Heat Load Index Research Articles

Conditions to evaluate differences among individual sheep and goats in resilience to high heat load index

Abstract Thirty-three yearling Katahdin sheep (KAT, 38.9 kg) and Boer (BOE, 28.6 kg) and Spanish goat wethers (SPA, 22.7 kg) were used to determine conditions appropriate for evaluating resilience to high heat load index (HLI). Grass hay (69% NDF and 9.5% CP) was consumed ad libitum with concentrate supplemented at 0.5% BW. Period 1 was 2 wk and periods 2–5 were each 1 wk. Target HLI for the five periods during the day/night was 70/70, 80/70, 90/76.5, 95/80.75, and 100/85, and measured HLI was 66/66, 80/75, 92/84, 97/86, and 101/89, respectively. Respiration rate increased with advancing period except from period 4–5 when there was a smaller decline for KAT than for BOE or SPA. Rectal temperature also increased as the experiment progressed until period 4 and was similar among animal types in period 5 when values for BOE and SPA were lower than in period 4, in contrast to similar values for KAT. Respiration rate at 13:00 and 17:00 h increased with advancing period up to a plateau at 150–155 breaths/min converse to much lower rates (i.e., 32–83) at 06:00 in periods 2–5. Respiration rate at 06:00 h differed more among days of period 5 than at 13:00 or 17:00 h, with values increasing from day 1–3 and thereafter generally declining from 118 to 37 breaths/min on day 7. Rectal temperature for KAT was lower than for goats early in period 5 but similar among animal types on days 6 and 7. In conclusion, a HLI in the range of 95/80.75 and 100/85 seems appropriate, periods longer than 1 wk appear necessary for full adaptation, and measures should occur during both night and day.

Using single-step genomic best linear unbiased predictor to enhance the mitigation of seasonal losses due to heat stress in pigs.

The purposes of this study were to analyze the impact of seasonal losses due to heat stress in pigs from different breeds raised in different environments and to evaluate the accuracy improvement from adding genomic information to genetic evaluations. Data were available for 2 different swine populations: purebred Duroc animals raised in Texas and North Carolina and commercial crosses of Duroc and F females (Landrace × Large White) raised in Missouri and North Carolina; pedigrees provided links for animals from different states. Pedigree information was available for 553,442 animals, of which 8,232 pure breeds were genotyped. Traits were BW at 170 d for purebred animals and HCW for crossbred animals. Analyses were done with an animal model as either single- or 2-trait models using phenotypes measured in different states as separate traits. Additionally, reaction norm models were fitted for 1 or 2 traits using heat load index as a covariable. Heat load was calculated as temperature-humidity index greater than 70 and was averaged over 30 d prior to data collection. Variance components were estimated with average information REML, and EBV and genomic EBV (GEBV) with BLUP or single-step genomic BLUP (ssGBLUP). Validation was assessed for 146 genotyped sires with progeny in the last generation. Accuracy was calculated as a correlation between EBV and GEBV using reduced data (all animals, except the last generation) and using complete data. Heritability estimates for purebred animals were similar across states (varying from 0.23 to 0.26), and reaction norm models did not show evidence of a heat stress effect. Genetic correlations between states for heat loads were always strong (>0.91). For crossbred animals, no differences in heritability were found in single- or 2-trait analysis (from 0.17 to 0.18), and genetic correlations between states were moderate (0.43). In the reaction norm for crossbreeds, heritabilities ranged from 0.15 to 0.30 and genetic correlations between heat loads were as weak as 0.36, with heat load ranging from 0 to 12. Accuracies with ssGBLUP were, on average, 25% greater than with BLUP. Accuracies were greater in 2-trait reaction norm models and at extreme heat load values. Impacts of seasonality are evident only for crossbred animals. Genomic information can help producers mitigate heat stress in swine by identifying superior sires that are more resistant to heat stress.

1717 Responses of hair sheep breeds to high heat load index conditions

1717 Responses of hair sheep breeds to high heat load index conditions

Impact of thermo-mechanical treatments on composition, solids loss, microstructure, and rheological properties of pasta filata–type cheese

Abstract The impact of thermo-mechanical treatments on cheese properties was investigated. Curd was mixed at different temperatures (60, 65, or 70 °C), for different lengths of time (3 or 6 min), and at different speeds (6, 9, or 12 rpm) in a torque rheometer. Specific mechanical energy, final curd temperature, and heat load index were measured to predict cheese properties. Considerable changes in cheese composition were observed depending on the mixing treatment, and fat loss was related to the mechanical energy imparted (R2 = 0.92). Microstructural changes in fat were considerable in mixed cheese, as observed by scanning electron microscopy and confocal laser scanning microscopy. Bulk water entrapped in the cheese structure increased with curd temperature and heat load (R2 = 0.60) but was not affected by the mechanical energy imparted. Rheological properties of young cheeses were not affected by the range of mixing treatments imposed.

Patterns of plant species richness and composition in deciduous oak forests in relation to environmental drivers

Local plant species richness and composition may vary across habitats and between plant taxonomic groups within temperate deciduous forests. Multi-taxon approach is therefore needed to provide a more detailed insight into determinants affecting vegetation structure. Fifty-four deciduous oak-dominated vegetation plots (20 m × 20 m) were sampled across central Slovakia (Stiavnicke vrchy Mts) in order to study the effect of environmental (soil, light, topographic) factors on species richness and composition patterns of two main assemblages of understorey layer (herb-layer vascular plants and ground-dwelling bryophytes). The number of recorded herb-layer vascular plants and ground-dwelling bryophytes was 12–48 (mean 28) and 0–11 (mean 4) species per plot, respectively. Generalized linear model revealed that species richness of herb-layer vascular plants was driven by canopy openness, altitude, soil pH/base saturation gradient and plant-available phosphorus. Canopy openness and heat load index accompanied by soil pH/base saturation gradient determined changes of the ground-dwelling bryophyte richness. Canonical Correspondence Analysis identified soil pH/base saturation gradient, canopy openness, soil silt and topography related predictors (altitude, slope, radiation) as the main drivers of the herb-layer vascular plant compositional variability. Species composition variation of ground-dwelling bryophytes was controlled by radiation and canopy openness.

Scale- and taxon-dependent patterns of plant diversity in steppes of Khakassia, South Siberia (Russia)

The drivers of plant richness at fine spatial scales in steppe ecosystems are still not sufficiently understood. Our main research questions were: (i) How rich in plant species are the natural steppes of Southern Siberia compared to natural and semi-natural grasslands in other regions of the Palaearctic? (ii) What are the main environmental drivers of the diversity patterns in these steppes? (iii) What are the diversity–environment relationships and do they vary between spatial scales and among different taxonomic groups? We sampled the steppe vegetation (vascular plants, bryophytes and lichens) in Khakassia (Russia) with 39 nested-plot series (0.0001–100-m2 plot size) and 54 additional 10-m2 quadrats across the regional range of steppe types and measured various environmental variables. We measured β-diversity using z-values of power-law species–area relationships. GLM analyses were performed to assess the importance of environmental variables as predictors of species richness and z-value. Khakassian steppes showed both high α- and β-diversity. We found significant scale dependence for the z-values, which had their highest values at small spatial scales and then decreased exponentially. Total species richness was controlled predominantly by heat load index, mean annual precipitation, humus content and soil skeleton content. The positive role of soil pH was evident only for vascular plant species richness. Similar to other studies, we found that the importance of environmental factors strongly differed among taxonomic groups and across spatial scales, thus highlighting the need to study more than one taxon and more than one plot size to get a reliable picture.

Isolation and patch size drive specialist plant species density within steppe islands: a case study of kurgans in southern Ukraine

The fragmentation and isolation of preserved habitat patches within intensive agricultural landscape threaten species survival in steppes. In Ukraine, <5 % of the original steppe area has survived, mostly in nature reserves, loess ravines and kurgans (burial mounds). The latter are small, but relatively numerous objects. The aim of this study was to investigate whether plant species density (= the number of species per plot) within small steppe patches on kurgans differs from that within large steppe enclaves in southern Ukraine. Another aim was to determine the influence of patch area, isolation and heat load index on species density on kurgans. Presence-absence data for vascular plant species were collected on plots of a size of 100 and 1 m2. Thirty kurgans and ten sites within large steppe enclaves were sampled. Every noted species was classified as specialist or generalist. For kurgans data on area and degree of isolation were collected. Additionally the heat load index for plots on kurgans was calculated. The density of habitat specialists was higher in larger steppe enclaves than on kurgans at both spatial scales. On kurgans the most important predictors of specialist density were isolation (negative) and kurgan area (positive). The density of generalists was positively affected by the heat load index. Kurgans can provide refuges for steppe plant species. However, our results show that over a longer time period, proximity to larger steppe refuges is important to maintain species diversity within these small patches.

Caracterización del ambiente térmico para la actividad ganadera bovina en el Valle del Cauca, Colombia

&lt;p&gt;La influencia del clima sobre el comportamiento de los animales ha sido demostrada desde hace muchos años. Variables climáticas como la temperatura (T, °C), humedad relativa (HR, %), radiación solar (Rs, W/m2) y velocidad del viento (Vv, m/s), por fuera de sus rangos normales, pueden desplazar a los rumiantes de su zona de confort, generando en estos impactos negativos sobre su comportamiento, productividad y reproducción. Con el fin de caracterizar el ambiente térmico de la actividad ganadera en el Valle del Cauca, se utilizaron 2 índices (índices de carga calórica para ganado de leche y carne) biometeorológicos para conocer la relación animal – ambiente. Los índices se aplicaron para los rangos climáticos más representativos del departamento (T= 20–35; HR= 60–100; Vv= 0-10), encontrándose que para las vacas lecheras en condiciones de T &gt;23, HR&gt;80 y 0 Vv iniciaban a presentar signos de estrés calórico, mientras que para el ganado de carne iniciaban con T&gt;25, HR&gt;60 y Vv&lt;1,5. En conclusión, estos índices, son indicadores útiles para determinar el grado de estrés calórico que se pueda presentar en las fincas durante ciertos momentos del día para determinados meses del año, ayudando a planificar acciones para controlar su efecto en el ganado bovino y con ello paliar los impactos en su comportamiento productivo y reproductivo.&lt;/p&gt;

Design and performance of demonstration house with active solar heating in the Qinghai–Tibet Plateau region

The project comprises 80 passive solar houses and 20 houses with combined passive and active solar heating in the Qinghai–Tibet Plateau region. The indoor thermal environment and the performance of the solar collection components are discussed through field testing during the coldest part and the transition part of the heating period. Moreover, the fractional energy savings, thermal efficiency, and fraction of the combined passive and active solar heating are analyzed. The results indicate that an auxiliary heat source should be used as a supplement. By comparing the heating of a passive solar house with a vernacular house, the energy savings of the passive solar house in the demonstration project were found to be approximately 62% during the study period. The thermal efficiency of the active solar heating system is 84.5%, and the solar energy utilization is 38.2%. The monthly average heat load index is 15.2 W m−2.

Effect of summer conditions and shade on the production and metabolism of Holstein dairy cows on pasture in temperate climate

For dairy cattle on pasture in temperate regions, it is largely unknown to what degree hot summer conditions impact energy metabolism, milk yield and milk composition and how effective shade is in reducing these negative effects. During the summer of 2012, a herd of Holstein cows was kept on pasture without access to shade (treatment NS). During the summers of 2011 and 2013, the herd was divided into a group with (treatment S) and a group without (treatment NS) access to shade. Shade was provided by young trees combined with shade cloths (80% reduction in solar radiation). A weather station registered the local climatic conditions on open pasture, from which we calculated daily average Heat Load Index (HLI) values. The effects of HLI and shade on rectal temperature (RT), blood plasma indicators of hyperventilation and metabolic changes due to heat stress, milk yield and milk composition were investigated. RT increased with increasing HLI, but was less for S cows than for NS cows (by 0.02°C and 0.03°C increase per unit increase of HLI, respectively). Hyperchloraemia (an increased blood plasma concentration of Cl-), a sign of hyperventilation, increased for NS cows but not for S cows. The plasma concentration of alkaline phosphatase, a regulator of energy metabolism in the liver, decreased with increasing HLI for NS cows only. Access to shade, thus, reduced the effect of HLI on RT, hyperchloraemia and the regulation of metabolism by the liver. As HLI increased, the plasma concentration of cholesterol decreased (indicating increased lipolysis) and the plasma concentration of creatinine increased (indicating increased protein catabolism). These effects did not differ between S and NS cows. For NS cows, after a lag-time of 2 days, the milk yield decreased with increasing HLI. For S cows, the milk yield was unaffected by HLI and its quadratic factor. The milk concentrations of lactose, protein and fat decreased as HLI increased, but only the effect on milk protein content was remediated by shade. In conclusion, access to shade tempered the negative effects of high HLI on RT, hyperchloraemia and a blood plasma indicator of changing energy metabolism (generally) as well as prevented the decrease in milk yield observed in cows without access to shade.

Effect of summer conditions and shade on behavioural indicators of thermal discomfort in Holstein dairy and Belgian Blue beef cattle on pasture

Using behavioural indicators of thermal discomfort, that is, shade seeking, panting scores (PS) and respiration rate (RR), we evaluated the effect of hot summer conditions and shade, for a herd of adult Holstein dairy cows and a herd of Belgian Blue beef cows kept on pasture in a temperate area (Belgium). During the summer of 2012, both herds were kept on pasture without access to shade (NS). During the summers of 2011 and 2013 each herd was divided into one group with (S) and one without (NS) access to shade. Shade was provided by young trees with shade cloth (80% reduction in solar radiation) hung between them. For S cows, we investigated how shade use was related to hot conditions as quantified by six climatic indices. The heat load index (HLI), which incorporates air temperature and humidity, solar radiation and wind speed, was the best predictor of the six indices tested. In 2011, there was a relatively high threshold for use of shade. When HLI=90, shade use probability reached 17% for dairy cows and 27% for beef cows. In 2013, however, at HLI=90, shade use probability reached 48% for dairy cows and 41% for beef cows. For animals from the NS treatment we determined the effect of hot summer conditions on RR and PS (with 0=no panting and 4.5=extreme panting). In both types of cattle, an increase in black globe temperature was the best predictor for increasing RR and PS. Furthermore, we determined how the effect of hot summer conditions on RR and PS was affected by the use of shade. Under hot conditions (black globe temperature ⩾ 30°C), >50% of the animals under shade retained normal PS and RR (PS<1 and RR<90 breaths per minute), whereas normal RR and PS were significantly less prevalent for animals outside shade. Our findings suggest that, even in temperate summers, heat can induce thermal discomfort in cattle, as evidenced by increases in shade use, RR and PS, and that shade increases thermal comfort.

Ameliorative Strategies to Sustain Livestock Production during Heat Stress

Ameliorative Strategies to Sustain Livestock Production during Heat Stress In the changing climate scenario, heat stress is of major concern among livestock owners as it affects drastically livestock production which otherwise contributes 40% of world agriculture GDP (gross domestic product). Hence there is an urgent need for reviewing the various strategies to counter the heat stress impact on livestock production. THI (temperature humidity index) may not be the ideal index to quantify heat stress impact on livestock as it does not take into account solar radiation and wind velocity. Hence, more appropriate agro-ecological zone specific indices like Dairy Heat Load Index (DHLI) which takes into account all cardinal weather parameters is the need of hour. Development of appropriate heat abatement strategies depends on the type of dairy operation practiced in a particular livestock farm. During heat stress, management strategies such as providing shade, sprinklers, fans, cold water, minimum handling, grazing during early morning and late evening hours might be very beneficial to improve livestock production..

Forest fires within a temperate landscape: A decadal and millennial perspective from a sandstone region in Central Europe

Abstract In Europe, fire is considered an integral part of forest dynamics only in the Mediterranean and in Fenno-Scandinavia. In Central Europe, the ecological role of fire is largely neglected and deemed unimportant. To fill this knowledge gap, we studied ancient and recent fires in temperate coniferous forests of a sandstone landscape. We used palaeoecological and contemporary forestry data to reveal wildfire events in the present-day landscape and in the distant past. Using linear regression and the ENFA method, we identified the factors influencing fire occurrences in the landscape on two time scales. Analyses of soil charcoal concentrations correspond with contemporary forestry data. The main driving factors affecting the incidence of fires were topographic features, namely the heat load index and presence of rocks. Additional important factors were forest composition features, especially the abundance of Pinus sylvestris . Even though the landscape is populated and attractive to tourists, present-day anthropogenic factors, surprisingly, have only marginal effects. Fires have been occurring in similar fire-prone habitats at least since the Subatlantic period, regardless of whether they were caused by humans or lightning. Our results therefore show that fire affects long-term forest vegetation development also in temperate forests of Central Europe. This has far reaching consequences for forest management because, contrary to prevailing beliefs, fire must be considered a natural driver of forest vegetation patterns even in this temperate region.

Landscape genetics and genetic structure of the southern torrent salamander, Rhyacotriton variegatus

Landscape genetic methods can be used to identify the most effective conservation measures to maintain functional connectivity among populations. Analyses of habitat factors that facilitate or restrict gene flow are particularly useful for species with specific habitat requirements and low dispersal rates. Rhyacotriton variegatus is a salamander species with low desiccation tolerance and a restricted geographic range, limited to the Pacific Northwest. Thus, we predicted that genetic distance would be positively correlated with climate and landscape variables that increase risk of desiccation. Two genetic distance measures, pairwise FST and proportion of shared alleles (DPS), suggested that gene flow was low among 19 sampling localities (367 total individuals) and genetic structure was high overall (DPS = 0.636 ± 0.010, FST = 0.330 ± 0.011; mean ± SD). Using both least-cost path and Circuitscape models of landscape resistance, we found that low stream cover, low canopy cover, high heat-load index, and short frost-free period all restricted gene flow among populations. We suggest that the conservation status of this species be revisited given this evidence of high genetic structure within the species, the level of habitat fragmentation in their range, and their reliance on dense canopy cover for dispersal. Maintaining stream corridors with buffers of dense canopy cover may maximize connectivity despite the pressures of timber harvest and urbanization.

Impact of heat stress on conception rate of dairy cows in the moderate climate considering different temperature–humidity index thresholds, periods relative to breeding, and heat load indices

The objectives of this retrospective study were to investigate the relationship between temperature-humidity index (THI) and conception rate (CR) of lactating dairy cows, to estimate a threshold for this relationship, and to identify periods of exposure to heat stress relative to breeding in an area of moderate climate. In addition, we compared three different heat load indices related to CR: mean THI, maximum THI, and number of hours above the mean THI threshold. The THI threshold for the influence of heat stress on CR was 73. It was statistically chosen based on the observed relationship between the mean THI at the day of breeding and the resulting CR. Negative effects of heat stress, however, were already apparent at lower levels of THI, and 1 hour of mean THI of 73 or more decreased the CR significantly. The CR of lactating dairy cows was negatively affected by heat stress both before and after the day of breeding. The greatest negative impact of heat stress on CR was observed 21 to 1 day before breeding. When the mean THI was 73 or more in this period, CR decreased from 31% to 12%. Compared with the average maximum THI and the total number of hours above a threshold of more than or 9 hours, the mean THI was the most sensitive heat load index relating to CR. These results indicate that the CR of dairy cows raised in the moderate climates is highly affected by heat stress.

Case study of skin temperature and thermal perception in a hot outdoor environment

Focusing on the understanding and the estimation of the biometeorological conditions during summer in outdoor places, a field study was conducted in July 2010 in Athens, Greece over 6 days at three different sites: Syntagma Square, Ermou Street and Flisvos coast. Thermo-physiological measurements of five subjects were carried out from morning to evening for each site, simultaneously with meteorological measurements and subjective assessments of thermal sensation reported by questionnaires. The thermo-physiological variables measured were skin temperature, heat flux and metabolic heat production, while meteorological measurements included air temperature, relative humidity, wind speed, globe temperature, ground surface temperature and global radiation. The possible relation of skin temperature with the meteorological parameters was examined. Theoretical values of mean skin temperature and mean radiant temperature were estimated applying the MENEX model and were compared with the measured values. Two biometeorological indices, thermal sensation (TS) and heat load (HL)-were calculated in order to compare the predicted thermal sensation with the actual thermal vote. The theoretically estimated values of skin temperature were underestimated in relation to the measured values, while the theoretical model of mean radiant temperature was more sensitive to variations of solar radiation compared to the experimental values. TS index underestimated the thermal sensation of the five subjects when their thermal vote was 'hot' or 'very hot' and overestimated thermal sensation in the case of 'neutral'. The HL index predicted with greater accuracy thermal sensation tending to overestimate the thermal sensation of the subjects.

Meta-analyses of habitat selection by fishers at resting sites in the pacific coastal region

The fisher (Pekania pennanti) is a species of conservation concern throughout the Pacific coastal region in North America. A number of radiotelemetry studies of habitat selection by fishers at resting sites have been conducted in this region, but the applicability of observed patterns beyond the boundaries of each study area is unknown. Broadly applicable information on habitat selection by fishers in this region would be useful for conservation planning and for informing forest management decisions in areas where intensive field studies have not been conducted. To provide such information, we conducted formal meta-analyses of habitat selection by fishers at resting sites in 8 study areas located from central British Columbia to the southern Sierra Nevada in California, including all areas that currently contain established fisher populations. Each study included in the meta-analyses measured environmental attributes at sites used by fishers for resting (i.e., the immediate vicinity of resting structures; typically ≤0.5 ha) and at random or systematically located sites representing resource availability in each study area. We selected 9 environmental attributes that we expected to be associated with fisher resting sites: slope, heat load index, percent cover of vegetation ≥2 m above the ground, volume of moderately decayed logs ≥26 cm in mean diameter, basal area of live conifers 51–100 cm in diameter at breast height (dbh), basal area of live hardwoods 51–100 cm in dbh, basal area of moderately decayed snags 51–100 cm in dbh, mean dbh of live conifers ≥10 cm in dbh, and mean dbh of live hardwoods ≥10 cm in dbh. Despite substantial variation in environmental conditions among study locations, our analyses revealed statistically significant summary effect sizes for each of the 9 environmental attributes we analyzed. Fishers selected sites for resting that had steeper slopes, cooler microclimates, denser overhead cover, a greater volume of logs, and a greater prevalence of large trees and snags than were generally available. Thus, in areas within the Pacific coastal region where fishers have not been studied and data on selection of resting sites are lacking, our findings provide empirical support for management or conservation actions for fishers that promote the retention or development of these environmental attributes. © 2013 The Wildlife Society.

COMPARING FUNCTIONAL DATA ANALYSIS AND HYSTERESIS LOOPS WHEN TESTING TREATMENTS FOR REDUCING HEAT STRESS IN DAIRY COWS

Various techniques are commonly used to reduce heat stress, including sprayers and misters, shading, and changes in feed. Oftentimes studies are performed where researchers do not control the times when animals use shading or other means available to reduce heat stress, making it hard to test differences between treatments. Two methods are used on data from a study where Holstein cows were given free access to weight activated “cow showers.” Functional data analysis can be used to model body temperature as a function of time and environmental variables such as the Heat Load Index. Differences between treatment groups can be tested using a Functional Bayesian MCMC model. Alternatively hysteresis loops, such as the ellipse, formed by a plot of air temperature or the Heat Load Index against body temperature over the course of a day can be estimated and their parameters used to test differences between cows with access to showers and cows without. Results from an R package hysteresis, which can estimate these loops and their parameters are illustrated. Functional data analysis allows for looser assumptions regarding the body temperature curve and the ability to look for differences between groups at specific time points, while hysteresis loops give the ability to look at heat stress over the course of a day holistically in terms of parameters such as amplitude, lag, internal heat load and central values.

Long-term changes in biological soil crust cover and composition

Communities change over time due to disturbances, variations in climate, and species invasions. Biological soil crust communities are important because they contribute to erosion control and nutrient cycling. Crust types may respond differently to changes in environmental conditions: single-celled organisms and bryophytes quickly recover after a disturbance, while lichens are slow growing and dominate favorable sites. Community change in crusts has seldom been assessed using repeated measures. For this study, we hypothesized that changes in crust composition were related to disturbance, topographic position, and invasive vegetation. We monitored permanent plots in the Columbia Basin in 1999 and 2010 and compared changes in crust composition, cover, richness, and turnover with predictor variables of herbivore exclosure, elevation, heat load index, time since fire, presence of an invasive grass, and change in cover of the invasive grass. Bryophytes were cosmopolitan with high cover. Dominant lichens did not change dramatically. Indicator taxa differed by monitoring year. Bryophyte and total crust cover declined, and there was lower turnover outside of herbivore exclosures. Lichen cover did not change significantly. Plots that burned recently had high turnover. Increase in taxon richness was correlated with presence of an invasive grass in 1999. Change in cover of the invasive grass was positively related to proportional loss and negatively related to gain. Composition and turnover metrics differed significantly over 11 years, though cover was more stable between years. This study can be a baseline for assessing change in crust composition due to anthropogenic influences.

Influences of forest roads and their edge effects on the spatial pattern of burn severity

Abstract Previous research has shown that forest roads are an important feature in many landscapes and have significant effects on wildfire ignition and cessation. However, forest road effects on burn severity have not been studied at the landscape level. Therefore, the overarching goal of our study is to identify the influences of road edge effects on the spatial patterns of burn severity. We analyzed six fires within the Okanogan–Wenatchee National Forest on the eastern slope of the Cascades mountain range of central Washington. We generated two categories for assessing road variables: (1) Primary Road Effect Zone (area within 150 m of the nearest road) and (2) Secondary Road Effect Zone (area from 150 m to 300 m to the nearest road). A regular sampling grid including one out of every 9 cells was created for each fire. These grids were intersected with burn severity data in the form of the Relative Differenced Normalized Burn Ratio (RdNBR), road distance category, stream distance, elevation, slope, terrain shape index, heat load index, canopy cover, and fuel type. We fit spatial regression models with RdNBR as the dependent variable. We found that high burn severity is less likely to occur in the Primary Road Effect Zone for most fires, although one fire exhibited the opposite relationship. Forest road edge effects were hypothesized to be an important determinant of burn severity because fragmentation created by roads alters the roadside fuel profile and environment and because road corridors create barriers to fire spread. Recognizing roadside effects on burn severity patterns highlights the need for further study of the range of effects that roads have on fuels and the fire environment and the potential for incorporating road effects into landscape-level assessments of fire risk.