Fire-scarred Trees Research Articles

Historic Frequency and Severity of Fire in Whitebark Pine Forests of the Cascade Mountain Range, USA

Whitebark pine (Pinus albicaulis Engelm.) is a foundation species of high elevation forest ecosystems in the Cascade Mountain Range of Oregon, Washington, and British Columbia. We examined fire evidence on 55 fire history sites located in the Cascade Range. To estimate dates of historic fires we analyzed 57 partial cross-sections from fire-scarred trees plus 700 increment cores. The resulting 101 fire events indicate fire has been a widespread component of Cascadian whitebark pine stands. Results are site specific and vary considerably. Whitebark pine stands appear to burn in a variety of severities and frequencies. Sites where fire intervals were detected ranged from 9 to 314 years, with a median of 49 years, and averaging 67 years. Fire intervals shortened significantly with higher latitudes. In assessing the most recent fire event at each site, overall, 56 percent burned as stand replacing events. In the 20th century, the number of fires diminished significantly. Due to conservation imperatives, re-introducing fire should be undertaken with extreme care to avoid substantial mortality of this endangered species.

Southern Annular Mode drives multicentury wildfire activity in southern South America

The Southern Annular Mode (SAM) is the main driver of climate variability at mid to high latitudes in the Southern Hemisphere, affecting wildfire activity, which in turn pollutes the air and contributes to human health problems and mortality, and potentially provides strong feedback to the climate system through emissions and land cover changes. Here we report the largest Southern Hemisphere network of annually resolved tree ring fire histories, consisting of 1,767 fire-scarred trees from 97 sites (from 22 °S to 54 °S) in southern South America (SAS), to quantify the coupling of SAM and regional wildfire variability using recently created multicentury proxy indices of SAM for the years 1531-2010 AD. We show that at interannual time scales, as well as at multidecadal time scales across 37-54 °S, latitudinal gradient elevated wildfire activity is synchronous with positive phases of the SAM over the years 1665-1995. Positive phases of the SAM are associated primarily with warm conditions in these biomass-rich forests, in which widespread fire activity depends on fuel desiccation. Climate modeling studies indicate that greenhouse gases will force SAM into its positive phase even if stratospheric ozone returns to normal levels, so that climate conditions conducive to widespread fire activity in SAS will continue throughout the 21st century.

Mixed-severity fire history at a forest-grassland ecotone in west central British Columbia, Canada.

This study examines spatially variable stand structure and fire-climate relationships at a low elevation forest-grassland ecotone in west central British Columbia, Canada. Fire history reconstructions were based on samples from 92 fire-scarred trees and stand demography from 27 plots collected over an area of about 7km2 . We documented historical chronologies of widespread fires and localized grassland fires between AD 1600 and 1900. Relationships between fire events, reconstructed values of the Palmer Drought Severity Index, and annual precipitation were examined using superposed epoch and bivariate event analyses. Widespread fires occurred during warm, dry years and were preceded by multiple anomalously dry, warm years. Localized fires that affected only grassland-proximal forests were more frequent than widespread fires. These localized fires showed a lagged, positive relationship with wetter conditions. The landscape pattern of forest structure provided further evidence of complex fire activity with multiple plots shown to have experienced low-, mixed-, and/or high-severity fires over the last four centuries. We concluded that this forest-grassland ecotone was characterized by fires of mixed severity, dominated by frequent, low-severity fires punctuated by widespread fires of moderate to high severity. This landscape-level variability in fire-climate relationships and patterns in forest structure has important implications for fire and grassland management in west central British Columbia and similar environments elsewhere. Forest restoration techniques such as prescribed fire and thinning are oftentimes applied at the forest-grassland ecotone on the basis that historically high frequency, low-severity fires defined the character of past fire activity. This study provides forest managers and policy makers with important information on mixed-severity fire activity at a low elevation forest-grassland ecotone, a crucial prerequisite for the effective management of these complex ecosystems.

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.

Frecuencia histórica de incendios (1779-2013) en bosques de pino-encino de la comunidad de Charcos, Mezquital, Durango

Historical fire regimes were reconstructed using dendrochronological methods to provide basic information for understanding this phenomenon. In order to reconstruct the fire history in a pine-oak forest in Mezquital, Durango, we collected 78 samples from different fire-scarred tree species (Pinus durangensis, P. arizonica, P. ayacahuite, P. teocote and Pseudotsuga menziesii); 73 and 27 % of the samples were taken from live and dead trees, respectively. By applying dendrochronological methods a total of 75 samples (96 %) and 535 fire scars were dated. Fire regimes were reconstructed from 1746 to 2013, with 1779 being the year of the first recorded fire. A mean fire interval (MFI) of 2.0 years and a Weibull median probability interval (WMPI) of 1.8 years (all scars) were reconstructed. Considering 25 % of scars or more (large fires), a MFI and a WMPI of 7.0 and 5.9 years, respectively, were determined. In total, 92.2 % of fires were categorized as having occurred in the spring and only 7.8 % in the summer. There was no significant (P < 0.05) influence of rainfall and the El Nino Southern Oscillation (ENSO) on fire frequency; however, extensive fires were positively associated with decreased rainfall and ENSO events (La Nina phase).

Dating fire events in Pinus heldreichii forests by analysis of tree ring cores

Bosnian pine (Pinus heldreichii Christ, also known as Pinus leucodermis Antoine) is a relict species found in isolated locations in the mountains of the Balkan Peninsula and Southern Italy. The forests are of high conservational value because they are extremely rich in rare and endemic species of plants and fungi. Yet, the natural history and disturbance regime of P. heldreichii ecosystems is not well understood. Fire traces show that fires played a major role, but there is very limited historical data. Therefore proxy methods to reconstruct past events have to be used. The analysis of tree rings provides such an opportunity. To our knowledge, there have been no attempts to use tree ring cores from P. heldreichii trees to date fire events. Our aim was therefore to test if tree ring cores collected with an increment borer could successfully be used to date fires and verify other tree ring indicators caused by the fire events. We tested an approach that was based on extracting multiple cores from fire-scarred trees and nearby standing trees without injuries. A total of 136 cores from 99 trees were collected from which we dated all 34 cores with fire scars. We found the exact fire years for 29 of the samples, and the remaining 5 samples were approximately dated. Up to 83% of all sampled trees had additional growth reactions, mostly suppressions lasting 5–10 years after the fire years.

Local-scale and regional climate controls on historical fire regimes in the San Juan Mountains, Colorado

In ponderosa pine and mixed conifer ecosystems of the Southwestern US, regional-scale climate tends to synchronize fire years among study sites and increase fire extent or severity within a forest. At landscape scales (1–100km2), fire frequency and severity may also be influenced by local-scale differences in elevation and aspect, including fire barriers in rugged terrain. This study examines local-scale and regional controls of past fire regimes in three tributary watersheds of the San Juan Mountains of southwestern Colorado. In each watershed, we sampled fire-scarred trees and tree age structure and identified fire years and cohorts of post-fire tree recruitment. Fire frequency varied by aspect, and we observed the largest differences between the north- and south-facing aspects in the two largest basins. Fire severity was also different by aspect, with low-severity fire regimes on south-facing slopes and mixed-severity fire on north-facing slopes. The majority of fire years were unique, single-basin fires, indicating a lack of synchrony of fire years among basins, which we attributed to fire barriers and rugged terrain. We conducted Superposed Epoch Analysis (SEA) on two groups of fire years, to show average climate conditions before and during fire years. The first group were unique single-basin fires (n=27) and the second group included all years when synchronous fire burned in two or three basins (n=15). Both groups had significantly dry Palmer Drought Severity Index (PDSI) values during the fire year (p<0.01), while the second group also showed significantly wet conditions for two years prior to the fire year (p<0.01). Steep topography and fire barriers likely reduced the influence of regional climatic on the frequency and timing of fires for individual basins, though fires still burned during years of regional drought. Rugged terrain also contributed to asynchronous fire years among basins and longer fire return intervals compared with other ponderosa pine and mixed conifer forests in the region.

Do Rules of Thumb Measure Up? Characteristics of Fire-Scarred Trees and Samples

Dendrochronologists studying fire history must be strategic in their search for fire-scarred tree samples. Because it is desirable to extend the period of analysis in a site by looking for old scars, recent scars, and trees with large numbers of scars, researchers have developed rules of thumb regarding which trees are most likely to meet these goals as well as where fire scars are most likely to be found. To test our assumptions and quantify patterns about tree and sample characteristics, we analyzed a dataset of 2800 samples and 16,036 scars. On average, logs had the oldest scars and live trees had the most recent scars, although both very old and very recent scars were found on snags and stumps. Scars tended to be located on the uphill sides of trees, particularly on steeper slopes. The number of years between pith date and first fire scar ranged from 2 to 473 years, with a median of 52 and a mean of 67. The data confirm that searching for a variety of sample types and looking on the uphill sides of trees are useful methods for efficient sampling and extending a fire history record.

Post-fire live residuals of maritime pine plantations in Portugal: Structure, burn severity, and fire recurrence

The drivers, characteristics and impacts of surface fire regimes in the Mediterranean Basin are poorly understood. We describe the post-fire structure of residual maritime pine (Pinus pinaster Ait.) patches in frequent-fire mountain landscapes of northern Portugal and relate it with burn severity and fire history. Live trees within each plot were measured and cumulative burn severity metrics were assessed at the tree and plot levels. Plot fire recurrence and fire intervals (mean, MFI; minimum, MinFI; and maximum, MaxFI) were calculated from a digitized fire atlas. Fire thinned from below, with a 15.5-cm diameter at breast height corresponding to 50% survival probability. Bole char and crown kill (or live crown base) heights (CKH) were correlated with live tree height; crown ratio averaged 0.38. Each patch burned 1–9 times since 1975, with a MFI range of 1.7–16years in multiple-fire plots. We found wide variation in stand height (7.8–22.5m), basal area (1.4–47.9m2ha−1) and tree density (14–2199ha−1) but single-storied structures prevailed. Higher fire recurrence was associated with lower stand density and higher percentage of fire-scarred trees, indicating cumulative thinning and cambium damage effects. Bole char height and CKH increased with longer fire intervals, i.e. with fuel accumulation and potentially higher fire intensity. MFI (accounting for 70% of the explanation), terrain aspect, and MaxFI explained 55% of plot-level variation in CKH using regression tree analysis. MFI <4.2years generated the lowest CKH. For stands with MFI ⩾4.2years, CKH increased on slopes facing east or south (drier and warmer) and was highest when MaxFI ⩾4.8years. Active crown fire was less likely in forest patches stocked at <20m2ha−1 and <200ha−1, which should decrease crown fire hazard and limit high-severity fire if combined with adequate pruning and surface fuel treatments every 3–5years. The study indicates that patches surviving a first-entry wildfire are likely to persist under a frequent fire regime, adding to the understanding of Mediterranean pines resilience to fire and providing quantitative empirical evidence useful to guide the management of fire-prone forests.

Comparison of Two Approaches for Determining Fire Dates From Tree Scars

Knowledge regarding the historic role of fire in forest ecosystems is often derived by dating fire scars. Fire history studies in boreal and western coniferous forests have used either complete or partial cross sections cut from fire-scarred trees. The occurrence of missing or false rings presents an obstacle to the accurate dating of individual fires. Two different techniques of dating partial cross sections of fire-scarred ponderosa pine (Pinus ponderosa Laws) were compared using the same samples. Method I involves the tabulation of raw dates followed by a subsequent adjustment based on synchronization with fire dates from adjacent trees. Method II uses correlations with master chronologies based on analysis of increment cores taken in the same region as the sampled fire scar sections. Method I is prone to error since the assumption that fire dates differing by a few years may actually be from the same year cannot be independently verified. Method II provides a higher degree of certainty with regard to the accuracy of individual dates because the cross dating of local patterns of ring widths circumvents the problem of absent or false rings. Eight samples from the Horse Pasture Plateau in Zion National Park, Utah, were dated by both methods. Agreement on dates derived by the two methods for 39 separate fire years was limited to only 26 percent. The average error of Method I was 1.0 year. Fire history studies using Method I are accurate enough for most managerial recommendations and some ecological interpretations, but they may lack the precision necessary to correctly identify fire years or differentiate small changes in fire frequency. The dendrochronological approach of Method II is preferable because of its greater reliability, especially in ecosystems where short fire intervals are common or where fires occur in consecutive years. FORESX SCI. 28:856861. ADDITIONAL

First known fire scar on a fossil tree trunk provides evidence of Late Triassic wildfire

Fire scars are well known to fire ecologists and dendrochronologists worldwide, and are used in dating fires and reconstructing the fire histories of modern forests. Evidence of fires in ancient forests, such as fossil charcoal (fusain), is well known to paleontologists and has been reported in geologic formations dating back to the Late Devonian. We describe what we conclude is a fire scar on a fossil tree trunk from the Late Triassic Chinle Formation of southeastern Utah (~200–225Ma). The external features of the prehistoric scar match those of modern fire scars better than those of scars created by other kinds of wounding events. The fossil specimen also exhibits a number of changes in wood anatomy similar to those reported in modern fire-scarred trees, including a band of very small tracheids that indicate growth suppression immediately associated with the scarring event; an area with a tangential row of probable traumatic resin ducts; and a significant increase in tracheid size following the scarring event that indicates a growth release. No fire scar resembling those in modern trees has previously been described in petrified wood as far as we can determine. The presence of a fire scar not only provides further evidence of ancient fires, but also shows that at least some individual trees survived them, indicating that fire could have been an ecological and evolutionary force in forests at least as early as the Late Triassic.

Fire history of Atlas cedar (Cedrus atlantica Manetti) in Mount Chélia, northern Algeria

The first fire history of the Cedrus atlantica forest of Chélia in northern Algeria is reconstructed from samples of 14 and 12 dead fire-scarred trees from lower and upper elevation stands respectively. Superposed epoch analysis is applied to summarize mean climate conditions before, during, and after sets of fire years in both stands. Prior to 1850, C. atlantica forests in both sites were characterized by high frequency and low intensity fire regimes. The sharp decline in the fire frequency after the mid-nineteenth century coincided with the promulgation of the first laws governing land and forest use in Algeria. Most fire events occurred in the summer, during the latter part of the growing season. No significant relationships were found between an October–June precipitation reconstruction and fire events. This could be due to anthropogenic and topographic factors. The findings of this study provide baseline knowledge on the ecological role of fire in the C. atlantica forest. This information is vital to support ongoing ecosystem management efforts in the region.

Modern fire regime resembles historical fire regime in a ponderosa pine forest on Native American lands

Forests on tribal lands in the western United States have seen the return of low-intensity surface fires for several decades longer than forests on non-tribal lands. We examined the surface fire regime in a ponderosa pine-dominated (Pinus ponderosa) forest on the Hualapai tribal lands in the south-western United States. Using fire-scarred trees, we inferred temporal (frequency and seasonality) and spatial (synchrony) attributes and regulators of the fire regime over three land-use periods (historical, suppression, modern) between 1702 and 2007. Patterns of fire frequency and synchrony were similar, but fire seasonality was dissimilar, between the historical and modern periods. Logistic regression and generalised linear mixed models identified a suite of variables representing fuels, climate and human land uses that were associated with the probability of a site burning. Combined, these results allow for valuable insights regarding past fire spread and variability in fire frequency throughout our study area. In some respects, the current distinct fire regime in our study area, which predominately consists of prescribed fires implemented since the 1960s, resembles the past frequent surface fire regime that occurred here and in similar forest types on non-tribal lands in the south-western United States. Our results will be useful for informing adaptive management throughout the region as climate warms.

Fire regime shift linked to increased forest density in a piñon–juniper savanna landscape

Piñon–juniper (PJ) fire regimes are generally characterised as infrequent high-severity. However, PJ ecosystems vary across a large geographic and bio-climatic range and little is known about one of the principal PJ functional types, PJ savannas. It is logical that (1) grass in PJ savannas could support frequent, low-severity fire and (2) exclusion of frequent fire could explain increased tree density in PJ savannas. To assess these hypotheses I used dendroecological methods to reconstruct fire history and forest structure in a PJ-dominated savanna. Evidence of high-severity fire was not observed. From 112 fire-scarred trees I reconstructed 87 fire years (1547–1899). Mean fire interval was 7.8 years for fires recorded at ≥2 sites. Tree establishment was negatively correlated with fire frequency (r=–0.74) and peak PJ establishment was synchronous with dry (unfavourable) conditions and a regime shift (decline) in fire frequency in the late 1800s. The collapse of the grass-fuelled, frequent, surface fire regime in this PJ savanna was likely the primary driver of current high tree density (mean=881treesha–1) that is &gt;600% of the historical estimate. Variability in bio-climatic conditions likely drive variability in fire regimes across the wide range of PJ ecosystems.

Fine-scale factors influence fire regimes in mixed-conifer forests on three high mountains in Mexico

We investigated the influence of broad- v. fine-scale factors on fire in an unusual landscape suitable for distinguishing the drivers of fire synchrony. Our study was conducted in the Sierra Madre Oriental mountain range, in north-eastern Mexico. We worked in nine sites on three parallel mountains that receive nearly identical broad-scale climatic influence, but between which fires are unlikely to spread. We collected and cross dated samples from 357 fire-scarred trees in nine sites in high-elevation mixed-conifer forests and identified fire dates. We used Jaccard similarity analysis to evaluate synchrony among sites and quantified relationships between climate and fire occurrence. Fires were historically frequent (mean fire interval ranged from 8 to 16 years in all sites) and dates of fire exclusion ranged from 1887 to 1962. We found low fire synchrony among the three mountains, indicating a strong influence of fine-scale factors on fire occurrence. Fire regime attributes were similar across mountains despite the independence of fire dates. La Niña events were associated with fire over time, although not significantly since the 1830s. Our results highlight the importance of scale in describing fire regimes and suggest that we can use fire history to understand controls on complex ecosystem processes and patterns.

Fire history, related to climate and land use in three southern Appalachian landscapes in the eastern United States

Fire-maintained ecosystems and associated species are becoming increasingly rare in the southern Appalachian Mountains because of fire suppression policies implemented in the early 20th century. Restoration of these communities through prescribed fire has been hindered by a lack of information on historical fire regimes. To characterize past fire regimes, we collected and absolutely dated the tree rings on cross sections from 242 fire-scarred trees at three different sites in the southern Appalachian Mountains of Tennessee and North Carolina. Our objectives were to (1) characterize the historical frequency of fire in southern Appalachian mixed pine-oak forests, (2) assess the impact of interannual climatic variability on the historical occurrence of fire, and (3) determine whether changes in human culture and land use altered the frequency of fire. Results demonstrate that fires burned frequently at all three sites for at least two centuries prior to the implementation of fire suppression and prevention in the early to mid 20th century. Composite mean fire return intervals were 2-4 yr, and point mean fire return intervals were 9-13 yr. Area-wide fires that burned across multiple stands occurred at 6-13-yr intervals. The majority of fires were recorded during the dormant season. Fire occurrence exhibited little relationship with reconstructed annual drought conditions. Also, fire activity did not change markedly during the transition from Native American to Euro-American settlement or during the period of industrial logging at the start of the 20th century. Fire activity declined significantly, however, during the fire suppression period, with a nearly complete absence of fire during recent decades. The characterization of past fire regimes should provide managers with specific targets for restoration of fire-associated communities in the southern Appalachian Mountains. The fire chronologies reported here are among the longest tree-ring reconstructions of fire history compiled for the eastern United States and support the hypothesis that frequent burning has played a long and important role in the development of forests in the southern Appalachian Mountains.

Privatization, Drought, and Fire Exclusion in the Tuul River Watershed, Mongolia

Global wildfire frequency and extent are expected to increase under projected climate change in the twenty-first century, yet little is known about how human activities might affect this trend. In central Mongolia, there has been a 2.5°C rise in spring and summer temperatures during the last 40 years and a decrease in moisture availability during the latter half of the twentieth century. Concurrently, Mongolia has experienced multiple shifts in socioeconomic systems during the twentieth century, most notably the establishment of a Soviet-backed communist economy in the 1920s and a rapid transition to privatization in the 1990s. Observed records of fire in the late twentieth century suggested that fire activity had increased, but no long-term data existed to place these trends in a historical context. Our objective was to identify spatial and temporal patterns in fire occurrence in the forest-steppe ecotone of the Tuul River watershed in the context of changing climatic and social conditions since 1875. We used fire-scarred trees to reconstruct past fire occurrence during the period 1875–2009. Our results indicate a significant association between human activity and fire occurrence independent of climatic variables. The greatest evidence for an anthropogenic fire regime exists following the transition to a free market economy during the early 1990s when land-use intensification near the capital city of Ulaanbaatar resulted in fire exclusion. We emphasize the importance of including socio-political variables in global models of wildfire potential, particularly where fuels limit fire activity.

Can scar-based fire history reconstructions be biased? An experimental study in boreal Scots pine

Determining forest fire history is commonly based on fire scar dating with dendrochronological methods. We used an experimental setup to investigate the impacts of low-intensity prescribed fire on fire scar formation 8 years after fire in 12 young managed Scots pine (Pinus sylvestris L.) stands. Five stands were between 30 and 35 years old and seven were 45 years old at the time of burning. A total of 217 fire scars were recorded in 142 trees. The number of separate scars per tree originating from a single fire ranged from 1 to 6, with 67% of the trees having just one scar. The proportion of fire-scarred trees out of all trees per plot ranged from 0% to 30%, averaging 16.5% in young stands and 2.8% in older stands. Four of the 12 burned plots did not have any trees with fire scars, and these were all in the older age group. This means that in the older stands, in only three of seven plots (43%) did the fire leave scars from which fire can potentially be detected and dated afterwards. Our results suggest that fire scar dating in Scots pine dominated forests may underestimate fire frequency, area, and the importance of historically common low-intensity surface fires in dendrochronological reconstructions of past fire histories.

Variability of warm/dry mixed conifer forests in southwestern Colorado, USA: Implications for ecological restoration

There is a need to quantitatively describe forest types and their associated natural fire regimes in the western US to understand their variability and to develop strategies to restore fire dependent landscapes to reduce ecological problems that might ensue from forest structure and fire regime generalizations. We established three study sites in warm/dry mixed conifer across a west–east transect in southwestern Colorado to determine variability in the historical fire regime and fire–climate relationships and to quantify how diverse warm/dry mixed conifer forest composition and structure are along the same west–east transect. At each study site we collected cross-sections from dead fire-scarred trees to reconstruct fire history and established study plots to characterize forest structure. The three warm/dry mixed conifer sites exhibited different fire histories. One site was characterized by numerous smaller fires as well as larger fires that appeared to burn most of the study site with the other two study sites characterized by relatively infrequent, large fire events. There were more unique fire years at each site than synchronous fire years shared by any sites. Current forest stand structure, after extended fire exclusion and past logging across the three sites, also varied with a reverse-J distribution indicating strong dominance by small trees for two of the study sites and a truncated age distribution at the other site. Our research illustrates that historical fire regime variability exists within the same vegetation type in a relatively small, ∼50km, geographic locality emphasizing the role that other topographic variables play in determining fire regimes and forest structure. Our findings demonstrate the need to develop site-specific reference conditions and for managers to exercise caution when extrapolating fire regimes and forest structure from one geographic locality to another given a projected warmer climate making conditions more favorable to frequent, large wildfires.

Low- to moderate-severity historical fires promoted high tree growth in a boreal Scots pine forest of Norway

Fire is the most important ecological factor governing boreal forest stand dynamics. In low- to moderate-severity fires, the post-fire growth of the surviving trees varies according to fire frequency, intensity and site factors. Little is known about the growth responses of Scots pine (Pinus sylvestris L.) following fires in boreal forests. We quantified changes in tree growth in the years following 61 historical forest fires (between 1210 and 1866) in tree-ring series collected from fire-scarred Scots pine trees, snags and stumps in Trillemarka nature reserve in south-central Norway. Basal area increment 10 years pre-, 5 years post-, and 11–20 years post-fire were calculated for 439 fire scars in 225 wood samples. We found a slight temporary growth reduction 5 years post-fire followed by a marked growth increase 11–20 years post-fire. Beyond 20 years post-fire, the long-term tree growth declined steadily up to approximately 120 years. Our results indicate that recurring fires maintained high tree growth in remnant Scots pines, most probably due to a reduction in tree density and thus decreased competition.