Cathy Whitlock

The Paleoecologic recod provides unique insights into the response of communities to environmental perturbations of different duration and intensity. Climate is a primary agent of environmental change and its long-term effect on the vegetation of the Yellowstone/Grand Teton region is revealed in a network of pollen records (Whitlock, 1993). Fire frequency is controlled by climate, and as climate changes so too does the importance of fire in shaping spatial patterns of vegetation. The prehistoric record of Yellowstone's Northern Range, for example, shows the response of vegetation to the absence of major fires in the last 150 years (Whitlock et al., 1991; Engstrom et al., 1991). In longer records spanning the last 14,000 years, periods of frequent fire are suggested by sediments containing high percentages of fire-adapted trees, including lodgepole pine and Douglas-fir, and high amounts of charcoal (Bamosky et al., 1987; Millspaugh and Whitlock, 1993; Whitlock, 1993). The primary...

Fire is an important form of natural disturbance in nearly all terrestrial ecosystems in the western United States, and it serves as a critical link between climate change and ecosystem response (Agee, 1990; Swetnam and Betancourt, 1998). The nature of these linkages depends on the time scale of interest. On short time scales, climate/weather and vegetation characteristics affect the fire conditions of particular years (and decades), as well as the dynamics of post-fire ecological succession. On centennial and millennial time scales, large-scale changes in climate alter regional fire regimes and vegetation composition. The linkages are especially complex in the western U.S., where fire regimes vary across environmental gradients and include frequent surface fires as well as infrequent stand-replacement events.

Information on past fire activity is provided by dendrochronological data and charcoal records from lake sediments (see Agee 1993; Patterson et al. 1987; Whitlock and Larsen 2002). These sources describe fire occurrence at different temporal and spatial scales of resolution, and together tree-ring and charcoal data offer a supplementary approach to fire reconstructions. Fire-scarred treering and stand-age information is limited to living trees, and in most regions yields fire reconstructions that span the last 500 years or less. Firescarred tree rings register fire events that were not lethal to the tree, whereas stand establishment dates identify the minimum age of the last severe fire. Dendrochronological records offer a high level of spatial resolution in that the location of the fire is identifiable, and a combination of tree-ring and stand-age data makes it possible to discern identify locations of high-severity and low-severity fires. Tree-ring records are also temporally prec...

Abstract Fire activity was reconstructed at five sites and vegetation history at three sites in northwest Tasmania, Australia in order to examine the climate and human drivers of environmental change in the region. Watershed-scale reconstructions of fire were compared to regional vegetation history. Fire activity was very low until ca. 12,000 cal yr BP. An early-Holocene fire maximum, ca. 11,800–9800 cal yr BP, occurred during the warmest interval of the Holocene as recorded by regional paleoclimate proxy records. This period of elevated burning was also coincident with an increase in arboreal sclerophyll plant taxa. A maximum in rainforest taxa occurred at ca. 8500-5800 cal yr BP concurrent with sharply diminished biomass burning compared with the early Holocene. The increase in rainforest taxa is attributed to elevated effective moisture during this period. Conditions were drier and variable in the late Holocene as compared with earlier periods. A rise in fire activity at ca. 4800-3200 cal yr BP was accompanied by an increase in sclerophyll taxa and decline of rainforest and subalpine taxa. Elevated palynological richness during the late Holocene co-occurred with high levels of charcoal suggesting that fires promoted high floristic diversity. At Cradle Mountain, there is no clear evidence that fire regimes or vegetation were extensively modified by humans prior to European settlement. Climate was the primary driver of fire activity over millennial timescales as explained by the close relationship between charcoal and climate proxy data.

Conservation efforts to protect forested landscapes are challenged by climate projections that suggest substantial restructuring of vegetation and disturbance regimes in the future. In this regard, paleoecological records that describe ecosystem responses to past variations in climate, fire, and human activity offer critical information for assessing present landscape conditions and future landscape vulnerability. We illustrate this point drawing on 8 sites in the northwestern United States, New Zealand, Patagonia, and central and southern Europe that have undergone different levels of climate and land-use change. These sites fall along a gradient of landscape conditions that range from nearly pristine (i.e., vegetation and disturbance shaped primarily by past climate and biophysical constraints) to highly altered (i.e., landscapes that have been intensely modified by past human activity). Position on this gradient has implications for understanding the role of natural and anthropog...

High-resolution records of geochemical data from four lakes in the Greater Yellowstone region were used to investigate watershed and lake history during the late-glacial and early-Holocene periods. Clastic input to regional lakes was high and variable during the early stages of lake development, when the surrounding landscape was geomorphically unstable and sparsely vegetated, and it decreased as vegetation gradually developed in each catchment. The decrease of clastic input was not regionally synchronous but occurred in a time-transgressive pattern from south to north. Long-term organic matter concentration and diatom production were inversely related to catchment erosion during the early stages of lake development and increased as temperatures warmed and in-lake nutrient concentrations increased. Similarly, calcite production usually was low following lake formation and increased over time, driven by climate change and its associated influences on lake-level, algal production, and lake thermal structure. Overall differences in the timing and pattern of geochemical change indicate that once the landscape had stabilized following deglaciation, changes in the geochemical character of the sediments were strongly influenced by local factors.

Wildfires across western North America have increased in number and size over the past three decades, and this trend will continue in response to further warming. As a consequence, the wildland-urban interface is projected to experience substantially higher risk of climate-driven fires in the coming decades. Although many plants, animals, and ecosystem services benefit from fire, it is unknown how ecosystems will respond to increased burning and warming. Policy and management have focused primarily on specified resilience approaches aimed at resistance to wildfire and restoration of areas burned by wildfire through fire suppression and fuels management. These strategies are inadequate to address a new era of western wildfires. In contrast, policies that promote adaptive resilience to wildfire, by which people and ecosystems adjust and reorganize in response to changing fire regimes to reduce future vulnerability, are needed. Key aspects of an adaptive resilience approach are (i) rec...

Mountain forests are among the most important ecosystems in Europe as they support numerous ecological, hydrological, climatic, social, and economic functions. They are unique relatively natural ecosystems consisting of long-lived species in an otherwise densely populated human landscape. Despite this, centuries of intensive forest management in many of these forests have eclipsed evidence of natural processes, especially the role of disturbances in long-term forest dynamics. Recent trends of land abandonment and establishment of protected forests have coincided with a growing interest in managing forests in more natural states. At the same time, the importance of past disturbances highlighted in an emerging body of literature, and recent increasing disturbances due to climate change are challenging long-held views of dynamics in these ecosystems. Here, we synthesize aspects of this Special Issue on the ecology of mountain forest ecosystems in Europe in the context of broader discussions in the field, to present a new perspective on these ecosystems and their natural disturbance regimes. Most mountain forests in Europe, for which long-term data are available, show a strong and long-term effect of not only human land use but also of natural disturbances that vary by orders of magnitude in size and frequency. Although these disturbances may kill many trees, the forests themselves have not been threatened. The relative importance of natural disturbances, land use, and climate change for ecosystem dynamics varies across space and time. Across the continent, changing climate and land use are altering forest cover, forest structure, tree demography, and natural disturbances, including fires, insect outbreaks, avalanches, and wind disturbances. Projected continued increases in forest area and biomass along with continued warming are likely to further promote forest disturbances. Episodic disturbances may foster ecosystem adaptation to the effects of ongoing and future climatic change. Increasing disturbances, along with trends of less intense land use, will promote further increases in coarse woody debris, with cascading positive effects on biodiversity, edaphic conditions, biogeochemical cycles, and increased heterogeneity across a range of spatial scales. Together, this may translate to disturbance-mediated resilience of forest landscapes and increased biodiversity, as long as climate and disturbance regimes remain within the tolerance of relevant species. Understanding ecological variability, even imperfectly, is integral to anticipating vulnerabilities and promoting ecological resilience, especially under growing uncertainty. Allowing some forests to be shaped by natural processes may be congruent with multiple goals of forest management, even in densely settled and developed countries.

... Perrott, 1983; 35 36' 117 42 NNWW Benson et al., 1990 Mono Lake (Lake Russell) Lajoie, 1968; Benson et al., 1990 38" 3' 118-46'NNWW Harney Basin Gehr, 1980 43 1Z 119 61 W Lake Lahontan Benson et al, 1990 40 0 119 30' DWW Fort Rock Basin SP Harrison, this report ...

The late-glacial period was characterized by rapid climate changes that resulted in significant ecosystem reorganizations worldwide. In western Colorado, one of the coldest locations in North American today, mountain environments during the late-glacial period are poorly known. Yet, archeological evidence indicates that Folsom-age Paleoindians were present in the region, perhaps even occasionally over-wintering in the Gunnison Basin during the Younger

The Klamath Mountains of northwestern California are a floristic hotspot and their diversity likely results from a combination of geological, ecological and historical factors (e.g., long-term climate change). To evaluate how climate change has influenced past composition, structure, and disturbance regime of the Klamath forests in different geological settings, vegetation and fire histories from four sites, Bolan (1), Sanger (in

Foy Lake, located in low elevation forests of northwestern Montana, provides records of annual-to-decadal-scale landscape change for the last 13,000 years. Sedimentary charcoal and pollen analyses were used to document fire-climate linkages in the Northern Rocky Mountains (NRM) to improve the interpretation of lake-sediment records of fire activity. This paper focuses on the climate controls that suppress and promote fire activity on seasonal-to-decadal time-scales and the ability of lake-sediment proxies from the NRM to record past fire activity occurring at different spatial and temporal scales. Annually-sampled charcoal in lake-sediment cores is compared with evidence of known fires identified from historic fire atlases and fire-scarred tree-ring studies. Historical records of fire near Foy Lake, including the AD 1910 fires that burned over two million acres in Idaho and Montana, are used as a baseline for the analysis of sedimentary charcoal influx during Holocene fire episodes. During recent drought and fire years in the NRM, anomalously higher-than-normal 500mb geopotential heights in summer extended across the Pacific and into northwestern North America and produced stronger westerlies, increased subsidence off the eastern north Pacific and western North America, and suppressed precipitation. Large fire years in the early 20th century, including AD 1910, are associated with above average spring precipitation, higher-than-normal spring temperatures, followed by lower-than normal summer precipitation. The long-term record of sedimentary charcoal and pollen at Foy Lake shows that fire activity (inferred from the frequency of charcoal peaks) was initially low during the early Holocene, increased between 7000 to 5000 cal yr BP, and then decreased from 3800 to 2200 cal yr BP. Fire frequency increased from 7 episodes/1000 years at 2200 cal yr BP to 14 episodes/1000 years at 800 cal yr BP. Fire episodes reached a maximum at ca. 500 cal yr BP and then decreased to present levels.

Background/Question/Methods Fire history is an essential part of Earth system science, but that recognition was not the case in the early 1970s when Herb Wright and Bud Heinselman described the fire history of the Boundary Waters Canoe Area. Subsequent paleofire studies led by students of Wright in the Midwest, Canada, New England, and western U.S. highlighted the importance of long-term fire information for understanding modern forests and their vulnerability to climate change. Significant advances in paleofire research in the last 30 years have built on these early studies. Recent investigations at regional to global scales point to climate as the primary driver of fire activity, and studies at local scales highlight the importance of prehistoric humans in altering ignitions and fuels. Among the outstanding questions are at what spatial-temporal scales do humans and climate jointly shape fire regimes and how can a long-term perspective best inform modern fire management. Results/C...

Publisher Summary This chapter reviews the cultural dynamics as a result of climatic changes in the Northwest Coast of North America. It reviews the paleoclimatic and archaeological records of this region to establish possible causal relationships between them. It suggests that on the Northwest Coast of North America, the middle Holocene was a time of changing climate and culture. The mid-Holocene climate of the Northwest Coast was cooler and wetter than the early Holocene, but warmer and somewhat drier than today. 5800 cal yr BP (5000 14C yr BP) is viewed as a major turning point in the prehistory of the Northwest Coast. Compared to the early Holocene, during the mid-Holocene the number of archaeological sites increased, their average size was larger, and shell middens became common, preserving bone and antler technologies as well as abundant faunal remains. To explain this, the study presents a synthesis of mid-Holocene environmental history based on records of pollen, plant macrofossil, charcoal, limnologic, glacial, and marine sediments. It indicates that the environmental changes during the transition from early Holocene to mid-Holocene and then late Holocene were registered throughout the Northwest Coast, and superimposed on these long-term shifts, were climate variations that took place more locally on annual-to-centennial time scales. Finally, it suggests a collaboration and frequent data sharing between paleoecologists and archaeologists as an obvious first step in approaching the effects of climate change on culture.

Ecological niche models predict plant responses to climate change by circumscribing species distributions within a multivariate environmental framework. Most projections based on modern bioclimatic correlations imply that high-elevation species are likely to be extirpated from their current ranges as a result of rising growing-season temperatures in the coming decades. Paleoecological data spanning the last 15,000 years from the Greater Yellowstone region describe the response of vegetation to past climate variability and suggest that white pines, a taxon of special concern in the region, have been surprisingly resilient to high summer temperature and fire activity in the past. Moreover, the fossil record suggests that winter conditions and biotic interactions have been critical limiting variables for high-elevation conifers in the past and will likely be so in the future. This long-term perspective offers insights on species responses to a broader range of climate and associated ec...

Fire-history reconstructions that extend beyond the age of living trees and sub-fossil wood are based on an analysis of particulate charcoal and other fire proxies preserved in the sediments of lakes and wetlands. The goal of such research is to document the long-term fire history ...

Forest/steppe boundaries are among the most dynamic ecosystems on Earth and are highly vulnerable to changes in climate and land use. In this study we examine the postglacial history of the Patagonian forest/steppe ecotone (41-43°S) to better understand its sensitivity to past variations in climate, disturbance, and human activity before European colonization. We present regional trends in vegetation and biomass burning, as detected by generalized additive models fitted to seven pollen and charcoal records, and compare the results with other paleoenvironmental data, as well as archeological and ecological information to (i) estimate postglacial fire trends at regional scales, (ii) assess the evolution of climate-vegetation-fire linkages over the last 18,000 calibrated (cal) years B.P., and (iii) evaluate the role of humans in altering pre-European landscapes and fire regimes. Pollen and charcoal data indicate that biomass burning was relatively low during warm/dry steppe-dominated l...

This fi eld guide focuses on the glacial geology and paleoecology beginning in the Paradise Valley and progressing southward into northern Yellowstone National Park. During the last (Pinedale) glaciation, the northern Yellowstone outlet glacier fl owed out of Yellowstone Park and down the Yellowstone River Valley into the Paradise Valley. The fi eld trip will traverse the following Pinedale glacial sequence: (1) deposition of the Eightmile terminal moraines and outwash 16.5 ± 1.4 10Be ka in the Paradise Valley; (2) glacial recession of ~8 km and deposition of the Chico moraines and outwash 16.1 ± 1.7 10Be ka; (3) glacial recession of 45 km to near the northern Yellowstone boundary and moraine deposition during the Deckard Flats readjustment 14.2 ± 1.2 10Be ka; and (4) glacial recession of ~37 km and deposition of the Junction Butte moraines 15.2 ± 1.3 10Be ka (this age is a little too old based on the stratigraphic sequence). Yellowstone’s northern range of sagebrush-grasslands and bison, elk, wolf, and bear inhabitants is founded on glacial moraines, sub-glacial till, and outwash deposited during the last glaciation. Floods released from glacially dammed lakes and a landslide-dammed lake punctuate this record. The glacial geologic reconstruction was evaluated by calculation of basal shear stress, and yielded the following values for fl ow pattern in plan view: strongly converging—1.21 ± 0.12 bars (n = 15); nearly uniform—1.04 ± 0.16 bars (n = 11); and strongly diverging—0.84 ± 0.14 bars (n = 16). Reconstructed mass balance yielded accumulation and ablation each of ~3 km3/yr, with glacial movement near the equilibrium line altitude dominated by basal sliding. Pollen and charcoal records from three lakes in northern Yellowstone provide information on the postglacial vegetation and fi re history. Following glacial retreat, *E-mails: [email protected]; [email protected]; [email protected]; [email protected]. Pierce, K.L., Licciardi, J.M., Krause, T.R., and Whitlock, C., 2014, Glacial and Quaternary geology of the northern Yellowstone area, Montana and Wyoming, in Shaw, C.A., and Tikoff, B., eds., Exploring the Northern Rocky Mountains: Geological Society of America Field Guide 37, p. 189–203, doi:10.1130/2014.0037(09). For permission to copy, contact [email protected]. © 2014 The Geological Society of America. All rights reserved. on May 20, 2014 fieldguides.gsapubs.org Downloaded from

Pollen and geochemical data from Little Lake, western Oregon, suggest several patterns of millennial-scale environmental change during marine isotope stage (MIS) 2 (14,100–27,600 cal yr B.P.) and the latter part of MIS 3 (27,600–42,500 cal yr B.P.). During MIS 3, a series of transitions between warm- and cold-adapted taxa indicate that temperatures oscillated by ca. 2°–4°C every 1000–3000 yr. Highs and lows in summer insolation during MIS 3 are generally associated with the warmest and coldest intervals. Warm periods at Little Lake correlate with warm sea-surface temperatures in the Santa Barbara Basin. Changes in the strength of the subtropical high and the jet stream may account for synchronous changes at the two sites. During MIS 2, shifts between mesic and xeric subalpine forests suggest changes in precipitation every 1000–3000 yr. Increases inTsuga heterophyllapollen at 25,000 and 22,000 cal yr B.P. imply brief warmings. Minimum summer insolation and maximum global ice-volumes ...

Records of past environmental change are critical for understanding the natural variability of the Earth's hydrologic system, including the frequency, duration, and spatial extent of drought and its ecological consequences. In the northern Rockies, periods of drought are controlled by the strength and position of the Aleutian low in winter and the northeastern Pacific subtropical high in summer. We present a 2000-year-long history of drought based on records of delta18O of authigenic carbonates, diatoms, charcoal, and pollen from Foy Lake (N 48°10', W 114°21', 1006 masl), located at lower treeline. The site preserves annually laminated sediments, which were analyzed in contiguous six-year intervals. The oxygen-isotope and diatom stratigraphy provide information on variations in effective moisture and consequent water-level change. Macroscopic charcoal records indicate times of high fire occurrence associated with summer drought, and pollen ratios of climatically sensitiv...