Forest Histories & Forest Futures

The climate changes projected for the future will have significant consequences for forest ecosystems and our ability to manage them. It is reasonable to ask: Are there historical precedents that help us understand what might happen in the future or are historical perspectives becoming irrelevant? What synergisms and feedbacks might be expected between rapidly changing climate and land–use in different settings, especially at the wildland–urban interface? What lessons from the past might help us plan for a changing world? Information on forest history comes from a variety of sources, including pollen and charcoal preserved in lake sediments spanning millennia, variations in tree–ring growth indices spanning centuries, and recent forest dynamics. In the last 10 years, considerable paleo–research has focused on the ecological consequences of abrupt climate change, and records of past forest conditions are often detailed enough to describe changes occurring on time scales of years to decades. From this rich and well–resolved database, we can find examples of rapid environmental change in the past, similar to that projected for the future, and examine the ecological consequences that ensued. Studies from the western U.S. and beyond reveal the synergistic effects of past climate and land–use change in shaping present forest composition and dynamics. In addition, networks of paleoecologic sites disclose regional and global patterns of vegetation and disturbance regimes and the widespread responses to large–scale changes in climate. Although the past does not hold an exact analogue for the future, essential lessons can be learned about the sensitivity and resilience of forests to extreme events, the potential rates of ecological change, the role of natural and anthropogenic disturbance as a catalyst of change, and the legacy of human activities on forest environments

Pollen and Vertebrates of the Early Neogene Haughton Formation, Devon Island, Arctic Canada

The Haughton Formation of northern Devon Island, arctic Canada, consists of sediments deposited in a lake that filled a large impact crater, which has been dated as early Miocene. The fossiliferous sediments contain a rich assemblage of pollen, some plant megafossils, and the only known early Neogene arctic vertebrates. Common pollen types are Pinus, Ericales, Corylus-type, Betula, and Alnus. Picea, Larix, Cupressaceae, and Ulmus/Zelkova also occur. These taxa, rarer hardwoods, and spores allow a vegetational reconstruction of a mixed conifer-hardwood forest. Climatic conditions were cool temperate with maritime influences. Vertebrates, including trout, smelt, swan, and four mammal genera, lend support to the climatic interpretation, and they also suggest considerable endemism for the mammals. The Haughton flora appears to be bracketed temporally by floras from various parts of the widely distributed Beaufort Formation.

Advances in fire history research and their application for ecosystem management and conservation

Paleoecology is a valuable tool for understanding the long-term ecosystem dynamics that underlie present environmental conditions.  Fire is an important form of disturbance in most terrestrial ecosystems, and increased levels of biomass burning in many parts of the world have raised concerns about the role of fire in transforming vegetation composition, extent, and function in the future.  Sedimentary charcoal records can help inform this discussion by providing fire-history information that spans a range of temporal and spatial scales.  At a regional to continental scale, climate emerges as the strong driver of past biomass burning, with warmer periods being associated with higher fire activity.  In many regions, humans have also significantly altered natural fire regimes through (1) igniting fires in places where fires were naturally rare, (2) lengthening the fire season through deliberate burning, (3) manipulating fuels through land-use activities, and (4) suppressing or eliminating natural fire

Holocene Dynamics of Temperate Rainforests in West-Central Patagonia

Analyses of long-term ecosystem dynamics offer insights into the conditions that have led to stability vs. rapid change in the past and the importance of disturbance in regulating community composition. In this study, we (1) used lithology, pollen, and charcoal data from Mallín Casanova (47°S) to reconstruct the wetland, vegetation, and fire history of west-central Patagonia; and (2) compared the records with independent paleoenvironmental and archeological information to assess the effects of past climate and human activity on ecosystem dynamics. Pollen data indicate that Nothofagus-Pilgerodendronforests were established by 9,000 cal yr BP. Although the biodiversity of the understory increased between 8,480 and 5,630 cal yr BP, forests remained relatively unchanged from 9,000 to 2,000 cal yr BP. The charcoal record registers high fire-episode frequency in the early Holocene followed by low biomass burning between 6,500 and 2,000 cal yr BP. Covarying trends in charcoal, bog development, and Neoglacial advances suggest that climate was the primary driver of these changes. After 2,000 cal yr BP, the proxy data indicate (a) increased fire-episode frequency; (b) centennial-scale shifts in bog and forest composition; (c) the emergence of vegetation-fire linkages not recorded in previous times; and (d) paludification in the last 500 years possibly associated with forest loss. Our results therefore suggest that Nothofagus-Pilgerodendrondominance was maintained through much of the Holocene despite long-term changes in climate and fire. Unparalleled fluctuations in local ecosystems during the last two millennia were governed by disturbance-vegetation-hydrology feedbacks likely triggered by greater climate variability and deforestation

In memoriam: John Platt Bradbury (1936–2005)

John Platt Bradbury, a former United States Geological Survey (USGS) geologist, and a long time and much valued editorial board member for the Journal of Paleolimnology, died of cancer (abdominal mesothelioma) on August 15, 2005, in the log home that he and his wife Vera Markgraf built in the mountains near Monte Vista, Colorado. Platt’s interest in paleolimnology developed during his graduate school years at the University of New Mexico, working with Roger Anderson and Walt Dean. He received his Ph.D. in 1967. He went on to do post-doctoral research at Yale University under G. Evelyn Hutchinson and then became an Assistant Professor at the University of Minnesota Limnological Research Center, where, among other projects, he worked on a multidisciplinary study of the Klutlan Glacier, Yukon Territory (Bradbury and Whiteside 1980). In 1975, he joined the Paleontology and Stratigraphy Branch of the USGS, where he offered a primary specialty in continental diatoms and secondary specialty in Quaternary palynology. Platt’s work focused on developing a continental diatom biostratigraphy for Miocene through Quaternary sediments and on paleoclimatic reconstructions from lacustrine records

Response of Pacific Northwest vegetation to large-scale changes in climate during the last 100,000 years [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): Paleoclimatic variations in western North America depend on a hierarchy of temporal and spatial controls that can be examined using a combination of modeling studies and data synthesis. ... The regional vegetation response to large-scale changes in the climate system of the last 21,000 years is used as a conceptual model to help explain earlier vegetation and climate at two localities

Pinus contorta invasions increase wildfire fuel loads and may create a positive feedback with fire

Invasive plant species that have the potential to alter fire regimes have significant impacts on native ecosystems. Concern that pine invasions in the Southern Hemisphere will increase fire activity and severity and subsequently promote further pine invasion prompted us to examine the potential for feedbacks between Pinus contorta invasions and fire in Patagonia and New Zealand. We determined how fuel loads and fire effects were altered by P. contorta invasion. We also examined post-fire plant communities across invasion gradients at a subset of sites to assess how invasion alters the post-fire vegetation trajectory. We found that fuel loads and soil heating during simulated fire increase with increasing P. contorta invasion age or density at all sites. However, P. contorta density did not always increase post-fire. In the largest fire, P. contorta density only increased significantly post-fire where the pre-fire P. contorta density was above an invasion threshold. Below this threshold, P. contorta did not dominate after fire and plant communities responded to fire in a similar manner as uninvaded communities. The positive feedback observed at high densities is caused by the accumulation of fuel that in turn results in greater soil heating during fires and high P. contorta density post-fire. Therefore, a positive feedback may form between P. contorta invasions and fire, but only above an invasion density threshold. These results suggest that management of pine invasions before they reach the invasion density threshold is important for reducing fire risk and preventing a transition to an alternate ecosystem state dominated by pines and novel understory plant communities.Fil: Taylor, Kimberley. State University of Montana; Estados UnidosFil: Maxwell, Bruce. State University of Montana; Estados UnidosFil: McWethy, David. State University of Montana; Estados UnidosFil: Pauchard, Aníbal. Universidad de Concepción; Chile. Universidad de Chile; ChileFil: Nuñez, Martin Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Whitlock, Cathy. State University of Montana; Estados Unido

Erroneously old radiocarbon ages from terrestrial pollen concentrates in Yellowstone Lake, Wyoming, USA

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in [Schiller, C. M., Whitlock, C., Elder, K. L., Iverson, N. A., & Abbott, M. B. Erroneously old radiocarbon ages from terrestrial pollen concentrates in Yellowstone Lake, Wyoming, USA. Radiocarbon, 63(1), (2021): 321-342, https://doi.org/10.1017/RDC.2020.118.Accelerator mass spectrometry (AMS) dating of pollen concentrates is often used in lake sediment records where large, terrestrial plant remains are unavailable. Ages produced from chemically concentrated pollen as well as manually picked Pinaceae grains in Yellowstone Lake (Wyoming) sediments were consistently 1700–4300 cal years older than ages established by terrestrial plant remains, tephrochronology, and the age of the sediment-water interface. Previous studies have successfully utilized the same laboratory space and methods, suggesting the source of old-carbon contamination is specific to these samples. Manually picking pollen grains precludes admixture of non-pollen materials. Furthermore, no clear source of old pollen grains occurs on the deglaciated landscape, making reworking of old pollen grains unlikely. High volumes of CO2 are degassed in the Yellowstone Caldera, potentially introducing old carbon to pollen. While uptake of old CO2 through photosynthesis is minor (F14C approximately 0.99), old-carbon contamination may still take place in the water column or in surficial lake sediments. It remains unclear, however, what mechanism allows for the erroneous ages of highly refractory pollen grains while terrestrial plant remains were unaffected. In the absence of a satisfactory explanation for erroneously old radiocarbon ages from pollen concentrates, we propose steps for further study.This research was supported by NSF Grant No. 1515353 to C. Whitlock and sampling in Yellowstone National Park was conducted under permits YELL-SCI-0009 and YELL-SCI-5054

Holocene Dynamics of Temperate Rainforests in West-Central Patagonia

Analyses of long-term ecosystem dynamics offer insights into the conditions that have led to stability vs. rapid change in the past and the importance of disturbance in regulating community composition. In this study, we (1) used lithology, pollen, and charcoal data from Mallín Casanova (47°S) to reconstruct the wetland, vegetation, and fire history of west-central Patagonia; and (2) compared the records with independent paleoenvironmental and archeological information to assess the effects of past climate and human activity on ecosystem dynamics. Pollen data indicate that Nothofagus-Pilgerodendron forests were established by 9,000 cal yr BP. Although the biodiversity of the understory increased between 8,480 and 5,630 cal yr BP, forests remained relatively unchanged from 9,000 to 2,000 cal yr BP. The charcoal record registers high fire-episode frequency in the early Holocene followed by low biomass burning between 6,500 and 2,000 cal yr BP. Covarying trends in charcoal, bog development, and Neoglacial advances suggest that climate was the primary driver of these changes. After 2,000 cal yr BP, the proxy data indicate (a) increased fire-episode frequency; (b) centennial-scale shifts in bog and forest composition; (c) the emergence of vegetation-fire linkages not recorded in previous times; and (d) paludification in the last 500 years possibly associated with forest loss. Our results therefore suggest that Nothofagus-Pilgerodendron dominance was maintained through much of the Holocene despite long-term changes in climate and fire. Unparalleled fluctuations in local ecosystems during the last two millennia were governed by disturbance-vegetation-hydrology feedbacks likely triggered by greater climate variability and deforestation.This work was supported by grants from the National Science Foundation (0966472, 0956552, 0602166), the National Geographic Society (7988-06), and the Department of Archaeology and Natural History at the Australian National University

ARTICLE EDUCATIONAL AND PSYCHOLOGICAL MEASUREMENT YASUDA ET AL. ASSESSMENT OF INTRAINDIVIDUAL VARIABILITY IN POSITIVE AND NEGATIVE AFFECT USING LATENT STATE-TRAIT MODEL ANALYSES

Intraindividual variability in positive and negative affect was assessed by the positive affect (Contentment, Joy, Vigor, Love, and Excitement) and negative affect (Depression, Hostility, Anxiety, Agitation, and Social Anxiety) subscales of the state version of the Comprehensive Personality and Affect Scales (COPAS) during a 3-week period. Using the latent state-trait model analysis, which takes both intraindividual variability and interindividual difference into account by controlling measurement error, it was shown that the variability could be measured reliably by the scores of the COPAS. In particular, a total of 56.9% to 63.5% and 48.2% to 60.6% of the reliable interindividual difference in positive and negative affect, respectively, was attributed to the intraindividual variability