WEB-BASED GIS FOR MAPPING FIRE REGIMES OF PECHORO-ILYCH RESERVE AND ITS ENVIRONS

The article is devoted to the description of the web-GIS for mapping fire regimes in the Pechora-Ilych reserve and its environs. The main purpose of the resource is to provide the results of mapping fire regimes in the designated area to a wide range of researchers in an accessible form. Web-GIS allows organizing and storing the received thematic spatial data. The resource performs research and educational functions. The structure of the web-GIS includes the following sections: the study area, fire frequency indicators, fire regimes, fire regime condition class, and fire cycles. The web GIS was created using the ArcGIS StoryMaps tool on the ArcGIS Online platform. All sections use data from the ArcGIS Living Atlas of the World. Web-GIS allows receiving reference information about the indicators of fire frequency, fire cycles and regimes, as well as their deviations within the boundaries of the Pechora-Ilych nature reserve, district forestries, and spatial units. In particular, the results of a retrospective statistical analysis of forest fire indicators within spatial units (fire frequency, mean fire interval, etc.) are available for users.

Fire history and dendroecology of Catoctin Mountain, Maryland, USA, with newspaper corroboration

Background Our study was designed to reveal a detailed forest fire history at Catoctin Mountain Park, Maryland, USA. We compared the ages of living trees to known fire dates in the dendrochronological record. Seasonality and years of fires in the dendrochronological record were juxtaposed with specific dates of fires recorded in newspapers. Results Twenty-seven pines (Pinus L.) captured 122 fire scars representing 58 distinct fire years between 1702 and 1951. Climate was significantly hotter and drier in the years of burns that affected at least two trees and was wetter two years prior. Thirty-three fires described in local newspapers were reported largely in the spring and fall months (68% between March and June, 32% between September and December). Ninety-one percent of fire scars in our tree-ring chronology had dormant seasonality. The mean fire interval was 5.47 ± 10.14 (SD; standard deviation) yr, and the Weibull median fire interval was 3.22 yr during the entire chronology. The longest fire-free interval was from 1952 to 2018. The size structure of living trees was biased toward smaller black gums (Nyssa sylvatica Marshall) and oaks (Quercus L.) that recruited in the 1930s and 1940s. Most living pitch pines (Pinus rigida Mill) recruited between 1890 and 1910, but a few individuals recruited before the 1850s. Diversity of tree stems smaller than 10 cm diameter at breast height (DBH) was generally lacking; the youngest tree >10 cm DBH in our study area had recruited by 1967. Conclusions The Catoctin Mountains experienced frequent fire during the 1800s and early 1900s. The causes of fires were diverse, including accidental ignitions and purposeful cultural burning for berry (Vaccinium L.) production. The current forest developed during a period of low deer density and after the demise of the charcoal iron industry ended an era of logging. The lack of fire since the 1950s has encouraged the development of a black gum dominated mid- and understory. Management with frequent fire would facilitate pine and oak regeneration.

Wood anatomy, fire wounds and dendrochronological potential of Prosopis pugionata Burkart (Fabaceae) in arid Argentine Chaco

Prosopis pugionata (Fabaceae) is a halophyte tree species that grows exclusively in Argentina’s arid environments, whose woodlands are mainly affected by fires and overgrazing. Here, we describe the wood anatomy and fire wounds of P. pugionata and their relationship with plant size and bark thickness. Besides, we attempt to determine the potential of P. pugionata for dendrochronological studies in order to date fire events throughout time. We tested the hypothesis that P. pugionataforms datable fire wounds, allowing its use for dendrochronological studies. The study area is located in the arid Argentine Chaco region. Seventeen individuals, varying from 15 to 65 years of age, were randomly sampled and bole disks were taken at 0.3, 1.3 and 2.3 m high. P. pugionatais a diffuse and semi-ring-porous hardwood species with growth rings delimited by marginal parenchyma bands. The bark is longitudinally fissured, with an average thickness of 0.19 cm, and a scarce increase with age. Seventy-seven percent of the samples showed fire wounds (). We identified fire scars (70%) and marks (30%), and differentiated them by wood growth interruption in the former. Sixty-one percent of fire wounds affected less than 20% of the cambial perimeter and there were no significant effects of age, bole diameter, bole height and bark thickness on the cambial damage percentage. After cross-dating, P. pugionata showed a mean correlation value between series of 0.5, which represents an accurate potential for dendrochronological studies. Twenty wildfires were dated from 1943 to 2007 in the study area with a fire frequency of 0.40 fires/year and a mean fire interval of 2.5 years. Wildfires frequency increased from 1980 to 0.48 fires/year and a mean fire interval of 2 years. Our results indicate that P. pugionata has the potential to date fires, considering its potential for dendrochronological studies, its ability to survive recurrent fires and forms identifiable wound scars in the wood.

Spatial interpolation and mean fire interval analyses quantify historical mixed-severity fire regimes

Tree-age data in combination with fire scars improved inverse-distance-weighted spatial modelling of historical fire boundaries and intervals for the Darkwoods, British Columbia, Canada. Fire-scarred trees provided direct evidence of fire. The presence of fire-sensitive trees at sites with no fire scars indicated fire-free periods over their lifespan. Sensitivity analyses showed: (1) tree ages used in combination with fire-scar dates refined fire boundaries without biasing mean fire return intervals; and (2) compared with derived conservative, moderate and liberal thresholds (i.e. minimum burn likelihood cut-off values), fixed thresholds generated area burned estimates that were most consistent with estimates based on the proportion of plots that recorded historical fires. Unweighted and weighted spatial mean fire intervals (50–56 and 58–68 years respectively) exceeded dendrochronological plot-level (38-year) estimates based on fire scars only. Including tree-age data from fire-sensitive trees to calculate landscape-level fire interval metrics lengthened the mean return intervals, better representing historical high-severity fires. Supplementing fire scars with tree ages better reflects the spatiotemporal diversity of fire frequencies and severities inherent to mixed-severity fire regimes.

Influence of short-interval fire occurrence on post-fire recovery of fire-prone shrublands in California, USA

In recent decades, fire frequency has increased with population growth at the wildland–urban interface in southern California, USA. Short intervals (<5 years) between successive fires can be detrimental to plant species that require longer intervals between fires to reach reproductive maturity. The resilience of vegetation to changes in fire regimes is of particular interest for shrublands in Mediterranean climates, which in general are susceptible to high frequencies of wildfire. Research on how fire has shaped the life histories of shrubs in Mediterranean climates is central to understanding how to protect sensitive habitat while allowing for the natural occurrence of wildfire in these regions. Frequently burned chamise chaparral shrublands in San Diego County, California, were mapped in the field with the aid of satellite imagery and analysed to investigate changes in vegetation condition and composition associated with short intervals between fires. Fire history, terrain and land-cover characteristics of mapped stands were tested to determine the factors associated with disturbed and converted vegetation. Results indicate that number of burns and mean fire interval are contributing factors in post-fire change in chaparral stands. Chamise chaparral is vulnerable to alteration and type conversion when fire return intervals are 4–5 years or less.

Drainage and agriculture impacts on fire frequency in a southern Illinois forested bottomland

Postsettlement (1909–2003) fire history of a forested bottomland in the Mississippi Embayment of southern Illinois, USA, was determined using fire-scar analysis. The study area is a forested bottomland hardwood site, with remnant pockets of the dominant presettlement bald cypress – tupelo (Taxodium–Nyssa) vegetation. Ditch drainage was installed in 1919, with agricultural clearing and abandonment varying throughout the early and mid-twentieth century. Commercial agricultural activities ceased after the site became part of a conservation area ca. 1950. The hydrology of the site was further modified in 1957 when it was inundated for waterfowl management. Both drainage and land clearing for agriculture were associated with increased fire frequency. Although drainage was a necessary precursor to agriculture across much of this landscape, land improvement played the stronger role in determining fire frequency. The mean fire interval for the study period (1895–1965) was 1.73 years, with a minimum of 1 year and a maximum of 15 years. This frequency contrasts with the complete fire exclusion that has prevailed in the area since 1965. These results have important implications for the maintenance and restoration of forested wetland ecosystems where the present fire regime differs dramatically from that under which the now-dominant forest vegetation developed.

Accurate estimation of mean fire interval for managing fire

Accurate fire-history data are needed if local management of fire or costly national plans for restoring and managing fire and forest structure are to succeed. Fire-history researchers often use fire scars and the composite fire interval method to reconstruct parameters of past fire regimes, such as the population mean fire interval, but the composite method has serious limitations. We modified an alternative non-composite fire interval method, the individual-tree fire-interval method, to derive a more accurate new method, the all-tree fire-interval method. A stochastic fire-scar generating model to assess the accuracy of the new method and its predecessors was then used. Three factors (scarring ratio, population mean fire interval, and tree age) that affect accuracy were varied in the model runs. More complexity (trees with varied scarring ratio between the first scar and successive scars) also was modelled to test the robustness of the method. The all-tree fire-interval method was shown to greatly improve accuracy and provide unbiased estimates of the population mean fire interval. The method also produced encouraging results when scarring was more complex. The new all-tree fire-interval method will require further research on the rates at which trees are scarred by fire, but this would be generally beneficial to understanding fire history.

Anthropogenic impact on past and present fire regimes in a boreal forest landscape of southeastern Norway

Fire-scarred wood samples from 50 stumps, snags, and living trees of Scots pine (Pinus sylvestris L.) were dendrochronologically cross-dated to describe an 800 year long fire history of Eldferdalen Nature Reserve (~6 ha) and its surroundings (~4000 ha) in southeastern Norway. In the western part of the study area, we recorded 55 different fires within a 200 ha area around the reserve between 1511 and 1759 and a mean fire interval in single samples of 24.6 years. The composite mean fire interval for the nature reserve was 10.5 years. Fire intervals were longer in the eastern part of the study area, with a single sample mean fire interval of 49.1 years. Only three fires were detected after 1759, the last one in 1822. Based on historical accounts, we assume that the high number of fires and short fire intervals were influenced by deliberate ignition for agricultural purposes, most likely burning to improve the conditions for cattle grazing and slash-and-burn cultivation. We suggest that the cessation of fires was influenced by the increased value of timber and mining activity, thereby leading to increased interest in conservation of the timber resources.

Fire regime in a conservation reserve in Chihuahua, Mexico

Fire regime characteristics were reconstructed from fire-scarred trees in the Tutuaca reserve, a newly designated protected area in the Sierra Madre Occidental of western Chihuahua. The reserve was created to protect thick-billed parrot nesting habitat (large snags) and a relict forest of Chihuahua spruce (Picea chihuahuana Martínez). We collected fire-scarred samples from conifers (Pinus ayacahuite Ehrenb., Pinus durangensis Martínez, and Pseudotsuga menziesii (Mirb.) Franco) in three 25-ha sites arrayed at different watershed positions, from a low site adjacent to the spruce trees up to the watershed divide. Fire analysis periods began in 1702, 1704, or 1761 and continued through the final fire in 1955 (two sites) or 1995. All sites had frequent fire regimes (mean fire interval (MFI) 3.9–5.2 years; MFI for years in which 25% or more of the samples were scarred: 6.9–8.4 years). Almost all fires occurred before cambial growth began or early during the season of cambial growth. Fire years were significantly dry, and the years immediately preceding fire were significantly wet. After 1955, no further fires occurred at two of the three study sites, a pattern similar to that observed elsewhere in northern Mexico. The third site had fires in 1987 and 1995. The extended fire-free period in portions of the Tutuaca landscape may result in fuel accumulation and eventually in severe wildfire. For effective conservation of fire-susceptible habitat features, managers should seek to incorporate surface fire as a management tool.

Ecology and ecophysiology of grasstrees

‘Xanthorrhoea…is in habit one of the most remarkable genera of Terra Australis, and gives a peculiar character to the vegetation of that part of the country where it abounds’ Robert Brown (1814). Grasstrees (arborescent Xanthorrhoea, Dasypogon, Kingia), with their crown of long narrow leaves and blackened leafbase-covered trunk (caudex), are a characteristic growth form in the Australian flora. Xanthorrhoea is the most widespread genus, with 28 species that are prominent from heathlands to sclerophyll forests. While leaf production for X. preissii reaches a peak in spring–summer, growth never stops even in the cool winter or dry autumn seasons. Summer rain, accompanied by a rapid rise in leaf water potential, may be sufficient to stimulate leaf production, whereas root growth is confined to the usual wet season. Grasstrees are highly flammable yet rarely succumb to fire: while retained dead leaves may reach >1000°C during fire, the temperature 100 mm above the stem apex remains <60°C and the roots are insulated completely. Immediately following fire, leaf production from the intact apical meristem is up to six times greater than that at unburnt sites. For X. preissii, pre-fire biomass is restored within 40 weeks; the mass of live leaves remains uniform from thereon, whereas the mass of dead leaves increases steadily. Leaves usually survive for >2 years. In X. preissii, the post-fire growth flush corresponds to a reduction in starch storage by desmium in the caudex. Minerals, especially P, are remobilised from the caudex to the crown following a spring fire, but accumulate there following an autumn fire. At least 80% of P is withdrawn from senescing leaves, while >95% K and Na are leached from dead leaves. Most stored N and S are volatilised by fire, with 1–85% of all minerals returned as ash. Despite monthly clipping for 16 months, X. preissii plants recover, although starch reserves are depleted by 90%, indicating considerable resilience to herbivory. Analysis of colour band patterns in the leafbases of X. preissii shows that elongation of the caudex may vary more than 5–50 mm per annum, with 10–20 mm being typical. Exceptionally tall plants (>3 m) may reach an age of 250 years, with a record at 450 years (6 m). Fires, recorded as black bands on the leafbases, in south-western Australia have been decreasing in frequency but increasing in variability since 1750–1850. Some grasstrees have survived a mean fire interval of 3–4 years over the last two centuries. In more recent times, some grasstrees have not been burnt for >50 years. The band-analysis technique has been used to show a downward trend in plant δ13C of 2–5.5‰ from 1935 to the present. Grasstrees are most likely to flower in the first spring after fire. A single inflorescence is initiated from the apical meristem, elongating at up to 100 mm day–1 and reaching a length up to 3 m, with one recorded at 5.5 m. This rapid rate of elongation is achieved through leaf (and inflorescence) photosynthesis and desmium starch mobilisation. The developing spike and seeds are vulnerable to a moth larva. Leaf production recommences from axillary buds and the trade-off with reproduction is equivalent to 240 leaves in X. preissii. Flowering and seed production are affected by time of fire. Grasstrees are mainly insect-pollinated. Up to 8000 seeds per spike are produced, although pre-dispersal granivory is common. Seeds are released in autumn and persist in the soil for <2 years. Most fresh seeds germinate in the laboratory but germination is inhibited by light. At any time, seedlings and juveniles may account for most plants in the population, although there may be up to an 80% reduction within 1 year of seedling emergence, often due to kangaroo herbivory. In the absence of fire, mortality of adults may be 4% per annum. Although few grasstree species are considered rare or threatened, their conservation requirements, especially in regard to a suitable fire regime, remain unknown. Grasstrees are particularly susceptible to the exotic root pathogen, Phytophthora cinnamomi, although recruitment among some species has been observed 20–30 years after pathogen invasion. Much remains to be known about the biology of this icon of the Australian bush.