Charcoal analysis of lake sediments is used to reconstruct long-term variations in fire occurrence that can complement and extend reconstructions provided by dendrochronological and historical records In the last 15 years, several papers have reviewed the methods for charcoal analysis of lake-sediment cores and its use as a tool for studying fire history (eg, Tolonen, 1986; Patterson et al, 1987; MacDonald et al, 1991; J S Clark, 1988a; J S Clark et al, 1998; Long et al, 1998; Whitlock & Anderson, in review) In most cases, pollen and charcoal data from the same cores are used to examine the linkages among climate, vegetation, fire, and sometimes anthropogenic activities in the past The growing use of charcoal analysis reflects a heightened interest within the paleoecological community to consider fire as an ecosystem process operating on long and short time scales, as well as an increasing need on the part of forest managers to understand prehistoric fire regimes In this chapter, we discuss issues of site selection, chronology, and methodology in charcoal analysis, based on recent advances in the discipline We also review the theoretical and empirical basis for charcoal analysis, including assumptions about the charcoal source area and the processes that transport and deposit charcoal into lakes Fire reconstructions based on lake-sediment records are derived from three primary data sources: particulate charcoal that provides direct evidence of burning; pollen evidence of fluctuations in vegetation that can be tied to disturbance; and lithologic evidence of watershed adjustments to fire, such as erosion or the formation of fire-altered minerals Charcoal analysis quantifies the accumulation of charred particles in sediments during and following a fire event Stratigraphic levels with abundant charcoal (so-called charcoal

Charcoal as a Fire Proxy

Particle motion and the theory of charcoal analysis: Source area, transport, deposition, and sampling

The difficulties of saving millions of species from extinction often cause conservationists to focus on a higher level of biological organization, the community. They do so for two reasons: (1) communities are considered important biological entities in their own right; and (2) conserving representative samples of communities is seen as an efficient way to maintain high levels of species diversity. This approach will work if the chosen communities contain almost all species. Because it potentially saves most but not all species, community conservation is a “coarse-filter” approach to the maintenance of biological diversity, and contrasts with the “fine-filter” approach of saving individual species. Paleoecological information on the distribution of plant taxa in North America, however, indicates that most modern plant communities are less than 8,000 years old and therefore are not highly organized units reflecting long-term co-evolution among species. Rather, they are only transitory assemblages or co-occurrences among plant taxa that have changed in abundance, distribution, and association in response to the large climate changes of the past 20,000 years. During periods when climate changes are large, communities are too ephemeral to be considered important biological entities in their own right. Large climatic changes are also likely to occur during the next century because of increased concentrations of CO2, and we therefore propose that the coarse-filter approach to selecting nature reserves should be more strongly influenced by the distribution of physical environments than by the distribution of modern communities. Ideally, nature reserves should also encompass a broad enough range of environments to allow organisms to adjust their local distribution in response to long-term environmental change and should be connected by regional corridors that would allow species to change their geographic distributions.



Resumen: Las dificultades en salvar millones de especies de extincion muchas veces lleva a los conservacionistas a enfocarse a un nivel mas alto de organizacion biologica: la comunidad. Ellos lo hacen por dos razones: 1. las communidades son consideradas entidades biologicas importantes en su derecho, y 2. conservando ejemplos representativos de las communidades se considera manera eficiente de mantener niveles altos de diversidad de especies. Esta aproximacion aproche trabaja si las comunidades escogidas contienen casi todas las especies. Al salvar potencialmente la mayoria, pero no todas las especies, la conservacion de comunidades es solo una aproximacion gruesa para el mantenimiento de la diversidad biologica, y contrasta con la mayor resolucion que representa el de salvar especies individuales. Sin embargo, informacion paleoecologico sobre la distribucion de la taxonomia de plantas en Norte America indica que las comunidades mas modernas de plantas tienen menos de 8,000 anos y por eso no son unidades bien organizadas reflejando coevolucion de largo plazo entre las especies. Mas bien, son ensamblajes transitorios o concurrentes entre la taxonomia de plantas que ban cambiado su abundancia, distribucion y asociacion en respuesta a cambios grandes climaticos de los ultimos 20,000 anos. Durante periodos cuando los cambios de clima son grandes, comunidades son muy efimeras para considerarse entidades biologicos importantes Cambios grandes climaticos tambienson probables durante el proximo siglo por las concentraciones crecientes de CO2, y nosotros, por esta razon proponemos que la aproximucion gruesa de seleccionar reservas de la naturaleza debe ser mas influenciada por la distribucion de ambientes fisicos que por la distribucion de comunidades modernas. Idealmente, las reservas de la naturaleza tambien deben considerar un rango suficientemente amplio de ambientes diferentes para permitir a los organismos a ajustar su distribucion local en respuesta a cambios ambientales de largo plazo. Asi mismo las reservas deben, en lo posible, formar corredores regionales que permitan a las especies cambiar su distribucion geograficas.

Paleoecology and the Coarse-Filter Approach to Maintaining Biological Diversity

Summary 1 Studies on the variability of natural fire regimes are needed to understand plant responses in a changing environment. Since vegetation changes might follow or trigger changes in fire frequency, climate models suggest that changes in water balance will accompany current global warming, and the response of fire regimes to Holocene hydro-climate changes and vegetation switches may thus serve as a useful analogue for current change. 2 We present high-resolution charcoal records from laminated cores from three small kettle lakes located in mixed-boreal and coniferous-boreal forest. Comparison with some pollen diagrams from the lakes is used to evaluate the role of the local vegetation in the fire history. Fire frequency was reconstructed by measuring the separation of peaks after detrending the charcoal accumulation rate from any background. 3 Several distinct periods of fire regime were detected with fire intervals. Between c. 7000‐3000 cal. year bp , fire intervals were double those in the last 2000 years. Fire frequency changed 1000 years earlier in the coniferous-boreal forest than in the mixedboreal forest to the south. The absence of changes in combustibility species in the pollen data that could explain the fire frequency transition suggests that the vegetation does not control the long-term fire regime in the boreal forest. 4 Climate appears to be the main process triggering fire. The increased frequency may be the result of more frequent drought due to the increasing influence of cool dry westerly Pacific air-masses from mid to late Holocene, and thus of conditions conducive to ignition and fire spread. In east Canada, this change matches other long-term climate proxies and suggests that a switch in atmospheric circulation 2‐3000 years ago triggered a less stable climate with more dry summers. Future warming is moreover likely to reduce fire frequency.

https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2745.2001.00614.x

Change of fire frequency in the eastern Canadian boreal forests during the Holocene: does vegetation composition or climate trigger the fire regime?

http://www.maforests.org/Lorimer%20and%20White%20-%20ES%20Habitat.pdf

Scale and frequency of natural disturbances in the northeastern US: implications for early successional forest habitats and regional age distributions

The changing character of vegetation and the effects of disturbance on vegetation are inferred from pollen, plant macrofossils, charcoal, and microlepidopteran larvel head capsules in sediment core...

Robert Stuckenrath

Papers

History of late- and post-glacial vegetation and disturbance around Upper South Branch Pond, northern Maine