The Holocene synthesis brings together new PIRE data, existing global paleofire datasets, and related work of the PIs to gain a better understanding of millennial-scale linkages among fire, climate, fuels, and people in temperate ecosystems. PIRE research in Tasmania, New Zealand, and the western U.S. and related work in Patagonia will provide a basis for circum-Pacific comparisons. This synthesis will consider the importance of large-scale climate drivers and their expression at regional and hemispheric scales. In particular, we will examine the link between paleofire patterns and Holocene variations in:
strength and position of the westerlies, sea-surface/air temperature gradients, onset or strengthening of ENSO and AAO variability
seasonal cycle of insolation, including carryover effects of winter and spring conditions into the following fire season
intensity of anthropogenic burning and land-use change, drawn from the archeological record.
Understanding these relationships will help address scientific debates about (1) the history and influence of southern Pacific ocean and atmospheric circulation on fire and vegetation, including that of the southern westerlies; (2) low- versus high-latitude teleconnections on past fire regimes; (3) submillennial-scale climate variability in shaping temperate fire regimes during the Holocene; (4) northern hemisphere versus southern hemisphere insolation anomalies in shaping fire regimes; and (5) the human signature on past fire regimes on islands and continents. The comparisons will also help identify how projected climate changes might alter patterns of fire and vegetation in the future.
The project has multiple-year objectives:
Year 2: An evaluation of existing charcoal and pollen sites and their relative position along present-day biophysical and bioclimatic gradients. The objective is to summarize environmental gradients represented by the current set of study areas and identify where critical data gaps exist in the coverage of sites. This initial analysis, led by McWethy and Higuera, will result in a full-authorship conceptual paper that lays out PIRE motivation and objectives.
Year 3-5: Research at the watershed scale in Tasmania, New Zealand, and Patagonia will result in a network of fire-climate-vegetation reconstructions needed to infer regional patterns of environmental change (i.e., changes in fuel, high- and low-area burned, fire frequency, intensity of human signal) over multiple time scales. Regional patterns will be related to modes of climate variability and teleconnection patterns, understood from NCEP data, independent paleoclimate data and model simulations, and broader understanding of human activity and land-use change. In this way, we will be able to compare the history of fire in similar and contrasting fuel types, climate, and human presence and evaluate environmental sensitivity of temperate forests to past climate changes over different spatial and temporal scales.
This synthesis effort is a major objective for PIRE and ties into many non-PIRE activities. It also involves non-PIRE collaborators, including Pat Bartlein (Univ. Oregon), Christy Briles (Monash Univ.) and Patricio Moreno (Univ. Chile). PIRE will consider adding a climate consultant to the team in Years 4 and 5 to help support this Holocene synthesis effort.
Haberle, Fletcher, Whitlock, Moreno (UChile), Bartlein (UOregon) and Iglesias (MSU) are working on a trans-Andean fire-climate comparison in Patagonia based on pollen and charcoal records from a network of lakes in southern Chile and Argentina. McGlone, Whitlock, McWethy, Wilmshurst, and Bartlein have discussed a comparison of Holocene climate variability in New Zealand and the Pacific Northwest. Whitlock and Briles are working on the history of fire in PNW rainforests (PIRE US-1/FS).
Year 2 Update:
This synthesis activity integrates research underway in New Zealand (NZ-1), Australia (Tas-1, Tas-3, Tas-4), the western U.S. (US-2) and Patagonia (non-PIRE projects) to better understand the long-term linkages between climate-fire-people in temperate forests across comparable environmental gradients. The research is supported by grants from the National Science Foundation, Australian National University, and Landcare Research. The project is just beginning, and activity will increase in the second half of the PIRE grant. Current efforts focus on describing regional fire-climate-people linkages, before making interhemispheric comparisons. Discussion of this project will be stimulated by a symposium, convened by Haberle and Whitlock at the Southern Connections meeting in Dunedin New Zealand. Further planning will occur at the PIRE meeting in New Zealand in Year 3.
An effort to broaden participation may be possible as a result of an international Fire Workshop to be held at the University of Venice in June 2012. This meeting is co-organized by Whitlock and partially supported by PIRE as well as the European Union. The goal of the workshop is to examine the anthropogenic contribution to biomass burning during the Holocene and its impact on greenhouse gas emissions over long periods of time. The workshop brings together fire scientists who examine different types of paleofire records (lake sediments, ice cores, marine, tree-rings) and those who utilize modeling approaches to reconstruct fire impacts at different scales. It represents an important cross-disciplinary effort to link charcoal records with other types of fire records so that we can better understand fire as an earth system process. This meeting will lead to a white paper outlining future research directions.