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Fire History in Ponderosa Pine and Mixed-Conifer Forests of the Jemez Mountains, Northern New Mexico
... The seasonal position of fire scars was identified through an approximate timing of individual fires relative to the growing season of the trees (Baisan and Swetnam, 1990;Touchan and Swetnam, 1995). The criteria used to define scar position were: ...
... This is could be related to the fact that Mount Chelia sites are pure stands of Atlas cedar and more open with a sparser understory than at either AGU or AEH. In other forest types, especially slightly flammable to highly flammable forests, various studies have reported different patterns in which fires were intense, with a large spatial extent and where the recorded events were highly synchronous between trees and sites (Touchan et al., 1995(Touchan et al., , 1996Fulé et al., 2008). ...
Forty-one fire-scarred samples from two new Cedrus atlantica sites in the Ouled-Yaâgoub Forest were collected and combined with the two previous sites from the Chelia Forest reported in Slimani et al. (2014) to develop a regional analysis of fire history in the Aurès Mountains, northern Algeria. Prior to 1850, cedar forests were characterized by high frequency, low-intensity surface fire regimes. Fire frequency declined after 1850 after the elimination of the Barbary lion and the enforcement of the first laws governing land and forest use in Algeria. Most of the fire events in both forests occurred in the summer season, the latter part of the growing season, or in the dormant season. We compared past fires occurrences and an October-June precipitation reconstruction. On a regional scale, precipitation was significantly reduced in the months prior to the fire occurrence. In addition, precipitation during the first year preceding the fire years was significantly above average. This study provides a baseline for planning and justifying improved ecosystem management programs.
... We examined responses of soil mites, collembolans, and nematodes to thinning with mastication alone or with prescribed fire in a P. ponderosa forest within Valles Caldera National Preserve, New Mexico. Ponderosa pine forests in the region historically experienced low-severity surface fires with decadal to subdecadal return intervals (Touchan et al., 1994;Dewar et al., 2021). The native Jemez Pueblo people heavily influenced fire regimes from the pre-colonial era until the late 1600s, increasing ignitions and reducing fuel connectivity (Swetnam et al., 2016). ...
Thinning, mastication, and prescribed fire are restoration treatments frequently employed in unnaturally dense second-growth Pinus ponderosa forests of the Western United States. Although a goal of these treatments is to restore ecosystem structure and function, little information is available regarding treatment effects on soil micro- and mesofauna, which comprise the overwhelming majority of metazoan forest inhabitants and occupy key positions in soil food webs. We quantified nematodes, mites, and collembolans in soil and litter habitats within untreated control, thinned (comprising thinning and masticating wood), and burned (comprising thinning and masticating, followed by broadcast burn) in P. ponderosa forest management units at Valles Caldera National Preserve in New Mexico, USA. We linked patterns in animal abundance to resource and habitat characteristics, hypothesizing that resources and available habitat for many taxa would increase with thinning and decrease with burning. Two years after thinning, densities of collembolans and nematodes in the thinned unit were higher than in the untreated control unit, but one year post-fire, their densities in the burned unit were similar to those of the untreated control unit. Mite abundance, however, was not elevated in the thinned unit and was lower in the burned unit. Although faunal communities were highly heterogeneous, a significant proportion of the variance in faunal abundances was explained by easily and inexpensively measured habitat and resource characteristics: bulk density, soil organic matter (SOM), pH, grass cover, and litter cover and depth. These findings demonstrate the abiotic and biotic factors that structure faunal habitats so that forest managers have a more complete understanding of the impacts of forest restoration treatments.
... Annual precipitation ranges from ~30 cm at the lower elevations to ~90 cm at higher elevations. Winter precipitation falls primarily as snow, with average accumulations of about 1300 mm (Touchan and Swetnam, 1995). ...
High-severity wildfire in arid regions has caused ecological state change, transforming previously forested areas into shrublands. This dramatically alters the microclimatic conditions, which can exceed the climatic tolerance of tree seedlings, rendering the likelihood of returning post-wildlife landscapes to their previous state relatively low. Characterizing microclimatic variability across severely burned landscapes could allow for identifying locations where seedling survival is more likely. We used a combination of small unmanned aircraft system imagery, satellite data and in-situ microclimate data recordings, together with a machine learning approach, to model monthly near-ground minimum, mean and max temperature as well as relative humidity and vapor pressure deficit in a previously forested area, which is now dominated by two different shrub species. Spatially explicit models predicted recorded microclimate well (r = 0.73 to 0.97), and model projections highlight that at any given location in the hottest month, the solar buffering capacity of existing vegetation can alter the maximum temperature by ∼12 °C, increase relative humidity by ∼20% and reduced vapor pressure deficit by 0.3mbar relative to open areas. By harnessing these microclimate refugia, the success rate of reforestation efforts in post-wildfire landscapes could be substantially increased and mitigate seedlings from climate warming at local scales.
... We identified the seasonality of fire occurrence by determining the exact location of the fire scar within the annual growth ring (Baisan and Swetnam, 1990) Data Analysis-In order to create the master fire chronology and perform statistical analysis, we used the FHX2 software, version 3.2 (Grissino-Mayer, 2001). We calculated summary statistics for the period of adequate sample depth, also known as the ''period of reliability,'' which consists of the period between the first and last occurrence of a minimum proportion of scarred samples in any given fire year (Touchan and Swetnam, 1995). For every year, we determined the appropriate period, when at least 25% of the total samples had scars. ...
Mexican forest ecosystems are exposed to a great variety of natural disturbances such as fire,
which is a key disturbance process influencing tree survival and regeneration. Nevertheless, forest fires are one
of the primary causes for which a large portion of the forest in Mexico is lost. Thus, the objectives of this
research were to determine (1) the pattern of occurrence of forest fires, and (2) their relationship with
precipitation and atmospheric circulation patterns. We reconstructed the historical forest fire regime from fire
scars of 22 sample trees in a coniferous forest stand on the mountain Cerro El Potosí in southern Nuevo León,
Mexico. Frequent surface fires characterized the site. The mean fire return interval for all fires was 11 years
and for the more-widespread fires (those that scarred ‡25% of all samples) was longer (15.7 years). The
Superposed Epoch Analysis indicated as not statistically significant the role of dry years as well for the
subsequent wet conditions for the period from 1881 to 2004.
... Despite the prevalent use of ponderosa pine (Pinus ponderosa) in dendroclimatology studies (second only to Douglas-fir, Pseudotsuga menziesii in North America in the International Tree-Ring Data Bank ITRDB), we still do not fully understand the possible mechanisms controlling the variability of ponderosa pine ring-width increment in some areas of the West. Given the occurrence of ponderosa pine in low-elevation forested environments, it is generally accepted as a good proxy for hydroclimate variability (site selection principle, Fritts 1976), evidenced by its use for stream flow (Smith and Stockton 1981;Woodhouse 2001), precipitation (Graumlich 1987;Touchan and Swetnam Multiple factors likely control ring-width variability of ponderosa pine across its broad range. Given that this species primarily occurs at warmer temperatures and lower elevations, it is typically considered to respond to water availability more than temperature, as species growing in colder temperatures and higher altitudes (e.g. ...
Despite the widespread use of ponderosa pine as an important hydroclimate proxy, we actually understand very little about its climate response in the Northern Rockies. Here, we analyze two new ponderosa pine chronologies to investigate how climate influences annual growth. Despite differences in precipitation amount and timing and large elevation differences (1820 m versus 1060 m), ring width at both sites was strongly driven by water availability. The mid-elevation, water-limited site responded well to previous fall precipitation whereas the wetter, high-elevation site responded to growing season precipitation and temperature. When precipitation and temperature were simultaneously accounted for using the standardized precipitation evapotranspiration index, ring-width response between sites converged and appeared nearly identical. Water stress drove the timing of ponderosa pine growth by a combination of factors such as strong water dependence, and determinate growth physiology, as indicated by lag-1 autocorrelation. When analyzing response to single-month climate variables, precipitation from growing-season months dominates. When we examined seasonal variables, climate from the previous year became more important. Temporal fidelity of the climatic response at both sites maintained significance across the historical record, although the relationship weakened at the low-elevation site. The collection of new tree-ring data sets such as these for central Idaho improves our understanding of ponderosa pine growth response to climate.
... Because fire-interval data are often skewed and are better fit by the Weibull distribution (Grissino-Mayer 1995), we used a Kolmogorov-Smirnov test for fit (in the FHX2 software) to ascertain which distribution best fit our data (Grissino-Mayer 2001). We defined the length of each chronology using a period of reliability (POR), defined as the portion of the chronology with a sample depth of ≥5 partial cross sections to ensure an accurate representation of fire activity (e.g., Grissino-Mayer 1995;Touchan and Swetnam 1995). We tested each chronology for temporal changes between the pre-Euro-American settlement (POR-1859) and the post-settlement (1860-2001) time periods. ...
We examined the fire history of 11 forest isolates surrounded by lava flows (kipukas) in central Oregon to determine historical differences in fire regimes between kipukas and the surrounding forest, and the role of spatial and environmental variables in fire occurrence. Tree-ring analysis and statistical comparisons show that historical agency records underestimate the number of fires based on the incidence of fire scars. Fires occurred more frequently on kipukas, were typically smaller, and were predominantly lightning-initiated. Except for three widespread fires, fires on kipukas and in the surrounding forest were largely asynchronous. The mean fire-return interval (MFRI) in the surrounding forest decreased following Euro-American settlement and increased on the kipukas with spot-fire removal. This suggests either that forest management and fire exclusion in the surrounding forest decreased fire spread to the kipukas, or that most fires originated on the kipukas. MFRI correlates strongly with distance to the nearest kipuka and a distance-weighted isolation index. The number of fires correlates with elevation change and distance to the nearest kipuka. Fire in naturally fragmented landscapes is influenced by the spatial arrangement of patches, environmental conditions, and human activities. Reconstructing fire histories from forest isolates in the context of their mainland counterparts may have methodological advantages and theoretical implications for forested landscapes characterized by human-imposed insularity.
To better understand fire regimes and their relation to climate in the seasonal tropical forests of continental Southeast Asia, we developed the first multi‐century tree‐ring based fire history chronology for the region. The chronology included 776 fire scars collected at Bidoup NuiBa National Park (BNNP) in the Central Highlands of Vietnam and spans the period 1636–2020. Fires were recorded in 116 years, representing 47% of the years covered by the 249‐year period between the first fire scar (1772) and the last (2020). While only 9% of years within the sampled BNNP forests experienced fires before 1905, 70% recorded fires between 1906 and 1963 and 90% showed evidence of fire after 1963. Fire occurrence was highly correlated with climate indices (wet season Nino 3.4 and dry season regional Palmer Drought Severity Index) during the period 1906–1963, but showed no significant correlation after 1963. Our fire reconstruction from BNNP suggests that the fire regime has shifted from one driven primarily by climate to one in which human activities dominate the occurrence of fire within these seasonal tropical landscapes.
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