The oyamel forests, as Abies dominated forests are commonly known as, register their largest distribution (95% of their population) along the Trans-Mexican Volcanic Belt (TMVB). Although efforts have ...been made to study these forests with various approaches, dendrochronology-based studies have been limited, particularly in pure Abies forests in this region. The objective of this study was to reconstruct fire regimes in an Abies religiosa forest in the Sierra Norte in the state of Puebla, Mexico. Within an area of 50-ha, we collected 40 fire-scar samples, which were processed and analyzed using dendrochronological techniques to identify 153 fire scars. The fire history was reconstructed for a period of 118 years (1896–2013), with low severity surface fires occurring mainly during in the spring (92.8%) and summer (7.2%). Over the past century, fires were frequent, with an mean fire interval (MFI) and Weibull median probability of (WMPI) of five years when considering all fire scars and less than 10 years for fires covering larger areas (fires recorded by ≥25% of samples). Extensive fires were synchronized with drought conditions based on Ring Width Indexes, Palmer Drought Severity Index (PDSI) and El Niño Southern Oscillation (ENSO). After 1983, we observed a change in fire frequencies attributed to regulated management. Longer fire intervals within the last several decades are likely leading to increased fuel accumulations and could potentially result in more severe fires in the future, threatening the sustainability of these forests. Based on our finding, we recommend management actions (silvicultural or prescribed fire) to reduce fuels and the risk of severe fires, particularly in the face of climatic changes.
To sustainably manage forests, it is important to understand the historical fire regimes including the severity, frequency, seasonal timing of fires as well as the relationship between climate and ...fire in order to develop management plans that mimic and/or complements the natural disturbance pattern. The objectives of this study were to reconstruct the natural fire regime within a
Pinus lumholtzii
site in order to understand the fire regimes within this forest type as well as adjacent high timber value mixed-pine forests where historical fire regimes are not available due to past timber harvesting activities. Using 36 fire-scarred trees, we reconstructed the historical fire regimes in San Dimas, Durango, México for the last 238 years. We found a pattern of frequent fires but an absence of fire since 1962, with most fires (98%) being recorded in the spring season. The lack of fire for over six decades within these historically frequent fire forests could result in high fuel accumulation. Such conditions in combination with increasing temperatures and aridity in the region could increase the risk of high severity wildfires that could jeopardize the sustainability of these forests and the human communities that these forests support.
Key message
Baldcypress, a long-lived species of riparian habitats, is sensitive to interannual climate variability. The annual radial growth is associated with the Standardized Precipitation ...Evaporation Index (SPEI) and Palmer Drought Severity Index (PDSI), both depending on a water balance.
The baldcypress (
Taxodium mucronatum
Ten.) is a long-lived species and Mexico’s national tree. The objective of this study was to analyze the dendroclimatic response of baldcypress at sites located on the transitional zone between the semiarid and subtropical regions of Mexico, known as the Middle Zone of the state of San Luis Potosi, Mexico. The first site, Los Peroles (LPO), is a wetland where the oldest known baldcypress specimens in Mexico are found. The second site, Rio Verde (RVDE), is a riparian site located along a tributary of the Moctezuma River that drains into the Gulf of Mexico. Two ring-width chronologies were analyzed. The first one from LPO with a length of 633 years and the second one from RVDE with a length of 423 years. The species responded positively to the seasonal January–July precipitation (
r
= 0.52,
p
= 0.001) and negatively to the maximum monthly temperature of January, May, and June (
r
= − 0.42, −0.46, and −0.34; respectively). The average chronology was significantly associated with the mean January–August Standardized Precipitation Evaporation Index (SPEI) (
r
= 0.62,
p
= 0.000). An SPEI reconstruction was developed for the period 1575–1996 where the most prolonged and severe droughts were found at 70-year peaks in the El Niño Southern Oscillation frequency band. The annual radial growth of the species is a suitable indicator of the January–August water availability, and is important information that can be used to establish water management strategies for this semiarid environment and to preserve millennial baldcypress specimens.
Cofre de Perote National Park (CPNP) in Veracruz, Mexico is part of the Transmexican Volcanic Belt, and its Pinus hartwegii forests reflect a balance between the various natural factors that ...represent the region's climatology and hydrology. Like many other areas in this region, the historical fire regimes of these forests and their relationship with climate are unknown, but are needed for sustainable management plans. The main objectives of this study were to reconstruct the historical fire regime in a Pinus hartwegii forest and decipher the influenced of climate. Our investigation focused in two study areas, Valle la Teta (VT) and Barranca Honda (BH). The VT study area was divided into three sites based on humidity and elevation: 1) Humid (VTH), 2) Dry Low (VTDL) and 3) Dry High (VTDH). The approximated area for each site was 30, 30, 35 and 50 ha, for VTH, VTDL, VTDH and BH, respectively. We collected 162 fire scarred samples to reconstruct the fire history for the last 550 years (1461−2013). The fire scarred samples contained 1240 fire scars, with most fires occurring in spring (95 %) or summer (5%). Prior to 1973, these sites were characterized by a frequent surface fire regime. In all four sites, the mean fire intervals ranged from 5 to 6 years (for fires that scarred ≥ 10 % of the samples) and 13–23 years (for fires that scarred ≥ 25 % of the samples). Extensive fires (≥ 10 %) coincided with significantly dry conditions based on the Standardized Precipitation Index (SPI), influenced by El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation Index (PDO). We also found a significant relationship between fire occurrence and ENSO, both in its warm phase, El Niño (21 fires ≥ 10 %) and in its cold phase, La Niña (32 fires ≥ 10 %). Synchronization of the cold phase of ENSO (La Niña) with the cold phase of the PDO (negative), facilitated severe drought conditions, resulting in fires with the greatest spatial extent. Since 1973, extensive fires have been absent from the study area most likely due to anthropogenic activities including active fire suppression. These results show a strong climate-fire relationship in these high elevation forests. The lack of fire in the last four decades is concerning and could potentially lead to unnatural stand-replacing fires, unless the historical fire regime is restored to maintain natural processes and increase forest resilience.
Tree rings have been used to reconstruct climatological variables in many locations around the world. Moreover, tree-rings can provide valuable insights into climatic variability of the last few ...centuries and, in some areas, several millennia. Despite the important development, that dendrochronology has had in recent decades to study the dendroclimatic potential of a large number of species present in different ecosystems, much remains to be done and explored. In addition to this, in the last few years more people (students, teachers and researchers) around the world are interested in implementing this science to extend the timeline of climate information backwards and understand how climate has changed on scales of decades, centuries or millennia. Therefore, the objective of this work is to describe the general aspects and basic steps needed to conduct a tree-ring climate reconstruction, from site selection and field sampling to laboratory methods and data analysis. In this method's video and manuscript, the general basis in tree-ring climatic reconstructions is explained so newcomers and students can use it as an available guide into this field of research.
Annual tree-ring patterns are a source of ecological and environmental information including the history of fires in forested areas. Tree-ring based fire histories include three fundamental phases: ...field collection, laboratory methods (preparation and dating), and data analysis. Here we provide step-by-step instructions and issues to consider, including the process for selecting the study area, sampling sites, plus how and which fire-scarred trees to sample. In addition, we describe fire-scar sample preparation and dating which are done in the laboratory. Finally, we describe basic analysis and relevant results, including examples from studies that have reconstructed fire history patterns. These studies allow us to understand the historical fire frequency, changes in those frequencies related to anthropogenic factors, and analyzes of how climate influences fire occurrence over time. The description of these methods and techniques should provide a greater understanding of fire history studies that will benefit researchers, educators, technicians, and students interested in this field. These detailed methods will allow new researchers to this field, a resource to start their own work and achieve greater success. This resource will provide a greater integration of tree-ring aspects within other studies and lead to a better understanding of natural processes with forested ecosystems.
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