A stand-replacing fire history in upper montane forests of the southern Rocky Mountains

2007 ◽  
Vol 37 (11) ◽  
pp. 2227-2241 ◽  
Author(s):  
Ellis Q. Margolis ◽  
Thomas W. Swetnam ◽  
Craig D. Allen

Dendroecological techniques were applied to reconstruct stand-replacing fire history in upper montane forests in northern New Mexico and southern Colorado. Fourteen stand-replacing fires were dated to 8 unique fire years (1842–1901) using four lines of evidence at each of 12 sites within the upper Rio Grande Basin. The four lines of evidence were (i) quaking aspen ( Populus tremuloides Michx.) inner-ring dates, (ii) fire-killed conifer bark-ring dates, (iii) tree-ring width changes or other morphological indicators of injury, and (iv) fire scars. The annual precision of dating allowed the identification of synchronous stand-replacing fire years among the sites, and co-occurrence with regional surface fire events previously reconstructed from a network of fire scar collections in lower elevation pine forests across the southwestern United States. Nearly all of the synchronous stand-replacing and surface fire years coincided with severe droughts, because climate variability created regional conditions where stand-replacing fires and surface fires burned across ecosystems. Reconstructed stand-replacing fires that predate substantial Anglo-American settlement in this region provide direct evidence that stand-replacing fires were a feature of high-elevation forests before extensive and intensive land-use practices (e.g., logging, railroad, and mining) began in the late 19th century.


Fire ◽  
2019 ◽  
Vol 2 (1) ◽  
pp. 14
Author(s):  
Lane Johnson ◽  
Ellis Margolis

Tree-ring fire scars, tree ages, historical photographs, and historical surveys indicate that, for centuries, fire played different ecological roles across gradients of elevation, forest, and fire regimes in the Taos Valley Watersheds. Historical fire regimes collapsed across the three watersheds by 1899, leaving all sites without fire for at least 119 years. Historical photographs and quaking aspen (Populus tremuloides Michx.) ages indicate that a high-severity fire historically burned at multiple high-elevation subalpine plots in today’s Village of Taos Ski Valley, with large high-severity patches (>640 ha). Low-severity, frequent (9–29-year median interval) surface fires burned on the south aspects in nearby lower elevation dry conifer forests in all watersheds. Fires were associated with drought during the fire year. Widespread fires commonly burned synchronously in multiple watersheds during more severe drought years, preceded by wet years, including fire in all three watersheds in 1664, 1715, and 1842. In contrast, recent local “large” wildfires have only burned within single watersheds and may not be considered large in a historical context. Management to promote repeated low-severity fires and the associated open stand structures is within the historical range of variability in the dry conifer forests of these watersheds. In the high-elevation, subalpine forests, different management approaches are needed, which balance ecological and socioeconomic values while providing public safety.



2015 ◽  
Vol 45 (1) ◽  
pp. 1-8 ◽  
Author(s):  
R. Justin DeRose ◽  
Karen E. Mock ◽  
James N. Long

High rates of triploidy have recently been described in quaking aspen (Populus tremuloides Michx.) of the Intermountain West, raising questions about the contributions of triploidy to stand persistence and dynamics. In this study, we investigated cytotype differences between diploid and triploid aspen clones using dendrochronological techniques. We used tree-ring data collected from stems within an aspen stand near Fish Lake, Utah, to test for differences in stem age, population structure, growth, and response to climate. This stand contains the well-known Pando clone, which is purported to be the largest organism documented on earth. Our results show that triploid aspen stems grew more rapidly than diploids, and that this difference was most pronounced early in stand development. Growth response to climate varied little between triploids and diploids, where wide rings were associated with cool, moist years, and narrow rings were associated with above-average growing season temperatures. Stand development processes and inherent genetic differences are mechanisms possibly controlling the observed differences in aspen ring width between triploids and diploids. Regardless of the mechanism, the results have specific management implications. Conventional regeneration methods involving coppicing and the associated intermediate treatments will promote asexually reproducing triploids, leading to static or reduced genetic diversity. Enhanced genetic diversity will be favored by management actions that explicitly account for (i) the potential existence of multiple cytotypes within a stand and (ii) the observed differences in growth rates between diploid and triploid individuals.



1996 ◽  
Vol 6 (3) ◽  
pp. 97 ◽  
Author(s):  
PM Brown ◽  
CH Sieg

Chronologies of fire events were reconstructed from crossdated fire-scarred ponderosa pine trees for four sites in the south-central Black Hills. Compared to other ponderosa pine forests in the southwest US or southern Rocky Mountains, these communities burned less frequently. For all sites combined, and using all fires detected, the mean fire interval (MFI), or number of years between fire years, was 16 years (± 14 SD) for the period 1388 to 1900. When a yearly minimum percentage of trees recording scars of ≥ 25% is imposed, the MFI was 20 years (± 14 SD). The length of the most recent fire-free period (104 years, from 1890 to 1994) exceeds the longest intervals in the pre-settlement era (before ca. 1874), and is likely the result of human-induced land use changes. Based on fire scar position within annual rings, most past fires occurred late in the growing season or after growth had ceased for the year. These findings have important implications for management of ponderosa pine forests in the Black Hills and for understanding the role of fire in pre-settlement ecosystem function.



Forests ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 700
Author(s):  
Julián Cerano-Paredes ◽  
Dante A. Rodríguez-Trejo ◽  
José M. Iniguez ◽  
Rosalinda Cervantes-Martínez ◽  
José Villanueva-Díaz ◽  
...  

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.



2001 ◽  
Vol 31 (7) ◽  
pp. 1205-1226 ◽  
Author(s):  
William L Baker ◽  
Donna Ehle

Present understanding of fire ecology in forests subject to surface fires is based on fire-scar evidence. We present theory and empirical results that suggest that fire-history data have uncertainties and biases when used to estimate the population mean fire interval (FI) or other parameters of the fire regime. First, the population mean FI is difficult to estimate precisely because of unrecorded fires and can only be shown to lie in a broad range. Second, the interval between tree origin and first fire scar estimates a real fire-free interval that warrants inclusion in mean-FI calculations. Finally, inadequate sampling and targeting of multiple-scarred trees and high scar densities bias mean FIs toward shorter intervals. In ponderosa pine (Pinus ponderosa Dougl. ex P. & C. Laws.) forests of the western United States, these uncertainties and biases suggest that reported mean FIs of 2-25 years significantly underestimate population mean FIs, which instead may be between 22 and 308 years. We suggest that uncertainty be explicitly stated in fire-history results by bracketing the range of possible population mean FIs. Research and improved methods may narrow the range, but there is no statistical or other method that can eliminate all uncertainty. Longer mean FIs in ponderosa pine forests suggest that (i) surface fire is still important, but less so in maintaining forest structure, and (ii) some dense patches of trees may have occurred in the pre-Euro-American landscape. Creation of low-density forest structure across all parts of ponderosa pine landscapes, particularly in valuable parks and reserves, is not supported by these results.



2020 ◽  
Vol 29 (12) ◽  
pp. 1072
Author(s):  
Alexis H. Arizpe ◽  
Donald A. Falk ◽  
Connie A. Woodhouse ◽  
Thomas W. Swetnam

The climate of the south-western United States and northern Mexico borderlands is marked by a bimodal precipitation regime with the majority of moisture arriving during the cool season via Pacific frontal storm systems, and intense convective storms during the North American Monsoon (NAM). The fire season occurs primarily during the arid foresummer in May and June, before the development of the NAM. Most tree-ring studies of fire climatology in the region have evaluated only the role of winter precipitation. We used tree-ring-width-based reconstructions of both winter and monsoon precipitation, coupled with fire scar reconstructions of fire history from mountain ranges in the US and Mexico, to quantify the historical role and interactions of both seasons of precipitation in modulating widespread fire years. Winter precipitation was the primary driver of widespread fire years in the region, but years with drought in both seasons had the highest fire frequency and most widespread fires. These relationships define a unique monsoon fire regime, in which the timing and amount of monsoon precipitation are important factors in limiting the length of fire season and regulating widespread fire years.



Trees ◽  
2021 ◽  
Author(s):  
Anastasia Christopoulou ◽  
Nikolaos M. Fyllas ◽  
Barbara Gmińska-Nowak ◽  
Yasemin Özarslan ◽  
Margarita Arianoutsou ◽  
...  

Abstract Key message Long Bosnian pine chronologies from different mountains are shaped by different climatic parameters and can help identify past drought events and reconstruct landscape histories. Abstract We developed a 735-year-long Pinus heldreichii chronology from the southern distribution limit of the species, expanding the available database of long Bosnian pine chronologies. Tree-ring growth was mainly positively correlated with growing degree days (GDD: r1950–2018 = 0.476) while higher temperatures during both winter and growing season also enhanced growth (TWT: r1950–2018 = 0.361 and TGS: 0.289, respectively). Annual precipitation, during both calendar and water years, had a negative but weaker impact on annual tree growth. The newly developed chronology correlates well with chronologies developed from the neighboring mountains. The years with ring width index (RWI) lower than the average were found to correspond to cool years with dry summers. Still, the newly developed chronology was able to capture severe drought events, such as those in 1660, 1687, and 1725. Several old living trees had internal scars presumably caused by fires. Therefore, old mature trees could be used for fire history reconstruction in addition to climate reconstruction. Although the presence of lightning scars indicates an important natural agent of fire ignition, human activities associated with animal grazing could also be an underlying reason for fires in the region.



2017 ◽  
Vol 38 (4) ◽  
pp. 630-640 ◽  
Author(s):  
Burke T Greer ◽  
Christopher Still ◽  
Grace L Cullinan ◽  
J Renée Brooks ◽  
Frederick C Meinzer


2017 ◽  
Vol 41 (4) ◽  
pp. 478-495 ◽  
Author(s):  
UK Thapa ◽  
S St. George ◽  
DK Kharal ◽  
NP Gaire

The climate of Nepal has changed rapidly over the recent decades, but most instrumental records of weather and hydrology only extend back to the 1980s. Tree rings can provide a longer perspective on recent environmental changes, and since the early 2000s, a new round of field initiatives by international researchers and Nepali scientists have more than doubled the size of the country’s tree-ring network. In this paper, we present a comprehensive analysis of the current tree-ring width network for Nepal, and use this network to estimate changes in forest growth nation-wide during the last four centuries. Ring-width chronologies in Nepal have been developed from 11 tree species, and half of the records span at least 290 years. The Nepal tree-ring width network provides a robust estimate of annual forest growth over roughly the last four centuries, but prior to this point, our mean ring-width composite fluctuates wildly due to low sample replication. Over the last four centuries, two major events are prominent in the all-Nepal composite: (i) a prolonged and widespread growth suppression during the early 1800s; and (ii) heightened growth during the most recent decade. The early 19th century decline in tree growth coincides with two major Indonesian eruptions, and suggests that short-term disturbances related to climate extremes can exert a lasting influence on the vigor of Nepal’s forests. Growth increases since AD 2000 are mainly apparent in high-elevation fir, which may be a consequence of the observed trend towards warmer temperatures, particularly during winter. This synthesis effort should be useful to establish baselines for tree-ring data in Nepal and provide a broader context to evaluate the sensitivity or behavior of this proxy in the central Himalayas.



2018 ◽  
Vol 48 (9) ◽  
pp. 1108-1113 ◽  
Author(s):  
Gabriel Sangüesa-Barreda ◽  
J. Julio Camarero ◽  
Jan Esper ◽  
J. Diego Galván ◽  
Ulf Büntgen

Long-term fluctuations in forest recruitment, at time scales well beyond the life-span of individual trees, can be related to climate changes. The underlying climatic drivers are, however, often understudied. Here, we present the recruitment history of a high-elevation mountain pine (Pinus uncinata Ram.) forest in the Spanish central Pyrenees throughout the last millennium. A total of 1108 ring-width series translated into a continuous chronology from 924 to 2014 CE, which allowed estimated germination dates of 470 trees to be compared against decadal-scale temperature variability. High recruitment intensity mainly coincided with relatively warm periods in the early 14th, 15th, 19th, and 20th centuries, whereas cold phases during the mid-17th, early 18th, and mid-19th centuries overlapped with generally low recruitment rates. In revealing the importance of prolonged warm conditions for high-elevation pine recruitment in the Pyrenees, this study suggests increased densification and even possible upward migration of tree-line ecotones under predicted global warming.



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