average of 2.5 million homes (2.2–2.8 million, 95% confidence interval) were threatened by human-started wildfires (within the perimeter and up to 1-km away). The number of residential homes in the WUI grew by 32 million from 1990–2015. The convergence of warmer, drier conditions and greater development into flammable landscapes is leaving many communities vulnerable to human-caused wildfires. These areas are a high priority for policy and management efforts that aim to reduce human ignitions and promote resilience to future fires, particularly as the number of residential homes in the WUI grew across this record and are expected to continue to grow in coming years.

Coastal Vulnerability under Extreme Weather

Communities like Santa Barbara, California appear to have it all – beaches, mountains, sunshine, moderate temperatures, small urban population, and close proximity to the large metropolis of Los Angeles. What is not to love? Climate change, drought, flammable vegetation, and naturally prevailing weather conditions make a significant portion of the population vulnerable in many ways. Earthquakes and tsunamis might come to mind, but perhaps more of a threat is fire and/or flooding at, on or near the wildland-urban interface. The recent Thomas fire in December of 2017 and subsequent flooding, debris flow and mudslides in Montecito that followed in January of 2018 highlight what coastal vulnerability means under the new normal of extreme wildfire and flooding danger for this region. This paper discusses the unique hazards along with local weather conditions that contribute to vulnerability. We then detail spatial analytics to assess, model and predict risks. Insights are offered for the Santa Barbara region associated with extreme weather vulnerabilities.

Increasing cuticular wax concentrations in a drier climate promote litter flammability

Several plant chemical traits (cellulose, tannins and terpenes) have been related to plant flammability. Contrastingly, no study has focused on the relationship between plant flammability and physico-chemical leaf litter traits with a focus on cuticular wax concentration. This study focuses on alkane cuticular waxes because of their relatively low flash point and storage in the cuticle of all vascular plant species. The sclerophyllous species Quercus coccifera is the model species since it is the main shrub species in the Mediterranean basin and all previously investigated sclerophyllous species feature a high cuticular wax content. Litter was collected in a Mediterranean garrigue where Q. coccifera grows under natural drought and recurrent aggravated drought (consisting of 5.5 years of rain restriction). These different drought conditions were expected to imply different alkane wax concentrations since one of the major roles of cuticular waxes is evapotranspiration limitation during drought. Litter flammability was assessed through ignition delay, flame residence time and flame height (assessed using an epiradiator) and gross heat of combustion (using an adiabatic bomb calorimeter). Results showed that the higher cuticular alkane concentrations reached under aggravated drought were associated with an increased leaf litter flammability as expected. These results confirm that all potentially flammable organic metabolites (terpenes as previously reported in other studies, and cuticular alkane waxes) are drivers of vegetation flammability. It is suggested that Q. coccifera flammability (considered as low to moderate), could increase under a drier scenario in the Mediterranean area. We hypothesize that fire severity would accordingly be intensified in shrubs dominated by this sclerophyllous species without necessarily increasing vulnerability of Q. coccifera to fire since this is a resprouter species after fire and is one of the main pioneer species during post-fire vegetation succession.

Increased aridity drives post-fire recovery of Mediterranean forests towards open shrublands.

Summary Recent observations suggest that repeated fires could drive Mediterranean forests to shrublands, hosting flammable vegetation that regrows quickly after fire. This feedback supposedly favours shrubland persistence and may be strengthened in the future by predicted increased aridity. An assessment was made of how fires and aridity in combination modulated the dynamics of Mediterranean ecosystems and whether the feedback could be strong enough to maintain shrubland as an alternative stable state to forest.A model was developed for vegetation dynamics, including stochastic fires and different plant fire‐responses. Parameters were calibrated using observational data from a period up to 100 yr ago, from 77 sites with and without fires in Southeast Spain and Southern France.The forest state was resilient to the separate impact of fires and increased aridity. However, water stress could convert forests into open shrublands by hampering post‐fire recovery, with a possible tipping point at intermediate aridity.Projected increases in aridity may reduce the resilience of Mediterranean forests against fires and drive post‐fire ecosystem dynamics toward open shrubland. The main effect of increased aridity is the limitation of post‐fire recovery. Including plant fire‐responses is thus fundamental when modelling the fate of Mediterranean‐type vegetation under climate‐change scenarios.

Prescribed burning in a mediterranean-climate region mitigates the disturbance by bushfire to a critical food resource for an endangered bird, the Carnaby\u2019s cockatoo

BackgroundPrescribed burning is used to reduce fire hazard in highly flammable vegetation types, including Banksia L.f. woodland that occurs on the Swan Coastal Plain (SCP), Western Australia, Australia. The 2016 census recorded well over 1.9 million people living on the SCP, which also encompasses Perth, the fourth largest city in Australia. Banksia woodland is prone to frequent ignitions that can cause extensive bushfires that consume canopy-stored banksia seeds, a critical food resource for an endangered bird, the Carnaby’s cockatoo (Calyptorynchus latirostris, Carnaby 1948). The time needed for banksias to reach maturity and maximum seed production is several years longer than the typical interval between prescribed burns. We compared prescribed burns to bushfires and unburned sites at three locations in banksia woodland to determine whether low-intensity prescribed burns affect the number of adult banksias and their seed production. Study sites were matched to the same vegetation complex, fire regime, and time-since-fire to isolate fire intensity as a variable.ResultsHeadfire rates of spread and differenced normalized burn ratios indicated that prescribed burning was generally of a much lower intensity than bushfire. The percentage survival of adult banksias and their production of cones and follicles (seeds) did not decrease during the first three years following a prescribed burn. However, survival and seed production were significantly diminished followed high-intensity bushfire. Thus, carrying capacity for Carnaby’s cockatoo was unchanged by prescribed burning but decreased markedly following bushfire in banksia woodland.ConclusionsThese results suggest that prescribed burning is markedly different from bushfire when considering appropriate fire intervals to conserve canopy habitats in fire-resilient vegetation communities. Therefore, low-intensity prescribed burning represents a viable management tool to reduce the frequency and extent of bushfire impacts on banksia woodland and Carnaby’s cockatoo.

Fire caused demographic attrition of the Tasmanian palaeoendemic conifer Athrotaxis cupressoides

AbstractThe temperate island of Tasmania is a global centre of plant endemism, with relictual lineages that persist in topographically rugged, wet and cool refugia. An iconic example of these palaeoendemic plants is the slow‐growing conifer, Athrotaxis cupressoides D. Don (Cupressaceae). The geographic range of A. cupressoides has shrunk since European settlement because of destructive anthropogenic fires. Inscription of the Tasmanian Wilderness World Heritage Area in 1982 provided formal protection for Tasmania's palaeoendemic taxa, but they remain vulnerable to lightning‐ignited landscape fires, which are becoming more frequent due to climate change. We surveyed stands across the species’ range and found that stands damaged by fires in the 20th century had higher grass cover and were more exposed to hot northerly winds than unburnt stands. A recruitment bottleneck was evident, with juveniles absent in 28% of unburnt and 47% of burnt transects. Transects on small islands in lakes had lower herbivore densities and less evidence of fire than comparable mainland transects. However, the island transects had lower densities of A. cupressoides seedlings and saplings, despite similar densities of adult trees, suggesting factors other than fire and herbivory contribute to the poor regeneration. We also studied the effects of a lightning fire in 2016, finding it killed 68% of stems overall, with stems less than 30 cm diameter and those scarred by previous fires more likely to die. These findings of high adult mortality and poor regeneration following fire suggest that the geographic range of A. cupressoides will contract due to the increasing frequency of lightning‐ignited fires. Management responses to the increasing risk of landscape fires now include establishment of seed banks, restoration planting and use of irrigation to protect stands from active fires, in addition to rapid suppression of ignitions and targeted planned burning to reduce fuel loads in surrounding flammable vegetation.

Morphological Placenta adaptations to maternal undernutrition in a bovine model

Humans and wildfires have historically driven landscape structure in the Mediterranean basin. The Iberian Peninsula is not an exception to that rule, and therefore, farmers, researchers, and governments seek alternative tools to minimize the loss of biodiversity and wildfire risks. Extensive livestock including beef cattle is currently promoted as a suitable management tool by European agro-environmental policies yet pieces of evidence exist regarding the reciprocal effects between cows and Mediterranean woody vegetation. In this work, we performed a field manipulation to evaluate whether free-ranging beef cattle without supplementary feeding, at high density (2 livestock units (LU)/ha) for a short period of time i.e. “boom and bust grazing” management, are able to adapt their grazing preferences to the Mediterranean woody vegetation without health impairment, and prevent from bush encroachment and wildfires. For our purposes, a native herd of 14 adult cows was kept captive without supplementary feeding in a 14 ha enclosure covered by Mediterranean vegetation for two months (April–June 2016). Plant and cattle fecal and blood samples were collected to assess diet composition (plant cuticle microhistological analysis), fecal nitrogen and protein contents of consumed plants, and the nutritional status (non-esterified fatty acids) of cattle. Our results showed that cattle adapted their feeding habits toward a more woody diet including potentially flammable taxa but with some detrimental effects on health status. Hence, cattle cannot control woody vegetation for long periods of time without supplementary feeding. Further research should be oriented to explore other alternative approaches to minimize the health impairment of cattle used for control flammable vegetation in Mediterranean regions.

Estimating Live Fuel Moisture Using SMAP L-Band Radiometer Soil Moisture for Southern California, USA

Live fuel moisture (LFM) is a field-measured indicator of vegetation water content and a crucial observation of vegetation flammability. This study presents a new multi-variant regression model to estimate LFM in the Mediterranean ecosystem of Southern California, USA, using the Soil Moisture Active Passive (SMAP) L-band radiometer soil moisture (SMAP SM) from April 2015 to December 2018 over 12 chamise (Adenostoma fasciculatum) LFM sites. The two-month lag between SMAP SM and LFM was utilized either as steps to synchronize the SMAP SM to the LFM series or as the leading time window to calculate the accumulative SMAP SM. Cumulative growing degree days (CGDDs) were also employed to address the impact from heat. Models were constructed separately for the green-up and brown-down periods. An inverse exponential weight function was applied in the calculation of accumulative SMAP SM to address the different contribution to the LFM between the earlier and present SMAP SM. The model using the weighted accumulative SMAP SM and CGDDs yielded the best results and outperformed the reference model using the Moderate Resolution Imaging Spectroradiometer (MODIS) Visible Atmospherically Resistance Index. Our study provides a new way to empirically estimate the LFM in chaparral areas and extends the application of SMAP SM in the study of wildfire risk.

Analysis of conductor clashing experiments

Conductor clashing is one of the possible mechanisms how an overhead power line can cause wildfires. During the contact of two bare conductors of the energized power line on different potentials, or in the case of an arc between them, generated heat can cause melting and vaporization of the conductor material. The pressure from the gasified metal may be high enough to eject the molten metal as small particles, which are then carried away by the wind. Consequently, molten or combusting metal particles expelled during faults will fall below or, supported by the wind, in the surrounding area of the power line which can result in ignition of the flammable vegetation on the ground. The important characteristics of the clashing fault are the energy of the arc and the erosion of the conductor material. The arc current and the arc duration determine the amount of material removed from the conductor, the size and number of the generated particles and the thermodynamic state of the particles. There are only a few published experimental researches dealing with the characteristics of the generated particles after the arcing of the conductors. All of them are laboratory simulations of the conductor clashing. This paper describes experiments of an overhead line conductor clashing in a live low-voltage distribution network protected by fuses, as well as observations noted during the experimentation and during the processing of the measured results. The aim of the experiments was to study the phase of the particle generation in realistic conditions in the electrical network and to investigate the operation of the power line protection in case of the conductor clashing at different places along the line. The data analysis of a series of experiments has shown the impact of the wind speed, the fault duration, the fault current magnitude as well as the impact of the conductor clashing site on the particle size and the number of particles.

The ecological uncertainty of wildfire fuel breaks: examples from the sagebrush steppe

Fuel breaks are increasingly being implemented at broad scales (100s to 10,000s of square kilometers) in fire‐prone landscapes globally, yet there is little scientific information available regarding their ecological effects (eg habitat fragmentation). Fuel breaks are designed to reduce flammable vegetation (ie fuels), increase the safety and effectiveness of fire‐suppression operations, and ultimately decrease the extent of wildfire spread. In sagebrush (Artemisia spp) ecosystems of the western US, installation of extensive linear fuel breaks is also intended to protect habitat, especially for the greater sage‐grouse (Centrocercus urophasianus), a species that is sensitive to habitat fragmentation. We examine this apparent contradiction in the Great Basin region, where invasive annual grasses have increased wildfire activity and threaten sagebrush ecosystems. Given uncertain outcomes, we examine how implementation of fuel breaks might (1) directly alter ecosystems, (2) create edges and edge effects, (3) serve as vectors for wildlife movement and plant invasions, (4) fragment otherwise contiguous sagebrush landscapes, and (5) benefit from scientific investigation intended to disentangle their ecological costs and benefits.

Emergent freeze and fire disturbance dynamics in temperate rainforests

AbstractThe coastal temperate rainforests of South and North America are part of the most biomass dense forest biome on the planet. They are also subject to rapid climatic shifts and, subsequently, new disturbance processes – snow loss‐driven mortality and the emergence of fire in historically non‐fire‐exposed areas. Here, we compare and contrast Southern and Northern Hemisphere coastal temperate rainforests of the Americas, two of the largest examples of the biome, via synthesis of current literature, future climate expectations and new downscaling of a global fire model. In terms of snow loss, a rapid decline in winter snow is leading to mass mortality of certain conifer species in the Northern Hemisphere rainforests. High‐elevation Southern Hemisphere forests, which are beginning to see similar declines in snow, may be vulnerable in the future, especially bogs and high‐water content soils. Southern Hemisphere forests are seeing the invasion of fire as an ecological force at mid‐to‐high latitudes, a shift not yet observed in the north but which may become more prominent with ongoing climate change. We suggest that research should focus on the flammability of seral vegetation and bogs under future climate scenarios in both regions. By comparing these two drivers of change across similar gradients in the Northern and Southern Hemispheres, this work points to the potential for emerging change in unexpected places in both regions. There is a clear benefit to conceptualising the coastal temperate rainforests of the Americas as two examples of the biome which can inform the other, as change is proceeding in similar directions but at different rates in each region.

Review of the use of remote sensing for monitoring wildfire risk conditions to support fire risk assessment in protected areas

Fire risk assessment is one of the most components of the management of fire that offers the framework for monitoring fire risk conditions. Whilst monitoring fire risk conditions commonly revolved around field data, Remote Sensing (RS) play key role in monitoring and quantifying fire risk indicators. This study presents a review of remote sensing data and techniques for fire risk monitoring and assessment with a particular emphasis on its implications for wildfire risk mapping in protected areas. Firstly, we concentrates on RS derived variables employed to quantify both the intrinsic and extrinsic factors that influence vegetation flammability. Thereafter, an evaluation of the prominent RS platforms such as Broadband, Hyperspectral and Active sensors that have been utilized for wildfire risk assessment Furthermore, we demonstrate the effectiveness in obtaining information that have operational use or immediate potentials for operational application in PA. RS techniques that involve extraction of landscape information from imagery were summarised. A review has concluded that in practices, a fire risk assessment that consider all factors that influence fire ignition and propagation is impossible to establish, however it is imperative to incorporate indicators or variables of very high heterogeneous.

Geographic variations in fine-scale vegetation patterns: aspect preferences of montane pine stands over Southern Appalachian landscapes

ABSTRACTLandscape mosaics commonly reflect local terrain interactions with broad-scale processes. In the northern hemisphere, insolation interacts with terrain such that south-facing slopes are warmer, drier, and have sparser and more flammable vegetation than north-facing slopes. These vegetation differences are reinforced through positive feedbacks. In the southern Appalachian Mountains, USA, south-facing slopes harbor xerophytic, fire-dependent pine stands within a hardwood-forest matrix. On certain landscapes, however, pines prefer west- and northwest-facing slopes. We examine pine distribution in the southern Appalachian Mountains (Virginia through Georgia), finding that pines prefer south- and southwest-facing slopes in the southern section of this region but west-, southwest-, and northwest-facing slopes in the northern section, suggesting that broad-scale processes interact differently with terrain in the two sections. To investigate these differences, we analyze three topo-climatic factors (topographic wetness, insolation, and wind) that may influence pine distributions, and discuss other potential influences (bedrock dip, soils, and ice storms). Insolation receipt can straightforwardly explain pine distribution on southern landscapes. No single explanation accounts fully for the anomalous northern pattern, but several mechanisms (especially wind and disturbances) may contribute. We present a conceptual model of these processes and the longer-term coevolution of pine forests with microclimates, fire regimes, soils, and landforms.

Effects of boom and bust grazing management on vegetation and health of beef cattle used for wildfire prevention in a Mediterranean forest

Humans and wildfires have historically driven landscape structure in the Mediterranean basin. The Iberian Peninsula is not an exception to that rule, and therefore, farmers, researchers, and governments seek alternative tools to minimize the loss of biodiversity and wildfire risks. Extensive livestock including beef cattle is currently promoted as a suitable management tool by European agro-environmental policies yet pieces of evidence exist regarding the reciprocal effects between cows and Mediterranean woody vegetation. In this work, we performed a field manipulation to evaluate whether free-ranging beef cattle without supplementary feeding, at high density (2 livestock units (LU)/ha) for a short period of time i.e. “boom and bust grazing” management, are able to adapt their grazing preferences to the Mediterranean woody vegetation without health impairment, and prevent from bush encroachment and wildfires. For our purposes, a native herd of 14 adult cows was kept captive without supplementary feeding in a 14 ha enclosure covered by Mediterranean vegetation for two months (April–June 2016). Plant and cattle fecal and blood samples were collected to assess diet composition (plant cuticle microhistological analysis), fecal nitrogen and protein contents of consumed plants, and the nutritional status (non-esterified fatty acids) of cattle. Our results showed that cattle adapted their feeding habits toward a more woody diet including potentially flammable taxa but with some detrimental effects on health status. Hence, cattle cannot control woody vegetation for long periods of time without supplementary feeding. Further research should be oriented to explore other alternative approaches to minimize the health impairment of cattle used for control flammable vegetation in Mediterranean regions.